[docker-syncd] Add timeout to force stop syncd container

[yozhao101]

Signed-off-by: Yong Zhao yozhao@microsoft.com

- Why I did it
When I tested auto-restart feature of swss container by manually killing one of critical processes
in it, swss will be stopped. Then syncd container as the peer container should also be
stopped as expected. However, I found sometimes syncd container can be stopped, sometimes
it can not be stopped. The reason why syncd container can not be stopped is the process
(/usr/local/bin/syncd.sh stop) to execute the stop() function will be stuck between the lines 164 –
167. Systemd will wait for 90 seconds and then kill this process.

164 # wait until syncd quit gracefully
165 while docker top syncd$DEV | grep -q /usr/bin/syncd; do
166 sleep 0.1
167 done

The first thing I did is to profile how long this while loop will spin if syncd container can be
normally stopped after swss container is stopped. The result is 5 seconds or 6 seconds. If syncd
container can be normally stopped, two messages will be written into syslog:

str-a7050-acs-3 NOTICE syncd#dsserve: child /usr/bin/syncd exited status: 134
str-a7050-acs-3 INFO syncd#supervisord: syncd [5] child /usr/bin/syncd exited status: 134

The second thing I did was to add a timer in the condition of while loop to ensure this while loop
will be forced to exit after 20 seconds:

After that, the testing result is that syncd container can be normally stopped if swss is stopped
first. One more thing I want to mention is that if syncd container is stopped during 5 seconds or 6
second, then the two log messages can be still seen in syslog. However, if the execution time of
while loop is longer than 20 seconds and is forced to exit, although syncd container can be
stopped, I did not see these two messages in syslog. Further, although I observed the auto-restart
feature of swss container can work correctly right now, I can not make sure the issue which syncd
container can not stopped will occur in future.

- How I did it
I added a timer around the while loop in stop() function. This while loop will exit after spinning
20 seconds.

- How to verify it

[lguohan]

retest mellanox please

[yxieca]

bash has a buildin variable ${SECONDS} for up seconds. You can use that instead.

[yozhao101]

Great suggestion! Updated.

[qiluo-msft]

Did you try timeout wait pgrep?

[yozhao101]

I tried this method. Actually pgrep command needs process name or partial process name as its argument. We are unable to use pgrep /usr/bin/syncd from host point of view since /usr/bin/syncd is the execution path in the syncd container.

[jleveque]

Retest vsimage please

[yxieca]

why not move this line to the top of the wile loop and remove line 169?

[yozhao101]

Do you mean we should modify the code like this?
start_in_secs=${SECONDS}
end_in_secs=${SECONDS}
timer_threshold=20
while docker top syncd$DEV | grep -q /usr/bin/syncd \ && [[ $((end_in_secs - start_in_secs)) -le $timer_threshold ]]; do
sleep 0.1

[lguohan]

why 20 seconds? what is the rationale?

[yozhao101]

This threshold 20 seconds is what we discussed in our weekly meeting. In the meeting, we decided to set the timer to be 20 seconds and wait for enough long time such that syncd process has a chance to exit.

[lguohan]

there must be some rationale to set it to 20 seconds, why not 10 seconds? can you explain it?

[yozhao101]

Actually when I tested the auto-restart feature of swss container, syncd container sometimes can be normally stopped and sometimes can not be stopped. The first thing I did is to profile how long this while loop will spin if syncd container can be normally stopped after swss container is stopped. The result is 5 seconds or 6 seconds. After that, in our meeting, we talked about to set a 20 seconds timer for this while loop before forcing syncd to exit. Please review the section of "Why I did it" of this PR for more details.

Sure, I can also try to set a 10 seconds timer to check whether it works or not.

[lguohan]

retest vsimage please

[lguohan]

retest vsimage please