How can gRPC client know about network loss/failure?

[deepakag...@gmail.com]

I have a gRPC server to whom i have connected my gRPC client (Java).

- the client is observing server streaming RPC, which is supposed to go on for couple of hours.

- When the server stopped, the client gets the information as gRPC invoked onError() method.

- but when the network was broken between server and client, the client doesn't even know about the problem, the streamobserver is idle and no activity.

In my scenario, if anything like this happens the client is supposed to retry the connection and invoke RPC again. 

So my question is how can i know about the network failure in the client.

[Eric Anderson]

You want to enable keep alive, via keepAliveTime on NettyChannelBuilder or OkHttpChannelBuilder.

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[deepakag...@gmail.com]

Hi Eric, thanks for the response but i have to problems

1) I am using grpc-java 1.0.1 which does not support this Interface (The product team has decided on grpc version)

2) The keepalive time is not fixed.

Also i have a doubt about the whether grpc java 1.0.1 can support http2. I found c based grpc 1.0.1 and grpc-java 1.0.1 has many different functions

On Tuesday, June 20, 2017 at 11:21:40 PM UTC+5:30, Eric Anderson wrote:

You want to enable keep alive, via keepAliveTime on NettyChannelBuilder or OkHttpChannelBuilder.

On Sun, Jun 11, 2017 at 10:54 PM, <deepakag...@gmail.com> wrote:

I have a gRPC server to whom i have connected my gRPC client (Java).

- the client is observing server streaming RPC, which is supposed to go on for couple of hours.

- When the server stopped, the client gets the information as gRPC invoked onError() method.

- but when the network was broken between server and client, the client doesn't even know about the problem, the streamobserver is idle and no activity.

In my scenario, if anything like this happens the client is supposed to retry the connection and invoke RPC again. 

So my question is how can i know about the network failure in the client.

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[Eric Anderson]

On Wed, Jun 21, 2017 at 3:10 AM, <deepakag...@gmail.com> wrote:

Hi Eric, thanks for the response but i have to problems

1) I am using grpc-java 1.0.1 which does not support this Interface (The product team has decided on grpc version)

Sorry, but the feature wasn't available in 1.0.x.

The only workaround in that case is to send "noop/trash" messages/RPCs periodically. Basically, TCP needs writes in order to discover read failures, so you generate noop writes on the TCP connection. If you receive GOAWAY from the server (like during server shutdown or server rotation), then any new RPCs will use a different connection, thus won't help you detect if the old connection is broken. Depending on your setup, that may not be much of a problem (e.g., if the server closes the connection soon after sending the GOAWAY). Using noop messages on the same RPC stream (by making it a bidi streaming RPC) wouldn't have that deficiency, but you'd also need to do the noop messages on all active streams and have to change more of your application logic.

2) The keepalive time is not fixed.

I don't understand this.

Also i have a doubt about the whether grpc java 1.0.1 can support http2. I found c based grpc 1.0.1 and grpc-java 1.0.1 has many different functions

I don't understand what you mean by functions. Could you explain more? It sounds like this is unrelated to the network break detection.

[deepakag...@gmail.com]

Ok. let me explain the complete scenario

1) I have a gRPC server which provides a server streaming RPC, my application is a client which needs to invoke this RPC and keep listening to the data written by the server (until the RPC is closed).

    The problem here is that in the server side if they detect that the connection has problem (while writing the data to the RPC), they consider this RPC as closed and client need to re-invoke it.

    In grpc java 1.0.1 i don't have mechanism in client to know the connection was broken and i need to restart the RPC.

   I have done some test, when we stop the server, in client side streamobserver, the overloaded method warning(String msg, Object... params) is invoked

   But when i disconnect the network between client and server, the server can get to know but client doesn't get to know about it and the observer keeps on idle.

2)  I am using NettyChannelBuider to build the channel with the gRPC server, (I hope all types of channelbuilder uses http2)

3)  If somehow I can convince the product team to upgrade the grpc-java version, will it be able to communicate with c based grpc 1.0.1 version server?