Hyperledger Foundation Meetups, 13 Nov 2020

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From YouTube: Hyperledger Budapest hosts "Reimplement your composer business network into Fabric Java chaincode"

Description

A virtual meetup hosted by Hyperledger Budapest. As Hyperledger Composer has become deprecated, it is an interesting question how existing composer business networks can be transformed or reimplemented in Fabric chaincode. In our online presentation we introduce the Hyperledger Fabric Java chaincode programming in details with a help of a user-case reimplementing a Composer Business Blockchain Network to Fabric Java Chaincode.

More about the event is at: https://www.meetup.com/Hyperledger-Budapest/events/264648253/

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Hyperledger – Open Source Blockchain Technologies

Hyperledger is an open source community focused on developing a suite of stable frameworks, tools and libraries for enterprise-grade blockchain deployments.
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So I dropped the link to the youtube, live stream page in chat so again, there's a chat there as well. So just keep an eye on that. Okay um and again, I usually we usually see maybe about 10 12 people over there as well, while uh the event's going so okay.

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Sounds great, uh so I would say I would just wait like five more minutes and then.

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Someone make you post a chat there as well, so just keep an eye on that um and yeah. I usually we usually see maybe about 10 12 people over there as well, so you're now host so um I'll need to drop in maybe like five ten minutes, but I'll hang on for a minute to see if there's any issues or anything, but you should have full access now.

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So in the meantime, let me just say: share my.

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I think I would say I would slowly start and I would basically start with a small introduction. So if, if anybody joins uh joining uh a little bit later on.

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Then then they do not miss practically the technical content.

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So basically, this is hyperledger budapest. We did almost a year break due to several reasons I mean mostly, I mean this year was the pandemic that blocked us pretty much, uh but we are basically relaunching uh hyperledger, budapest.

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uh It looks that day that it's it's budapest. It's.

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In hungary uh we we used to have, and we still have a pretty good uh technical community and audience as well for blockchains uh for different blockchain technologies. uh I mean hyperledger, is I mean not hyperledger, but consortium blockchain is is certainly not the major focus, but I mean still there's a huge interest, uh basically for for for consolation, blockchain technologies as well. uh What we usually do.

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On an open community basis is to give like mostly technical presentations.

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um Sometimes we have, or we invite speakers uh from from business area as well. But again as I mentioned so basically, hungary is is more more stronger in terms of technical competence and all the answers, perhaps not so much on on use cases, but.

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Anyway, this is an open community, so.

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If you feel like joining us or if you have an interest for making presentations uh on any hyperledger technologies or use cases, then then feel free just to contact me and then we can. We can lightly negotiate and schedule something.

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So what I'm gonna do today is basically do a little bit more technical presentations uh on hyperledger fabric and especially hyperledger fabric java programming.

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It's going to be both chain code programming and basically, some some client programming as well. It.

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Will be a high level.

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Overview uh with.

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Some with some real code examples as well so so expect some coding as well.

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I will have some slides uh as a general overview, both from hyperledger fabric and from the chain code and and java programming of hyperledger fabry. So what I'm gonna do is somehow keep switching uh between the slides and between the coding examples. So practically I will. I will just uh uh iterate a couple of slides and then I just uh plunge into the code details uh and then, and vice versa,.

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uh So basically,.

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I mean the idea was: was for this presentation of that you used to have one very great tool that was hyperledger composer, uh which was mainly for for, like business analysts, uh doing something very fast uh on a.

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Hyperledger fabric or hyperledger basis- and unfortunately is I mean this tool is, is is not not available anymore. I mean it's still available if you, if you, if you want it, but you can't really use it in integration with david newest hyperledger fabric releases, so.

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The idea was, if it's possible, to do something similar in terms of of the native hyperledger fabric programming like like chain code and and client and well unfortunately, it's not so easy, but I do what you can do.

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Pretty fast and and in an easy way,.

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So this was basically the introduction, uh so not quite sure if people still joining or if you have any questions.

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Related to to the budapest community or to.

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To hyper ledger generally, if so, I can try to answer so. If so, then, one way of just putting in the chat.

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The other way is to put into the youtube channel.

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Which I try to open parallely.

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So I guess I see pretty.

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Much which I'm trying to open.

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One question is, I mean all the content will be recorded as far as I know, and the slides and the and the and the presentations and the code fragments.

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As well as well will be checked in uh practically to to github, and I will share share them so yeah.

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So uh then, let me start basically with the presentation and with some of the technical content.

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And let's be sure that I'm still sharing my screen.

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C

Basically, uh I'm gonna start with fabric development. uh We will see how exactly hyperledger fabric uh which components hyperledger fabric uh has, but basically I will start from a more more on a little bit. Software developer perspective. So let me imagine you want to do something with hyperledger fabric um this something might be even for proof of work, application or proof of concept application. uh It might be something as a small demonstration as well.

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It can actually be something as a full-scale project as well, uh but anyway, uh if you want to start with hyperledger fabric development, you should consider basically three major blocks: free building blocks.

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Building blocks in terms of of programming experience and in terms of I mean release.

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Process as well so, first what you have in the middle, that's hyper ledger fabric, uh it's basically a lot of containerized infrastructure. So first I mean independently. If you just want to do some kind of a demo or if you want to do something as a fuse project, uh you need practically developers or experienced people with experience with containerized infrastructure.

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uh This containerized infrastructure is the first run, docker.

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So what I'm gonna show is basically just very simple scripts.

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You want to in a more serious way, then you need competence with docker, uh it might be even kubernetes or openshift as well, and we get some best scripts, basically as well. So setting up the whole hyperledger fabric infrastructure requires some competence uh in containerized infrastructure.

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Unfortunately, and there are two side stars tests here- uh one is basically chain code chain code is basically the smart contract of hyperledger fabric or it can be regarded as kind of a small component that runs inside hyperledger fabric, and there are three languages uh that you can implement chain code with, one is java. Second, one is javascript and the third one is google, uh so it's these are.

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Not really, you know anything anything you can. You want to write stuffs, but basically.

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Chain codes is a very limited container, with very limited programming model and and possible calls. So it's really something special, not full-scale java, javascript or google application. So that's chain code uh and there's another programming task. It's your client application, so you need to have your client. uh Your client looks that way. Basically, if you want to communicate with the hyperledger fabric network, it has some special grpc communication.

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So what you usually don't want to do is that you implement this. This grpc communication from sketch, but rather what you do is that there's an sdk by hyperledger fabric which helps you this kind of development.

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So practically this sdk implements all of the grpc communication uh what's available here and then, basically, you can do it in an easy, easy and fast way, uh setting up your client application.

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So the point is: uh usually you could say you. You could theoretically program in any programming language, your client application, but the point is that your sdk is available in java, javascript and and and perhaps go again. uh Go is not so much uh a favorite language here, so it's rather java and javascript. So if you want.

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Use your or implement your current application without much effort, then you should use actually the official sdk sdk, so basically java and javascript android go. That is supported. So that's! Basically, our fabric development roadmap.

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It's a little bit of questions, I mean if you, if you just consider.

