- Why I did it
Initially, we used Monit to monitor critical processes in each container. If one of critical processes was not running
or crashed due to some reasons, then Monit will write an alerting message into syslog periodically. If we add a new process
in a container, the corresponding Monti configuration file will also need to update. It is a little hard for maintenance.
Currently we employed event listener of Supervisod to do this monitoring. Since processes in each container are managed by
Supervisord, we can only focus on the logic of monitoring.
- How I did it
We borrowed the event listener of Supervisord to monitor critical processes in containers. The event listener will take
following steps if it was notified one of critical processes exited unexpectedly:
The event listener will first check whether the auto-restart mechanism was enabled for this container or not. If auto-restart mechanism was enabled, event listener will kill the Supervisord process, which should cause the container to exit and subsequently get restarted.
If auto-restart mechanism was not enabled for this contianer, the event listener will enter a loop which will first sleep 1 minute and then check whether the process is running. If yes, the event listener exits. If no, an alerting message will be written into syslog.
- How to verify it
First, we need checked whether the auto-restart mechanism of a container was enabled or not by running the command show feature status. If enabled, one critical process should be selected and killed manually, then we need check whether the container will be restarted or not.
Second, we can disable the auto-restart mechanism if it was enabled at step 1 by running the commnad sudo config feature autorestart <container_name> disabled. Then one critical process should be selected and killed. After that, we will see the alerting message which will appear in the syslog every 1 minute.
- Which release branch to backport (provide reason below if selected)
201811
201911
[x ] 202006
Some syncd containers are still based on Debian Stretch, and thus do not have Python 3 available. For these containers, we must still rely on Python 2 to run supervisord_dependent_startup and supervisor-proc-exit-listener.
**- Why I did it**
We were building a custom version of Supervisor because I had added patches to prevent hangs and crashes if the system clock ever rolled backward. Those changes were merged into the upstream Supervisor repo as of version 3.4.0 (http://supervisord.org/changes.html#id9), therefore, we should be able to simply install the vanilla package via pip. This will also allow us to easily move to Python 3, as Python 3 support was added in version 4.0.0.
**- How I did it**
- Remove Makefiles and patches for building supervisor package from source
- Install Python 3 supervisor package version 4.2.1 in Buster base container
- Also install Python 3 version of supervisord-dependent-startup in Buster base container
- Debian package installed binary in `/usr/bin/`, but pip package installs in `/usr/local/bin/`, so rather than update all absolute paths, I changed all references to simply call `supervisord` and let the system PATH find the executable to prevent future need for changes just in case we ever need to switch back to build a Debian package, then we won't need to modify these again.
- Install Python 2 supervisor package >= 3.4.0 in Stretch and Jessie base containers
Add the same mechanism I developed for the SwSS service in #2845 to the syncd service. However, in order to cause the SwSS service to also exit and restart in this situation, I developed a docker-wait-any program which the SwSS service uses to wait for either the swss or syncd containers to exit.
- This PR allows supervisord to log syncd exit events to syslog
- Syncd dockers now are built from docker-config-engine instead of docker-base
- Supervisord in all syncd dockers now call syncd_start.s which is installed by sonic-sairedis repo
- Consolidate config.sh and start.sh scripts into one script (start.sh)
- Solve issue #435 - All dockers now run supervisord as their ENTRYPOINT
- All stdout/stderr output from processes managed by supervisord is now sent to syslog instead of their own files
- Supervisord log messages are now also sent to syslog
- Removed unused smartmontools package from docker-platform-monitor
