[
https://issues.apache.org/jira/browse/SSHD-1070?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17191465#comment-17191465
]
Thomas Wolf commented on SSHD-1070:
-----------------------------------
{quote}
1. Could this cause a deadlock?
{quote}
I think it should not, since a {{put()}} that succeeds then executes in the
same thread {{startWriting()}}, and {{startWriting()}} calls itself once a
buffered element has been written to process the rest of the queue. So
eventually there should be space again, and a pending {{put()}} should then
succeed.
What you describe, though, is exactly what happens in the SSHD-1069 case (all
threads only reading, no thread is writing), but since that problem already
existed before, it isn't caused by this change. I wonder if it happens because
the {{ChannelAsyncOutputStream}} delays the write until there'd be enough
window space; but if all threads are busy reading I don't see where a thread
would request a window adjust and eventually retrigger the pending write.
{quote}
2. The performance of asynchronous frameworks will be degraded...
{quote}
Perhaps. But the whole process here doesn't seem to be very asynchronous
anyway, with the same thread initiating the write. I didn't check in detail
what the {{ChannelAsyncOutputStream}} does ; I don't see it using different
threads for writing... I would expect different connections to use different
{{BufferedIoOutputStreams}} in any case. With a fixed thread pool for reading
and writing it seems to me that it is always possible that a fast connection is
slowed down by slower connections, or that a fast connection starves slower
ones.
Adding yet another queue like you suggest will just re-introduce the problem of
unbounded queues again, and then we can get OOMEs again.
But feel free to provide a better fix.
> OutOfMemoryError when use port forwarding
> -----------------------------------------
>
> Key: SSHD-1070
> URL: https://issues.apache.org/jira/browse/SSHD-1070
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 2.5.1
> Reporter: Feng Jiajie
> Priority: Major
> Time Spent: 20m
> Remaining Estimate: 0h
>
> Hi [~gnodet], I found this commit implemented asynchronous port forwarding:
> [https://github.com/apache/mina-sshd/commit/45f84aab59b2e11d72942cffe9d810e37ab64959#diff-33823b8546f71d77bb1d653358ecde70]
> However, when a large amount of data is returned from upstream application,
> it is possible to cause an OOM in SSHD.
> Step1. SSHD server:
> {code:java}
> import org.apache.sshd.common.FactoryManager;
> import org.apache.sshd.common.PropertyResolverUtils;
> import org.apache.sshd.common.util.security.SecurityUtils;
> import org.apache.sshd.server.SshServer;
> import org.apache.sshd.server.forward.AcceptAllForwardingFilter;
> import org.apache.sshd.server.keyprovider.SimpleGeneratorHostKeyProvider;
> import java.io.IOException;
> import java.nio.file.Paths;
> public class TestSshd2 {
> public static void main(String[] args) throws IOException,
> InterruptedException {
> SecurityUtils.setAPrioriDisabledProvider("BC", true);
> SshServer sshd = SshServer.setUpDefaultServer();
> sshd.setPort(12133);
> sshd.setKeyPairProvider(new
> SimpleGeneratorHostKeyProvider(Paths.get("/tmp/aa.key")));
> sshd.setPasswordAuthenticator((username, password, session) -> true);
> sshd.setForwardingFilter(AcceptAllForwardingFilter.INSTANCE);
> sshd.start();
> Thread.sleep(100000000);
> }
> }
> {code}
> Step2. start ssh client and iperf3 server:
> {code:java}
> ssh -o 'ExitOnForwardFailure yes' -p 12133 -f -x -N -T -L
> 0.0.0.0:15678:127.0.0.1:12345 test5@127.0.0.1
> iperf3 -s -p 12345
> {code}
> Step3. run iperf3 client:
> {code:java}
> iperf3 -c 127.0.0.1 -i 1 -t 120 -p 15678 -P 8 --reverse
> {code}
> *-R, --reverse run in reverse mode (server sends, client receives)*
> SSHD will receive a lot of data but will not be able to forward it in time.