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The middle you can't avoid having like docker or or containerized infrastructure, specialist or or know how a little bit if.

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You, if you consider like chain wood and client.

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Application I mean you can choose your programming language, uh so one way of choosing is like saying that hey, we got some java developers, so we write both chain code and client application in java, because that's the competence, what we have uh that's one way of of doing things. um The second one which is typical is that you get one developer for chain code and the totally friendly developer for for your client application.

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So like usually, if your client application is in is in javascript is in node.js, then then you say that hit and let it write our client application in javascript and then the would so I mean I personally don't like writing smart contract in javascript, because the language might be not so you know, efficiency efficient uh in terms of security.

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So one way of solving this problem is like changing.

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Basically, some of the some of the programmers in uh in blockchain space uh have very good goal competence. So, like uh you get one programmer for chain code for who you get you get the rest of your application in in ogs in javascript, and you get some dockerized containerized infrastructure. That's a second way of doing things.

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So let me start here a little bit. The.

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Technical presentation- and let me just show some demonstration.

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So if you want to uh basically uh install a full hyperledger fabric form, uh you get some.

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uh So there's an official official way of installing it.

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It looks that way that, with a certain commands, uh the full farm is downloaded with a lot of sample applications uh and with practically all of your docker images that you want to use. I do not install it at the moment, but I previously installed it so after after successful installation, what you get is a folder which is called fabric samples.

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uh It is not necessary to use your fabric samples, but the point is so I I always say that if.

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You want to do some some hyperledger fabric development, the.

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Easiest way of doing is is to start from things that are working um if you, if you want to start everything from scratch, on the one hand, you need a lot of expertise. You need a lot of competence and yeah, so it's gonna be a long and sometimes boring process as well.

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If you want to do it in a fast way, like prototyping, for instance, or because you do not have so much hyperledger fabric experience, the easiest way is to start with fabric fabric samples and again so, if you install the whole environment, the whole hyperledger fabric, uh then these fabric samples.

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Will be installed as well anyway, just one comment, so you can find basically.

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Github repository as well.

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Fabric samplers.

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So if you need like further information, uh you find everything in github. uh This is actually an open source project. I just skipped the introduction. I focus more on like doing something something live, but basically the whole project is open source. You find practically everything on on github, uh including these fabric samples part as well.

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So what I'm gonna.

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Plunging into a more theoretical stuffs is that.

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I will start a hyperledger fabric.

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Network first, I have to basically stop my running hypeology fabric network.

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Just one more comment: uh so if you expect.

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Something similar that you that you saw practically in hyperledger, oh.

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Like things in an easy way- and you can practically forget it, um so this is a very much um you know technical stuff of doing things. uh So, basically you need to do a lot of things with with the common prompt, basically uh and at the end, you can just call commands uh with the help of a command prompt application.

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So it's not so fancy and not so spectacular for the first one, um there's there's a lot, there's a lot of implementation and a lot of uh like technical stuffs inside so let me just start basically hyperledger fabric network.

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It looks that way that, under your fabric, samples, which is again uh which is installed as you install hyperledger fabric, there are a couple of uh basically examples that are prepared.

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Let me just zoom in a little bit.

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So if you just go inside the folder, you see a lot of.

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Things uh and then what I'm gonna experiment with is the test network. So one way of starting like a simple hyperledger fabric is to go to the test network folder.

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And here there's: there's the network command bash script.

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Then there are a couple of things uh that I can give as a parameter.

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And let me just choose one uh fully functioning parameter set so.

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What I'm gonna do I'm I'm going to bring up a hyperledger fabric network uh with creating a channel called my channel and a couple of certificate authorities?

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That's what I'm gonna do and I will explain just in a second what this create channel channel and certificate authority means, but if I just give a command it looks that way that it brings up my hyperledger fabric network. So again, uh if you still remember the first slide, we are in the middle. Basically, we we are with docker and best scripts and what we are doing is we start our first hyperledger fabric network uh they're still.

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Not much programming, I mean there's an example.

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Chain code as well, which I'm just going.

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Basically, uh this is the best clip. This is docker files that I'm basically starting at the moment, so.

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Let's just have one second.

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Takes a while, but it succeeded.

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So if there's no like a big fancy error message at the end, then.

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Everything is working and what you can do is to check uh with the docker command if your containers has been started and what we can see at the moment uh that we get like something as b.

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uh We get something it's an order.

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And we get a couple of certificate authorities: okay, so I'm quite sure how much you're familiar with these words, but I prepared a slide as well.

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So basically, uh what we have in hyperledger fabric, uh we get two two views and so again I'm in the middle. Basically, I'm with the hyperledger containerized infrastructure, uh which you saw running with dockers, and and you can do it with kubernetes as.

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Well, uh it's a little more complicated but manageable.

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So concentrating in the middle, we got like two views: uh one is a physical architecture and the other one is the logical architecture. So what you see so here, basically with these docker components, is your physical architecture and your physical architecture looks that way that you get many different components.

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uh These are docker components uh you get like an ordering service, an ordering.

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Service in the middle that.

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Might behave so that might have one component or several components as well, but it is responsible to put the transactions on a block and create a new block in order in a way that double spending is avoided, so ordering service does nothing just creates a new block practically then you get something as peers, peers uh peer work, in a way that it has several functionality.

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One functionality is that it source your it stores your blockchain, so the whole blockchain is basically here somewhere.

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There's a database here as well, but, surprisingly your location.

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Is not in the database, it is usually appear in a file folder uh and what peer does it practically simulates transaction? And it's writes to the ledger? Okay, so this is peer. uh You got a separate database as well the database again, it's not for the full object, but it's practically just for a part of it. It's usually your state. So your state is the last I mean the newest block of your blockchain, so it's the state of the world and that's what's stored in your code david and you get something as chain code again.

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Chain code is basically your smart contract. It's called smart contract in in hyperledger fabric, so everything which is your smart contract, is here in your chain code container.

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Okay- and this is again one separate one and that's something as less certificate authority. It's not so much visible at the moment, but if I just make it.

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Smaller you find here a certificate authority, so it looks that way that hyperlooger fabric is a so-called punishing blockchain uh permission. Blockchain means a couple of things. um First, I mean even at the transaction side, not everything for everybody available. So if you just you know, I mean imagine, ethereum uh anybody want to use the the ethereum network can use it without any permission you just download metamask get some transaction uh get some heater just track and roll, and you can do it.

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So this is a so-called permission blockchain. So it looks that way that, if you're a user of the system, uh you need to have some permissions to have to do anything with dbd network, and these permissions can be configured so like.

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You can see that I have some administrator permission. I can. I can change something on the infrastructure. You can say that here I get some some elevated privileges.

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uh For one of the application, which is usually one of your chain code, so I can do things differently uh and we can see that I got some permissions that I can read out something from the ledger and we can see that you don't have any permission at all, neither neither seeing nor nor creating transactions nor nor editing and editing anything.

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So this kind of permissions are administrated by public key infrastructure by 509 certificates and certificate authority is responsible for issuing such certificates. These certificates.

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um There's another point which is interesting: I'm not going to go very much into the deepest.

