** Description changed:
[Impact]
Ruby processes can sometimes get stuck in a loop consuming 100% CPU, as
described upstream and in the debian bug report. It has most commonly
been seen in the puppet agent.
[Test Case]
It's not easy to reproduce. It has been suggested that this script eventually
reproduces the problem:
while nice -n19 /opt/puppetlabs/puppet/bin/ruby sched_yield_loop.rb; do
:; done
Where sched_yield_loop.rb comes from "https://bugs.debian.org/cgi-
bin/bugreport.cgi?att=1;bug=876377;filename=sched_yield_loop.rb;msg=22"
I personally haven't seen it happen with the script, but maybe it could
take days.
[Regression Potential]
Races with threads can be hard to reproduce, and so can regressions.
Patch has been applied upstream and to debian for more than a year now.
[Other Info]
- Not at this time.
+ Bionic has ruby 2.5.1 and it has this fix already, as do all later ubuntu
releaes.
[Original Description]
Ubuntu 16.04
ruby 2.3.1-2~16.04.12
kernel 4.4.0-148-generic
We've noticed an issue across multiple servers where puppet agent will
seem to get stuck and consume 100% CPU for days or weeks on end until
manually killed.
root@ps-prod-jenkins-qa-ui02:~# ps aux|grep -i puppe[t]
root 1412 0.0 0.2 143716 38680 ?Ssl Jun11 0:39
/usr/bin/ruby /usr/bin/puppet agent
root 34884 74.4 0.3 286848 53724 ?Rs Jun23 1141:44 puppet
agent: applying configuration
root 111481 94.1 0.3 288572 54996 ?Rs Jun18 8642:32 puppet
agent: applying configuration
root 128479 54.8 0.3 286744 53596 ?Rs 10:30 250:17 puppet
agent: applying configuration
Strace shows it in a sched_yield() loop:
root@ps-prod-jenkins-qa-ui02:~# strace -p 34884 -c
strace: Process 34884 attached
^Cstrace: Process 34884 detached
% time seconds usecs/call callserrors syscall
-- --- --- - -
100.000.002130 0123189 sched_yield
-- --- --- - -
100.000.002130123189 total
Some googling shows this is a common issue which was supposedly
fixed/backported to ruby 2.3:
https://tickets.puppetlabs.com/browse/PA-1743
https://bugs.ruby-lang.org/issues/13794
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=876377
The following open Ubuntu bugs look to be having the same issue and
suggest that this fix made it into Debian but never made it into Ubuntu:
https://bugs.launchpad.net/ubuntu/+source/pcs/+bug/1783161
https://bugs.launchpad.net/ubuntu/+source/pcs/+bug/1772998
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https://bugs.launchpad.net/bugs/1834072
Title:
Puppet agent using 100% CPU, in sched_yield() loop. Looks like an
issue with ruby2.3 which has been fixed but not yet made it into
Ubuntu.
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