Hyperledger Foundation Fabric, 10 May 2022

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From YouTube: Essential Components of Smart Contracts in Hyperledger Fabric

Description

A virtual meetup hosted by Hyperledger NYC on May 10, 2022 with Navil Rodrigues briefly review how blockchain smart contracts or chaincodes work in Hyperledger Fabric. The architecture of Hyperledger Fabric, by design, comes with essential components that are vital to the operation of enterprise blockchain applications. Smart contracts, or chaincodes, in Hyperledger Fabric play a more vital role than other components. Indeed, as a professional Hyperledger Fabric developer, you should gradually master all aspects of chaincodes from logical design to development, testing and deployment. No prior technical knowledge is needed.

To follow this presentation, you can read the below article:
https://training.linuxfoundation.org/blog/an-overview-of-essential-components-of-smart-contracts-in-hyperledger-fabric/

Additional Fabric training and certification resources are at:
https://www.hyperledger.org/learn/training

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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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License
Creative Commons Attribution license (reuse allowed)

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Hyperledger fabric developer, thank you again to him for volunteering to present today on the components of smart contracts within hyperledger fabric.

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I invite you to ask any questions here in the chat on the zoom or if you're tuning in from the youtube link, feel free to drop any questions in the chat, and I will get them answered by neville whenever there's a break in the presentation. But uh the veal floor is yours um thanks again for presenting and again feel free to reach out with any questions. Everyone thank.

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You chris thank you for the introduction, so hello, everyone, my name is neville rodriguez. I am certified hyperledger fabric developer from linux foundation and I have experience in developing full stack applications as well as decentralized applications using hyperledger fabric and ethereum.

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At present, I am working at machine learning rise.

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As a blockchain developer,.

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And responsibilities.

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Includes designing.

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And deploying solutions by gathering functional requirements from the client, so so this will be the agenda for our today's meet. We will be briefly discussing the overview of hyperledger fabric. Then we will be comparing it with the ethereum, which is public blockchain.

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We will be deep, diving into the fabric, smart contracts, the class structure and as well as the stub interface, after which we will see different apis that are being used for interacting with the ledger data and after a while, we will go with the sample fabric contract that I have created for our today's meetup.

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So we will be going through it and have discussions so moving on appalachian.

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Okay, so in 2015, linux foundation founded the hyperledger project as open source collaborative effort created to advanced cross industry, blockchain technologies. So apology.

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Fabric was first.

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Project that was contributed to hybrid umbrella, and currently it is governed by a diverse set of maintainers from multiple organizations.

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So what makes hapless fabric different is that it is private and permission, meaning that only authorized entities are allowed to access the network, unlike permissions, less blockchain bearing anyone can participate and contribute to the network.

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So the transactions must be written in the ledger in order in which they occur and bad transaction should be rejected. So this process is called consensus, so in hyperlogy fabry we follow a three-way process. The first one is pin endorsing. So whenever transaction is being sent over the network, it is by the anderson peers, uh after which, uh once they are endorsed, uh those uh the endorsed transaction is again sent to the order node wherein those are ordered and after which again those transactions are validated.

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So, as we know, application fabric is permissioned. uh Identities are first android through certificate authority. So when we enroll using certificate authority, we get two keys which are, namely public and private key. So private key is basically the one which is kept to be hidden and the public key is spread throughout the network or or it is shared among the parties in the network, so using private key, an actor in the network, digitally signs their transactions and sends over their info.

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The msp, on the other hand, is easily able to validate if the transaction is coming from the valid actor or not so this is the process usually goes through. So the next is uh smart contracts in hyperlogy fabric supports general purpose programming languages, so this uh so, for example, java node.js go. These are general purpose programming language which is used to design for building software that can be used among different application domains rather than domain-specific language, for example, html sql. So these are domain, restricted languages so coming towards channels.

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So these are sub networks in the blockchain network, for example, some transaction parties, uh one in the network, might be competitors and want their transactions to be hidden from the rest of the network. So in such cases to maintain.

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Privacy between the actors participating in the network can use a channel into the network, so basically it is.

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A network in the network.

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So coming to a differentiation factor, so the most common difference being is ethereum is permissionless, so as it is public and anyone can participate, any unknown identity can participate and contribute to the network to keep it up and running.

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So they do this because they earn native points after uh mining block on that network, whereas there is no such concept in permission blockchain. So the identities that participate in the network are authorized are already authorized uh by membership service provider, and they are the only ones which are allowed to the network.