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Because this is a this is a very long story, uh so this is.

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A permission blockchain even in the infrastructure sense as well. So uh from the infrastructure point of view, you know I mean if, if you look, ethereum ethereum is a permissionless network, both from a user.

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Perspective and from the infrastructure perspective as well so um in infrastructure means. If I want to join the network, I can download my node and I can do it without any permissions in ethereum. It's not the same with hyperledger fabric in hyperledger fabric. If I want to join the network, I need to have kind of a permission from the rest of the system, and this.

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Permission is from attacking a point of view.

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Again, administrated with kind of a public private keys. So if I'm a server or if I'm a new peer and if I want to join the network, I need to have some public private keys and some certificates again, that is issued by a certificate authority.

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So it's a little again it's a more complicated story, but.

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Certificate authority basically issues the certificates that are relevant throughout the network for any kind of authorization, uh practically.

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So a lot of lab box, but not least we get some client application.

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And client application wants to communicate with our network with the help of an sdk. ah This is practically the sdk as the.

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Sdk here, so this is the physical architecture. uh If you just take a look, we find here some of the corner.

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So like we get 1p, let's appear 0 dot, org 1 we get another beer, that's appear. 0.2. uh We get some ordering service, that's the order. Example.Com we get some certificate authority for order, air force for organization, one and organization. um There are many ways of configuring hyperledger fabric, so this is one working uh constellation.

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You can have like thousands of different uh setup uh depending on how many peers? How do you want to have your chain code coach db? How many.

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Ordering components: do you want how want to structure your certificates, authorities and so on and so on?.

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I will go a little bit more in details a little bit later.

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So you have something as well as the logical architecture.

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And your logical architecture is yes, somehow related to this physical one. So in hyperledger fabric you got something as organizations on the logical level organization is something that you know. I mean you want to build a network between between several big companies. Then, usually these big companies are organizations.

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uh We got something for each organization you can define actually one or two peers, and one of the other important stuff is channel.

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Channel channel is a blockchain, so.

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It looks that way that hyper ledger fabric doesn't give you the opportunity to build up one blockchain, but it gives us gives you the opportunity to build up several totally different blockchains. So you get here like four organizations. This is organization, one it's like. I don't know uh hyperledger organization. This is organization. Two, it's I don't know word bank. This is organization.

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Three, it's I don't know, bmw um so like big companies, then you can have practically a channel which is again a separate blockchain, uh and this blockchain is used just for these three organizations visible just for these free organizations and can.

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Be administrated but just by free organizations.

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uh You can have an organization for as well, it's like, I don't know ngo and then.

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You can set up a totally different blockchain. That's an isolated blockchain! That's an isolated.

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Channel uh between organization, two and organization, four, and this channel two is visible and administrated just by these big organizations. So if we just go back, we can say actually that, like the peers, has something as a.

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As an organization, so it is not so much.

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With the scenario, but basically with this scenario, we got two organizations organization, one and organization two and for each organization there's one peer, so there's a peer zero for organization, one uh there's the ps0 phone organization too, and basically that's all ordering services independent from the organization and then basically, there's there's certificate authorities as well: two certificates authorities for the two organizations and and one certificate authority for the order- and it's not so much visible. But if you still remember with this command create channel, I created actually a channel as well.

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So this command creates a channel between organization, one and organization, two uh and configures. It.

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Without problem.

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One more thing which should be taken care.

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Looks that way that chain code is your smart contract and you install your smart contract, your your chain code for a channel. So if you have like a business application uh which has a chain code which has something something cool inside like in java, then you install it for a specific channel.

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So let me take a look: uh what's going.

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Let me see some some application as well, so we got the second command and it looks that way that the first command actually created a channel uh and created some organizations and some peers and some certificate authorities. But what we want to do is to basically uh have some java application on on top, so the next command. What I'm gonna execute.

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Says that there's a deployed chain code uh deploy something to my channel and I can put a language minus language java. So if I just execute this command, then what's happening. Is that there's an example java application which is configured under test network? I will show just in a second and this this example. uh Our java application uh will be.

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Installed so I hope this is still working.

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Anyway, this is friday. This is 13., so I mean I. I would expect that something was wrong with my demonstration.

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So I hope everything is still working so looks.

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So it looks great so what basically happened if you go to the fabric samples, folder.

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Basically, a chain code folder and in the chain code folder, you see several demos, uh one demo is this fab car uh fab card and uh yeah there's no hint for that. But basically, when you did this command, basically this fab car demo was installed. So under this fab car you find this chain code in several languages and one is java. So.

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Basically, this java application was needed for uh anyway, uh what we can do. I will do it in.

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A little bit more uh advanced way uh before, showing showing the example. So if you want to do practically, if you want to develop a new java chain code in a very easy and fast way, uh what you can do is just to go to this. This folder copy this folder, like saying this, is gonna, be my fab card.

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And then play with it a little bit.

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C

Basic idea, basically, is that the easiest way of doing something uh is to have something which is working uh and modifying a little bit. So that's what I basically did uh and I will show this fab car demo in a second.

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So what was installed is basically something uh which.

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Is a very simple fabric: car example: uh what.

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You can do you can have like different models of of cars. You can write these cars into the ledger with the create car command and you can query all cars from the ledger with a query. All cars command and you can have some smaller.

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Transactions as well like changing the car.

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And I think that so basically, uh this fab car demo uh without going very much deep into the code, have free transactions. You can create a new car, uh you can query all possible cars and what you can do is you can change the car owner? Basically, okay. So that's a very simple free transaction demonstration.

C

So as this was practically installed, we got some magic here how this chain code was installed. But what you see at the end that we executed the query on the on the installed uh installed chain code, and this could avoid query all cars and basically, what you see here at the end or all cars, what we read these are the these are the cars in the system.

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What can you do with this? uh Unfortunately, there's no nice way.

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Of of doing something with this car example, uh one way of playing this with that is that it looks that way uh that you can use your command prompt to uh to work a little bit with this. With this example, where this is installed, car example and what you have to do, unfortunately, is to configure your environment variables uh again. This is a permissioned ledger, so basically, you need to have some permissions uh to work with the network.

C

It looks that way that, in this very simple example, is all your all of your all of your stuffs has have been generated. So basically, uh uh you can find all of the so-called crypto staffs and x uh 509 certificates.

C

uh I will just put it in a github repo, but anyway, if you configure in a correct way, your your environment, variables, I mean especially what's important- is that you have these certificates, the certificates, showing your client identity, with which you communicate with the networks. So it means that you are allowed to communicate with the network at all. So, if everything cool, what you can do is to test your application with the help of a command prompt, and it looks that way.

C

If you install hyperledger fabric, you you get a couple of comments uh like one two, two most important comments are peer chain quote query and peer chain code in invoke one practically queries, your ledger: there is your application and the second one executes a transaction. Okay, it's very, very simple, not so simple, but from from not so simple to get it alive. But from a conceptual perspective, it's not so complicated, so what's happening here.

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Is that I will just try.

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To query my ledger and what I did again after setting, of course, my environment variables.

