RedisException: BUSY Redis is busy running a script.

[michalpelech-cz]

Hi, we started having problems with Redis cache generating errors in PHP and the site crashes sometimes.

These are the errors from PHP error.log:

[26-Feb-2024 05:17:33 UTC] RedisException: BUSY Redis is busy running a script. You can only call SCRIPT KILL or SHUTDOWN NOSAVE. in /home/www/cc.cz/subdomains/www/wp-content/object-cache.php:559
Stack trace:
#0 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(559): Redis->ping()
#1 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(256): WP_Object_Cache->__construct()
#2 /home/www/cc.cz/subdomains/www/wp-includes/load.php(856): wp_cache_init()
#3 /home/www/cc.cz/subdomains/www/wp-settings.php(131): wp_start_object_cache()
#4 /home/www/cc.cz/subdomains/www/wp-config.php(120): require_once('...')
#5 /home/www/cc.cz/subdomains/www/wp-load.php(50): require_once('...')
#6 /home/www/cc.cz/subdomains/www/wp-admin/admin-ajax.php(22): require_once('...')
#7 {main}

Here are some error message from Redis:

523:M 26 Feb 2024 08:35:49.728 # Lua slow script detected: still in execution after 5055 milliseconds. You can try killing the script using the SCRIPT KILL command. Script SHA1 is: 3acb4595a5e180effab92dbb7fb0b87ab2b302a0

This is my Redis Object Cache settings:

Status: Připojeno
Client: PhpRedis (v5.3.7)
Drop-in: Valid
Disabled: No
Ping: 1
Errors: []
PhpRedis: 5.3.7
Relay: Not loaded
Predis: 2.1.2
Credis: Not loaded
PHP Version: 8.1.21
Plugin Version: 2.5.0
Redis Version: 6.0.16
Multisite: No
Metrics: Enabled
Metrics recorded: 4830
Filesystem: Writable
Global Prefix: "wp_"
Blog Prefix: "wp_"
WP_REDIS_TIMEOUT: 10
WP_REDIS_READ_TIMEOUT: 10
WP_REDIS_PLUGIN_PATH: "/home/www/cc.cz/subdomains/www/wp-content/plugins/redis-cache"
WP_REDIS_SELECTIVE_FLUSH: false
Global Groups: [
    "blog-details",
    "blog-id-cache",
    "blog-lookup",
    "global-posts",
    "networks",
    "rss",
    "sites",
    "site-details",
    "site-lookup",
    "site-options",
    "site-transient",
    "users",
    "useremail",
    "userlogins",
    "usermeta",
    "user_meta",
    "userslugs",
    "redis-cache",
    "blog_meta",
    "network-queries",
    "site-queries",
    "user-queries"
]
Ignored Groups: [
    "counts",
    "plugins",
    "theme_json",
    "themes"
]
Unflushable Groups: []
Groups Types: {
    "blog-details": "global",
    "blog-id-cache": "global",
    "blog-lookup": "global",
    "global-posts": "global",
    "networks": "global",
    "rss": "global",
    "sites": "global",
    "site-details": "global",
    "site-lookup": "global",
    "site-options": "global",
    "site-transient": "global",
    "users": "global",
    "useremail": "global",
    "userlogins": "global",
    "usermeta": "global",
    "user_meta": "global",
    "userslugs": "global",
    "redis-cache": "global",
    "blog_meta": "global",
    "network-queries": "global",
    "site-queries": "global",
    "user-queries": "global",
    "counts": "ignored",
    "plugins": "ignored",
    "theme_json": "ignored",
    "themes": "ignored"
}
Drop-ins: [
    "advanced-cache.php v by ",
    "Redis Object Cache Drop-In v2.5.0 by Till Krüss"
]

I tried set these constants:

`define( 'WP_REDIS_TIMEOUT', 10 );`
`define( 'WP_REDIS_READ_TIMEOUT', 10 );`
`define( 'WP_REDIS_FLUSH_TIMEOUT', 10 );`
`define( 'WP_REDIS_SELECTIVE_FLUSH', false );`

But with no results, the errors still appear.

