How to using same TCP connection for http2.0 and async in okhttp3? - okhttp

Question

Move from https://github.com/square/okhttp/issues/6051
This is a problem with okhttp keepalived connections, I wonder how to deal with this issue.
OkHttpClient httpClient = new OkHttpClient.Builder()
.sslSocketFactory(factory, (X509TrustManager) TRUST_MANAGERS[0])
.hostnameVerifier((s, sslSession) -> true)
.protocols(Arrays.asList(Protocol.HTTP_2, Protocol.HTTP_1_1))
.retryOnConnectionFailure(true)
.connectionPool(new ConnectionPool(5, 60, TimeUnit.SECONDS))
.build();
Request request = new Request.Builder()
.url("https://example.com/")
.build();
int count = 2;
long startTime = System.currentTimeMillis();
final CountDownLatch countDownLatch = new CountDownLatch(count);
for (int i = 1; i <= count; ++i) {
httpClient.newCall(request).enqueue(new Callback() {
#Override
public void onFailure(Call call, IOException e) {
System.out.println(Thread.currentThread().getName() + "-failed-" + e.getMessage());
finish();
}
#Override
public void onResponse(Call call, Response response) throws IOException {
finish();
}
private void finish() {
countDownLatch.countDown();
}
});
}
countDownLatch.await();
System.out.println("Time: " + (System.currentTimeMillis() - startTime) );
System.exit(0);
}

Answer 1

Use LoggingEventListener if you want to see what is going on.
Generally when we first connect we can't know ahead of time that a single connection will be http/2 and able to serve both requests. So when the connection pool is empty, OkHttp will establish 2 connections, discover they are both http/2 and then disconnect one.
So likely both requests use a single connection, but you see two established.
You have a few options
1) Don't worry, let it create two connections temporarily, and OkHttp will close one as soon as it realises it has two HTTP/2 connections.
2) Use a warmup request to create the first request, then only create secondary requests to the same host once you have received a connectionAcquired event on that first request.
But I'd encourage you not to worry and just let OkHttp do it's thing.