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uh Command, which created actually all of my all of the possible cars uh cars in the network.

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So after having.

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I can really actually there's one more command, it's. It says clearly, one car. So if I want to just play with the network, I can clear one car as well.

C

It looks that way uh that there's a query, car and there's basically there's an ident there's an id uh it's like one car 11 is is my car, uh which I'm gonna kill with him, and if I do it, there's an error that.

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Basically, discard 11 doesn't exist, okay,.

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So it's actually not a malfunctioning, but it's something which should be known or which should work. So what I can do is that I.

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Can try to invoke a transaction.

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That practically writes in one such a car, so it looks actually a little bit more complicated, but what I'm doing is from a common prompt. I call a peer chain code invoke transaction and this transaction calls basically a create card. So it's a create car transaction, and this create car transaction has got couple of arguments so like uh this car will be car 11. uh This is like a primary key for my for my car that caused actually an error uh previously.

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And then I don't know, uh I'm pretty much. You know east european. So let's have this romance but quite sure, if you guys know it. Let's have this. I don't know blue and.

C

I don't know which is this last argument, so these are like characteristics of the car. uh It's like x66.

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So as soon as I have this transaction uh and next secure this transaction, I can see that I have a chain called execution uh which was successful and as soon.

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As I repeat, my previous.

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uh Peer chaincode query, command.

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For car 11, then I should basically get back the result of that. I just wrote in uh into the system. So it's like uh it's like uh that's the result. It's owner, that was the owner. That was the model, was leave anyway. Color was blue and then make was basically travant.

A

And yeah- and this looks nice, so this is the answer I have brought in something to pleasure, and the information is is is really that okay, so let's get some some some some more fun so.

C

Again, uh the easiest way is to start. Is that practically you go to fabric samples chain code? uh You get fab card, you get you get java and you just copy this application. So that's what I did basically.

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The point is here: this is a java application.

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A

C

Complicated, I will show it basically in a second. What's important, is I mean one thing is.

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That it's sometimes just difficult.

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B

C

Get everything from scratch is because it's a java graded project and then you need to have exactly the I mean the proposed gradle settings, which is sometimes not very much documented, so like one way of really getting this alive, is that you just download your your hyperledger fabric version, which gives your fabric samples.

B

And then, if, under your fabric, samples you go to chain.

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Code and you find one java examples uh that must be working and that must be having the the right gradle settings.

C

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So after I go to car and I take it and I think I'm I'm having basically I'm having a slide.

C

So after this brief uh that wasn't an intro introduction, it was a little bit more, but let me take a look: uh how do you program actually, actually, your channel your smart contract.

A

So I prepared practically one slide.

C

And so basically hyperledger fabric consensus is a little bit more complicated and quite sure, if you, if you wear that, probably we won't have much time to go into the details.

B

But the point is from a chain code: perspective is not so.

A

Complicated so on the other on the one.

C

Hand what you have you get your client application, uh which has basically the sdk or we can say taxi gateway as well, that sends transaction basically for you. So if I just go back uh to my command prompt, uh so like this peer chain code invoke, was a trans transaction that I sent into the ledger. It was uh not by a real client application, but just by command prompt, but basically that's the same, and actually query is a special transaction as well, which doesn't cause uh something that stay changed.

A

But and namely he can be.

C

So I send these transactions to my chain code and in my chain code, uh the names of the contracts, uh the names and contracts and the transactions uh so which transaction should be executed for transaction call is handled by decorators.

C

We got like two major decorator one is transaction and the second one is is contract.

A

So if we just take a look on this stop card, thermo.

A

B

See basically, a fab car demo.

C

B

C

And this fab card fab car object is our main contract. Basically, and it looks that way that so this is basically a pretty simple java object, uh which implements a contract interface, but what's more important, is that the fact that this is basically a smart contract in a chain code uh is administrated in a way that we got a couple of decorators and once such a decorator is like contract?

C

It's, uh so let me put it that way. uh Basically, you get so the idea is pretty similar actually to the to the fabric composer. You shouldn't.

B

Have something a smart contract or contract.

A

Here uh because, basically, what you have is transaction.

C

uh But contract is something which groups a couple of transactions. It can be built up in a much better way, with the help of a java object as well and well, I would say so basically there's contract, because I mean you know where there's like smart contracts. So it's like a more fancy way of programming, blockchain and seeing anything on blockchain. um So.

B

It's not necessary from a logical point of view that you.

C

Have contract but basically uh so you get already here contracts as well, so this is one.

B

Contract, it means this is a java object that provides input.

C

For your transactions.

B

Okay and you get a lot of information.

A

And so, and so you got.

B

One more decorator before your class- and this is default.

C

Default means that basically uh so this this object, I mean these services. The transactions of this object can be called without giving the the name of the of the class. uh I will show in a couple of seconds example for them and what's more important, is you got something as transaction.

B

So you got like function, calls and.

C

Before your function course, you get a decorator called transaction. So if you have this transaction uh before your function, call then basically.

A

uh The system will know.

C

That, if you call your transaction from uh from a client application, like query, call or the other one was sierra, create new call, I'm not quite sure this is something I might create new call. This is this: is the create create war? So if you call this transaction from a from a client application and.

B

If you have a java in java object installed, that has.

C

The decorator of of, on the one hand, contract on the other hand, transaction, then, basically, the function after your transaction will be called okay. I think it's pretty straightforward. So, for instance, we got here in this code. The query core query card implementation.

B

It's again a simple java or javascript sorry java method.

C

In an object which has the transaction decorator before you find like the create car here as well, it's again a simple call of basically with the transaction decorate decorator.

C

There are two specialties here.

B

uh And worth mentioning, you get usually.

C

A special transaction called init, ledger and init ledger looks that way. So what you have.

A

Here is that your.

C

Thing is running in this container, uh but from a physical point of view, but as soon as on your chain code, it doesn't start automatically.

C

So what you need to have is to have some special transaction uh which is mapped into this init ledger uh call, and this after calling this init ledger practically there's gonna, be a service object um from your from your chain code, so it will be initialized from a programming.

B

Point of view, what you can do is to is to give some really initialization uh after this function. So after.

C

Calling init ledger. Basically, what we do is that we pre-populate here a couple of data couple of different cars are pretty simple.

A

Okay, so basically, this is the programming model. uh You got the client.

C

uh Transactions are coming in in your chain code. You need to have some contracts uh and some transaction decorators, and as soon as you have it, basically, the incoming transactions are redirected to your to your code.

C

So that's one thing, there's a second part of your chain code and the question is of course okay. I mean I get a transaction, I get my code. So what do I do with my code?.

C

And what you do is your code is again not too complicated.

A

uh There are atomic ledger operations.

C

Atomic ledger operations are: put state, get state and delete state. So what you can do, basically, you can put something in the ledger. You can read out something in from the.

A

C

And practically you can you can delete a state from your ledger. Certainly I say deleting you don't delete anything from the ledger. It looks that way. The delete state deletes that just something from the from the word state, so I mean the historical values will be, will be accessible, so what I do basically as a chain called programmer. I program a couple of transactions and these transactions we'll write something to the ledger, read out something from the ledger or or delete something from the ledger practically, and I give some logics in the middle.