I had also problem to flush cache with WP CLI wp cache flush command:

RedisException: read error on connection to 127.0.0.1:6379 in /home/www/cc.cz/subdomains/www/wp-content/object-cache.php:1643
Stack trace:
#0 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(1643): Redis->flushDB()
#1 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(149): WP_Object_Cache->flush()
#2 phar:///home/www/cc.cz/bin/wp/vendor/wp-cli/cache-command/src/Cache_Command.php(163): wp_cache_flush()
#3 [internal function]: Cache_Command->flush()
#4 phar:///home/www/cc.cz/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Dispatcher/CommandFactory.php(100): call_user_func()
#5 [internal function]: WP_CLI\Dispatcher\CommandFactory::WP_CLI\Dispatcher\{closure}()
#6 phar:///home/www/cc.cz/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Dispatcher/Subcommand.php(497): call_user_func()
#7 phar:///home/www/cc.cz/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Runner.php(441): WP_CLI\Dispatcher\Subcommand->invoke()
#8 phar:///home/www/cc.cz/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Runner.php(464): WP_CLI\Runner->run_command()
#9 phar:///home/www/cc.cz/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Runner.php(1295): WP_CLI\Runner->run_command_and_exit()
#10 phar:///home/www/cc.cz/bin/wp/vendor/wp-cli/wp-cli/php/WP_CLI/Bootstrap/LaunchRunner.php(28): WP_CLI\Runner->start()
#11 phar:///home/www/cc.cz/bin/wp/vendor/wp-cli/wp-cli/php/bootstrap.php(83): WP_CLI\Bootstrap\LaunchRunner->process()
#12 phar:///home/www/cc.cz/bin/wp/vendor/wp-cli/wp-cli/php/wp-cli.php(32): WP_CLI\bootstrap()
#13 phar:///home/www/cc.cz/bin/wp/php/boot-phar.php(20): include('...')
#14 /home/www/cc.cz/bin/wp(4): include('...')
#15 {main}
Error: Error establishing a Redis connection. To disable Redis, delete the `object-cache.php` file in the `/wp-content/` directory.

Can I somehow find out where the problem is?
Thanks for any help.

[tillkruss]

Can you post your full wp-config.php with all secret redacted?

[michalpelech-cz]

Here it is:

<?php
define('WP_CACHE', true); // Added by WP Rocket

// ** MySQL settings ** //
/** The name of the database for WordPress */
define( 'DB_NAME', '***' );

/** MySQL database username */
define( 'DB_USER', '***' );

/** MySQL database password */
define( 'DB_PASSWORD', '***' );

/** MySQL hostname */
define( 'DB_HOST', 'localhost:3306' );

/** Database Charset to use in creating database tables. */
define( 'DB_CHARSET', 'utf8' );

/** The Database Collate type. Don't change this if in doubt. */
define( 'DB_COLLATE', '' );

/**
* Authentication Unique Keys and Salts.
 *
 * Change these to different unique phrases!
 * You can generate these using the {@link https://api.wordpress.org/secret-key/1.1/salt/ WordPress.org secret-key service}
 * You can change these at any point in time to invalidate all existing cookies. This will force all users to have to log in again.
 *
 * @since 2.6.0
 */
define('AUTH_KEY',         '***');
define('SECURE_AUTH_KEY',  '***');
define('LOGGED_IN_KEY',    '***');
define('NONCE_KEY',        '***');
define('AUTH_SALT',        '***');
define('SECURE_AUTH_SALT', '***');
define('LOGGED_IN_SALT',   '***');
define('NONCE_SALT',       '***');
/**#@-*/
/**
 * WordPress Database Table prefix.
 *
 * You can have multiple installations in one database if you give each a unique
 * prefix. Only numbers, letters, and underscores please!
 */
$table_prefix  = 'wp_';
/**
 * WordPress Localized Language, defaults to English.
 *
 * Change this to localize WordPress. A corresponding MO file for the chosen
 * language must be installed to wp-content/languages. For example, install
 * de_DE.mo to wp-content/languages and set WPLANG to 'de_DE' to enable German
 * language support.
 */
define('WPLANG', 'cs_CZ');
/**
 * For developers: WordPress debugging mode.
 *
 * Change this to true to enable the display of notices during development.
 * It is strongly recommended that plugin and theme developers use WP_DEBUG
 * in their development environments.
 */
// define('WP_DEBUG', false);

define( 'WP_DEBUG', false );
define( 'WP_DEBUG_DISPLAY', false );
define( 'WP_DEBUG_LOG', true );
define( 'WP_ENV', 'production' );

/* SSL */
define( 'FORCE_SSL_LOGIN', true );
define( 'FORCE_SSL_ADMIN', true );

/* SECURITY */
define( 'DISALLOW_FILE_EDIT', true );

/* Specify maximum number of Revisions. */
define( 'WP_POST_REVISIONS', '3' );

define( 'CC_EVENT_TYPE_ID', 8923 );

define( 'WP_REDIS_CONFIG', [
	'group_flush' => 'incremental',
]);

define( 'WP_REDIS_TIMEOUT', 10 );
define( 'WP_REDIS_READ_TIMEOUT', 10 );
define( 'WP_REDIS_FLUSH_TIMEOUT', 10 );
define( 'WP_REDIS_SELECTIVE_FLUSH', false );

/* That's all, stop editing! Happy blogging. */
/** Absolute path to the WordPress directory. */
if ( !defined('ABSPATH') )
	define('ABSPATH', dirname(__FILE__) . '/');
/** Sets up WordPress vars and included files. */
require_once(ABSPATH . 'wp-settings.php');

[michalpelech-cz]

I don't know if it can be related, but these issues started the day when we updated Yoast SEO and Yoast SEO Premium to the latest version. It might not be related, but just in case.