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So next comes is the governance, so in ethereum, ethereum developers are responsible for managing and implementing changes to the protocol. For example, as you might have heard, it is migrating to the proof of stake, so it is uh it is. It was decided by the ethereum developers, and now it is in the migration phase. So, but whereas in hyperlogic fabric it is governed by linux foundation so coming to the decentralization part, uh ethereum is completely decentralized, as anyone can participate in the network, whereas in hyperledger fabric a consortium or a group which forms a network.

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Is the one who controls the network so coming to the consensus mechanism? Currently ethereum uses proof of work, so proof of work is basically uh when a miner into the network has to contribute, has to solve a puzzle in order to and I've got the transactions onto the network. So the miners basically compete with each other in order to record their transactions and uh once the transaction is recorded, uh the other miners can validate.

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Easily validate.

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That particular transition in hyperledger fabric, as it is a permissioned network. uh We can use a pluggable consensus mechanism like a byzantine for tolerance, presenting.

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So coming to the throughput, as discussed uh since proof of work requires lot of computation bar the throughput achieved in this type of consensus. Algorithm is very less so it it is around 30 transactions for tps and in hyperledger fabric. We can stretch these transactions per second to up to 20 000.

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So in ethereum, smart contract language, which is commonly and mainly used, is solidity, whereas application fabric provides options like node.js, golang and java.

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So, coming to the main part fabric, smart contract overview, so so, basically before businesses can transact with each other, they must define a common set of contracts covering common terms, data rules, concept, definition and processes.

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A smart contract defines the rules between different organization in executable. They are used to implement the governance rules, governance rules for the business object so that they can be automatically enforced when the smart contract is executed.

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For example, smart contract might ensure that a car delivery is made in specified time frame or funds which are to be released, are arranged or are released in a specified terms in a specified uh specific interval time when smart contract is approved and verified by the transaction parties in the network, it is packaged and deployed onto the network.

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So we can see this container uh packaged container into the network, and this package container is often referred as chain code.

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So coming to the contract class, so this is how the contact class is in the fabric contact api. So the first is constructor.

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Constructor in the contact class.

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Accepts name as an optional input parameter, so this is basically used to name your smart contract. The name is not provided then the class name is used.

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Then we have each contact method, so this function is used to identify if the object passed as an input is of type contact. If it is true, it returns successful check. So.

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Then comes the before.

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Transaction, so, as you can see, there.

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A ctx ctx parameter, so this is basically a context object. So.

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Whenever there is a transaction function,.

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We need to pass this context object. It is the first argument which contains the implement of chamber stub interface. We will be looking into this interface into the next slide, so this chain code.

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Interface uh has encapsulates api to interact with the world state private collections and the other.

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Proposals uh this ctx, which is context objects, also provides a client identity of type client identity which provides the details about the transaction creator like identity of the client and ms paid.

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So so this before transaction is a function which is invoked before any transaction functions in the smart contract and invoked. We can override this default function and can implement our own logic then comes after transaction.

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The function is invoked when a particular transaction function.

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In so this, this comes at a later part. So again we can override this default method and use our own logic, then, is unknown transaction. So this is basically a function which is invoked when a requested transaction by transaction created does not match any of the function present in the smart contract.

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So again, we can override this default method and use our own logic then comes the create context method. This function is used to create own custom transaction object which can be accessed by additional processing.

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Transaction functions are invoked.

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Then comes the get name. This is a simple get function which uh is used to return the content.

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So this is how contact is structured uh in chain code, so we will be diving deep into it when we will be referring to sample smart contracts for starter. This is uh the lead where a chain code resides. Then there is a test folder where we specify where.

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We write test cases.

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In order to test a smart contract, we have uh index.js.

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Wherein uh is basically an entry point which exposes uh the smart contract which is present in the leap directory? And then we have package.json, where we specify the dependencies.

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So coming towards the chainboardstub interface, so it has two important methods, namely you need an invoke, so these two methods are called in response to received transaction init method that will serve as initialization function during instantiation or during chain code upgrade process.

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If we specify this flag fabric ensures that in it is invoked before any other transaction function, it allows the user to initialize the chain code and the ability to add initial data to the ledger.

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So then comes the invoke method. uh This is followed by the clients to submit transaction processor that allows to use the thing code to read and write data on the channel later.

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To the distributed ledger data representation.

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So in here we represent data in two states, so first is world state and then is blockchain. So.

