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From "Sam Gardner (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (SSHD-557) MINA SSHD deadlocks upon multiple concurrent HTTP downloads over locally-forwarded ports
Date Thu, 17 Sep 2015 15:23:07 GMT

    [ https://issues.apache.org/jira/browse/SSHD-557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14802994#comment-14802994
] 

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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