Hyperledger Foundation Hyperledger Global Forum 2018, 27 Dec 2018

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From YouTube: Workshop: Introduction to Hyperledger Sawtooth - Murat Anil Oner & Elias Haase, B9lab - Part 3

Description

Getting to Know Hyperledger Sawtooth
Hyperledger Sawtooth introduces many new concepts that challenge traditional approaches to system architecture. Start building your Sawtooth vocabulary, get acquainted with the network components and architecture. You will also run your first network and interact with it using the command line interface and REST API.
Key Sawtooth definitions
General architecture overview
What is the Journal?
How does the validator network work?
How to deal with permissions
Starting Your First Network
How to use the command line interface
Interacting through REST API

Transaction Families
A transaction family is a set of rules or transaction types that you allow on your ledger. In this module, you will learn why transaction families are integral to Hyperledger Sawtooth framework and understand how the basic ones work. In addition, you will discover how Seth (Sawtooth Ethereum) can be used to run Ethereum smart contracts on a Sawtooth network.

On basic transaction families
IntegerKey: the simplest transaction family
Identity: a more complex but useful transaction family
BlockInfo: how to get key information about blocks
XO: a blockchain game
What is Seth?
How to deploy EVM contracts on a Sawtooth network
SDKs
You cannot limit your interaction with the network to the command line interface. In this module, we will practice sending transactions to the network with clients and discover how new transaction families can be created. We will focus on the Python SDK.
Introduction to the Python SDK
How to send transactions to a Sawtooth network in Python
How to implement a new transaction family
How to handle events
Seth
We will be deploying EVM contracts on our Sawtooth network and learn how Seth works.

Introduction to Seth
How does the Seth EVM implementation differ from Ethereum's implementation
How to deploy EVM contracts in Sawtooth Networks

Hands On
As part of the course we will be building a small proof-of-concept application together
Your Instructors Murat Anil Oner
Anil is a self-taught, lifelong developer with a MSc in Biophysics at the Technical University Munich. He has worked with many programming languages (and built his own), higher mathematics, and has been part of research projects in particle physics, electrotechnics and computer-based simulations. He has experience with embedded systems, cryptography and has even written code for a particle accelerator

Elias Haase
Elias started programming in his early teens and has spent the past 10 years planning, building and running systems. His background is in Artificial Intelligence. Since the early days of bitcoin he has been following the progress of blockchain tech, was around when Ethereum became a thing in 2014 and gathered experience with smart contracts / trustless computation since the early days.

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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.
It serves as a neutral home for various distributed ledger frameworks including Hyperledger Besu, Fabric, Sawtooth, Indy, as well as tools like Hyperledger Avalon, Cactus and libraries like Hyperledger Aries, Ursa. Learn more about Hyperledger projects: https://www.hyperledger.org/use

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#Hyperledger #Blockchain

A

Under will explain you set and how it works and what.

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So there is a integration for a term or in theory of integration, for a vergence output called set, and we are going to.

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We will talk about the differences you have to look at from the perspective of developing the application which will used I mean it could be that you have already or UI. You have already your RPC calls and then you have your contract and then you want to have private blockchain. Then you have, of course, many options yet, but if you have a perfect now they have subs, which you can use. You can use kora another quorum.

B

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We don't necessarily.

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Like you know, they have practices we've made. It welcome sex.

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Yeah right say.

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It is so setters transection for moving like oral transaction performance resolved before to start set. You can just try to follow the set documentation.

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Yep. Let's see.

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If we can see the different components, it has a client side, client set transaction processor and our pcs, our so usually we have already sauted API, which you could also use instead our. But that is more difficult, because in this case you would need to know structure of all the messages so just had. Rpc is like to juice in the RPC from from material I think you're going to talk about, but it actually is okay, so it has different components: for instance, RPC server, one is transaction processor.

B

You saw already transaction processor and that, if you follow this, it will not work. There's small repo change and that's why you need to use this digital file with place to talk a file in your in the university electron.

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Then you can, you can start at so I'm going start just with docker compose up.

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Okay, so what do we have? We have how well data like last time and we have with epi sub tres API, so there's a sub Network running and in addition, we have transaction processor for set and RPC, and in addition to that, we have also block in for transaction processor that sure that that's all had for getting information about a blockchain and we have settings transaction processor, so juice, all the setting transaction processor already.

