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tillkrusstillkruss
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Introduce flush timeouts (#491)
Adds the `WP_REDIS_FLUSH_TIMEOUT` constant (defaults to `5` seconds)
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6 files changed

+71
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‎CHANGELOG.md

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Original file line numberDiff line numberDiff line change
@@ -9,6 +9,7 @@
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- Renamed `.redis-write-test.tmp` test file to `object-cache.tmp`
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- Call `redis_object_cache_error` action before `wp_die()`
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- Allow `WP_REDIS_PLUGIN_PATH` to be defined elsewhere
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- Added experimental flush timeout (defaults to `5` seconds)
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## 2.4.4
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‎FAQ.md

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@@ -138,6 +138,14 @@ This can happen when Redis Server runs out of memory and no `maxmemory-policy` w
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Alternatively, you can set the `WP_REDIS_MAXTTL` constant to something relatively low (like `3600` seconds) and flush the cache.
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</details>
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<details>
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<summary><code>Flushing the cache causes timeout</code></summary>
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This can happen when the dataset in Redis Server is quite large. Consider increasing `WP_REDIS_READ_TIMEOUT` and `WP_REDIS_FLUSH_TIMEOUT` to 5-10 seconds.
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146+
Alternatively, starting with Redis 6.2, setting the `lazyfree-lazy-user-flush` in the `redis.conf` configuration directive to `yes` changes the default flush mode to be asynchronous.
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</details>
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<details>
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<summary>Unable to flush the cache</summary>
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‎README.md

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@@ -36,12 +36,12 @@ The Redis Object Cache plugin comes with vast set of configuration options. If y
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| `WP_REDIS_PATH` | | The path to the unix socket of the Redis server |
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| `WP_REDIS_SCHEME` | `tcp` | The scheme used to connect: `tcp` or `unix` |
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| `WP_REDIS_DATABASE` | `0` | The database used by the cache: `0-15` |
39-
| `WP_REDIS_PREFIX` | | The prefix used for all cache keys to avoid data collisions, replaces `WP_CACHE_KEY_SALT`. Should be human readable, not a "salt". |
40-
| `WP_REDIS_PASSWORD` | | The password of the Redis server. Supports Redis ACLs arrays: `['user', 'password']` |
39+
| `WP_REDIS_PREFIX` | | The prefix used for all cache keys to avoid data collisions (replaces `WP_CACHE_KEY_SALT`), should be human readable and not a "salt" |
40+
| `WP_REDIS_PASSWORD` | | The password of the Redis server, supports Redis ACLs arrays: `['user', 'password']` |
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| `WP_REDIS_MAXTTL` | `0` | The maximum time-to-live of cache keys |
42-
| `WP_REDIS_CLIENT` | | The client used to communicate with Redis. Defaults to `phpredis` when installed, otherwise `predis`. Supports `phpredis`, `predis`, `relay` |
42+
| `WP_REDIS_CLIENT` | | The client used to communicate with Redis (defaults to `phpredis` when installed, otherwise `predis`), supports `phpredis`, `predis`, `relay` |
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| `WP_REDIS_TIMEOUT` | `1` | The connection timeout in seconds |
44-
| `WP_REDIS_READ_TIMEOUT` | `1` | The timeout in seconds when reading/writing |
44+
| `WP_REDIS_READ_TIMEOUT` | `1` | The timeout in seconds when reading/writing |
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| `WP_REDIS_IGNORED_GROUPS` | `[]` | Groups that should not be cached between requests in Redis |
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<details>
@@ -50,7 +50,8 @@ The Redis Object Cache plugin comes with vast set of configuration options. If y
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| Configuration constant | Default | Description |
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| ------------------------------------ | ----------- | --------------------------------------------- |
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| `WP_CACHE_KEY_SALT` | | Deprecated. Replaced by `WP_REDIS_PREFIX` |
53-
| `WP_REDIS_RETRY_INTERVAL` | | The number of milliseconds between retries |
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| `WP_REDIS_FLUSH_TIMEOUT` | `5` | Experimental. The timeout in seconds when flushing |
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| `WP_REDIS_RETRY_INTERVAL` | | The number of milliseconds between retries (PhpRedis only) |
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| `WP_REDIS_GLOBAL_GROUPS` | `[]` | Additional groups that are considered global on multisite networks |
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| `WP_REDIS_METRICS_MAX_TIME` | `3600` | The maximum number of seconds metrics should be stored |
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| `WP_REDIS_IGBINARY` | `false` | Whether to use the igbinary PHP extension for serialization |
@@ -69,11 +70,11 @@ The Redis Object Cache plugin comes with vast set of configuration options. If y
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Options that exist, but **should not**, **may break without notice** in future releases and **won't receive any support** whatsoever from our team:
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72-
| Configuration constant | Default | Description |
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| ----------------------------- | ----------- | ------------------------------------------------------------------- |
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| Configuration constant | Default | Description |
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| ----------------------------- | ----------- | --------------------------------------------------------------------- |
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| `WP_REDIS_GRACEFUL` | `false` | Prevents exceptions from being thrown, but will cause data corruption |
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| `WP_REDIS_SELECTIVE_FLUSH` | `false` | Uses terribly slow Lua script for flushing |
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| `WP_REDIS_UNFLUSHABLE_GROUPS` | `[]` | Uses terribly slow Lua script to prevent groups from being flushed |
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| `WP_REDIS_SELECTIVE_FLUSH` | `false` | Uses terribly slow Lua script for flushing |
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| `WP_REDIS_UNFLUSHABLE_GROUPS` | `[]` | Uses terribly slow Lua script to prevent groups from being flushed |
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</details>
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‎includes/class-plugin.php

