Linux – How to find the .pid file for a given process

linuxmonitmonitoringpid

I'm setting up monit and want to monitor a given python application. Monit does this by looking at the .pid files for processes, but I don't know where this would be.

I also tried creating my own simple executable and running it- here too I can't figure out where the .pid file is created.

And do all processes have a .pid file?

Best Answer

You'll usually find the PID files for daemonized processes in /var/run/ on Redhat/CentOS-style systems.

Short of that, you can always look in the process init script. For instance, the SSH daemon is started with the script in /etc/init.d/sshd. Sometimes the PID will be defined there (search for pid, PID, PIDFILE, PID_FILE, etc.).

However, most other daemons on RHEL-style systems source the /etc/init.d/functions script for some common features.

# Set $pid to pids from /var/run* for {program}.  $pid should be declared
# local in the caller.
# Returns LSB exit code for the 'status' action.
__pids_var_run() {
        local base=${1##*/}
        local pid_file=${2:-/var/run/$base.pid}

For anything that sources /etc/init.d/functions, the PID will live in /var/run/*.pid.

For custom applications, the PID will be defined in a wrapper script (hopefully). Most developers I know follow the same convention as the daemons above, though.

If you do encounter something without a PID file, remember that Monit can monitor on a process string patern as well.

Related Solutions

Monitoring thin with monit

dunno if you solved this already yet I will reply anyway. =)

The way you do it theres a few things off.

First of all you want to monitor a "cluster" so you need to monitor each node respectively.

Secondly you need to restart the respective thin node, not in /etc/init.d.

it would look something like:

check process thin-81 with pidfile /yourapphere/tmp/pids/thin.81.pid
        start program = "/usr/bin/thin -d -e production  start -p 81"
        stop program = "/usr/bin/thin stop -Ptmp/pids/thin.81.pid"

        if 3 restarts within 5 cycles then timeout
        if totalmem is greater than 150.0 MB for 2 cycles then restart
        if cpu is greater than 80% for 2 cycles then restart
        if failed port 81 protocol http with timeout 30 seconds for 2 cycles then restart
        group thin

check process thin-82 with pidfile /yourapphere/tmp/pids/thin.82.pid
        start program = "/usr/bin/thin start -d -e production -p 82"
        stop program = "/usr/bin/thin stop -Ptmp/pids/thin.82.pid"

        if 3 restarts within 5 cycles then timeout
        if totalmem is greater than 150.0 MB for 2 cycles then restart
        if cpu is greater than 80% for 2 cycles then restart
        if failed port 82 protocol http with timeout 30 seconds for 2 cycles then restart
        group thin

something along those lines depending how you set up your thin "cluster"

Monit: check process without pidfile

In monit, you can use a matching string for processes that do not have a PID. Using the example of a process named "myprocessname",

check process myprocessname
        matching "myprocessname"
        start program = "/etc/init.d/myproccessname start"
        stop program = "/usr/bin/killall myprocessname"
        if cpu usage > 95% for 10 cycles then restart

Maybe if you check to see if CPU load is at a certain level for 10 monitoring cycles (of 30-seconds each), then restart or kill, that could be an option. Or you could use monit's timestamp testing on a file related to the process.

Best Answer

Related Solutions

Monitoring thin with monit

Monit: check process without pidfile

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