B

So what we are going to do is we just want to start or jump into the container for the client for set client.

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So, and here we have.

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You see, we have.

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Client, and also something we are going to need, this solves which we will need to compile the smart contracts written in for duty, so I'm going just I'm going to just do all the steps you can also see in the content. The first thing we need is creating some keys. It's always the same he's at users.

B

Yep doesn't work.

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Perhaps such as Testaments.

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Okay doesn't know all just fabric stuff, so look.

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Okay, so we have here key, which is encrypted.

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So, let's import this key, this means just creating.

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Now it's perfect.

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B

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Because the documentation space.

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Thanks and then you can, then we can create with this key which we imported. We can create an account. So this is the very first step we have.

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So just try it 50 nights burgers, one for evil looks like the network is not fine for.

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And it's not running because of a problem or just into the question of time.

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And four down four down, you will need the same compost value you used to start the network, so you have to go to the same place or.

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C

E

This kind of ridiculous.

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Because I hope now their mobile network, one I.

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Mean even issued, if you can't do it, if you can't run the comets now an input letter, because we have everything regarding the stupid. So let's just let their accounts as we.

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So- and we have an address now.

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The interesting thing is how to deploy a contract.

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The contract included in the super story is also but out of date, so you will need to update the contract and we will have a look at.

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At a contract which will be similar to the transaction family we saw before this is deemed key, so it has exactly the same functions like the transaction process or transaction family we saw before you can set and increase the crease or get so that's deployed is contract. First, we need to compile it scored, contracts.

B

So episodes oh, it's golden.

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So there we have to find a record of the contract which we will need to use to the Pali contract. So you need to cover pastéis.

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So just keep in mind, you will need to update this. You will need to replace this contract.

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Okay. So that's how we create contract here is the binary code. We can see it's.

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Small, let's do it, let's copy and paste.

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Something like.

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It's not competition right so instead and there is the concept of capsule obesity in a fryer. You don't really need this. You don't really need, so we don't want to have multiple functional solutions.

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This we have a.

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Section about salt, which include.

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That means I mean you can see it. Your contract is created so now it's time to call this contract and there different ways for that contract. We are going to do everywhere, low level, I'm call with a term Jesus EBI. So we need to start not and then I don't know about you. Then we are going to import this library so.

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We're just doing.

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Because the it's just an easy way, I.

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If you want something like that, then the data is not just a function name, it needs to be the the encoded call the encoded function with the all the parameters, that's what we are going to have to do. They're going to create this.

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So in the course you can already find first set in know and get an and so on how how to create this encode.

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Doesn't allow you to calculate the to calculate the hatch of a function that does not have a parameter for some reason, we've been trying to figure out. What this is is the problem is itself. So if you haven't get a function, maybe to give it a even if it's humans, we don't usually stupidly, give it a.

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Let's try to set.

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So set meets the key in our contract. It's a bit different. It's a bit different from.

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It's a bit different from the transaction processor we saw before because it doesn't want to have string as a name. It wants to have integer as key, so we are going to have to introduce the palace say: let's try the first one and give it a no change.

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So and the other thing we are going to going to need is of course we want to see you want to see if it's really set. So let's have order of jobs, we can go and call the contract.

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Call now, first, we need the address of the contract, that's something you can find here or you can also show let you show what with the contract, show and a control, and now we need the data we want to call. Let's see what happens if you don't set, this doesn't work so see what happens. It's registered.

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It's still something it isn't about it. Let's see and Nick responds into it. What looks.

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Doesn't differentiate between gets called like just really calls or read or call which state changing call which issues a transaction? So you need to give the key that you're using because if you calling a state changing function and selecting a new.

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Transaction is created, so that means.

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Now it works so, let's check if it's set.

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So for that we have same contract same account, we just need different call so and there we can see this sent steps T the painful way to call a contract.

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Now there there is also the RPC which we didn't include here, because it doesn't work very well, but we can have a look at what it's Paulsen, maybe try one too cold. So.

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And they have the time to fix it.

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So within probably the next week or two or even if you upgrade.

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Person but you're on the frontier.

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So just set RPC it's already running in one of the containers, so we can try just comment which works so to account roll here and see.

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And see here something, so if you want to the point to do a call on the contract, actually it doesn't work, but you can see the functions or the calls they're spotted on the set documentation and the travel team is already also working with the sets together to make it make it able to work with set and use web tree and traffic together. I think this is just a question of of time.

