Attila Kanto created KNOX-864:
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Summary: Knox init scripts are not Upstart compatible
Key: KNOX-864
URL: https://issues.apache.org/jira/browse/KNOX-864
Project: Apache Knox
Issue Type: Improvement
Components: Server
Affects Versions: 0.11.0
Reporter: Attila Kanto
It is critical that we have a service that can auto-restart during crashes and
reboots. On Amazon Linux this tasks are done by Upstart.
By default Upstart will track the life cycle of the first PID that it executes
in the exec or script stanzas (defined in the Upstart config file), however,
most Unix services will "daemonize", meaning that they will create a new
process (using fork(2)) which is a child of the initial process. This is what
also happens when when gateway.sh or ldap.sh is invoked.
In order to track the right PID, Upstart must determine the final process ID
for a job, and in case of daemonized processes it needs to know how many times
that process will call fork(2).
Upstart supports the followings:
* *expect fork*: Upstart will expect the process executed to call fork(2)
exactly once.
* *expect daemon*: Upstart will expect the process executed to call fork(2)
exactly twice
Unfortunately none of the above cases fits to gateway.sh and ldap.sh, since
they are calling fork many times and Upstart always tracks the wrong PID.
According to Upstart doc
http://upstart.ubuntu.com/cookbook/#how-to-establish-fork-count if the
application you are attempting to create a Job Configuration File does not
document how many times it forks, you can run it with a tool such as strace(1)
which will allow you to count the number of forks:
{code}
[root@ip-10-0-4-107 ~]# strace -o /tmp/strace.log -fFv su -c
"/usr/hdp/current/knox-server/bin/gateway.sh start" knox
Starting Gateway succeeded with PID 25528.
[root@ip-10-0-4-107 ~]# sudo egrep "\<(fork|clone)\>\(" /tmp/strace.log | wc |
awk '{print $1}'
86
{code}
Ambari had similar issues in the past:
https://issues.apache.org/jira/browse/AMBARI-14842
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