How to Handle gRPC Server Reconnection After Redeployment?

How to Connect to gRPC Server After Redeployment

In gRPC, the clientconn.go code manages reconnections automatically. However, if the server pod is recycled, the stream will break and needs to be re-established. To address this issue, follow these steps:

Process Requests

func (grpcclient *gRPCClient) ProcessRequests() error {
    defer grpcclient.Close()    

    go grpcclient.process()
    for {
        select {
            case <-grpcclient.reconnect:
                if !grpcclient.waitUntilReady() {
                    return errors.New("failed to establish a connection within the defined timeout")
                }
                go grpcclient.process()
            case <-grpcclient.done:
                return nil
        }
    }
}

Process Requests:

func (grpcclient *gRPCClient) process() {
    reqclient := GetStream() // Get a new stream after reconnecting
    for {
        request, err := reqclient.stream.Recv()
        log.Info("Request received")
        if err == io.EOF {          
            grpcclient.done <- true
            return
        }
        if err != nil {
            grpcclient.reconnect <- true
            return
        } else {
            // Process requests
        }
    }
}

Check Connection State

func (grpcclient *gRPCClient) waitUntilReady() bool {
    ctx, cancel := context.WithTimeout(context.Background(), 300*time.Second) // Define the timeout for waiting
    defer cancel()

    currentState := grpcclient.conn.GetState()
    stillConnecting := true

    for currentState != connectivity.Ready && stillConnecting {
        // Wait for state change
        stillConnecting = grpcclient.conn.WaitForStateChange(ctx, currentState)
        currentState = grpcclient.conn.GetState()
        log.WithFields(log.Fields{"state: ": currentState, "timeout": timeoutDuration}).Info("Attempting reconnection. State has changed to:")
    }

    if stillConnecting == false {
        log.Error("Connection attempt has timed out.")
        return false
    }

    return true
}

These modifications will allow the gRPC client to automatically re-establish the stream and continue processing requests after the server is redeployed.

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