On my last article where I tried to give an introduction and basic usage of supervisord process monitoring, I figured that there are two missing features there which someone should know about/aware of. Which are, interacting with supervisord web interface and using a plugin with supervisord.
So, today, In this small article, I will try to cover these two to make your supervisord experience more easier/better. Lets start with the built-in web interface.
Supervisord Web Interface:
To access the basic web interface, edit the supervisord configuration file(located at /etc/supervisord.conf) in the following section:
[inet_http_server] ; inet (TCP) server disabled by default port=127.0.0.1:9001 ; (ip_address:port specifier, *:port for all iface) ;username=user ; (default is no username (open server)) ;password=123 ; (default is no password (open server))
You just have to comment out the first two-line to get it working. After that, run the supervisord in no daemon mode(with -n param) and you should be able to see something like below in the console log:
2014-07-08 05:25:40,558 CRIT Server 'inet_http_server' running without any HTTP authentication checking
Which means that, it started properly. Now, test the web interface at http://127.0.0.1:9001 url, which will look like something like below:
As you can see on the screenshot, you can start/stop/restart, see status, log etc right from your browser. Pretty cool! Isn’t it?
Third Party Web Interface:
There are some available third-party web interfaces available which might be helpful to integrate on a web application. You can find details about them on supervisod third-party libraries page. Besides easy integration with a web application, some of them also facilitate monitoring more than one server from single web interface, which is useful in many cases.
To use a plugin for additional functionality to our existing supervisord installation, it can be easily configurable via the same configuraiton file.
A very useful such package is superlance. It is a plugin that includes few very useful plugins for supervisord. I will show you one example configuration here for the ‘memmon’ plugin here. ‘Memmon’ is a plugin that monitors the memory used by the processes and can restart the processes as soon as they go beyond the given boundary size.
After having superlance on system, edit the configuraiton file as below for the memmon plugin:
[eventlistener:memmon] command=memmon -p my-bg-tasks=170MB -m firstname.lastname@example.org events=TICK_60
The above configuration will cause momemon to monitor memory usage over 170MB and restart if goes beyond that. It also attaches an event to send signal every 60 seconds. Now, if the configuration is OK, after start the supervisord again, with no daemon mode(with -n param), you should see something similar to the following line on std log:
2014-07-08 05:25:41,564 INFO spawned: 'memmon' with pid 1600
To test this, try to keep the memory allowance low and feed your worker process with large data, you should eventually see that, the worker restarted with separate process id.
So, I hope this article will be helpful to you in some extent. You are most welcome to question/ provide feedback/suggestions via comments. Keep in touch!