LockableRepository.php

<?php declare(strict_types=1);

namespace MyApp\Adapter\Repository\Couchbase;

use CouchbaseException;

class LockableRepository
{
  
    // ....
  
    /**
     * Attempt to acquire lock and return lock data, otherwise return nothing.
     *
     * This is used by the lock handler to determine whether we were able to
     * acquire a lock. If it was locked (return falsey), it waits and tries
     * again up to a point. You can see the usage in a class that extends this.
     */
    public function attemptToAcquireLock(string $key, int $lockSeconds): array?
    {
        $bucketName = $this->getBucketName();
        try {
            $doc = $this->couchbaseCluster->
                openBucket($bucketName)->
                getAndLock($key, $lockSeconds);
        } catch (CouchbaseException $exception) {
            $code = $exception->getCode();
            if ($code === COUCHBASE_ETMPFAIL) {
                return null;
            }
            throw $exception;
        }
        return [
            'type' => 'couchbase',
            'lock_id' => $doc->cas,
            'bucket_name' => $bucketName,
            'value' => $doc->value,
        ];
    }
  
  
    /**
     * When storing an entity, get the couchbase unlock options.
     *
     * This is abstracted to shorten an otherwise long store method in each
     * repo that extends this. It also allows failing early by returning an
     * empty array. If this were not abstracted I'd have to wrap the rest of
     * this in an if/else, increasing indentation and code size.
     */
    protected function getCouchbaseUnlockOptionsForStore(
        string $docKey,
        bool $wasLockedDuringCurrentProcess,
        bool $dangerouslySkipLocking
    ): array {
        // wait for and acquire lock if something else has locked this
        if ($dangerouslySkipLocking) {
            return [];
        }
        if (!$wasLockedDuringCurrentProcess) {
            $this->lockAndGetCouchbaseData($docKey);
        }
        $lockId = $this->lockHandler->getLockId($docKey);
        return ['cas' => $lockId];
    }
  
    /**
     * If it's locked, wait for the lock to be released, then get and lock the
     * document and return the json value of the couchbase doc.
     */
    protected function lockAndGetCouchbaseData(string $docKey): string
    {
        // passing a callable to waitAndAcquire. This callable attempts to
        // acquire a lock, returning lockData if it succeeds, and returning
        // falsey if it fails. See waitAndAcquire method documentation for
        // more details.
        $lockData = $this->lockHandler->
            waitAndAcquire($docKey, [$this, 'attemptToAcquireLock']);
        return $lockData['value'];
    }
}