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The world state in hydrology fabric.

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Can be denoted.

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With two database, one is level db.

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And the other is caused b so.

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Level db is the database.

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That comes with default with hyperledger fabric. uh It is actually very fast and uh then.

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Comes the couchdb.

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So it comes into play when you want to perform rich periods like, for example,.

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Greater than less than.

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Etcetera, so so the.

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World state basically holds.

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Current and latest values, it is used to fetch or the smart contract fetches data from the uh world state because it is rather quickly uh then, rather than traversing.

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The blockchain and fetching.

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The files from there so states recorded in the ledger are represented as key value pairs, so in blockchain uh the any record uh so the world state, any modifications that are being made to the world state a store is a transaction slot is a blockchain.

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So so the transaction forms formed are collected inside the block and appended to the blockchain. The blockchain data structure is immutable and cannot be and once altered can never be modified.

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So these are uh some of the common apis which chain code system interface, provides the first being put state so input state. We specify key and value. So this is basically an uh insertion operation into the blockchain. So this is when we specify we give the key value pass, that we want to update to.

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Is the get state.

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It accepts a key as an input parameter which, which is used to fetch the corresponding value to the key. Then there.

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Is a delete state.

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Function, so this method is used to delete a data from the void state. So whenever we use this delete state, uh the.

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Word state is updated.

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But uh uh the data.

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Is not deleted from the blockchain.

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So yeah so logging in general, so as as discussed previously, so we need to uh package the chain code and then we need to deploy the chain code on the running container. So once once it is deployed, we we get that particular chain code as a container docker container. So uh by by running this command docker locks and specifying the container id, uh we will be able to see the locks that are being generated when that particular chain code is involved.

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So this uh this basically helps developer, ease the development process for identifying the issues and resolving them.

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On to the sample chain code that I have prepared, so so this.

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Where sample contact is written, so I will quickly start sharing my.

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You can see I.

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Have cloned this to my visual editor? So here is the simple contact which extends the contact class from the fabric contact api, and we have defined three functions, put function which is used to update the laser.

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Then there is a gate function which is used to get the value for a corresponding key, and then there is a delete function which is used to remove that particular key from the state. So, as you can see after which, after defining these three functions, put get delete, we export.

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Is later being imported into this index.js file, and you can see we have exported this simple contact as this simple contact file and this model dot export contacts. We are basically specifying this simple contact as an array at a parameter.

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Okay, then we have this package.json file, so this is the start command, which is uh ran by peers into the network in order to run the smart contract, and this is a test script which we will be looking into looking into it in few minutes. uh So this is basically yeah.

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So then we have engines.

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So node version should be greater than 12 and the npm module should be greater than 5. Then we have dependencies. So this is fabric contact aba, which I have discussed earlier, which contains the contact class, and then there is a fabric steam api, which also is a dependency which is needed when creating contract.

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Then these are their dependencies, so we don't have to include them during.

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Build so these are basically used dependency when we want to test our channel, we want to make sure that our chain code is properly tested and it is error free, so coming.

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To the test cases.

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This is initialization stuff.

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And we are, we have written test cases for three functions, so, first being the boot function. So in here we are taking the simple contract context: simple content object. Then we are performing a put operation by passing the transaction context, and then we pass the asset key and asset value, so asset dot, key and estimator value is 100 in black.

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Passing basically 100 as a key and value as black. So after this we perform a gate state operation in order to get value for the past corresponding key, and this should assert that uh the past value and the written value is true.

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Okay, then we have get function in here. We first run.

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The negative test case.

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uh As uh discussed earlier, it will first create one contract object. Then we will insert uh we will perform insert operation by passing the transaction context by passing the asset key and asset value, after which we will try to get that particular asset using the wrong key, which is one zero one, as we have.

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Stored the asset with.

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Key hundred and value is black, so these data won't be fetched and that's why we will be getting an.

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So this will be the error. We will be getting class at one, zero one does not exist and uh then we will uh check uh for the positive test cases. So in here we declare as discussed uh it will create one simple contact object, which is the contract object. Then we will perform the update operation and we will check if the return value is equal to the black, which.

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And it should pass. Similarly, this is a delete function. uh First, we check for the delete operation uh with the first. We delete.

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The uh wrong value, and then we will check is uh positive- is like if the deleted value is not found in the void state, so we will run this test cases. So there is a script in package.json.