C

So that's basically hyperledger fabric chain code programming. So let me take a look. How this fab car example looks that way.

A

So this is like.

C

Mentioned this is the create car transaction. I get a decorator at the beginning, so basically uh the system recognizes that this is really a create car uh transaction.

C

What's important is that at the beginning, I have something as a context, and so, with the help of the context I got, I got practically access uh for the hyperledger fabric functionalities, so I get a stab and, with the help of the stop, I can get state put state or delete state okay. So this is practically the reference for the hyperledger fabric functionalities.

C

The rest is parameter. So what you see here, if you still remember, I created a car, you find basically a key. I mean that that's the id id for your car. You have something as uh make model caller and owner of your car. These are just custom examples, custom parameters uh that are that are presented here. Okay, so basically uh what's happening here.

B

That for the first round I have a stub, uh and this stuff again is.

C

With the help of a context, is a kind of an access for your hyperledger fabric environment. So, what's happening is for the first run. I try to read out the state of this key and repealing of the state of this key means that I try to read out the information from the ledger for this key for this, given key.

C

And why is it important it's because it's a create current transaction, so I mean this logic. Looks that way up that. Basically, I try to create the information. If I don't find this information, I throw basically I mean if I don't find this information, that's good, because that's a good credit card. Otherwise, if I find this information, I throw an error message.

C

So that's what's happening here.

A

B

There's no no error.

C

The second part is basically creating a new car.

C

It looks that way that what I do is I create a car.

B

C

Car object is basically something.

A

Which has these properties these parameters.

C

And what I do is I do a put state. It's a put string state where I have a key and for this certain key I put the serialized object into the ledger, so going a little bit more into the ledger, what's happening on the ledger side.

C

So basically, this is how your ledger generally looks like it looks that way that you get blocks in your blocks. You have the headers and it's of course it's connected with, like cryptographic, hash pointers, but basically.

A

The content of your ledger is specifically key, even.

C

So here I get something as an identity, one uh with some value one. uh I get some identity, two, it's again a key. We can call it as key two as well with some value too as well. I got some identity free with some value free as well, and basically the evolution of the ledger is the evolution of these skill value pairs. So, as you, as you see, see here in the next block, I get I get a new value for id1 for id2 for id3.

C

This should be id3 anyway and then in the next block, I get again a new value for id1id2 and id3 as well. um So this is the ledger, but in a from practical point of view, what you have here basically, is that uh you don't just store simple id and value pairs, but but what you saw is basically kind of serialized object.

C

So what if I have here, is not a simple value, but it's something which is a more complicated business object like a car, and I serialize this car to json, and I write it to the ledger so going back to this example of what you basically see here as a create car transaction. Is that.

B

I create a new car.

C

Which is a simple object? Actually, so you can see that uh going to the car.

B

This is a pretty simple object, uh which has some.

A

Some serialization hints um somehow in between.

B

And what you do is basically, I just create one new car object and I just serialize this car object and I just write into the ledger. After.

C

The key of the car, this serialized object, so pretty simple. Okay, so basically that's what you do from a chain called development perspective. um There are some other operations as well, but that's what you that you use.

B

Normally, generally, you just try.

C

To try to do some transactions, something pretty similar as soon as in hyperledger composer, for instance, you just model some transactions.

C

um You write your object in java with contracts and transaction decorators having these transactions as as functions, and you implement some logic and basically, at the end of the day, you use something as writing into the state. I mean writing into the ledger, reading out from the ledger and deleting something from ledger, basically, and usually what you, what you do you do not use like uh atomic operators, but basically what you do is that you.

B

Use something as a complex object that you serialize in a json.

C

And you write the serialized json object to the ledger and read out from the ledger and basically that's all. That's all chain called development uh uh that searching code development independently from the languages as well, and but that's chenko development for, for instance, in uh in javascript.

A

So let me just try an example.

C

uh What I did basically here, uh this is already not the original fab car, but I extended a little bit with a very very simple example, and as you see here so this is my major contract. uh It's it has the contract and default uh basically a decorator as well. I just extended with.

B

Two uh transactions and again, these two transactions are just uh two java functions uh for the object uh having this transaction decorator and the first transaction is set practically hello message. It looks that.

A

Way that the first file movement is my contact.

C

Followed all of the hyperledger function function, fabric functionalities and I get one parameter: that's basically the message. So what I do I'm getting this tab for the first run, which implements practically this state functionality for the ledger and very simple: I do a put string state so practically for a given key. I just hard coded this key. I think I put this information into the ledger and I get the second transaction. uh It's again, nothing special!

C

It's the hello from chain code, which does exactly the same, are just reading out the same piece of information from the ledger, with the help of a get string, state, okay,.

A

C

It for me, so this is a very, very simple example, this extension of fab card, so, let's see how we can how we can how we can practically uh uh install and test this a very simple functionality.

C

So what I need to do.

B

Is that for the first run, I can stop.

A

My network, uh it's not necessary that I stopped, but basically uh let me show that as well, so I can stop the network. uh It's again with.

A

uh Have fabric samples test network and there's a test network.

C

uh Script and then simple down, it closes basically all of my docker objects.

A

And it's doing, I think I'm gonna have some some errors so basically.

C

B

Brings down your network and it.

A

Deletes your crypto material as well, that is required for authentication, but that will be uh newly generated actually.

B

So what I have to do, unfortunately,.

C

This so again, uh the easiest way of doing things is to is to hack a little bit, something which is already working, um so you can install your new chain code actually uh from scratch. um I probably have some hints for that.

B

But the easiest way is to install your new uh chaincode is to.

C

Just to hack a little bit your your your scripts and it looks.

B

That way, if I go to the fabric samples.

B

I find this network dot sh as well.

C

But what I have basically, the deploy deploy, cc dot, sh file.

B

C

In this file, uh it's pretty easy to find uh the code fragment that installs, the java application. Okay, so it actually it's a general script that installs.

B

uh That can install javascript go and java as well.

C

But if you go to java, you can very easily find basically uh from which source uh is your. Is your application uh practically installed? So what I'm gonna do here? I again.

A

What I did just for easy start, I copied this project.

A

B

Mean especially the java part of your fab car project,.

C

And I created a new folder called my code and under my code I copied for the first and exactly the same javascript and on the other hand, I just extended with a couple of things. Okay. So what I want to do is that I want to install that stuff and.

B

Not the default application, so you find here two folders uh to pass this for this java part. So what I'm do I'm just.

A

Comment again and comment commenting out uh so basically what I do.

B

Is that I will not.

C

Install the fabca java example, but I will install my code java example uh and again here under.

B

Chain code, michael.

C

A

That's gonna be installed so as soon as I have it. uh Let me just.

A

So I'm just starting the.

A

A

It takes a while actually, but it's not so.

A

A

I mean this part generates uh the crypto material. uh It brings brings up practically. uh Actually, your your your uh your components, your local components, its channel.

A

That's an encore peer update.

