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https://issues.apache.org/jira/browse/SSHD-557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14802994#comment-14802994
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Sam Gardner edited comment on SSHD-557 at 9/17/15 3:22 PM:
-----------------------------------------------------------
Increasing the number of worker threads does help, but isn't a real solution I
don't think. For our use case, we could reasonably expect ~150 concurrent
downloads (for now, that number can increase in the future). I'd rather not
deal with the performance overhead of configuring many hundreds (or even
thousands) of threads.
was (Author: sgardner):
Increasing the number of worker threads does help, but isn't a real solution I
don't think. For our use case, we could reasonably expect ~150 concurrent
downloads (for now, that number can increase in the future). Since {{flush()}}
calls happen fairly constantly and there is no way for a thread to get out of
the locked state, I don't think we have any guarantee that the threads would
not all eventually become locked, not to mention the performance hit that would
come from configuring 1000s of different threads.
> MINA SSHD deadlocks upon multiple concurrent HTTP downloads over
> locally-forwarded ports
> ----------------------------------------------------------------------------------------
>
> Key: SSHD-557
> URL: https://issues.apache.org/jira/browse/SSHD-557
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 0.14.0, 1.0.0
> Environment: Fedora 21, kernel 3.17.4-301, OpenJDK 1.8.0_51-b16
> Reporter: Sam Gardner
> Assignee: Goldstein Lyor
> Labels: sshd
> Fix For: 1.1.0
>
> Attachments: AbstractUserAuth.java, setup-tunnels-remote.sh,
> setup-tunnels.sh, ssh-load-remote.sh, ssh-load.sh,
> sshd-core-0.14.0-jar-with-dependencies.jar,
> sshd-core-1.0.0-jar-with-dependencies.jar
>
>
> SSHD-Core 1.0.0 deadlocks when multiple concurrent downloads are in progress
> over ChannelOutputStreams
> In both Mina-SSHD 0.14.0 and 1.0.0 the server will become deadlocked if
> multiple concurrent downloads are started over a locally-forwarded TCP
> socket. In this state the process is still alive and client connections stay
> open, but no data can be transmitted and new connections will not be accepted
> - when inspected via telnet, the SSH port will not even return a banner.
> Inspection of the hung process using the {{jstack}} tool shows that each NIO
> worker thread is in the following state: {noformat}
> "sshd-SshServer[36f6e879]-nio2-thread-4" #14 daemon prio=5 os_prio=0
> tid=0x00007f219c009000 nid=0x34c6 in Object.wait() [0x00007f21c8439000]
> java.lang.Thread.State: WAITING (on object monitor)
> at java.lang.Object.wait(Native Method)
> - waiting on <0x00000000d799f9b0> (a
> org.apache.sshd.common.channel.Window)
> at java.lang.Object.wait(Object.java:502)
> at org.apache.sshd.common.channel.Window.waitForSpace(Window.java:175)
> - locked <0x00000000d799f9b0> (a
> org.apache.sshd.common.channel.Window)
> at
> org.apache.sshd.common.channel.ChannelOutputStream.flush(ChannelOutputStream.java:126)
> - locked <0x00000000d799fa68> (a
> org.apache.sshd.common.channel.ChannelOutputStream)
> at
> org.apache.sshd.server.forward.TcpipServerChannel$1.messageReceived(TcpipServerChannel.java:156)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:220)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker.invokeDirect(Invoker.java:157)
> at
> sun.nio.ch.UnixAsynchronousSocketChannelImpl.implRead(UnixAsynchronousSocketChannelImpl.java:553)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:276)
> at
> sun.nio.ch.AsynchronousSocketChannelImpl.read(AsynchronousSocketChannelImpl.java:297)
> at
> java.nio.channels.AsynchronousSocketChannel.read(AsynchronousSocketChannel.java:420)
> at
> org.apache.sshd.common.io.nio2.Nio2Session.doReadCycle(Nio2Session.java:247)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:224)
> at
> org.apache.sshd.common.io.nio2.Nio2Session$2.onCompleted(Nio2Session.java:212)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler$1.run(Nio2CompletionHandler.java:34)
> at java.security.AccessController.doPrivileged(Native Method)
> at
> org.apache.sshd.common.io.nio2.Nio2CompletionHandler.completed(Nio2CompletionHandler.java:31)
> at sun.nio.ch.Invoker.invokeUnchecked(Invoker.java:126)
> at sun.nio.ch.Invoker$2.run(Invoker.java:218)
> at
> sun.nio.ch.AsynchronousChannelGroupImpl$1.run(AsynchronousChannelGroupImpl.java:112)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> These are the steps to reproduce:
> # Start up approximately 200 separate SSH sessions with one local forward to
> an HTTP server:
> {{ssh -N -LXXXXX:<HTTP_SERVER>:80 account@<MINA_SSHD_SERVER>}}
> ## To simplify this process, I modified
> [org.apache.sshd.server.auth.AbstractUserAuth|^AbstractUserAuth.java] to
> always accept requests - this makes it possible to create the sessions on the
> same client (though I've also reproduced this on separate clients as well).
> ## This [script|^setup-tunnels.sh] will setup the client sessions as
> background processes
> # With the above sessions alive and backgrounded, fetch large files
> concurrently from the HTTP server over multiple forwarded ports:
> {{wget http://localhost:XXXXX/hugefile}}
> ## This [script|^ssh-load.sh] will start {{wget}} downloads in the above
> manner.
> # After a time, the {{wget}} downloads will stop progressing, and inspection
> of the SSH server process via {{jstack <PID>}} will show each of the
> {{nio2-thread-[0-9]}} threads in the deadlocked state.
> Note: I previously filed SSHD-539 on this, and have since reproduced it on
> vanilla MINA SSHD-Core without our proprietary modifications and running
> outside of Tomcat.
> The JAR files I used to reproduce are attached to this ticket as well.
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