spin in serf

[jeffkaufman]

We have a report of the serf thread getting into 100% cpu usage. Symbolized backtrace:

Thread 10 (Thread 0x7f9e3bac3700 (LWP 17903)):
#0  0x00007f9e505a4b10 in serf_bucket_aggregate_prepend_iovec () from /usr/lib/apache2/modules/mod_pagespeed.so
#1  0x00007f9e505a17e0 in ssl_encrypt () from /usr/lib/apache2/modules/mod_pagespeed.so
#2  0x00007f9e5059f048 in common_databuf_prep () from /usr/lib/apache2/modules/mod_pagespeed.so
#3  0x00007f9e5059f0ac in serf_databuf_read () from /usr/lib/apache2/modules/mod_pagespeed.so
#4  0x00007f9e5059ef42 in serf_default_read_iovec () from /usr/lib/apache2/modules/mod_pagespeed.so
#5  0x00007f9e505a46c8 in read_aggregate () from /usr/lib/apache2/modules/mod_pagespeed.so
#6  0x00007f9e505a3f90 in serf__process_connection () from /usr/lib/apache2/modules/mod_pagespeed.so
#7  0x00007f9e5059ebda in serf_event_trigger () from /usr/lib/apache2/modules/mod_pagespeed.so
#8  0x00007f9e5059ed4f in serf_context_run () from /usr/lib/apache2/modules/mod_pagespeed.so
#9  0x00007f9e5059a515 in net_instaweb::SerfUrlAsyncFetcher::Poll(long) () from /usr/lib/apache2/modules/mod_pagespeed.so
#10 0x00007f9e5059ae25 in net_instaweb::SerfThreadedFetcher::SerfThreadFn(apr_thread_t*, void*) () from /usr/lib/apache2/modules/mod_pagespeed.so
#11 0x00007f9e54d26b50 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#12 0x00007f9e54a7070d in clone () from /lib/x86_64-linux-gnu/libc.so.6
#13 0x0000000000000000 in ?? ()

[jeffkaufman]

This is in a forked copy of serf's ssl_buckets.c, which is very out of date. The file has changed a lot, and this section has a lot of extra checks. I suspect this bug is fixed upstream.

We've been meaning to update our copy of serf for a while. I'll do it now.

[jeffkaufman]

Targeting this for the initial 1.10 beta: our copy of serf is heavily modified, enough that this is too complex a change for a 1.9 point release.

[jeffkaufman]

This is very likely fixed with the upgrade to the latest stable serf in 468997a

[crowell]

note that this updated serf is only in branch 33, and is not present in current stable or beta 1.9.32.x releases..

[jeffkaufman]

Yes, this fix will go out in 1.10.

We integrate very tightly with serf, so its upgrade is intrusive enough that including it in a 1.9 bugfix release would be iffy.