custody-probe

custody-probe

supervisorctl status reports the state of each process controlled by Supervisor: running, stopped, fatally crashed. However it does not display the state of subprocesses. This becomes a problem when using Supervisor for local development of microservices, where the processes launched by Supervisor are not the servers themselves but rather build processes, which in turn launch the servers. The process tree might look something like this:

supervisord
  - gulp (using gulp-nodemon)
    - node

If node crashes, gulp will remain healthy, and so supervisorctl status will fool you into thinking that all services are running when they're not.

If you're using custody as a front-end to Supervisor, you can fix this by adding a single line of code to your webserver:

require('custody-probe')('app');

Now if the "app" webserver crashes, custody will report "app" in state "FATAL" and will only switch back to "RUNNING" when the webserver comes back up.

Installation

npm install --dev custody-probe

Usage

if (process.env.NODE_ENV === 'development') {
  require('custody-probe')('NAME_OF_PROGRAM');
}

If you've installed this as a dev dependency (recommended) you'll need to restrict it to running in your development environment, as shown using process.env.NODE_ENV.

The argument to custody-probe is the name of the Supervisor program to which this Node process belongs. Find the name of the program in your supervisord.conf file like [program:NAME_OF_PROGRAM].

(The program name is usually what's shown in the name column of supervisorctl status and custody, too, except if you have associated the program with a Supervisor group, in which case the column will read NAME_OF_GROUP:NAME_OF_PROGRAM.)

We recommend you add the probe to only 1 (one) process controlled by each program, since as of v1.0.0 custody only has support for displaying one process' state (in addition to what Supervisor reports normally). If you add the probe to more processes within the same program, the states will overwrite each other.

Configuration

By default, custody uses /usr/local/var/custody to store information and to enable probe->custody communication. You can override this directory by specifying the CUSTODY_PROC_DIR environment variable.

Contributing

We welcome bug reports and feature suggestions!