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https://issues.apache.org/jira/browse/SSHD-152?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13280981#comment-13280981
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Gunnar Wagenknecht edited comment on SSHD-152 at 5/22/12 2:17 PM:
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{quote}
Honestly, if the use case is that the sshd log is forwarded through an ssh
channel, I don't really see how we can get rid of those issue easily.
{quote}
Frankly, that wasn't the use case. Logback is configured to log to
System.out.But for some reason some other component (Karaf?) switched
System.out to the sshd channel.
{quote}
Ideas welcomed though.
{quote}
I think the safest option would be that sshd somehow is able to detect that
logging is indirectly wired to the same ChannelOutputStream and then skip all
logging events in such a case. But I'm afraid that none is possible in a clean
way without sshd knowing details about the environment (Karaf + Logback).
was (Author: gunnar):
{quote}
Honestly, if the use case is that the sshd log is forwarded through an ssh
channel, I don't really see how we can get rid of those issue easily.
{quote}
Frankly, that wasn't the use case. Logback is configured to log to
System.out.But for some reason some other component (Karaf?) switched
System.out to the sshd channel.
> Logging may cause deadlock.
> ---------------------------
>
> Key: SSHD-152
> URL: https://issues.apache.org/jira/browse/SSHD-152
> Project: MINA SSHD
> Issue Type: Bug
> Affects Versions: 0.5.0
> Reporter: Gunnar Wagenknecht
> Assignee: Guillaume Nodet
>
> I'm not really sure what I did but I think I somehow managed to deadlock my
> system using SSHD in combination with Logback console appender.
> Thread 1
> {noformat}
> Thread [Thread-21] (Suspended)
> owns: ChannelOutputStream (id=481)
> owns: ConsoleOutputStream (id=482)
> owns: PrintStream (id=483)
> owns: Object (id=202)
> waited by: Thread [...] (Suspended)
> waited by: Thread [...] (Suspended)
> waited by: Thread [...] (Suspended)
> waited by: Thread [NioProcessor-2] (Suspended)
> waited by: Thread [...] (Suspended)
> waited by: Thread [...] (Suspended)
> waited by: Thread [...] (Suspended)
> waited by: Thread [...] (Suspended)
> waited by: Thread [...] (Suspended)
> waited by: Thread [...] (Suspended)
> owns: OutputStreamWriter (id=484)
> waiting for: Window (id=485)
> Object.wait(long) line: not available [native method]
> Window(Object).wait() line: 503
> Window.waitForSpace() line: 146
> ChannelOutputStream.flush() line: 104
> ConsoleOutputStream.flush() line: 97
> ConsoleOutputStream.write(int) line: 83
> ConsoleOutputStream(OutputStream).write(byte[], int, int) line: 116
> PrintStream.write(byte[], int, int) line: 480
> PrintStream(FilterOutputStream).write(byte[]) line: 97
> ThreadPrintStream.write(byte[]) line: 245
> ConsoleTarget$1.write(byte[]) line: 36
> PatternLayoutEncoder(LayoutWrappingEncoder<E>).doEncode(E) line: 103
> ConsoleAppender<E>(OutputStreamAppender<E>).writeOut(E) line: 193
> ConsoleAppender<E>(OutputStreamAppender<E>).subAppend(E) line: 217
> ConsoleAppender<E>(OutputStreamAppender<E>).append(E) line: 108
> ConsoleAppender<E>(UnsynchronizedAppenderBase<E>).doAppend(E) line: 88
> AppenderAttachableImpl<E>.appendLoopOnAppenders(E) line: 64
> Logger.appendLoopOnAppenders(ILoggingEvent) line: 285
> Logger.callAppenders(ILoggingEvent) line: 272
> Logger.buildLoggingEventAndAppend(String, Marker, Level, String,
> Object[], Throwable) line: 473
> Logger.filterAndLog_2(String, Marker, Level, String, Object, Object,
> Throwable) line: 464
> Logger.debug(String, Object, Object) line: 542
> ChannelOutputStream.flush() line: 119
> ...
> {noformat}
> Thread 2
> {noformat}
> Thread [NioProcessor-2] (Suspended)
> owns: Object (id=150)
> waiting for: Object (id=202)
> owned by: Thread [Thread-21] (Suspended)
> waiting for: Window (id=485)
> ConsoleAppender<E>(OutputStreamAppender<E>).subAppend(E) line: 217
> ConsoleAppender<E>(OutputStreamAppender<E>).append(E) line: 108
> ConsoleAppender<E>(UnsynchronizedAppenderBase<E>).doAppend(E) line: 88
> AppenderAttachableImpl<E>.appendLoopOnAppenders(E) line: 64
> Logger.appendLoopOnAppenders(ILoggingEvent) line: 285
> Logger.callAppenders(ILoggingEvent) line: 272
> Logger.buildLoggingEventAndAppend(String, Marker, Level, String,
> Object[], Throwable) line: 473
> Logger.filterAndLog_1(String, Marker, Level, String, Object, Throwable)
> line: 445
> Logger.debug(String, Object) line: 538
> ServerSession.handleMessage(Buffer) line: 119
> ...
> {noformat}
> I think that one thread is waiting for Window to expand. The SSHD logger has
> a console appender. Unfortunately, the wait happends within a write by
> console appender. Thus all other threads that also log to the console will
> block because they wait for the Logback console appender lock.
> I think that a Logback console appender should not write to the SSHD console
> by default. Can this be disabled somehow?
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