server side push

[chirag shah]

Hello

As we know, Server-side  notification/push can be achieved by multiple ways depending upon what you want to achieve.

In my use-case , the built-in  HTTP/2 SERVER_PUSH frames  based approach is NOT feasible.

Another approach is web-socket. But that does not fit very well with HTTP/2

Web-push API is also not a good fit because it is based on service-worker and more heavy-weight compared to some in-line technology.

 

In this context, I believe I can do it with HTTP/2 + server-side-event  and leverage Event-Source Mechanism.

 

However , I  am interested in exploring if some streaming-based gRPC  API can help me.

Basically, in my use-case I want the server to send the data if/when available with  him.

So in simple terms

I invoke one gRPC server-side streaming API in asynchronous, non-blocking mode and then continue on my client-side browser work.

The implementation of gRPC server-side code will just push the data whenever available by calling     streamObserver.onNext(response);

If data is not available the server-side method will just sleep for a while before checking for the next time.

Basically, the underlying design here is the HTTP/2 stream that is spawned will remain open forever on that TCP connection.

Do you think this is scalable enterprise level architecture ?  Can we keep the HTTP/2 stream open for long time ?

 

 

Thanks.

[Kun Zhang]

HTTP/2 stream can be opened for a long time and used to push messages when they become available.

If you have L4 load-balancer in front of the server, you may want to configure NettyServerBuilder.maxConnectionAge() so that the server will tear off connections that have lived for too long, so that the client will automatic reconnect and the load-balancer can rebalance the connections to servers.

[chirag shah]

Thanks Kun  for clarifying.

So basically I can use long-lasting stream and push message when they available as showing in below stock update snippet.

 

public class StockServiceImpl extends StockServiceGrpc.StockServiceImplBase
{
       public void stockUpdate(StockServiceOuterClass.HelloRequest request,    StreamObserver<StockServiceOuterClass.HelloResponse> streamObserver)
       {
           //run a loop 
           {
        //check if response object can be constructed by checking our DB
        //if it can be , then create it and hand it over to the streamObserver
  
              StockServiceOuterClass.HelloResponse response =  StockServiceOuterClass.HelloResponse.newBuilder().setStockInfo(“new data from DB”).build();
       streamObserver.onNext(response);  

       //but if NO new data available in DB, just sleep for a while like
              Thread.sleep(30 sec);
              //check again if any data is available in our DB to create a response object
    }

// When you are fully done, you amy call onCompleted.
//technically this line will close the underlying http/2 stream which I would not do it very quickly
streamObserver.onCompleted();
  }
}