Top Tips for Passing the Blockchain CBDH Exam on Your First Try

Chaincode is a decentralized transactional program, running on the validating nodes. As with every chaincode, it implements the Chaincode interface in particular, Init and Invoke functions. Init is called during Instantiate transaction after the chaincode container has been established for the first time, allowing the chaincode to initialize its internal data. Invoke is called to update or query the ledger in a proposal transaction. Updated state variables are not committed to the ledger until the transaction is committed.

There are two parts: 1. Business Network Archive which essentially captures the core data in a business network, including the business model, transaction logic, and access controls, the Business Network Archive packages these elements up and deploys them to a runtime. Business Network Archive files are stored as “.bna” files. AND 2. Composer Playground which is web-based tool allows developers to learn Hyperledger Composer, model out their business network (domain), test that network, and deploy that network to a live instance of a blockchain network. The playground keeps the development model in browser storage, allowing them to be easily uploaded or downloaded.

So not all peer nodes are same. There are different types of peer nodes with different roles in the network: Endorser peer Anchor peer Orderer peer Endorser peer Peers can be marked as Endorser peer (Endorsing peer). Upon receiving the “transaction invocation request” from the Client application the Endorser peer Validates the transaction. Check certificate details and roles of the requester. Executes the Chaincode (Smart Contract) and simulates the outcome of the transaction. But it does not update the ledger. At the end of the above two tasks the Endorser may approve to disapprove the transaction. As only the Endorser node executes the Chaincode (Smart Contract) so there is no necessity to install Chaincode in each and every node of the network which increases the scalibility of the network. Anchor peer Anchor peer or cluster of Anchor peers is configured at the time of Channel configuration. Just to remind you, in Hyperledger Fabric you can configure secret channels among the peers and transactions among the peers of that channel are visible only to them. Anchor peer receives updates and broadcasts the updates to the other peers in the organization. Anchor peers are discoverable. So any peer marked as Anchor peer can be discovered by the Orderer peer or any other peer. Orderer peer Orderer peer is considered as the central communication channel for the Hyperledger Fabric network. Orderer peer/node is responsible for consistent Ledger state accross the network. Orderer peer creates the block and delivers that to all the peers. Orderer is built on top of a message oriented architecture. There are two options are currently available to implement Orderer peer: Solo: Suitable for development. Single point failure. Solo should not be used for the production ready network. Kafka: Production ready Hyperledger Fabric network uses Kafka as the Orderer implementation. Kafka is a messaging software that has high throughput fault tolerant feature.

Client Node: That initiates the transaction 2. Peer Nodes: Commits Transaction & keeps the data in sync across the ledger 3. Ordered: They are the communication backbones and responsible for the distribution of the transactions

This web-based tool allows developers to learn Hyperledger Composer, model out their business network (domain), test that network, and deploy that network to a live instance of a blockchain network. The playground keeps the development model in browser storage, allowing them to be easily uploaded or downloaded. The playground also allows for CRUD (create, read, update, delete) operations to be performed on asset transactions which are created and logged. Composer playground offers a repository of sample business networks that can provide a base for building your own business network.