> log when OOM:
> {code:java}
> 17:52:25.195 [sshd-SshServer[5bcea91b](port=12133)-nio2-thread-1] WARN
> org.apache.sshd.common.io.nio2.Nio2Session -
> exceptionCaught(Nio2Session[local=/127.0.0.1:33524, remote=/127.0.0.1:12345])
> Exception handler threw OutOfMemoryError, closing the session: GC overhead
> limit exceeded17:52:25.195
> [sshd-SshServer[5bcea91b](port=12133)-nio2-thread-1] WARN
> org.apache.sshd.common.io.nio2.Nio2Session -
> exceptionCaught(Nio2Session[local=/127.0.0.1:33524, remote=/127.0.0.1:12345])
> Exception handler threw OutOfMemoryError, closing the session: GC overhead
> limit exceeded at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:37)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126) at
> sun.nio.ch.Invoker.invokeDirect(Invoker.java:157) at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implWrite(UnixAsynchronousSocketChannelImpl.java:736)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.write(AsynchronousSocketChannelImpl.java:382)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.write(AsynchronousSocketChannelImpl.java:399)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doWriteCycle(Nio2Session.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.startWriting(Nio2Session.java:404)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.finishWrite(Nio2Session.java:495)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.handleCompletedWriteCycle(Nio2Session.java:465)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:429)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:426)17:52:25.639
> [sshd-SshServer[5bcea91b](port=12133)-nio2-thread-6] WARN
> org.apache.sshd.common.io.nio2.Nio2Session -
> exceptionCaught(Nio2Session[local=/127.0.0.1:33530, remote=/127.0.0.1:12345])
> Exception handler threw OutOfMemoryError, closing the session: GC overhead
> limit exceeded at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.lambda$completed$0(Nio2CompletionHandler.java:38)
> at java.security.AccessController.doPrivileged(Native Method) at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:37)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126) at
> sun.nio.ch.Invoker.invokeDirect(Invoker.java:157) at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implWrite(UnixAsynchronousSocketChannelImpl.java:736)17:52:26.045
> [sshd-SshServer[5bcea91b](port=12133)-nio2-thread-2] DEBUG
> org.apache.sshd.common.io.nio2.Nio2Session -
> exceptionCaught(Nio2Session[local=/127.0.0.1:33522, remote=/127.0.0.1:12345])
> caught OutOfMemoryError[GC overhead limit exceeded] - calling
> handler17:52:26.045 [sshd-SshServer[5bcea91b](port=12133)-nio2-thread-2]
> DEBUG org.apache.sshd.server.forward.TcpipServerChannel -
> exceptionCaught(TcpipServerChannel[id=3,
> recipient=4]-ServerSessionImpl[test5@/127.0.0.1:53702]) signal close
> immediately=false due to OutOfMemoryError[GC overhead limit
> exceeded]17:52:26.045 [sshd-SshServer[5bcea91b](port=12133)-nio2-thread-2]
> DEBUG org.apache.sshd.server.forward.TcpipServerChannel -
> close(TcpipServerChannel[id=3,
> recipient=4]-ServerSessionImpl[test5@/127.0.0.1:53702])[Graceful] state
> already Graceful17:52:26.794
> [sshd-SshServer[5bcea91b](port=12133)-nio2-thread-3] WARN
> org.apache.sshd.common.io.nio2.Nio2Session -
> exceptionCaught(Nio2Session[local=/127.0.0.1:33528, remote=/127.0.0.1:12345])
> Exception handler threw OutOfMemoryError, closing the session: GC overhead
> limit exceeded at
> sun.nio.ch.AsynchronousSocketChannelImpl.write(AsynchronousSocketChannelImpl.java:382)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.write(AsynchronousSocketChannelImpl.java:399)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doWriteCycle(Nio2Session.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.startWriting(Nio2Session.java:404)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.finishWrite(Nio2Session.java:495)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.handleCompletedWriteCycle(Nio2Session.java:465)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:429)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:426)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.lambda$completed$0(Nio2CompletionHandler.java:38)17:52:26.045
> [sshd-SshServer[5bcea91b](port=12133)-nio2-thread-2] DEBUG
> org.apache.sshd.common.io.nio2.Nio2Session -
> close(Nio2Session[local=/127.0.0.1:33522, remote=/127.0.0.1:12345]) Closing
> immediately at java.security.AccessController.doPrivileged(Native
> Method)17:52:26.869 [sshd-SshServer[5bcea91b](port=12133)-nio2-thread-2]
> DEBUG org.apache.sshd.common.io.nio2.Nio2Session -
> doCloseImmediately(Nio2Session[local=/127.0.0.1:33522,
> remote=/127.0.0.1:12345]) closing
> socket=sun.nio.ch.UnixAsynchronousSocketChannelImpl[connected
> local=/127.0.0.1:33522 remote=/127.0.0.1:12345] at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:37)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126) at
> sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)17:52:27.568
> [sshd-SshServer[5bcea91b](port=12133)-nio2-thread-6] DEBUG
> org.apache.sshd.common.io.nio2.Nio2Session -
> exceptionCaught(Nio2Session[local=/127.0.0.1:33530, remote=/127.0.0.1:12345])
> caught OutOfMemoryError[GC overhead limit exceeded] - calling
> handler17:52:27.568 [sshd-SshServer[5bcea91b](port=12133)-nio2-thread-6]
> DEBUG org.apache.sshd.server.forward.TcpipServerChannel -
> exceptionCaught(TcpipServerChannel[id=7,
> recipient=8]-ServerSessionImpl[test5@/127.0.0.1:53702]) signal close
> immediately=false due to OutOfMemoryError[GC overhead limit
> exceeded]17:52:27.568 [sshd-SshServer[5bcea91b](port=12133)-nio2-thread-6]
> DEBUG org.apache.sshd.server.forward.TcpipServerChannel -
> close(TcpipServerChannel[id=7,
> recipient=8]-ServerSessionImpl[test5@/127.0.0.1:53702])[Graceful] state
> already Graceful at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implWrite(UnixAsynchronousSocketChannelImpl.java:736)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.write(AsynchronousSocketChannelImpl.java:382)
> {code}
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscr...@mina.apache.org
For additional commands, e-mail: dev-h...@mina.apache.org
