Issue #3498940 by berdir: Optimize bin cache tags and last write timetamp

src/Cache/CacheBase.php

@@ -7,6 +7,7 @@ use Drupal\Component\Assertion\Inspector;
 use Drupal\Component\Serialization\SerializationInterface;
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Cache\CacheBackendInterface;
+use Drupal\Core\Cache\ChainedFastBackend;
 use Drupal\Core\Site\Settings;
 use Drupal\redis\RedisPrefixTrait;
 
@@ -126,10 +127,34 @@ abstract class CacheBase implements CacheBackendInterface {
     $this->setPermTtl();
   }
 
+  /**
+   * Checks whether the cache id is the last write timestamp.
+   *
+   * Cache requests for this are streamlined to bypass the full cache API as
+   * that needs two extra requests to check for delete or invalidate all flags.
+   *
+   * Most requests will only fetch this single timestamp from bins using the
+   * ChainedFast backend.
+   *
+   * @param string $cid
+   *   The requested cache id.
+   *
+   * @return bool
+   */
+  protected function isLastWriteTimestamp(string $cid): bool {
+    return $cid === ChainedFastBackend::LAST_WRITE_TIMESTAMP_PREFIX . 'cache_' . $this->bin;
+  }
+
   /**
    * {@inheritdoc}
    */
   public function get($cid, $allow_invalid = FALSE) {
+
+    if ($this->isLastWriteTimestamp($cid)) {
+      $timestamp = $this->client->get($this->getPrefix() . ':' . $cid);
+      return $timestamp ? (object) ['data' => $timestamp] : NULL;
+    }
+
     $cids = [$cid];
     $cache = $this->getMultiple($cids, $allow_invalid);
     return reset($cache);
@@ -325,6 +350,10 @@ abstract class CacheBase implements CacheBackendInterface {
       if ($cache->valid && !$this->checksumProvider->isValid($cache->checksum, $cache->tags)) {
         $cache->valid = FALSE;
       }
+
+      // Remove the bin cache tag to not expose that, otherwise it is reused
+      // by the fast backend in the FastChained implementation.
+      $cache->tags = array_diff($cache->tags, [$this->getTagForBin()]);
     }
 
     // Ensure the entry does not predate the last delete all time.

src/Cache/PhpRedis.php

@@ -5,6 +5,7 @@ namespace Drupal\redis\Cache;
 use Drupal\Component\Serialization\SerializationInterface;
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Cache\CacheTagsChecksumInterface;
+use Drupal\Core\Cache\ChainedFastBackend;
 
 /**
  * PhpRedis cache backend.
@@ -82,6 +83,11 @@ class PhpRedis extends CacheBase {
    */
   public function set($cid, $data, $expire = Cache::PERMANENT, array $tags = []) {
 
+    if ($this->isLastWriteTimestamp($cid)) {
+      $this->client->set($this->getPrefix() . ':' . $cid, $data);
+      return;
+    }
+
     $ttl = $this->getExpiration($expire);
 
     $key = $this->getKey($cid);

src/Cache/Predis.php

@@ -2,6 +2,7 @@
 
 namespace Drupal\redis\Cache;
 
+use Drupal\Core\Cache\ChainedFastBackend;
 use Predis\Client;
 use Drupal\Component\Serialization\SerializationInterface;
 use Drupal\Core\Cache\Cache;
@@ -83,6 +84,11 @@ class Predis extends CacheBase {
    */
   public function set($cid, $data, $expire = Cache::PERMANENT, array $tags = []) {
 
+    if ($this->isLastWriteTimestamp($cid)) {
+      $this->client->set($this->getPrefix() . ':' . $cid, $data);
+      return;
+    }
+
     $ttl = $this->getExpiration($expire);
 
     $key = $this->getKey($cid);

src/Cache/Relay.php

@@ -6,6 +6,7 @@ use Drupal\Component\Assertion\Inspector;
 use Drupal\Component\Serialization\SerializationInterface;
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Cache\CacheTagsChecksumInterface;
+use Drupal\Core\Cache\ChainedFastBackend;
 use Drupal\Core\Site\Settings;
 
 /**
@@ -97,6 +98,11 @@ class Relay extends CacheBase {
    */
   public function set($cid, $data, $expire = Cache::PERMANENT, array $tags = []) {
 
+    if ($this->isLastWriteTimestamp($cid)) {
+      $this->client->Set($this->getPrefix() . ':' . $cid, $data);
+      return;
+    }
+
     $ttl = $this->getExpiration($expire);
 
     $key = $this->getKey($cid);

tests/src/Kernel/ChainedFastWithRedisCacheTest.php

+<?php
+
+namespace Drupal\Tests\redis\Kernel;
+
+use Drupal\Component\Datetime\TimeInterface;
+use Drupal\Core\Cache\ChainedFastBackend;
+use Drupal\Core\Cache\PhpBackend;
+
+/**
+ * Tests Redis cache backend using GenericCacheBackendUnitTestBase.
+ *
+ * @group redis
+ */
+class ChainedFastWithRedisCacheTest extends RedisCacheTest {
+
+  /**
+   * Creates a new instance of ChainedFastBackend.
+   *
+   * @return \Drupal\Core\Cache\ChainedFastBackend
+   *   A new ChainedFastBackend object.
+   */
+  protected function createCacheBackend($bin) {
+    $consistent_backend = \Drupal::service('cache.backend.redis')->get($bin);
+    $consistent_backend->setMinTtl(10);
+    $fast_backend = new PhpBackend($bin, \Drupal::service('cache_tags.invalidator.checksum'), \Drupal::service(TimeInterface::class));
+    $backend = new ChainedFastBackend($consistent_backend, $fast_backend, $bin);
+    // Explicitly register the cache bin as it can not work through the
+    // cache bin list in the container.
+    \Drupal::service('cache_tags.invalidator')->addInvalidator($backend);
+    return $backend;
+  }
+
+}