Worker

Workers are required to process asynchronous tasks. These must be set up and configured in the system.

The workers are set up with the help of Supervisor. Supervisor is a process control system that enables processes to be monitored and restarted if necessary.

sudo apt-get install supervisor

Every channel needs a worker of its own. A worker handles the messages of one channel only - the changes the CMS reports for www are handled by the worker of www. It knows its channel from the path bin/console is called by: /var/www/example.com/www/app/bin/console is the channel www of the host example.com, /var/www/example.com/preview/app/bin/console the channel preview. Alternatively the channel can be set with the environment variable RESOURCE_ROOT.

The workers are configured in a configuration file that is stored in /etc/supervisor/conf.d/. For www and preview, the configuration could look like this:

/etc/supervisor/conf.d/example.com-worker.conf

[program:example.com-www-worker]
command=/var/www/example.com/www/app/bin/console messenger:consume --all
user=www-data
numprocs=2
redirect_stderr=true
stdout_logfile=/path/to/log/dir/example.com-www-worker.out.log
autostart=true
autorestart=true
process_name=%(program_name)s_%(process_num)02d

[program:example.com-preview-worker]
command=/var/www/example.com/preview/app/bin/console messenger:consume --all
user=www-data
numprocs=1
redirect_stderr=true
stdout_logfile=/path/to/log/dir/example.com-preview-worker.out.log
autostart=true
autorestart=true
process_name=%(program_name)s_%(process_num)02d

The worker also handles the changes the CMS reports - see Indexing. messenger:consume --all covers them; without a running worker, published articles do not reach the search index.

See supervisorctl for more information on how to manage Supervisor.