Is it possible to use gRPC with hyperledger-chaincode, and if so, how to avoid errors during calls on the test network?

php editor Xigua is here to answer your questions. Yes, you can use gRPC with Hyperledger Chaincode. gRPC is a high-performance, open source remote procedure call (RPC) framework that enables your Chaincode to communicate with other services. To avoid errors during calls on the test network, there are several steps you can take. First, make sure your test network is configured and running correctly. Second, check your code and configuration files to ensure you are using gRPC correctly. Finally, have appropriate error handling and logging so that any issues are discovered and resolved promptly. With these steps, you should be able to avoid errors during calls on your test network and communicate using gRPC smoothly.

Question content

I want to use grpc in fabric chaincode to achieve cross-chain communication instead of using fabric sdk. But when I call the chaincode function on fabric-sample/test-network, I always get an error.

error: endorsement failure during invoke. response: status:500 message:"error in simulation: failed to execute transaction eb5e480bd4075a767f56ae263741ca0f5f19620ef88952e26b7f1952bdbe83cd: could not launch chaincode chaincode_1.2:d3f97f15a635e73d3de230c8e5899e5fb95a68cf897c03e19f9e4eeca7ca3fd5: chaincode registration failed: container exited with 2"

Can anyone tell me what causes this error? Is there a bug in my chaincode or grpc cannot be used in chaincode functions?

My chaincode for grpc:

func (s *smartcontract) begin(ctx contractapi.transactioncontextinterface) error {
    server.main()
    return nil
}

func (s *smartcontract) client(ctx contractapi.transactioncontextinterface) error {
    // client.clientfunc is the client main function
    client.clientfunc(xt, r, sign, m)
}

server.go

func main() {
    listen, err := net.listen("tcp", ":9090")
    if err != nil {
        fmt.printf("failed to listen: %v", err)
        return
    }
    grpcserver := grpc.newserver()
    pb.registersendserviceserver(grpcserver, &server{})
    err2 := grpcserver.serve(listen)
    if err2 != nil {
        fmt.printf("failed to serve: %v", err2)
        return
    }
}

client.go

func Clientfunc(Xt *btcec.PublicKey, R *btcec.PublicKey, s *big.Int, m []byte) []byte {
    conn, err := grpc.Dial("127.0.0.1:9090", grpc.WithTransportCredentials(insecure.NewCredentials()))
    if err != nil {
        log.Fatalf("did not connect: %v", err)
    }
    defer conn.Close()
    client := pb.NewSendServiceClient(conn)
    output := &pb.SignInput{
        XtX: Xt.X().Int64(),
        XtY: Xt.Y().Int64(),
        M:   m,
        RX:  R.X().Int64(),
        RY:  R.Y().Int64(),
        S:   s.Int64(),
    }
    resp, _ := client.Send(context.Background(), output)
    return resp.GetM()
}

Solution

Who can tell me what causes this error?

See hyperledger fabric v2.x/ Log Control for details, what can tell you what caused Error 500 (Internal Server Error) is the server log

Depends on how you run it:

docker logs <chaincode_container_id>
kubectl logs -n <namespace> <pod_name>
oc logs -n <namespace> <pod_name>

This may be due to an issue in your chaincode (such as a bug in the grpc code), or it may be due to the environment in which the chaincode is running.

From your code, you might consider not starting the grpc server in chaincode (server.main()). Chaincode runs within a hyperledger fabric network and does not handle network communication like a standalone application.
Instead, you should make the grpc server a separate service that runs independently, and the chaincode can then communicate with that service as needed.

Plus client.clientfunc()The function seems to establish the grpc connection, send the request, and wait for the response. This is a synchronous operation and may cause problems if the response takes a long time to arrive. It's best to use asynchronous operations (i.e. send a request and handle the response in a callback function) to avoid blocking chaincode execution.
And... you shouldn't ignore errors from client.send() ;)

Make sure your grpc server does not require secure connections, otherwise grpc.withtransportcredentials(insecure.newcredentials()) (insecure connections without ssl/tls) will fail.

In general, it is recommended to handle communication with external systems (e.g. via grpc) within the fabric client application, rather than within the chaincode itself.

If I just want to use chaincode instead of fabric application, is there a way to communicate between organizations on different channels?

Communication between organizations on different channels can be complex, as it is a fundamental aspect of the hyperledger fabric design that channels are isolated from each other to maintain data privacy.

You may consider:

• Chain code function: An organization can call a chain code function on its own channel, which in turn calls a chain code function on another channel. This is possible because chaincodes can be associated with multiple channels.
  Note that this approach has a limitation that the second function call does not belong to the same transaction as the first function call, so if the first transaction fails, it cannot be rolled back.

• Dual Membership: An organization can belong to multiple channels. Therefore, it can read data from one channel and write data to another channel. However, this is done in two separate transactions, so atomicity is not guaranteed.

• Private Data Collection (pdc): If the goal is to share private data between specific organizations (or even across different channels), PDC may be an option. pdc allows a defined subset of organizations on a channel to endorse, submit, or query private data without distributing the data to all organizations on the channel.

• Interoperability Solutions: There are also more advanced solutions for blockchain interoperability being developed, such as interledger protocol (ilp), Can be used to move data or assets between different fabric networks (even between completely different types of blockchain networks).
  However, these technologies are still largely in the research and development stage and may not be ready for production use yet.

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