A

It's a little bit like matrix. You know, I mean you have to find a bug in the in your log file, so.

B

I have this so the next step that I'm going to do is to install.

C

The java application again what I did uh it's not going to be anymore, exactly the same built in example java application, but I just made a new reference basically uh to my modified application.

A

So we I bring up my special.

A

A

A

So it again takes a little bit.

B

But what's happening is uh this: is the install process for the chain code in the in the pier, and so it looks pretty.

C

Much the same uh because I just extended the code a little bit, but.

B

If you just scroll up, I think somewhere, it can be seen that basically not the original application was used, but my modified one here. You can, for instance, see that actually this my my code was used, which is again pretty much the same as as fab car.

B

Unfortunately, in the script we have some some some.

A

C

Tests as well like at the end that focuses on this fab car example. So if I just restructure.

A

Reorganize it very strongly, then I might get some errors, but so the.

B

Installation is a success, so what I'm gonna try is that take a look if these two transactions that I wrote in, which is practically uh hello from chain code and the set hello message, is working.

A

And I do it. Similarly, as previous.

C

So basically, I have like two commands in the command prompt that.

A

Are pre-configured and one.

B

Is very simple: hello from chain code.

A

I think this should be chain code, let's see if it works, so, let's see if it works. So let me just take a look and try to give something. So it says basically that this contract method is not to be found, and the reason is that I can't really spell.

B

So this is, this should be hello from chain code, but for some reasons I wrote it hello from chain cook which might be funny but anyway, uh so let me just repair it uh and then, if I save it's supposed to be a hello from chaincode, it gives back nothing and the reason is for that is simple. uh It's.

C

Because because there's nothing configured.

B

Anyway, if you like call, it function, a transaction which is not defined. You.

C

Get this error message.

A

Which is, I mean pretty good at this at this moment, that we that we got that.

B

So let me just try it out and write something to the ledger.

A

It's again, basically giving a transaction uh from a common line, and again this is a peer chain coding.

B

Command with that, we can just initiate.

C

Transaction uh and what I'm just doing is that I'm calling the set hello message uh command uh with some arguments called hello message. So what should be happening in this sense.

B

Is that this gem function called set hello message: should.

C

Be called with the contacts with the new error message, uh based on the context, I get a stop based on the stop. I have the put.

B

State functionality that, for a certain.

C

This is a static key puts into the ledger. This new message.

A

So, let's take a look: if it's.

C

A

uh It looks great so it was successful.

B

uh And then, if I just have again my my.

C

Query, uh which is again uh basically a trans, it's called transaction, it's not a real transaction, but it's uh it requires this transaction decorator and basically based on this transaction decorator, the hello chain code uh function is called which basically gets the context. uh Based on the context I get to stop. Based on this tab, I can read out a state from the ledger for this statically uh coded uh key hello uh id.

A

And I just give back this hello message, and this is the hello message. So if I just run that I have my new message.

A

B

I think I'm having a lot of materials still, but perhaps I'm not quite sure if, if I want to go very much into the details at the moment, so I would say I would just stop here and then, if there's any questions, then I would I'm.

C

Happy to answer a little bit more in details uh regarding generally.

B

For high pleasure fabric uh chain code, development.

A

So one way of doing this is that I stop sharing and I take a look if there's question in the.

B

uh Yes, so there's this one question actually of it's a guidance for a genesis, blog.

A

And unfortunately, it's not so simple, but let me just take a look at actually the youtube channels. Man.

B

Yeah so there's this one question actually of it's a guidance for a genesis block and unfortunately it's not so simple. But let me just take a look at actually a youtube channel.

B

So then let me just let me just try to answer the questions.

A

A

I'm not quite sure how I can handle basically or early youtube as well.

A

B

So if you have any.

A

B

Easier for me, if you just drop into this uh zoom, uh but anyway, uh there's one question: if there's a possibility to install hyper ledger fabric on mac.

C

um Honestly, I don't know, uh but I think it's it should be possible uh what you need. You need to install docker. So if you, if you can run docker and docker compose, then it should run actually.

B

I think it might so I'm not quite sure how how much uh memory you have. uh Perhaps so, I'm not quite sure if, like uh four gig is enough, but if you have like eight gig area.

C

Then you can, you can easily install basically hyperledger fabric, uh if you, supposing that you can install docker and docker compose.

B

And both components are running, but I think that should be possible. uh uh Then the question is actually for for genesis. uh That was the genesis transaction.

A

So then let me share my screen again and let me just try to.

A

Give a little bit more details what's happening here.

A

B

So the best idea actually is, is not to go so much into the details into like genesis, block and and stuff like that. um But the point is uh that this test network, uh what you see here, uh has a lot of configuration. Basically. So um if you, if you build up your your your own hyperledger fabric, then these are the stuff that you that do you do it manually and you need to know how to do it. So it's not so not so easy.

B

uh You get here something as a docker, so, like all of your docker components that I've shown are here so here you can.

C

Like that, this is like your your certificate authority organization, one your certification authority organization to your certification authority order. You get here like.

A

C

C

Which is hidden in european and there's a coach tv possibility as well. If you use coach db, you have something as an extended degree for your system.

B

uh These are your peers as well, and in these folders you find a lot of other uh stuffs as well. So one is at creating your ledger.

B

There's two things: uh one is creating your.

C

Crypto material and the second one is, is having your different configurations.

A

A

Transaction should be not quite.

B

Sure I find it yes, so the thing is the following: uh it looks that way that, based on your crypto material and different configurations,.

C

uh You can create your your channel configuration uh that actually includes your genesis.

B

File, um there's actually more than one uh such a. I think, there's more than one such a such a channel configuration uh because you have one for for as a system channel for your ordering service and you can find one for your channel as well, but I've never gone very much deep into the detail. How this stuff looks like the point is that you have something as a tool.

A

C

If you don't want to use this uh whole scripting, then you need to basically use a tool uh which is config transaction generation. This config takes the gen and this will be installed uh practically as a binary. As you install hyperledger fabric and with the help of this tool, uh you can create your genesis block. I mean it's again, your full whole channel configuration which includes which includes both your genesis.

B

Block and some other configurations as well and you can set some of the properties of your genesis block so like if you say, like here's, a here's, a profile towards an organization channel, uh then there's a configuration file.

A

Which is seeing this config.

B

Transaction.Yaml and with the help of this file, uh this gives the parameterization of your of your channel configuration and of your genesis file as well. So like this configuration file has a lot of details. But basically what you can do is that I didn't mention in that in details, but it.

C

Looks that way, if you just take a look on the physical fabric architecture that, like you, get several peers several chain code components so.

B

What you can, for instance, configure that.

C

When do you regard your transaction as valid, and you can have.

B

These so called endorsement policies. Endorsement policies like I send my transaction to the chain code and basically, in all these components, running my java code um and I regard uh a seven trans transaction. uh If all of the chain called.

C

Java code uh uh says exactly the same or has exactly the same result and same output, and if one of these chain code components doesn't give me the the same.

B

Answer the same result as the other one. Then then,.

C

I don't accept.

B

C

uh This kind of a transaction, so it's something which can be configured it's. It says.

