Allow enabling HTTP/2 PING and disabling read timeout for streams

[kohenkatz]

The default okhttp readTimeout is 10 seconds, which is too short for many uses of streaming RPCs. As an alternative way to detect broken connections, HTTP/2 provides a PING mechanism. okhttp has pings disabled by default, but they can be enabled by calling pingInterval() on the builder. Streaming calls can set readTimeout to 0 to disable the read timeout and rely only on the ping timeout, if desired.

The problem is that there is not an easy way to change the okhttp settings for unary vs. streaming calls, and we still want to have a read timeout for the unary calls.

I thought it would be easiest to fix this by extending ConnectOkHttpClient to customize the client object and then call the parent method using the customized client, but ConnectOkHttpClient would need to be open instead of final to allow this.

I ended up doing this, which feels like a nasty hack:

class PingingConnectClient(client: OkHttpClient): HTTPClientInterface {
    private val internalUnaryClient = ConnectOkHttpClient(client)
    private val internalStreamClient = ConnectOkHttpClient(client.newBuilder()
        .pingInterval(30, TimeUnit.SECONDS)
        .readTimeout(0, TimeUnit.SECONDS)
        .build())

    override fun unary(request: HTTPRequest, onResult: (HTTPResponse) -> Unit): Cancelable {
        return internalUnaryClient.unary(request, onResult)
    }

    override fun stream(
        request: HTTPRequest,
        onResult: suspend (StreamResult<Buffer>) -> Unit
    ): Stream {
        return internalStreamClient.stream(request, onResult)
    }
}

[pkwarren]

@kohenkatz - This seems like a reasonable request. Would it work for you to just change the constructor to:

class ConnectOkHttpClient @JvmOverloads constructor(
    private val unaryClient: OkHttpClient = OkHttpClient(),
    private val streamClient: OkHttpClient = unaryClient,
) : HTTPClientInterface {

Then in stream, we'd just update to use streamClient.

[kohenkatz]

@pkwarren Yes, that sounds like it would do what I want.