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https://issues.apache.org/jira/browse/SSHD-1173?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17614680#comment-17614680
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Thomas Wolf commented on SSHD-1173:
-----------------------------------
{quote}Try explaining the above to a customer will be nightmarish.{quote}
Why? "There was an interoperability problem between Apache MINA sshd and some
other SSH implementations. We fixed the problem by setting a configuration
option in Apache MINA sshd."
{quote}I strongly urge you to reconsider keeping this option.{quote}
Why should we keep an option that produces wrong behavior? No. [PR
251|https://github.com/apache/mina-sshd/pull/251] removes the options, and
makes Apache MINA sshd always behave as if they were {{true}}. The explanation
for the customer then becomes "There was a bug in Apache MINA sshd that caused
interoperability problems with some SSH implementations. We fixed the problem
by upgrading the Apache MINA sshd version to one in which this bug was fixed."
I tried to explain what the change does in the
[CHANGES|https://github.com/apache/mina-sshd/blob/9010fa7e09642c7a3d3481d673b2025ce7391f57/CHANGES.md#channel-windows].
> SFTP worker threads got stuck while processing PUT methods against one
> specific SFTP server
> -------------------------------------------------------------------------------------------
>
> Key: SSHD-1173
> URL: https://issues.apache.org/jira/browse/SSHD-1173
> Project: MINA SSHD
> Issue Type: Question
> Affects Versions: 2.6.0
> Reporter: Pavel Pohner
> Priority: Critical
> Labels: SFTP, mina, sshd
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Hey guys,
> Recently I've encountered one remote SFTP server, that causes SFTP worker
> threads to enter TIMED_WAITING state, from which they do not recover. Please,
> take a look into this thread dump:
> {code:java}
> SFTP-worker-3 #2155 prio=5 os_prio=0 cpu=61692.09ms elapsed=1136151.86s
> tid=0x00007fe41c005800 nid=0x18808 in Object.wait()
> [0x00007fe145b1d000]SFTP-worker-3" #2155 prio=5 os_prio=0 cpu=61692.09ms
> elapsed=1136151.86s tid=0x00007fe41c005800 nid=0x18808 in Object.wait()
> [0x00007fe145b1d000] java.lang.Thread.State: TIMED_WAITING (on object
> monitor) at java.lang.Object.wait(java.base@11.0.10/Native Method) - waiting
> on <no object reference available> at
> org.apache.sshd.common.future.DefaultSshFuture.await0(DefaultSshFuture.java:69)
> - waiting to re-lock in wait() <0x00000006e3bbc420> (a
> org.apache.sshd.common.channel.IoWriteFutureImpl) at
> org.apache.sshd.common.future.AbstractSshFuture.verifyResult(AbstractSshFuture.java:109)
> at
> org.apache.sshd.common.io.AbstractIoWriteFuture.verify(AbstractIoWriteFuture.java:39)
> at
> org.apache.sshd.common.io.AbstractIoWriteFuture.verify(AbstractIoWriteFuture.java:30)
> at
> org.apache.sshd.common.future.VerifiableFuture.verify(VerifiableFuture.java:43)
> at
> org.apache.sshd.sftp.client.impl.DefaultSftpClient.send(DefaultSftpClient.java:292)
> at
> org.apache.sshd.sftp.client.impl.SftpOutputStreamAsync.flush(SftpOutputStreamAsync.java:210)
> at
> org.apache.sshd.sftp.client.impl.SftpOutputStreamAsync.write(SftpOutputStreamAsync.java:141)
> at java.io.InputStream.transferTo(java.base@11.0.10/InputStream.java:705) at
> com.mina.command.Put.replyInto(Put.java:55) at
> com.sftpserver.MinaSftpHandler.channelReadInternal(MinaSftpHandler.java:251)
> at
> com.sftpserver.MinaSftpHandler.lambda$channelRead$0(MinaSftpHandler.java:125)
> at com.sftpserver.MinaSftpHandler$$Lambda$392/0x0000000800764040.run(Unknown
> Source) at
> java.util.concurrent.Executors$RunnableAdapter.call(java.base@11.0.10/Executors.java:515)
> at
> java.util.concurrent.FutureTask.run(java.base@11.0.10/FutureTask.java:264) at
> java.util.concurrent.ThreadPoolExecutor.runWorker(java.base@11.0.10/ThreadPoolExecutor.java:1128)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(java.base@11.0.10/ThreadPoolExecutor.java:628)
> at java.lang.Thread.run(java.base@11.0.10/Thread.java:834)
> {code}
> Seems like the thread is waiting for lock in
> org.apache.sshd.common.future.DefaultSshFuture.await0(DefaultSshFuture.java),
> I'm currently not sure what thread holds the lock and why it's not ever
> released.
> Also, I'm not able to reproduce this, but it constantly happens to all the
> PUT methods targeting one specific remote server (which I don't own), so I
> suppose there would be something odd with the remote server, but it doesn't
> mean, that we shouldn't be able to deal with that.
> Have you ever seen such behavior? Could it be Mina sshd's bug? (seems like
> verify() in
> org.apache.sshd.sftp.client.impl.DefaultSftpClient.send(DefaultSftpClient.java:292)
> is called without any timeout, which then defaults to LONG.MAX here: at
> org.apache.sshd.common.future.VerifiableFuture.verify(VerifiableFuture.java:43),
> shouldn't we have configurable timeout here? or what's the point of default
> timeout? what are we really waiting for in at
> org.apache.sshd.common.future.DefaultSshFuture.await0(DefaultSshFuture.java:69)?)
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