HTTP/2 uses non-daemon threads

The following one-line program does not close properly on Java 9:

public static void main(String[] args) throws IOException {
    System.out.println(new OkHttpClient.Builder().build().newCall(new Request.Builder().url("https://google.de").build()).execute());
}

It hangs for a very significant amount of time after the request is already finished before it allows the program to quit.

This a little modified version works flawlessly and allows the program to quit immediately after the request is finished.

public static void main(String[] args) throws IOException {
    System.out.println(new OkHttpClient.Builder().protocols(Collections.singletonList(Protocol.HTTP_1_1)).build().newCall(new Request.Builder().url("https://google.de").build()).execute());
}

Running on Java 8 also fixes the problem, as there HTTP 1.1 is used, not HTTP 2.0.

The problem is a hanging non-deamon thread called OkHttp google.de. Here you have the stacktrace of the thread when the program should quit:

"OkHttp google.de@1876" prio=5 tid=0x11 nid=NA runnable
  java.lang.Thread.State: RUNNABLE
	  at java.net.SocketInputStream.socketRead0(SocketInputStream.java:-1)
	  at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
	  at java.net.SocketInputStream.read(SocketInputStream.java:171)
	  at java.net.SocketInputStream.read(SocketInputStream.java:141)
	  at sun.security.ssl.SSLSocketInputRecord.read(SSLSocketInputRecord.java:425)
	  at sun.security.ssl.SSLSocketInputRecord.bytesInCompletePacket(SSLSocketInputRecord.java:65)
	  at sun.security.ssl.SSLSocketImpl.bytesInCompletePacket(SSLSocketImpl.java:918)
	  - locked <0x792> (a java.lang.Object)
	  at sun.security.ssl.AppInputStream.read(AppInputStream.java:144)
	  - locked <0x793> (a sun.security.ssl.AppInputStream)
	  at okio.Okio$2.read(Okio.java:140)
	  at okio.AsyncTimeout$2.read(AsyncTimeout.java:237)
	  at okio.RealBufferedSource.request(RealBufferedSource.java:68)
	  at okio.RealBufferedSource.require(RealBufferedSource.java:61)
	  at okhttp3.internal.http2.Http2Reader.nextFrame(Http2Reader.java:95)
	  at okhttp3.internal.http2.Http2Connection$ReaderRunnable.execute(Http2Connection.java:608)
	  at okhttp3.internal.NamedRunnable.run(NamedRunnable.java:32)
	  at java.lang.Thread.run(Thread.java:844)

I find it quite strange that this thread is hanging on a socketRead operation, while the request is already finished successfully.

[swankjesse]

We built a new TaskRunner abstraction that will allow HTTP/2 threads to be daemons in 4.3.

[yschimke]

Will be fixed in 4.5.