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7244639e7c
Created project structure, fixed typos. Implemented connect.go and getAllAssets.go. The latter uses an assetTransferBasic struct which provides a simple API for basic asset operations like create, transfer, etc. Added transact.go with some util functions. Using google uuid package to generate random UUIDs for the transactions. Implemented pretty printing of JSON results. Implemented app.go entry point with error handling. The existing commands are getAllAssets, transact and listen. They can be called from the command line via: "go run . <command> <command> ...". They will be executed in order and if a command is not known an the application panics and aborts before executing any of the commands. Implementing listen.go. Added checkpointer, context setups, call to BlockEvents and all the interfaces needed for parsing. Started implementing the interfaces needed to represent a block bottom up in structs. Finished NamespaceReadWriteSet, ReadWriteSet and EndorserTransaction. Signed-off-by: Stanislav Jakuschevskij <stas@two-giants.com>
115 lines
5.5 KiB
Markdown
115 lines
5.5 KiB
Markdown
# Off-chain data store sample
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The off-chain data store sample demonstrates:
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- Receiving block events in a client application.
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- Using a checkpointer to resume event listening after a failure or application restart.
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- Extracting ledger updates from block events in order to build an off-chain data store.
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## About the sample
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This sample shows how to replicate the data in your blockchain network to an off-chain data store. Using an off-chain data store allows you to analyze the data from your network or build a dashboard without degrading the performance of your application.
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This sample uses the block event listening capability of the [Fabric Gateway client API](https://hyperledger.github.io/fabric-gateway/) for Fabric v2.4 and later.
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### Application
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The client application provides several "commands" that can be invoked using the command-line:
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- **getAllAssets**: Retrieve the current details of all assets recorded on the ledger. See:
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- TypeScript: [application-typescript/src/getAllAssets.ts](application-typescript/src/getAllAssets.ts)
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- Java: [application-java/app/src/main/java/GetAllAssets.java](application-java/app/src/main/java/GetAllAssets.java)
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- **listen**: Listen for block events, and use them to replicate ledger updates in an off-chain data store. See:
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- TypeScript: [application-typescript/src/listen.ts](application-typescript/src/listen.ts)
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- Java: [application-java/app/src/main/java/Listen.java](application-java/app/src/main/java/Listen.java)
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- **transact**: Submit a set of transactions to create, modify and delete assets. See:
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- TypeScript: [application-typescript/src/transact.ts](application-typescript/src/transact.ts)
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- Java: [application-java/app/src/main/java/Transact.java](application-java/app/src/main/java/Transact.java)
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To keep the sample code concise, the **listen** command writes ledger updates to an output file named `store.log` in the current working directory (which for the Java sample is the `application-java/app` directory). A real implementation could write ledger updates directly to an off-chain data store of choice. You can inspect the information captured in this file as you run the sample.
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Note that the **listen** command is restartable and will resume event listening after the last successfully processed block / transaction. This is achieved using a checkpointer to persist the current listening position. Checkpoint state is persisted to a file named `checkpoint.json` in the current working directory. If no checkpoint state is present, event listening begins from the start of the ledger (block number zero).
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### Smart Contract
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The asset-transfer-basic smart contract is used to generate transactions and associated ledger updates.
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## Running the sample
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The Fabric test network is used to deploy and run this sample. Follow these steps in order:
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1. Create the test network and a channel (from the `test-network` folder).
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```bash
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./network.sh up createChannel -c mychannel -ca
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```
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1. Deploy one of the asset-transfer-basic smart contract implementations (from the `test-network` folder).
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```bash
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# To deploy the TypeScript chaincode implementation
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./network.sh deployCC -ccn basic -ccp ../asset-transfer-basic/chaincode-typescript/ -ccl typescript
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# To deploy the Go chaincode implementation
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./network.sh deployCC -ccn basic -ccp ../asset-transfer-basic/chaincode-go/ -ccl go
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# To deploy the Java chaincode implementation
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./network.sh deployCC -ccn basic -ccp ../asset-transfer-basic/chaincode-java/ -ccl java
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```
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1. Populate the ledger with some assets and use eventing to capture ledger updates (from the `off_chain_data` folder).
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```bash
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# To run the TypeScript sample application
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cd application-typescript
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npm install
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npm start transact listen
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# To run the Java sample application
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cd application-java
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./gradlew run --quiet --args='transact listen'
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```
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1. Interrupt the listener process using **Control-C**.
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1. View the current world state of the blockchain (from the `off_chain_data` folder). You may want to compare the results to the ledger updates captured by the listener in the `store.log` file.
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```bash
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# To run the TypeScript sample application
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cd application-typescript
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npm --silent start getAllAssets
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# To run the Java sample application
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cd application-java
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./gradlew run --quiet --args=getAllAssets
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```
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1. Make some more ledger updates, then observe listener resume capability (from the `off_chain_data` folder). Note from the transaction IDs recorded to the console that the listener resumes from exactly after the last successfully processed transaction.
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```bash
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# To run the TypeScript sample application
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cd application-typescript
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npm start transact
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SIMULATED_FAILURE_COUNT=5 npm start listen
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npm start listen
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# To run the Java sample application
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cd application-java
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./gradlew run --quiet --args=transact
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SIMULATED_FAILURE_COUNT=5 ./gradlew run --quiet --args=listen
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./gradlew run --quiet --args=listen
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```
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1. Interrupt the listener process using **Control-C**.
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## Clean up
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The persisted event checkpoint position can be removed by deleting the `checkpoint.json` file while the listener is stopped.
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The recorded ledger updates can be removed by deleting the `store.log` file.
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When you are finished, you can bring down the test network (from the `test-network` folder). The command will remove all the nodes of the test network, and delete any ledger data that you created. Be sure to remove the `checkpoint.json` and `store.log` files before attempting to run the application with a new network.
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```
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./network.sh down
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```
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