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@@ -946,13 +946,7 @@ public function do_admin_actions() {
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);
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948948
if ( $result ) {
949-
try {
950-
$predis = new Predis();
951-
$predis->flush();
952-
} catch ( Exception $exception ) {
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// phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
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error_log( $exception );
955-
}
949+
(new Predis)->flush();
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}
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/**
@@ -982,13 +976,7 @@ public function do_admin_actions() {
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$result = $wp_filesystem->delete( WP_CONTENT_DIR . '/object-cache.php' );
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984978
if ( $result ) {
985-
try {
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$predis = new Predis();
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$predis->flush();
988-
} catch ( Exception $exception ) {
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// phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
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error_log( $exception );
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}
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(new Predis)->flush();
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}
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/**
@@ -1534,7 +1522,7 @@ public function on_deactivation( $plugin ) {
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wp_unschedule_event( $timestamp, 'rediscache_discard_metrics' );
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}
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1537-
wp_cache_flush();
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(new Predis)->flush();
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if ( $this->validate_object_cache_dropin() && $this->initialize_filesystem( '', true ) ) {
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$wp_filesystem->delete( WP_CONTENT_DIR . '/object-cache.php' );

‎includes/class-predis.php

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@@ -22,9 +22,10 @@ class Predis {
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/**
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* Connect to Redis.
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*
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* @param int|null $read_timeout The read timeout in seconds.
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* @return void
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*/
27-
public function connect() {
28+
public function connect( $read_timeout = null ) {
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// Load bundled Predis library.
2930
if ( ! class_exists( '\Predis\Client' ) ) {
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require_once WP_REDIS_PLUGIN_PATH . '/dependencies/predis/predis/autoload.php';
@@ -39,7 +40,7 @@ public function connect() {
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'port' => 6379,
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'database' => 0,
4142
'timeout' => 1,
42-
'read_timeout' => 1,
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'read_timeout' => $read_timeout ?? 1,
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];
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4546
$settings = [
@@ -128,13 +129,26 @@ public function connect() {
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}
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130131
/**
131-
* Invalidate all items in the cache.
132+
* Flushes the entire Redis database using the `WP_REDIS_FLUSH_TIMEOUT`.
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*
133-
* @return bool True on success, false on failure.
134+
* @param bool $throw_exception Whether to throw exception on error.
135+
* @return bool
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*/
135-
public function flush() {
137+
public function flush( $throw_exception = false ) {
138+
$flush_timeout = defined( 'WP_REDIS_FLUSH_TIMEOUT' )
139+
? intval(WP_REDIS_FLUSH_TIMEOUT)
140+
: 5;
141+
136142
if ( is_null( $this->redis ) ) {
137-
$this->connect();
143+
try {
144+
$this->connect( $flush_timeout );
145+
} catch ( Exception $exception ) {
146+
if ( $throw_exception ) {
147+
throw $exception;
148+
}
149+
150+
return false;
151+
}
138152
}
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140154
if ( defined( 'WP_REDIS_CLUSTER' ) ) {
@@ -143,23 +157,43 @@ public function flush() {
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$this->redis->flushdb( $master );
144158
}
145159
} catch ( Exception $exception ) {
160+
if ( $throw_exception ) {
161+
throw $exception;
162+
}
163+
146164
return false;
147165
}
148-
} else {
149-
try {
150-
$this->redis->flushdb();
151-
} catch ( Exception $exception ) {
152-
return false;
166+
167+
return true;
168+
}
169+
170+
try {
171+
$this->redis->flushdb();
172+
} catch ( Exception $exception ) {
173+
if ( $throw_exception ) {
174+
throw $exception;
153175
}
176+
177+
return false;
154178
}
155179

156180
return true;
157181
}
158182

183+
/**
184+
* Flushes the entire Redis database using the `WP_REDIS_FLUSH_TIMEOUT`
185+
* and will throw an exception if anything goes wrong.
186+
*
187+
* @return bool
188+
*/
189+
public function flushOrFail() {
190+
return $this->flush( true );
191+
}
192+
159193
/**
160194
* Builds a clean connection array out of redis clusters array.
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*
162-
* @return array
196+
* @return array
163197
*/
164198
protected function build_cluster_connection_array() {
165199
$cluster = array_values( WP_REDIS_CLUSTER );

‎includes/cli/class-commands.php

+3-12
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@@ -173,20 +173,11 @@ public function update_dropin() {
173173
*/
174174
protected function flush_redis() {
175175
try {
176-
$predis = new Predis();
177-
$predis->connect();
176+
return (new Predis)->flushOrFail();
178177
} catch ( Exception $exception ) {
179-
return $exception->getMessage();
180-
}
178+
error_log( $exception ); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
181179

182-
try {
183-
$predis->flush();
184-
} catch ( Exception $exception ) {
185-
// phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log
186-
error_log( $exception );
180+
return $exception->getMessage();
187181
}
188-
189-
return true;
190182
}
191-
192183
}

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