Jonathan Hurley created AMBARI-18824:
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Summary: MOTD Can Prevent WebHCat From Shutting Down
Key: AMBARI-18824
URL: https://issues.apache.org/jira/browse/AMBARI-18824
Project: Ambari
Issue Type: Bug
Components: ambari-server
Affects Versions: 2.4.0
Reporter: Jonathan Hurley
Assignee: Jonathan Hurley
Priority: Blocker
Fix For: 2.4.2
There was code added in AMBARI-12695 (later corrected by AMBARI-18684) which
tries to kill WebHCat if it doesn't stop with its own stop command.
Both patches use the {{as_user}} function to wrap the call in a bash login:
{code}
ps -p `su hcat -l -s /bin/bash -c 'cat /var/run/webhcat/webhcat.pid'`
>/dev/null 2>&1
{code}
This, however, causes problems where there is a MOTD:
{code}
ERROR: Process ID list syntax error.
********* simple selection ********* ********* selection by list *********
-A all processes -C by command name
-N negate selection -G by real group ID (supports names)
-a all w/ tty except session leaders -U by real user ID (supports names)
-d all except session leaders -g by session OR by effective group name
-e all processes -p by process ID
-q by process ID (unsorted & quick)
T all processes on this terminal -s processes in the sessions given
a all w/ tty, including other users -t by tty
g OBSOLETE -- DO NOT USE -u by effective user ID (supports names)
r only running processes U processes for specified users
x processes w/o controlling ttys t by tty
*********** output format ********** *********** long options ***********
-o,o user-defined -f full --Group --User --pid --cols --ppid
-j,j job control s signal --group --user --sid --rows --info
-O,O preloaded -o v virtual memory --cumulative --format --deselect
-l,l long u user-oriented --sort --tty --forest --version
-F extra full X registers --heading --no-heading --context
--quick-pid
********* misc options *********
-V,V show version L list format codes f ASCII art forest
-m,m,-L,-T,H threads S children in sum -y change -l format
-M,Z security data c true command name -c scheduling class
-w,w wide output n numeric WCHAN,UID -H process hierarchy
{code}
That's not good - why is it giving us back a bad command syntax? Here's the
reason:
{code}
[root@ijzs-c229todgsecha-r6-re1-3 ~]# su hcat -l -s /bin/bash -c 'cat
/var/run/webhcat/webhcat.pid'
This is MOTD message :)
25672
{code}
*The MOTD is messing up the output from commands for the {{hcat}} user. Because
we rely on the error code of {{ps}}, the same non-zero code is used for a bad
command and a missing process ID*.
Since the PID is world-readable, we don't need to run the {{only_if}} checks as
a separate user.
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