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So, basically, that is how you can how you can use set. You can have a look at the command line, interface again and maybe try on your own.

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Of by one thing I didn't mention has, if you look at the account, you show me a conscious.

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If you look at account, you will see something like commissions, so that's not something that you can find in material. It's a different approach from Hobart abroad, which is also out here. So you have different kind of permissions. Also, and you can see you can see what the meaning of each permission is no documentation.

E

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So in the meantime, for those who are who've already, it's done and.

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We've gotten a contract going on Seth off of those who still waiting for assessing Seth installation I just want to quickly go through just a bit of solidity intro so that we can play around a little bit. um So let me just cook you to that display.

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All right, actually, let me just.

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So I'm just quickly going to walk through first of all for the contract development I recommend the easiest way that you can do. This right now is go to remix to the theory at all, which is a browser-based solidity editor that lets. You also get out some of the encoding stuff and so on. So it's the easiest way to velop. You can type around I'm also going to put this the the code that we're writing now on to the learning platform, so you can copy it in the third subsection after we've done this, don't peek!

A

Yet I want to ask you some questions. If you answer too quickly, I know that you've picked okay. So, first of all solidity there's a bit of a weird mix between like JavaScript and C, with some data types. It's turing-complete it's you know it's kind of stateful. If you call a function, it either gets executed or not at all, so it's atomic execution and each so it on on the VM. It's it's really like a way to see to see a list of transactions. So it's an abstract representation of a list of transactions.

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It doesn't really exist anywhere like no. Where is the contract itself stored? But because you read the transactions themselves, you build the state, and this thing then the smart code, the contract, the solidity to contract is just a way for you to interact with that.

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So let's just quickly build one, and so the whole thing.

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Because you thought of Tolkien just you know, because everyone's been doing that for the past year and a half and has collected millions. And now everyone has to pay back the money.

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So the convention is that the contract name is uppercase.

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We saw we're building this we're basically building a simple token that works on an account basis. So what with implementing is a mapping from addresses to to numbers so that for each address we can keep a balance, so the addresses in Seth are basically what we did earlier with Pam file, we're creating this.

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Basically, it's a key pair and it allows us to allocate both. You know the the currency and on the theorem, or in this case, when I create a contract. It is the identity that I use to interact with that contract, so within a contract, I can both use the caller identity and other identities to allocate stuff or I can do access, control and stuff like that. So therefore, that solidity has a an address type.

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Has an address type and that is address conveniently and we are creating a mapping so I'm mapping it I'm mapping, unsigned integers to the others, because we're doing balances and for now we're just doing them without the ability to have negative balance. So this is the name normally, if you want the, if you want to create a getter function, normally and probably soon set, all you need to do is make it public, but at the moment we have not made this work properly because we can't probably generate the function.

A

Hash will get there, but you found it nice cool, so he sold spit. We might just hire you on the spot and basically you know it'll. It will work. It is definitely possible, so this is kind of best practice, so we've got the balances. Now.

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What what do we need to do? First, when we set up this contract? What what do we need in order to be able to advocate tokens.

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We are gonna need a constructor that allocates the tokens in the first place, so we create a constructor and.

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We then need to allocate this, so we are going to not bla Montes balances, and since this is a mapping, we are going to access the relevant position by accessing the account or the position of the sender of the message in solidity. All of the things that are connected to the transaction of that calls. This function are accessible through message, dots. So it's good. My sister says sender. You've got message with value and you know all of these things time stamp, etcetera.

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So know this a lot of times them, but you can access all of those functions through the message dot. So in this case we want the key identify the public key identifier of the sender of this transaction, which in set terms, means I'm using my identity, my so to identity to craft the transaction. Through this you know, through using the set transaction family interface, which then uses the set key to sign the the abstract representation of that transaction.

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To call this function, which can thinks it's operating on on simulate like I guess so it's to the grinder bad, but it's fun nonetheless. So we're just going to set this to 500,000.

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Because we're creating so one of the interesting things that we see with the smart contracts initially was that I can create balanced allocation and I can kind of create an artificial scarcity, so I'm just creating a glass castle yeah there are 500,000 tokens and if I don't build in and they mechanism to add more tokens, I can't add more tokens. So that's it right, and so that's what we have that.

