Colvin Cowie created SOLR-15558:
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Summary: Solr stop doesn't handle zombie processes
Key: SOLR-15558
URL: https://issues.apache.org/jira/browse/SOLR-15558
Project: Solr
Issue Type: Bug
Security Level: Public (Default Security Level. Issues are Public)
Reporter: Colvin Cowie
When calling solr stop on linux, this command is used
_CHECK_PID=`ps auxww | awk '\{print $2}' | grep -w $SOLR_PID | sort -r | tr -d
' '`_
[https://github.com/apache/solr/blob/122c88a0748769432ef62cc3fb94c2226dd67aa7/solr/bin/solr#L871]
If Solr has stopped but remains as a zombie process then its process entry will
remain in the table, so _ps auxww_ will continue to show the PID even after
kill -9. So that results in something like this, with 3 minutes wasted waiting
for a dead process to exit.
_[2021-07-21T09:15:12.365Z] Sending stop command to Solr running on port 8983
... waiting up to 180 seconds to allow Jetty process 12622 to stop gracefully._
_[2021-07-21T09:18:13.551Z] [|] Solr process 12622 is still running; jstacking
it now._
_[2021-07-21T09:18:21.806Z] 12622: Unable to open socket file
/proc/12622/root/tmp/.java_pid12622: target process 12622 doesn't respond
within 10500ms or HotSpot VM not loaded_
_[2021-07-21T09:18:21.806Z] Solr process 12622 is still running; forcefully
killing it now._
_[2021-07-21T09:18:21.806Z] Killed process 12622_
_[2021-07-21T09:18:31.678Z] ERROR: Failed to kill previous Solr Java process
12622 ... script fails._
But the output of ps auxww does identify Zombie processes under STAT:
_USER PID %CPU %MEM VSZ RSS TTY *STAT* START TIME COMMAND_
_root 12622 1.4 0.0 0 0 pts/1 *Z*
10:42 0:26 [java] *<defunct>* _
So the CHECK_PID could filter out Zombies.
Obviously the bigger issue is why the process has ended up as a Zombie (in this
case it was because of
[https://blog.phusion.nl/2015/01/20/docker-and-the-pid-1-zombie-reaping-problem/]
and not specifying "--init" when running Solr inside a docker container) so
maybe a message warning that the process is a zombie is worth having, so that
the user has an opportunity to do something about it.
Note from [~mdrob]
{quote}That seems like a reasonable check to add, the only caution I would
advise
is that a lot of developers use macs for local testing so make sure that
whatever flags you invoke are generally cross platform compatible, or
hidden behind appropriate conditions.{quote}
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