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SubjectAccept() problem
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<DIV><FONT face=Arial size=2>BUG: In a load balancing enviornment going through
hardware such as a<BR>server-iron, apache can be flooded with requests (this
could be due to a<BR>traffic spike) and will eventually stop responding.&nbsp;
The load balancer will<BR>then remove that server from 'active' status, because
it fails to respond to<BR>http health checks.&nbsp; In most cases, only a few of
the children ever recieve<BR>requests.&nbsp; Because of the limited children
actually responding to requests,<BR>the load-balancer will never put the server
back to 'active' status,<BR>therefor leaving the server down, until its children
are killed (killing the<BR>parent, and restarting apache.&nbsp; a -HUP WILL NOT
WORK!).<BR><BR>Info:&nbsp; This is NOT, and I stress, is NOT an apache
bug!&nbsp; All children are<BR>healthy, and are either locked, waiting to become
the next child with<BR>accept(15, or the one is on accept(15&nbsp; (If you have
it setup to use the<BR>serialized accept) or there is the trampling herd if
not.&nbsp; Either way, it is<BR>affected.&nbsp; The bug, appears to be with the
kernel.&nbsp; We have been able to<BR>make this problem occur on kernel 2.2.9
and 2.2.12. 2.2.13, and 2.2.14pre6.&nbsp; </FONT></DIV>
<DIV><FONT face=Arial size=2>We believe the bug is in the (buggy) wake-one code
that was beggining to be </FONT></DIV>
<DIV><FONT face=Arial size=2>included in kernel 2.2.8 or so (however, this is
just speculation, I'll leave it up </FONT></DIV>
<DIV><FONT face=Arial size=2>to the guru's to tackle this one. :) ).&nbsp; We
have been UNABLE to reproduce this </FONT></DIV>
<DIV><FONT face=Arial size=2>failure on the latest development kernel
2.3.28.<BR></FONT></DIV>
<DIV><FONT face=Arial size=2>This is a difficult to reproduce bug, however,
given a<BR>load-balancing setup, it is very obvious, because of the certain
conditions<BR>met.&nbsp; (requests MUST stop going to the affected server,
otherwise children<BR>will respawn, and act normally.)&nbsp;&nbsp; Single server
users will notice a<BR>'slowdown' period, that lasts anywhere from 30 seconds to
a few minutes,<BR>while the system kicks back into gear.<BR><BR>I am not sure if
I'm properly subscribed to this list, so please CC <A
href="mailto:admin@ztnet.com">admin@ztnet.com</A> with any responses.&nbsp;
Thanks.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>Zach<BR></DIV></FONT></BODY></HTML>
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