B

The endorsement policy, and, for instance, such an endorsement policy, can be configured uh with the help of this config transaction.yaml and, for instance, this is such an information uh which can be written into your genesis file with the help of this.

B

Where was it again with the help of this uh config tx gen command, uh which refers to this file, uh especially a part of this part of this file, and this.

C

Is like the two word channel, so this is like here the the channel configuration.

B

Including your genesis file for your channel and there should be somewhere nor for the organization as well. I think.

A

uh Especially where it.

A

Is uh your configuration will be.

C

Will be practically created, so here's.

B

Your uh this is probably your uh your genesis block, and this is probably your not quite sure if it's your channel configuration but.

C

Basically, these are, these are the so-called artifacts.

B

uh That are generated uh based on uh uh I mean that are required actually for for starting your uh channel and you're starting your farm and including your genesis block as well.

C

I think you can even look and look into the details uh with some special encoding.

A

B

So, actually, if I answer this question, uh it's okay, it's something which is which is very much deep technical.

B

So if it is not necessary- or I mean one thing is: if you need your your own production really high pleasure fabric uh environment, then you need to make some consideration on your on your on your genesis, block on your peers on your organizations and so on and so on. So in this sense you have to rewrite here almost everything or do everything from scratch. uh But if you just want to make some development, or especially some experimentation with javascript chain code in hyperledger fabric, then the easiest way.

B

Is not to carry about uh just use uh practically and modify a little bit this uh this. uh These.

A

Examples so if I answer the question, I hope it was a little bit more detailed than expected.

B

So it's it's again such a topic uh from that I could do like again, one and a half hour presentation alone.

C

A

Is that is there any other.

B

Question, let me just start again.

A

And take a look at in the youtube channel.

C

From that, I could do.

A

C

B

So uh there's one thing: what do you think the best uh is to understand the code code of fabric, I'm not quite sure which code do you? Do you think? So, if you like mean basically the the chain code, the chain code is not so complicated. uh If you want to understand the chain code, uh the best way uh is to is a size short, basically uh just copy the fat car just playing with that and just start to start to extend a little bit um so again.

B

What I did basically is that I extended with some extra functionalities. I showed one just one example for hello from chain code, but basically you can instead like wheels and and via service and so on, and so on. uh That's the best way, if you want to understand the the the middle so not the development part, but the but the containerized infrastructure side. So all of these scripts that are shown, then it's more complicated.

B

So you need to have a lot of uh devops and containerized infrastructure experience and then basically the best way is perhaps not to start here, but really to try to to to do your own infrastructure either from these scripts or from some some some some examples from the web and then do with your infrastructure and then read through everything that you find practically as high pleasure fabric, documentation and so on. And so on. So um from from a conceptual perspective, uh doing like chain code development and doing like uh client-side development in hyperledger fabric.

C

B

C

What's more complicated.

B

Is to deal with the whole infrastructure, that's that stuff in hyperledger fabric. So if.

C

You just want to developing chain code. That's that's the best way. If you want to set up your own productivity infrastructure, that's going to be a fight.

A

So I can show some external.

B

Client application as well there's one question here about.

A

So let me just show it.

A

Somehow I do not have the best practice of of taking a look in the youtube channel and zoom, primarily.

B

But I try to do.

C

B

Basically, uh if you want to use a client application and not your.

C

What you can do again is that you can basically start with the fabric, samples and the fabric samples.

B

uh There's a fab car, folder and.

C

In the fab car you find client applications, so one folder is here java.

B

And if you open this fab car or if you just copy it.

C

And copy it and open it again, I think I copied it and opened it again. As my.

B

Code, then, what you basically find is an example for a client application.

B

And this is again a client application. This is a java application. uh The easiest ways to is to start with a client java application is to take.

C

A look in the fabric samples uh because it's not.

B

Really, I think it's marvin already, but it has for you basically the basic structure so like which maven repository you need and so on and so on, um and this example.

A

Has like free, um let me just uh I have one slide about this, this one as well.

B

So if you, if you want to access hyperledger fabric from a client side, uh what you need is a client application that has this sdk and in fabric two uh there's a there's, a new so-called gateway. That makes you more.

C

Easier to access your hyperledger fabric.

B

I mean in the in the original versions uh like one years ago. It was pretty complicated to program everything, but at the moment there's something.

C

As a gateway, which makes you really easy to reach your all, I pleasure fabric network, uh basically.

B

It has like three components: uh it has something which is your network description. uh Your network description looks that.

B

That's a json file from your whole whole.

C

Architecture so like describing the peers, the organizations, the ordering stories and so on, um it can be realized in two ways. One is static and the second one is more dynamic. um If you choose static, then.

B

You need to do write practically all all uh configuration in details so like how many peers do you have? Where are the peers? Where are your organization where's, your ordering service, how you can access your ordering service and so on and so on? um You can use dynamic as well if it's dynamic, as far as I know, it's enough to to to write less as your configuration it's because there's still.

A

Discoveries and then.

C

Discovery service.

B

uh Practically informs your client uh on infrastructure changes as well and on on give some information. How you are your high percent fabric infrastructure? Look like.

C

uh So this is a cool feature actually because uh less problem for for developers.

B

um So you get something as a gate gateway, there's something as parameters, static or dynamic, and there's one big issue. Actually one big thing that I was not very much talking about. That's your there's, an identity wallet on the client side as well. It's it looks that way again. This is a this is practically a.

A

Permission blockchain slowly.

B

Auto authorized to be authorized somehow um to access the network, and this is what.

C

You get here in your identity wallet, so basically here you store your uh your identity certificate to communicate with the network. So if.

A

I just go back and take a look. This is my job.

B

C

Basically, this is my client application, so it looks that way. I got.

B

Free very simple java file.

A

B

The one is, I mean the first two.

C

Is practically getting this identity uh in your wallet.

A

Okay, so if you see like.

B

If you see like enroll admin and register user, uh both both are basically responsible.

C

Just for getting this identity into into your bullet.

B

You find your wallet here as well. What I'm gonna do I'm.

A

Gonna delete uh these two identities.

B

And then I mean, without just going very much into the details, what you have to do you have to for the first one getting an administrator enrollment. So if I just used it, I connect with the certificate authority and I get one x.

B

uh This is an x 509 certificate, including public and private keys, which is an administrator kind of an administrator.

A

User, you can find it as an administrator user.

B

And with this administrator user I can register user. This will be like a client-side user and after that, with this client-side user, I'm gonna use the network. So as soon as I have.

B

It uh what's happening is that there's an app user.id and that user.id is basically again an x509 certificate, including private and public keys. As.

C

Well- and this is your identity, so this is your client side identity that you want to use the network bit or from.

A

And as soon as.

B

Things you get this client application. This.

C

Client application looks that way, there's a very simple main command from the application, so nothing's fancy, but basically you need to have like, or two things are configured here. One is the the wallet so basically uh there's an information where you find these identities.

B

And the second one is the network configuration and the network configuration, looks that.

A

Way, it's pretty.

B

Complicated and it's not even stored here, but it looks that way.

