Pavel Pohner created SSHD-1173:
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Summary: 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
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([email protected]/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([email protected]/InputStream.java:705) at
com.mono.mina.command.Put.replyInto(Put.java:55) at
com.mono.sftpserver.MinaSftpHandler.channelReadInternal(MinaSftpHandler.java:251)
at
com.mono.sftpserver.MinaSftpHandler.lambda$channelRead$0(MinaSftpHandler.java:125)
at
com.mono.sftpserver.MinaSftpHandler$$Lambda$392/0x0000000800764040.run(Unknown
Source) at
java.util.concurrent.Executors$RunnableAdapter.call([email protected]/Executors.java:515)
at java.util.concurrent.FutureTask.run([email protected]/FutureTask.java:264)
at
java.util.concurrent.ThreadPoolExecutor.runWorker([email protected]/ThreadPoolExecutor.java:1128)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run([email protected]/ThreadPoolExecutor.java:628)
at java.lang.Thread.run([email protected]/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 confirugable 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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