![]() Pidfile /var/vcap/sys/run/redis/redis.pid And that configuration file can specify to run redis-server in daemonized mode and the pidfile location: daemonize yes ![]() You can provide this command with a configuration file path. Many applications will allow you to run them in "daemonized" mode and to specify the path to the pidfile.įor example, to run the Redis key-value store you run the redis-server command. The best way to create a pidfile is to delegate it to the process you are running. This file is called a PID file or pidfile. Monit expects that after gorouter_ctl start completes there will be a file created /var/vcap/sys/run/gorouter/gorouter.pid that contains the process ID of the running process. In the monit example above, we tell monit how to find the expected process ID: check process gorouter It does this by watching process IDs, aka PIDs.Įach process that runs on Linux has a process ID. In addition to taking instruction from BOSH about starting/stopping processes, Monit wants to be able to detect when a process has died and restart it. Your wrapper script must setup all environment variables.Īdditionally, for security it is a good idea to change from root user to another user to run processes. The start/stop commands are run as the root user and they start with a very very minimal environment.Īssume that $PATH and all other common environment variables are blank or do not contain the contents you expect. So we know that the gorouter_ctl script will ALWAYS be available at /var/vcap/jobs/gorouter/bin/gorouter_ctl, which is why we can put this hardcoded full path in the monit file: check process gorouter I find the flat templates of Pivotal’s BOSH releases to be harder to comprehend at a glance (e.g. That is, I would move templates/gorouter_ctl.erb into templates/bin/gorouter_ctl.erb. Personally, in all my BOSH releases I prefer to keep the same structure within the templates/ folder as it will be in production. Why does templates/gorouter_ctl.erb become bin/gorouter_ctl? Because the job template’s spec file said so. When the job template is deployed, it will be available at: /var/vcap/jobs/gorouter/bin/gorouter_ctl. The job template gorouter_ctl.erb file is located within the BOSH release at jobs/gorouter/templates/gorouter_ctl.erb. Quick recap of the relationship between BOSH job templates and the resulting files on a BOSH job instance: The start section of the real script does a lot more setup prior to running the /var/vcap/packages/gorouter/bin/gorouter command ( source. The allow the start and stop argument it includes a case statement and the pseudo code for starting/stop the gorouter process is: case $1 in In the example above, gorouter_ctl is an executable shell script ( source). It is common in BOSH job templates to use a single monit wrapper script for both start and stop instructions. That is, this monit file assumes there is a single gorouter_ctl script that can be run with either start or stop as the first command-line argument.Īlternately, two scripts could have been written and the monit file could have used them. When monit is told to stop processes it is configured above to again run the gorouter_ctl script, but with the argument stop. If monit ever detects that the process has stopped running, then it will again run gorouter_ctl start to restart the process. When monit is told to start all processes, monit will run the gorouter_ctl script with the argument start. Removing the file paths & timeout to make it easier to read: check process gorouter Stop program "/var/vcap/jobs/gorouter/bin/gorouter_ctl stop" Start program "/var/vcap/jobs/gorouter/bin/gorouter_ctl start" With pidfile /var/vcap/sys/run/gorouter/gorouter.pid Here is the monit file for running the gorouter in cf-release ( source). The most common syntax used by BOSH job templates is to start/stop a process. (Thanks Abhi for the first example!) Basic example This text will be removed by BOSH because of the "if" statement above. One way to "comment out" the contents of a monit file is to use ERb templating. ![]() To do nothing, make your monit file empty. So can a BOSH job template, via monit, do absolutely nothing? Yes.Ĭopy and paste the following into your job template’s monit file and when you deploy it it will do nothing. ![]() ![]() And BOSH releases must have a monit file. So to write BOSH releases you need to learn some monit syntax and to write monit wrapper scripts. On each running BOSH job server, BOSH delegates to the monit daemon to use these monit files to start/stop processes. When you are writing a BOSH release, each job template (the folders within the jobs/ folder of a release) contains a single monit file. There are some interesting basics and interesting top tips for using monit with BOSH. Writing your own BOSH release/configuration management is relatively simple – you get monit, and monit is relatively simple. ![]()
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