Cron tasks lock tasks from other groups

This article provides a solution for the Adobe Commerce on cloud infrastructure issue related to certain long-run cron jobs blocking other cron jobs.

Affected products and versions

Adobe Commerce on cloud infrastructure Pro plan architecture
Onboard earlier than May 2019

Issue

On Adobe Commerce for cloud, when you have complex cron tasks (long-run tasks), they might lock other tasks for execution. For example, the indexers' task reindexes invalidated indexers. It can take a few hours to finish, and it will lock other default cron jobs like sending emails, generating sitemaps, customer notifications, and other custom tasks.

Symptoms:

The processes executed by cron jobs are not performed. For example, product updates are not applied for hours, or customers report not receiving emails.

When you open the cron_schedule database table, you see the jobs with missed status.

Cause

Previously, in our cloud environment, the Jenkins server was used to run cron jobs. Jenkins will only run one instance of a job at a time; consequently, there will only be one bin/magento cron:run process running at a time.

Solution

Contact Adobe Commerce support to have self-managed crons enabled.
Edit the .magento.app.yaml file in the root directory of the code for Adobe Commerce in the Git branch. Add the following:
```
  crons:
  cronrun:
  spec: "* * * * *"
  cmd: "php bin/magento cron:run"
```
Save the file and push updates to the Staging and Production environments (the same way you do it for Integration environments).

NOTE

There's no need to transfer old cron configurations where multiple cron:run are present to the new cron schedule; the regular cron:run task, added as described above, is enough. Though, it is required to transfer your custom jobs if you had any.

Check if you have self-managed cron enabled (only for Cloud Pro Staging and Production)

To check if the self-managed cron is enabled, run the crontab -l command and observe the result:

Self-managed cron is enabled, if you are able to see the tasks, like the following:

username@hostname:~$ crontab -l    # Crontab is managed by the system, attempts to edit it directly will fail.
SHELL=/etc/platform/username/cron-run    MAILTO=""    # m h dom mon dow job_name    * * * * * cronrun

The self-managed cron is not enabled if you are not able to see the tasks and get the "you are not allowed to use this program" error message.