On Cloud Platform environments, advanced custom tasks can be scheduled using the scheduled jobs feature or triggered through Drush cron.
Limitations
When creating custom scheduled jobs, the following limitations apply:
- Commands in scheduled jobs can’t be longer than 255 characters. If you must run a command longer than 255 characters, you must incorporate it by running a shell script you run as a scheduled job.
- The
%character is a special character in cron commands. If your command uses this special character, be sure to precede it with a backslash (\). For example:your_log_file_$(date +\%F).log. - Commands entered should always provide absolute paths to ensure correct execution as shown in the following examples.
- Cron jobs configured to use Acquia’s cron-wrapper.sh script through the Cloud Platform user interface or Cloud API v2 will use the PHP memory limit configured for your environment (by default, 128 MB).
- All other scheduled jobs, including cron jobs triggered manually through Drush, have a maximum PHP memory limit of 512 MB.
The maximum duration of code deploy tasks is 1 hour. Exceeding this time will stop the task, and the original code will remain.
If you find your scheduled jobs failing to complete, try defining them to use Drush cron instead of the Acquia cron-wrapper.sh script to take advantage of the greater memory limit available to CLI commands. For related information, see Debugging cron.
Custom Drush commands
You can define scheduled jobs that explicitly trigger specific actions using Drush.
When attempting this, keep in mind the following:
- Include a
--root=/var/www/html/${AH_SITE_NAME}/docrootargument, or use a Drush site alias, or prefix your command with acdthat switches to the correct folder. - Use the Drush version appropriate for your Drupal and module version(s).
- Test your Drush commands while SSH’d into your environment before adding them to your scheduled jobs to ensure everything works. To do this:
- Type
cd $HOMEto switch to your home folder before running it to ensure it will run within the scheduled job’s available environment. - If using a site alias, ensure you pick from the available list shown by Drush. See Using Drush aliases.
- Type
Running a shell script
You can create scheduled jobs to run shell scripts you have written.
The following example assumes you have added scripts/my-script.sh to your repository:
/var/www/html/${AH_SITE_NAME}/scripts/my-script.sh
Scheduled job output
When a scheduled job runs and the output does not redirect to stdout, the cron user sends an email to the application user on the same infrastructure.
Cloud Platform saves the email in /var/mail. If the messages are never picked up or cleared, the messages fill the disk. This might cause issues, including bringing down your application.
To avoid issues, you must include a logging statement in scheduled jobs. For example, you can use the following statement by replacing [site-uri] with the base URL to the website where you want to run cron:
/usr/local/bin/drush --uri=http://[site-uri] --root=/var/www/html/${AH_SITE_NAME}/docroot -d -v cron &>> /var/log/sites/${AH_SITE_NAME}/logs/$(hostname -s)/drush-cron.log
In the preceding example, &>> /var/log/sites/${AH_SITE_NAME}/logs/$(hostname -s)/drush-cron.log logs the cron output to a drush-cron.log file in the infrastructure’s logs directory. The output log file is rotated along with the other logs in the logs directory. This log file is rotated only if the file is named drush-cron.log. For more information, see About Cloud Platform logging.
To improve usability, you can add a timestamp to the log messages. For example, you can replace [site-uri] with the base URL to the website where you want to run cron.
/usr/local/bin/drush --uri=http://[site-uri] --root=/var/www/html/${AH_SITE_NAME}/docroot -d -v cron 2>&1 | awk '{print "["strftime("\%Y-\%m-\%d \%H:\%M:\%S \%Z")"] "$0}' &>> /var/log/sites/${AH_SITE_NAME}/logs/$(hostname -s)/drush-cron.log
You must run this command as a standalone script as it exceeds the 255 character limit for scheduled jobs.