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So after running npm test, it will run this script and, as you can see, all the test cases have been passed. We can be assured that the functions that we have wrote are working as expected. This was very basic example.

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And avail we do have a quick question here. So how can npm security package updates and fabric dependencies be managed.

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Actually has to be checked regularly.

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Like what are the dependencies that have been currently used and as you might be, knowing that, if there is any new version that is being released, uh they they mention like what is the issue and what? What.

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Issues are being resolved.

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So yeah so keeping.

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Regular check on the packages that has been added as dependencies.

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And checking regularly, what are the vulnerabilities that can be affected and mitigating those.

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Great thank you yeah, and then what kind of digital certificate is used in hyperledger.

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So it is x509 format, so this is the type of digital signature certificate that is being.

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Used x.509 standard.

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Just a minute.

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Can you also explain examples of world state with examples and how the dell state is useful.

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Sure can you also explain examples of uh the world state and then how the dell state is useful.

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uh Basically, why are we using? Is uh we want uh operations uh to be very quickly, quick right? So that's why the any transactions that are being done are first uh represented on the world state right. So, uh but uh we, if in case of failure, the world state, is deleted. We using the blockchain that we have, that is a laser that is distributed across the parties. We can.

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Reform the world state using that blockchain log file.

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That answer the question.

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uh I think so, then jerry feel free to reply there, um a follow-up on what, if the fab, what a fabric does not support the new npm package in regards to the uh original question around the package updates.

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uh I didn't quite understand the question like.

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What happens if fabric does not support the new npm package.

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uh Then we need to use the npm package that is supported, like the lts version and as fabric is continuously evolving. Like uh the latest version being 2.4, it is better to stick to the lts that is being offered in order to.

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Be away from any vulnerabilities that have been introduced in the previous versions.

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Great thank you yeah, so so coming to the uh certifications that are provided by linux foundation. So uh this depends on what aspects you want to be like if you want to gradually master, if you want to be on the administrative side or if you want to develop a set. So these are.

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Are being provided so fabric administrative, certified application fabric administrator is more focused on on the devops perspective, like deploying.

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The consortium.

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And all the network related properties and then there is chfd which is certified hyperledger fabric developer. This is more focused on the developer perspective like developing.

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Error-Free chain codes.

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And knowing the fundamentals, and also it includes how client interaction is being done uh using nbn packages that have been provided from uh by the fabric application fabric. So these are the two certifications and based on the uh your likings, you can choose any of them or both of them. If you want to master the blockchain application so yeah, so uh so. Regarding.

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Training and consulting.

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So uh if you have any service related queries, you can dm me or mathews and on linkedin he is a leading author of hands-on development.

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Smart contracts, development in high pleasure flatbed and it is acknowledged by a brand then professor, so yeah that was.

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Was the resources that.

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In creating this meta and yeah.

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Thank you. Everyone.

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And if there are any questions, I'm happy to answer it.

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Awesome thanks neville. We have another one saying uh you know in ethereum we have erc standards. Is there something similar that we have for smart contracts within hyperledger.

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uh We do have eic support, so you can refer to fabric samples, and that is very good example for esc20 representation in hyperlogic.

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Yeah but it will be like.

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Like it should be between the organization, so it will be restricted to the consumption that has been formed and will not be public.

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um This is probably more for like the overarching hyperledger group, but um is an admin certification still good uh to obtain if you're not necessarily a developer,.

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So within hyperledger you have the certified hyperledger fabric administrator and then the certified hyperledger fabric developer that you were going into.

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You're not a developer, is it's still good to acquire an admin certification.

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Yes, it is based on your liking, so developer perspective will be more of a like programming and having a background in programming. But administrative will also have some aspects of programming, but it will be mostly related in maintaining the network uh making sure that the network is up and running and seeing if all the containers and entities involved in the network are properly running.

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Making sure that the network is up and running.

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Great um so hyperledger fabric certification is provided by uh the linux foundation, and the blockchain council uh is one better than the other. Are they both equal.

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So I would this will be my personal opinion, but I would prefer going with the linux foundation, one as those are really uh like challenging and it really tests you like, if you're really qualifiable for that and.

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If you are ready with.

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It so it will, uh you need to prepare it. You need to rate the dogs, have ledger dogs. You need to perform all the fabric, samples that are present in the ketub representation, and you need to practice a lot in order to pass this examination, so my preference will be going with the linux function once.

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Got it can the sample chain code be run using mini fabric rather than the full hyperledger fabric, docker setup.

