From cc5b79a1cb132d2083d96f46107dceb68dfa364e Mon Sep 17 00:00:00 2001
From: Erick Hitter <ehitter@gmail.com>
Date: Mon, 3 Mar 2014 21:37:38 -0800
Subject: [PATCH] Improve behaviour when Redis is unavailable
* Catches connection exceptions rather than triggering fatals
* Forces all cache lookups to use the internal cache when Redis is unavailable
---
object-cache.php | 76 ++++++++++++++++++++++++++++++++++++------------
1 file changed, 58 insertions(+), 18 deletions(-)
diff --git a/object-cache.php b/object-cache.php
index 10152a1..364499c 100644
--- a/object-cache.php
+++ b/object-cache.php
@@ -190,14 +190,21 @@ class WP_Object_Cache {
*
* @var Predis\Client
*/
- public $redis;
+ private $redis;
+
+ /**
+ * Track if Redis is available
+ *
+ * @var bool
+ */
+ private $redis_connected = false;
/**
* Holds the non-Redis objects.
*
* @var array
*/
- public $cache = array();
+ private $cache = array();
/**
* List of global groups.
@@ -269,18 +276,33 @@ class WP_Object_Cache {
// Use Redis PECL library if available, otherwise default to bundled Predis library
if ( class_exists( 'Redis' ) ) {
- $this->redis = new Redis();
- $this->redis->connect( $redis['host'], $redis['port'] );
+ try {
+ $this->redis = new Redis();
+ $this->redis->connect( $redis['host'], $redis['port'] );
+
+ if ( isset( $redis['database'] ) ) {
+ $this->redis->select( $redis['database'] );
+ }
- if ( isset( $redis['database'] ) ) {
- $this->redis->select( $redis['database'] );
+ $this->redis_connected = true;
+ } catch ( RedisException $e ) {
+ $this->redis_connected = false;
}
} else {
- require_once 'predis/autoload.php';
- $this->redis = new Predis\Client( $redis );
+ try {
+ require_once 'predis/autoload.php';
+ $this->redis = new Predis\Client( $redis );
+
+ $this->redis_connected = true;
+ } catch ( Predis\Connection\ConnectionException $e ) {
+ $this->redis_connected = false;
+ }
}
- unset( $redis );
+ // When Redis is unavailable, fall back to the internal back by forcing all groups to be "no redis" groups
+ if ( ! $this->redis_connected ) {
+ $this->no_redis_groups = array_unique( array_merge( $this->no_redis_groups, $this->global_groups ) );
+ }
/**
* This approach is borrowed from Sivel and Boren. Use the salt for easy cache invalidation and for
@@ -295,6 +317,15 @@ class WP_Object_Cache {
$this->blog_prefix = ( is_multisite() ? $blog_id : $table_prefix ) . ':';
}
+ /**
+ * Is Redis available?
+ *
+ * @return bool
+ */
+ protected function can_redis() {
+ return $this->redis_connected;
+ }
+
/**
* Adds a value to cache.
*
@@ -343,7 +374,7 @@ class WP_Object_Cache {
$derived_key = $this->build_key( $key, $group );
// If group is a non-Redis group, save to internal cache, not Redis
- if ( in_array( $group, $this->no_redis_groups ) ) {
+ if ( in_array( $group, $this->no_redis_groups ) || ! $this->can_redis() ) {
// Check if conditions are right to continue
if (
@@ -387,12 +418,14 @@ class WP_Object_Cache {
public function delete( $key, $group = 'default' ) {
$derived_key = $this->build_key( $key, $group );
- // Remove from no_mc_groups array
- if ( in_array( $group, $this->no_redis_groups ) ) {
+ // Remove from no_redis_groups array
+ if ( in_array( $group, $this->no_redis_groups ) || ! $this->can_redis() ) {
if ( isset( $this->cache[$derived_key] ) ) {
unset( $this->cache[$derived_key] );
return true;
+ } else {
+ return false;
}
}
@@ -416,7 +449,10 @@ class WP_Object_Cache {
}
$this->cache = array();
- $result = $this->parse_predis_response( $this->redis->flushdb() );
+
+ if ( $this->can_redis() ) {
+ $result = $this->parse_predis_response( $this->redis->flushdb() );
+ }
return $result;
}
@@ -433,7 +469,7 @@ class WP_Object_Cache {
public function get( $key, $group = 'default' ) {
$derived_key = $this->build_key( $key, $group );
- if ( in_array( $group, $this->no_redis_groups ) ) {
+ if ( in_array( $group, $this->no_redis_groups ) || ! $this->can_redis() ) {
if ( isset( $this->cache[$derived_key] ) ) {
$this->cache_hits++;
return is_object( $this->cache[$derived_key] ) ? clone $this->cache[$derived_key] : $this->cache[$derived_key];
@@ -471,7 +507,7 @@ class WP_Object_Cache {
$derived_key = $this->build_key( $key, $group );
// If group is a non-Redis group, save to internal cache, not Redis
- if ( in_array( $group, $this->no_redis_groups ) ) {
+ if ( in_array( $group, $this->no_redis_groups ) || ! $this->can_redis() ) {
$this->add_to_internal_cache( $derived_key, $value );
return true;
@@ -501,7 +537,7 @@ class WP_Object_Cache {
$offset = (int) $offset;
// If group is a non-Redis group, save to internal cache, not Redis
- if ( in_array( $group, $this->no_redis_groups ) ) {
+ if ( in_array( $group, $this->no_redis_groups ) || ! $this->can_redis() ) {
$value = $this->get_from_internal_cache( $derived_key );
$value += $offset;
$this->add_to_internal_cache( $derived_key, $value );
@@ -530,7 +566,7 @@ class WP_Object_Cache {
$offset = (int) $offset;
// If group is a non-Redis group, save to internal cache, not Redis
- if ( in_array( $group, $this->no_redis_groups ) ) {
+ if ( in_array( $group, $this->no_redis_groups ) || ! $this->can_redis() ) {
$value = $this->get_from_internal_cache( $derived_key );
$value -= $offset;
$this->add_to_internal_cache( $derived_key, $value );
@@ -688,7 +724,11 @@ class WP_Object_Cache {
public function add_global_groups( $groups ) {
$groups = (array) $groups;
- $this->global_groups = array_unique( array_merge( $this->global_groups, $groups ) );
+ if ( $this->can_redis() ) {
+ $this->global_groups = array_unique( array_merge( $this->global_groups, $groups ) );
+ } else {
+ $this->no_redis_groups = array_unique( array_merge( $this->no_redis_groups, $groups ) );
+ }
}
/**
--
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