Magento 2 – How to Create Cron Job for Custom Module

cronmagento2

Setting up cron for a custom module what I believe I need to do is create a \etc\crontab.xml for the module.

What I also believe is happening is when the cron job magento cron:run runs all jobs in the table cron_schedule are executed (as long as time <= scheduled_at).

If this is correct, how does my job run_my_module for my custom module (my\module) get in cron_schedule? I've run magento cron:run manually but don't see my job in the table. What am I missing?

Best Answer

Schedule is generated periodically during magento cron:run execution. Period is defined separately for each cron group in the admin panel (Stores -> Configuration -> Advanced -> System -> Cron). New job will be scheduled only when Generate Schedules Every minutes pass after previous generation.

Implementation can be found here \Magento\Cron\Observer\ProcessCronQueueObserver::_generate

Related Solutions

Magento 2 – Custom Module Cron Job Not Running

You need to do one of the following options:

1) Use <group id="default"> in vendor/module/etc/crontab.xml

2) Create your own vendor/module/etc/cron_groups.xml with the following:

<?xml version="1.0"?>
<!--
/**
 * path:
 * magento_home/app/code/vendor/module/etc/cron_groups.xml
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Cron:etc/cron_groups.xsd">
    <group id="custom_group">
        <schedule_generate_every>1</schedule_generate_every>
        <schedule_ahead_for>4</schedule_ahead_for>
        <schedule_lifetime>2</schedule_lifetime>
        <history_cleanup_every>10</history_cleanup_every>
        <history_success_lifetime>60</history_success_lifetime>
        <history_failure_lifetime>600</history_failure_lifetime>
        <use_separate_process>1</use_separate_process>
    </group>
</config>

This will then show up in your backend Stores->Configuration->Advanced->System under Cron.

To test : php bin/magento cron:run --group="custom_group"

Magento 2 – How Cron Job Works

Configure Magento cron job scheduler

By defining <schedule> in crontab.xml, you're setting up periods when Magento should schedule that process. To be able to schedule a job, you have to run Magento Cron scheduler - and that's what you did. But, if you want to run your cron job in defined period continuously, you'll have to configure Magento Cron scheduler to be run in the background.

In order to do that, you'll have to insert following lines into your cron. * * * * * <path to php binary> <magento install dir>/bin/magento cron:run * * * * * <path to php binary> <magento install dir>/update/cron.php * * * * * <path to php binary> <magento install dir>/bin/magento setup:cron:run

<path to php binary> most often is /usr/bin/php5 (you can find it by typing "whereis php5" or "whereis php" in command line).

<magento install dir> is path of your Magento instance.

More information how to set cron jobs can be found at http://devdocs.magento.com/guides/v2.0/config-guide/cli/config-cli-subcommands-cron.html.

Background on Magento cron jobs implementation:

There are cron jobs defined at the system level, and they can be considered as real cron jobs. You can check those cron jobs by typing "crontab -e" in the command line for the current user.

On the other side, Magento offers the sophisticated configuration of cron jobs, but they are not "real" cron jobs. They are all invoked programmatically through one real cron job, by executing "bin/magento cron:run".

So, when you execute:

* * * * * <path to php binary> <magento install dir>/bin/magento cron:run

this is what is happening in Magento cron job scheduler (pseudo-code):

...
// runs all scheduled jobs (until limit is reached, configurable in Magento Admin)
foreach ($pendingCronJobs as $_job) {
    $_job->run();
}

// generate new schedules for upcoming cron jobs
$this->generateNewSchedule();

// clean up old entries
$this->cleanUpOldEntries();
...

If you want to check more thoroughly how it looks behind the scenes, check Magento\Cron\Observer\ProcessCronQueueObserver, method execute()

Cron job groups

As you can see from Magento\Cron\Observer\ProcessCronQueueObserver, all scheduled cron jobs will be executed sequentially, one by one. It means that cron job (which is in "execution" state) will block the others from being executed until it's finished.

This can make troubles, especially if you have some long running cron jobs.

Magento2 offers the possibility to configure different groups for cron jobs. On that way, you can split cron jobs by putting long-running cron job into separate group(s).

More information about cron groups can be found at:

devdocs.magento.com/guides/v2.0/config-guide/cron/custom-cron-ref.html