Process Management – Ensure a Process is Always Running

fastcgimonitoringprocess-management

I started hosting sites a while back using Cherokee. For external sources (FastCGI, etc) it has an option to launch the process if it can't find one running on the designated socket or port. This is great because it means if PHP or a Django site falls over (as they occasionally do) it restarts it automatically.

On a new server using PHP-FPM I couldn't use Cherokee (it has a bug with PHP) so I've moved to NGINX. I really like NGINX (for its config style) but I'm having serious issues with processes falling over and never respawning. PHP does this sometimes but Django sites are more of a problem. I've created init scripts for them and they come up on boot but this doesn't help me if they conk out between reboots.

I guess I'm looking for a FastCGI proxy. Something that, like Cherokee, knows what processes should be running on which sockets/ports and respawns them on-demand. Does such a thing exist? Is there any way to build this into NGINX (for ease of config)?

Best Answer

How about daemontools and specifically the supervise tool

supervise monitors a service. It starts the service and restarts the service if it dies. Setting up a new service is easy: all supervise needs is a directory with a run script that runs the service.

Related Solutions

How to ensure a program is always running but without root access

I posted this on a similar question

If you have a cron daemon, one of the predefined cron time hooks is @reboot, which naturally runs when the system starts. Run crontab -e to edit your crontab file, and add a line:

@reboot /your/command/here

I'm told this isn't defined for all cron daemons, so you'll have to check to see if it works on your particular one

How to see what processes are running

From the ps man page:

-e Select all processes. Identical to -A.

Thus, ps -e will display all of the processes. The common options for "give me everything" are ps -ely or ps aux, the latter is the BSD-style. Often, people then pipe this output to grep to search for a process, as in xenoterracide's answer. In order to avoid also seeing grep itself in the output, you will often see something like:

 ps -ef | grep [f]oo

where foo is the process name you are looking for.

However, if you are looking for a particular process, I recommend using the pgrep command if it is available. I believe it is available on Ubuntu Server. Using pgrep means you avoid the race condition mentioned above. It also provides some other features that would require increasingly complicated grep trickery to replicate. The syntax is simple:

pgrep foo

where foo is the process for which you are looking. By default, it will simply output the Process ID (PID) of the process, if it finds one. See man pgrep for other output options. I found the following page very helpful:

http://mywiki.wooledge.org/ProcessManagement

Best Answer

Related Solutions

How to ensure a program is always running but without root access

How to see what processes are running

Related Question