How do I read a pid file in cfengine?

Question

How do I read a pid file in cfengine 3 and restart that process if it isn't running?

Answer 1

In cfengine 2, I used something like:

processes:
  "httpd" restart "/etc/init.d/apache restart"

In cfengine 3, restarting of processes must be coded as a separate commands.

processes:
   "httpd"
     restart_class => "start_httpd";

commands:
  start_httpd::
    "/etc/init.d/apache restart";

This will define the class "start_httpd" if httpd is not running. Then will run the init script to make sure it starts. See the cf3 reference manual for a deeper explanation of how the restart_class works.

Answer 2

Instead of looking at the PID file directly, I'd try to let Cfengine 3 manage your selected service/process. For Cfengine 3 you can use the following code (it might not be perfect, but it works):

body common control {
    version => "1.0";
    bundlesequence => { "check_services" };
}

bundle agent check_services {
    vars:
        "services" slist => { "apache2", "mysql" };
        "init_scripts_path" string => "/etc/init.d"; 

    processes:
        "$(services)"
            comment => "Check if the processes for '$(services)'",
            restart_class => "restart_$(services)";

    commands:
        "${init_scripts_path}/${services} start"
            comment => "Restarting the service",
            ifvarclass => "restart_${services}";

}

Please note that I wrote this Cfengine 3 script for an Ubuntu client, so you might have to adopt it to your needs and distribution.

You can download this code snippet here.