A

A

So basically, the past.

B

There's a connection minus or general, uh which is generated automatically at setting up the network. So if you still remember, as I said this setup network stripped, it's like network dot, sh create channel my channel and so on. Then not just the docker components were started, but basically something which is, which is a connection description for the client has been generated as well and it can be found somewhere.

B

So I'm not quite sure if I find it, but there should be somewhere here. I think that should be under test network organizations, peer organization.

A

So if I just grew to favorite examples, test network organizations, peer organizations, org one, what was this and connection minus org.

B

uh So this is the connection file basically.

C

So you don't need to worry about, because in this example, it is generated automatically. But if you want to set up your network manually, it's something that you should configure, so it can be pretty stressy. As you see it describes your.

B

Client, your organization.

B

Some certificates, urs certificate authorities.

A

And so on and so on. So that's what.

B

You need here uh for your java.

A

B

And if you have it, uh you have some uh some initialization.

C

For for gateway, so again gateway is the is the sdk with which you access the network and if, if everything working again, the programming is, is pretty simple, uh what you do is uh first, you.

B

Get your your your channel, that's my.

C

Channel then you get your contract, that's your contract and.

B

What you can do, there's like two uh two commands. One is evaluate transaction and the second.

A

One is submit transaction so.

B

Again, similarly, as the command prompt, uh what you can send is you send an evaluate transaction for, like we uh calling the query all car uh function of your of your of your chain code and what you can do is to submit transaction.

C

B

Again, it's pretty much the same. It sends a transaction which is the create car and it has some some more functionalities.

A

So let me just comment out this part and let me just run.

B

B

So, as you see here what's happening, I started with video cars and this was the video world cars command and it runs okay, and after that I had just one error. uh There was something it says, basically, that car.

A

10 doesn't exist uh not quite sure why I have part time. I think it's like change or something.

B

But like let me just have, let me just put it out and saying I just create a new car. So again, as you see this is this is very simple: just submit transaction and evaluate transaction costs. So I have my create card like let me just certain that we do not have any problem that we have just again: vd car 13 and basically just.

C

C

A

So this is again the query workers and.

B

So there's not much. I don't write out anything by create car, but what you can see that the credit card for car 13 gives back actually the stuff that I that I configured here so basically.

C

It looks great.

B

I could have something here as a result of submit transaction as well, not quite sure which which object you get, uh but I'm sure that's that's possible to show something, but basically it looks that way.

A

um I can show as well.

B

How it looks like with the extended functionality so basically what.

C

I'm doing here is that I extend it with this hello message, the whole stuff, so what I'm gonna do is to basically submit one transaction. uh It's again.

B

It's a transaction call for set hello message and then the message is hello from java client and then I have something which is an evaluate transaction uh which again I just sent to the ledger, calling the hello from chain code and then basically, I'm just showing the result.

A

And let me just comment out the rest, so I think it's not gonna work because it I will. But let me just take a look.

B

So my cars are still here and I think car 13 uh exist already so my create car.

A

Will give me practically an error and it stops the whole application. But let me just give a shot.

C

So this is the video all cars.

C

And exactly so, we got an error.

B

Message and the error message says: uh transaction return with failure. Car 13.

C

Already exists in simulation, so that was the create car here. So what I'm.

A

Gonna do and just increase this one by one and let me just increase by one as well, and let me just take a.

A

A

So I got the video cards.

B

As you see, I I get the query card as well, so this is query card and I do not have result for reset hello message, but I have reside for the practically the get hello message uh and then it says that hello from java client. So it is exactly the same stuff that I wrote here in the ledger here.

B

So it looks well um just to summarize a little bit so again, as you see. Basically I mean I mean the programming part is not so difficult because what you need to have is you initialize your gateway and then, after that you have a couple of costs practically.

A

For instructions.

B

Something from the ledger, the difficult part is setting up your full infrastructure and having the correct parameters in your in your client application. That's what difficult! But for that I would propose to start from an example: that's working and then this example is like here like under fab car and test network and your chain code in fab card or is working practically. So you have, you know like more fun of of making development uh than like with scratching, uh then, with setting up your whole high pleasure fabric from scratch.

A

B

A

This question as well so.

B

A

B

A

If there's any more question just starting again, just.

A

B

So there's like two questions. uh One is like.

B

So how can I get better with writing chain codes, so I mean I mean I yes, so this is not an easy way of of of of making development. uh There's there's one initiative actually are doing something as a hyperledger fabric, like development environment that practically runs somehow in your in your ide, integrated development environment. It's I don't know microfabric or something similar is the name, but I'm not quite sure how far you get. I mean how far these guys get this with this project.

B

um Until that point I mean I would propose this approach, so so what you simply do is to download your fabric samples and then set up everything so be sure that everything is running and then basically start from from a working example, uh start from a working fab, car uh make some modification be sure it works, and so on and so on and after that start, some client be sure it works and so on. So that would be my my best advice actually for the for the development part.

B

uh It's it's not so nice at the moment, as working with with other uh other. uh Let me put it that way: programming, programming environments, but, like I mean so, my personal thing is, if you just so like I do occasionally like ethereum development as well, and so like ethereum is, is.

C

A way not so nice to develop not so visible, it's not like you know. I mean.

B

Like developing a front end and then and then making something as a feedback right away, but again so basically there's there's an initiative, I'm not quite sure the name. But I can take a look uh and then and then give it for you guys uh an initiative that basically, everything is working uh somehow in an integrated development environment and it gives a much better development.

B

Experience so I'm not quite sure if I just skipped somebody or some.

A

B

Yes, so let me just know if, if I just missed some question, uh I think I pretty much answered that was but anyway, if there's no more question, uh that's what I meant actually for today, as uh hyperledger budapest technical session. uh I I'm sure it was pretty much technical. I I hope I hope you could follow it. uh I try to do it in a in a you know in a very much step-by-step way.

B

um The point is basically that so like I like java development, but basically java development in hyperledger fabric is, is more or less the least documented stuff. So, uh for this reasons again so best is just to.

C

Take a look on the on the working practices.

B

If you write like in a chain code in in java, uh go is the most documented uh way of doing it and then for the client side application the best documentation is for is for for javascript, basically, but again it's manageable in java as well.

B

So if there's no more question, uh then I would basically just stop here and then again. So this is hyperledger budapest. uh We try to do meetings uh regularly uh like in two months, uh not just uh technical sessions, but perhaps some some business uh business topics as well, uh reaching some business audience and if you just feel like you know, I'm making presentations or having some some good topics in terms of hyperledger products uh or or even consortium. Blockchains, then just let me know, and then I'm sure I mean I mean we can.

B

We can arrange some some other presentations as well. Apart from me,.

B

So if there's no more questions answers, then I would like you thank you very much for the whole audience that you took part. Actually I mean I mean, even in friday, friday afternoon, even friday, on the 13th and then surprisingly, everything went very, very smoothly, so uh perhaps friday day, 13 is not so not so unlikely unlucky day.

B

Nevertheless, uh so.

A

B

You thanks a lot for your for your for your attention and then see you next.

B

B