Better Drupal 8 Batch Services

Better Drupal 8 Batches
Cause “just do it like D7” is like using hand powered a ferry: it
gets the job done in the hardest way possible.

Batch Overview
● Drupal batch processing is great for doing long running jobs when you can
leave a browser open or you need a simple UI to a process.
● It is just as easy for a developer to use as Feeds and more reliable.
● It is built around the best concepts Drupal 5 could give us, the DX is just a
little wonky.
● All the advice on D8 batches basically says: “It didn’t change”. But everything
else did!

Quick batch how-to
A typical batch process starts with a form, that generates an array of tasks,
which reference PHP functions that implement callback_batch_operation(), and
finally calls function that implements callback_batch_finish().
callback_batch_operation() each call to is passed a collection of parameters
followed by an array called $context that allows for intra and inter task messages.
Any given task can be called once, or a thousand times.
Task runs should be short so Drupal can reboot strap as needed.
callback_batch_finish() is called when everything is done, or fails, to report
outcome.

Why do we need a new interface?
We don’t. Then why
are we
here?
The current solution
works well enough to
drive the Drupal 8
installer, bulk operations,
and lots of other things.

Why do we want a new interface?
● All the advice on D8 batches basically says: “It didn’t change”. But everything
else did!
● The batch array definitions are obscure and hard to remember.
● Current patterns require either inserting procedural code into your project or
your create a class with a bunch of static functions.
○ Both limit your ease of access to other Drupal services since you are pulling them into a global
or static context.
● Having a service that can run as a more standard service it makes your new
code more standard with everything else.

Introducing Batch Service Interface
Sandbox Project: https://www.drupal.org/sandbox/acrosman/3025562
Provides an interface that defines the service, an abstract class of helper functions
to do all the static work, and a silly example module to prove it works. All you have
to do is define the service, define the form, provide your list of tasks (functions in
the class), and let it run. It handles array prep for batch, instantiating services, and
related elements.

Simple form with simple code
public function submitForm(array &$form, FormStateInterface $form_state) {
$data = [
'message_count' => $form_state->getValue('message_count'),
];
$batch = $this->exampleBatchService->generateBatchJob($data);
batch_set($batch);
}

Generate the batch job
public function generateBatchJob($data) {
$ops = [];
for ($i = 0; $i < $data['message_count']; $i++ ) {
$ops[] = [
'logMessage' => ['MessageIndex' => $i + 1],
];
}
return $this->prepBatchArray($this->t('Replace Users'), $this->t('Starting
Batch Processing'), $ops);
}

Define Worker Method
public function logMessage($data, &$context) {
// We could do something interesting here.
$this->logger->info($this->getRandomMessage());
if (!isset($context['results']['message_count'])) {
$context['results']['message_count'] = 0;
}
$context['results']['message_count']++;
}

And we’re done...
public function doFinishBatch($success, $results, $operations) {
drupal_set_message($this->t('Logged %count quotes', ['%count' =>
$results['message_count']]));
}

Okay there is a little funkiness
class ExampleBatchService extends AbstractBatchService {
/**
* Must be set in child classes to be the service name so the service can
* bootstrap itself.
*
* @var string
*/
protected static $serviceName = 'batch_example.example_batch';

Let’s see it go...then look at the code...

Related Core Effort
These will be better, if they are ever finished...
Make batch itself a service:
https://www.drupal.org/project/drupal/issues/2875151
Create an interface and an initiator:
https://www.drupal.org/project/drupal/issues/2959723

Better Drupal 8 Batch Services

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