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<div>Hi!</div>
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<div>Finally, I found the cause ...</div>
<div>It seems, that the option "Use SSH port forwarding to tunnel sound systems connections through firewalls" under Session precerences/Media/Sound is responsible for the many sockets in CLOSE_WAIT state. I checked it several times, and if the option is not activated, then there are no sockets in CLOSE_WAIT state. I don't know why, and since I don't need this options I am not going to dig deeper.</div>
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<div>Cheers</div>
<div>Swizzly</div>
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<div style="margin: 0px 0px 10px;"><b>Gesendet:</b> Donnerstag, 30. April 2015 um 11:00 Uhr<br/>
<b>Von:</b> "swizz ly" <swizz.ly@gmx.ch><br/>
<b>An:</b> "x2go-user@lists.x2go.org" <x2go-user@lists.x2go.org><br/>
<b>Betreff:</b> [X2Go-User] sshd CLOSE_WAIT problem</div>
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<div>Hi!</div>
<div> </div>
<div>It happens time to time on our x2go server, that the CPU usage goes almost 100% on a single CPU. The high usage is caused by the sshd process which runs the <username>@notty, in PS it looks like this:</div>
<div><span style="font-family: courier new , courier , monospace;">root 32768 25441 7 Apr28 ? 03:14:44 sshd: myuser<a href="orm@notty" target="_parent">@notty</a></span></div>
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<div>An strace of the process shows that the number of open files reached the predefined limit:</div>
<div><span style="font-family: courier new , courier , monospace;">...<br/>
accept(7, 0x7fff6d2bccb0, [128]) = -1 EMFILE (Too many open files)<br/>
socket(PF_FILE, SOCK_DGRAM|SOCK_CLOEXEC, 0) = -1 EMFILE (Too many open files)<br/>
select(4096, [3 5 7 8 9], [], NULL, NULL) = 1 (in [7])<br/>
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0<br/>
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0<br/>
...</span><br/>
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<div>Increasing the limit "nofile" solves the high CPU problem only temporarily, as the number of open files increases with the time monotonously (at a rate of ~1/20 sec).</div>
<div>Checking the files opened by the given process shows, the following</div>
<div><span style="font-family: courier new , courier , monospace;">...</span></div>
<div><span style="font-family: courier new , courier , monospace;">sshd 32768 root 8499u IPv4 1542181459 0t0 TCP loopback:30028->loopback:51585 (CLOSE_WAIT)<br/>
...</span></div>
<div>The number of such CLOSE_WAIT entries is several thousands.</div>
<div>Netstat shows a similar view:</div>
<div><span style="font-family: courier new , courier , monospace;">...</span></div>
<div><span style="font-family: courier new , courier , monospace;">tcp 0 0 127.0.0.1:30028 127.0.0.1:38163 CLOSE_WAIT 32768/sshd</span></div>
<div><span style="font-family: courier new , courier , monospace;">...</span></div>
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<div>After increasing the limit of open files I logged the strace of the process during a period when the number of CLOSE_WAIT connections increases (see attached file).</div>
<div>The user is doing nothing, he is just logged in with x2go, but doesn't run any active processes, he doesn't even use the server.</div>
<div>Has anyone experienced the same problem or has any explanation for this behaviour?</div>
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<div>Regards</div>
<div>Swizzly</div>
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