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Yes, I think mini fabric is, is a way to quickly make the network up without going into much more network data.

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I haven't had an opportunity to try mini fabric, so yeah.

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um Any examples of before transfer and after transfer use cases of chain code.

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uh As I discussed.

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Digital certificate.

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Right, so what we can do at the client side is, we can have some attributes, for example, attributes like client type equal to uh user, and then there can be an attribute like type equal to admin, okay, so using before transaction.

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uh We can check this at attribute, so I had told we whenever a transaction function is invoked on the smart contract level- okay, uh it it has the context, object. Okay, from the context.

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uh We get this client identity parameter, using which we can face the attributes that are present in the digit uh certificate that is generated for the transaction grade, and we can write a logic over there that who needs who can be who can access and who cannot. So. This can be one example, and after transaction can be uh like, for example, uh like uh giving a console message like you have successfully completed executing this transaction function with the following parameters, and we can maybe console those parameters that are being obtained after performing the transaction function.

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Great um any tips or advice, uh as you prepared for the high pressure fabric for developers, training course and certification.

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There is one very good.

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High pleasure fabric, like.

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Contributor, you can search it. Okay, I will just type in here, so his name is.

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uh Sessions and his data repository- that is one thing, uh the other.

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Docs, you can go through them, you can try to understand them. Then you can go through fabric samples. That is a very good source and also if you need specialized training, you can approach matthews and he has very good resources and he has.

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Very good industry-wide.

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Got it as we're comparing ethereum with hyperledger fabric, one is public, the other is private. So how can we determine the number of transactions per second regarding the number of nodes in a public and private blockchain? Not being the same, so I think the overarching question is: um how do we deem it possible to compare a public blockchain with a private one.

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Okay, so the transactions that are being executed, uh so it all, depends on uh the.

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Consensus mechanism.

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That is being used, okay, so in ethereum. Currently it is proof of work, okay, so in proof of work, it is very like uh uh you.

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Can say energy consuming and.

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Very, uh like uh compute intensive process. Okay, so it takes time like.

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Has to solve that puzzle and only the one who is able to solve the puzzle uh is able.

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Out of the transaction.

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So, uh at a at a particular instance of time it can only has the limit like it cannot compute more than that. Similar thing happens with the bitcoin as well, but in hyperledger fabric, as there is uh not such mechanism like miners,.

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Are not competing with each.

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Other right, so it is, it is governed with a set of organization itself, so we can remove this.

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Solving the puzzle and that's when there are variations like practical byzantine fault, tolerance crashboarders, which which, uh which are the types that are used to execute the transactions very fast, like.

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It can be stretched to 20 000 transactions per second, so this is this is when this is why.

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A different mechanism.

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Mechanism is used on based.

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On the network that.

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Is of like yeah.

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Awesome. Thank you.

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Any other questions right now.

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All right great, well, uh thanks again nabeel for this great presentation um and thanks again to everyone who attended and asked such uh thoughtful questions. Hello,.

B

Sorry, sir, I have one question. I have one question yeah it's regarding the hyperledger fabric, developer, certification.

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So suppose, uh if I'm going to give that a examination, so does they are going to provide uh the network setup or did I have to do the network setup and write the whole chain code or they are going to provide the complete environment? I just have to write the chain code, so that is my question.

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Yeah, so I will answer this question, so you don't.

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Set up any network or you don't have to make that network up, so you will be giving given a programming a set of equations uh and.

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You have to solve them.

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Example, adding a function into.

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The chain adding a function into the existing chain or modifying the chain code- functionalities yeah, yes, so you don't have to so. Basically, we just have to do the uh uh changes related to chain code right. The network is already up so for a detailed. You can go through the syllabus of this okay, so it's not only about making changes to the chain code, but it also includes things like uh executing the application.

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General life cycle.

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The chain code.

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Yeah, so you can go through the syllabus, you will get to know more yeah uh yeah, but uh while giving the examination did we have to do the means uh we just have to write the chain code right. We, we should not be worried about the network uh stuff right right, yeah yeah. Thank you.

A

Okay seems like we're all good here, but again, thanks to everyone who attended. Apologies for the issues with the uh link to the zoom, not getting posted properly in the meetup group, but uh hopefully we're able to resolve that um any questions uh feel free to reach out to nabeel and again greatly appreciate everyone's participation and uh especially neville for presenting such an insightful meetup. To that.

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You for attending.

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It thanks everyone.