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To make this public as well.

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So you might see all the solidity contracts like I, think pre 4.2, where the constructor is a function that has the same name as the contract, but this is the this is the newest notation, or this is the most up-to-date notation right. So what else we need, and for the token, what kind of what else do we need to build for it to make sense?

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Any ideas I mean right. Now, it's really just one one person having five.

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So I send a sentence, a transaction mechanism right, so we are going to build a function and it's going to call do to be calls and token. Now we want the amounts and we want who gets it so we're using address. No actually a quick one on the on the accessing here.

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What's in traditional mapping like if you, if you do a mapping or if you do an array in in other languages, what would be the problem of this constructor? If nothing else has happened before.

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Exactly so, usually you'll receive the problem that if you haven't initialized that it doesn't exist, but in solidity contracts all of the storage for that contract is already allocated entirely and zeroed out, so everything exists and it's Sarah, hmm which means that if I access this it's zero, which is also important to realize that if you are using in a variable that you haven't allocated or haven't, set or have an initialized properly, then you might just send currency or tokens to the address zero, which means it's lost forever. If you can.

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Actually, if you, if you and I, have a laughs, you can go onto the theorem block Explorer and you can look at the zero zero X zero address and it has a bunch of Ethernet. This happens all the time and then it's done. No one has the key for that.

A

So if you want to burn a lot of ether, you can just send it to zero okay. So it's going to do the recipient here now in this function. What do we do.

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Yeah, of course sorry I know this is very obvious, but it's also the afternoon service trying to keep it alive. So we do the same thing and we first decrease.

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First decrease by amounts, and then we increase.

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We increase by much so.

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Usually it's best practice to first reduce and then increase, because, depending on what you're doing there is there are, there is a possibility that you can build what is called a re-entrance II vulnerability into your contract, which means, if you are calling so these contracts live as objects in the in the address space of set, which means that they universally accessible throughout the network.

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It's the same for a theory now I can call the function if I know how a contract looks like and I have the interface to operate, to connect to it and deal with it. I can call from this contract. I can call another contract and call a function in that contract. I can also send you know if I can craft the transaction in the function and I can execute that now, if I'm, if I'm interacting with another contract, that contract is malicious, it is possible.

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That is that you create what is called a reentrant, see part where the contract on the other end will call back the function that you just executed at that point, and it will go back to the point that it jumps into the contract. So you keep looping around and then you execute the last bit at the end. So you you come out at the end and obviously this will go as long as there is.

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So it is possible that if you do this the wrong way and you're dealing with the you know with an unknown contract, or you know it's kind of a dynamic situation. It might be that you keep looping around and you think you're updating the right things, but you don't so.

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This is usually where you just assume. Maybe something goes wrong: I'm just going to decrease fast because before I'm going to create, but usually like, this might need to be a problem in this case, because we're not dealing with external function calls or transactions endings. But it's just something to keep in mind in this case.

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Obviously, the function is, is going to be executed completely or not at all right and then because until I speak to you I'm there and we figure out how to encode the balances functions, we're just going to quickly create a getter function as well and just easier and I'm going to give it a thing here.

A

mmm So we want to tell it so this is a public function, it is static and it returns a youant.

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And then we just return the balance.

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Cool so um I would say there is there? Is this contract in in the learning material? So in this latest example section you can find it. You can copy that, and what I would like you to do is first of all make this work. The deploy is to set interact with it, so call a function and then adapted so that- and there are two tasks at the at the end in the section so allow for it to have negative balances and and completely so the the exercises.

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Are in the Banach.

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Material- let's just take 10-15 minutes to try it out. Are you still compiling.

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And otherwise, if you're still compiling, you can go into remix and kind of just play around with the contract a little bit see what comes out.

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No, it's this big.

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So, set at the moment only supports.

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Salute the compiler version, zero point five and later.

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And on remix the, if you click on so once you have something that compiles with a zero point. You know like 0.5 or up. You can see details here. So annals showed you how to do this so see compiling into bytecode. You can also use the object in the bite, coloured jason here, which is the same thing. So this is a web interface that uses salty to generate this, and this is basically this is the smart contract that you deploy and set.

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D

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This is just get balance, balance.

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Which is cool, see.

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We have any success.

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Can you add to view so I can use this.

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Can you try this.