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Advanced cron and scheduled job tasks on Acquia Cloud Platform

On Acquia 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 Acquia 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.

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}/docroot argument, or use a Drush site alias, or prefix your command with a cd that 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 $HOME to 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.

Running a shell script

You can create scheduled jobs to run shell scripts you have written.

Note

Acquia recommends using a shell script for running complex or long cron commands. This method ensures complex commands can be stored in version control when necessary, enables more controlled error logging, and prevents potential problems submitting the commands to the Cloud Platform interface.

The following example assumes you have added scripts/my-script.sh to your repository:

/var/www/html/${AH_SITE_NAME}/scripts/my-script.sh

Note

Acquia highly recommends adding your shell scripts to your source code repository. Acquia also recommends adding a library or scripts folder to your repository in the same directory as acquia-utils and docroot.

Scheduled job output

When a scheduled job runs, and the output isn’t redirected to stdout, the cron user sends an email to the application user on the same infrastructure. For environments running on Cloud Classic infrastructure, Cloud Platform saves the email in /var/mail. This output is not saved on Acquia Cloud Next infrastructure.

Important

On Cloud Classic infrastructure, if the messages are never picked up or cleared, the messages fill the disk, which can cause serious problems, including possibly bringing down your application.

To avoid issues, scheduled jobs must always include a logging statement. For example, you could use the following statement, replacing [site-uri] with the base URL to the website where you want to run cron:

/usr/local/bin/drush10 --uri=http://[site-uri] --root=/var/www/html/${AH_SITE_NAME}/docroot -dv cron &>> /var/log/sites/${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, where the output will be rotated along with the other logs in the logs directory. The log file will be rotated only if the file is named drush-cron.log. For more information, see About Cloud Platform logging.

To improve usability, you can also add a timestamp to the log messages, as displayed in the following example, replacing [SITEURL] with the base URL to the website where you want to run cron. You must run the following example as a standalone script, because it exceeds the 255 character limit for scheduled jobs. The following example serves as a general guide for creating similar scripts:

/usr/local/bin/drush10 --uri=http://[SITEURL] --root=/var/www/html/${AH_SITE_NAME}/docroot -dv 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

For environments running on Acquia Cloud Next infrastructure, logs will be stored in /shared/logs instead of the aforementioned /var/log/sites/ directory.