[michalpelech-cz]

I'm posting some new errors from the PHP error.log, maybe that will help:

[01-Mar-2024 06:15:30 UTC] RedisException: socket error on read socket in /home/www/cc.cz/subdomains/www/wp-content/object-cache.php:1826
Stack trace:
#0 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(1826): Redis->eval()
#1 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(1726): WP_Object_Cache->{closure}()
#2 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(162): WP_Object_Cache->flush_group()
#3 /home/www/cc.cz/subdomains/www/wp-content/plugins/wordpress-seo/src/builders/indexable-link-builder.php(710): wp_cache_flush_group()
#4 /home/www/cc.cz/subdomains/www/wp-content/plugins/wordpress-seo/src/builders/indexable-link-builder.php(623): Yoast\WP\SEO\Builders\Indexable_Link_Builder->update_incoming_links_for_related_indexables()
#5 /home/www/cc.cz/subdomains/www/wp-content/plugins/wordpress-seo/src/builders/indexable-link-builder.php(136): Yoast\WP\SEO\Builders\Indexable_Link_Builder->update_related_indexables()
#6 /home/www/cc.cz/subdomains/www/wp-content/plugins/wordpress-seo/src/integrations/watchers/indexable-post-watcher.php(209): Yoast\WP\SEO\Builders\Indexable_Link_Builder->build()
#7 /home/www/cc.cz/subdomains/www/wp-includes/class-wp-hook.php(326): Yoast\WP\SEO\Integrations\Watchers\Indexable_Post_Watcher->build_indexable()
#8 /home/www/cc.cz/subdomains/www/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters()
#9 /home/www/cc.cz/subdomains/www/wp-includes/plugin.php(517): WP_Hook->do_action()
#10 /home/www/cc.cz/subdomains/www/wp-includes/post.php(4771): do_action()
#11 /home/www/cc.cz/subdomains/www/wp-includes/post.php(4862): wp_insert_post()
#12 /home/www/cc.cz/subdomains/www/wp-admin/includes/post.php(453): wp_update_post()
#13 /home/www/cc.cz/subdomains/www/wp-admin/post.php(227): edit_post()
#14 {main}

And here are some logs after updating the plugin to the latest version 2.5.1:

[01-Mar-2024 07:49:57 UTC] RedisException: socket error on read socket in /home/www/cc.cz/subdomains/www/wp-content/object-cache.php:559
Stack trace:
#0 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(559): Redis->ping()
#1 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(256): WP_Object_Cache->__construct()
#2 /home/www/cc.cz/subdomains/www/wp-includes/load.php(856): wp_cache_init()
#3 /home/www/cc.cz/subdomains/www/wp-settings.php(131): wp_start_object_cache()
#4 /home/www/cc.cz/subdomains/www/wp-config.php(114): require_once('...')
#5 /home/www/cc.cz/subdomains/www/wp-load.php(50): require_once('...')
#6 /home/www/cc.cz/subdomains/www/wp-blog-header.php(13): require_once('...')
#7 /home/www/cc.cz/subdomains/www/index.php(17): require('...')
#8 {main}

[01-Mar-2024 07:49:57 UTC] PHP Fatal error:  Uncaught Error: Call to a member function get() on null in /home/www/cc.cz/subdomains/www/wp-content/object-cache.php:193
Stack trace:
#0 /home/www/cc.cz/subdomains/www/wp-includes/option.php(599): wp_cache_get()
#1 /home/www/cc.cz/subdomains/www/wp-includes/option.php(164): wp_load_alloptions()
#2 /home/www/cc.cz/subdomains/www/wp-includes/theme.php(319): get_option()
#3 /home/www/cc.cz/subdomains/www/wp-includes/theme.php(332): get_template()
#4 /home/www/cc.cz/subdomains/www/wp-includes/l10n.php(1306): get_template_directory()
#5 /home/www/cc.cz/subdomains/www/wp-includes/l10n.php(1331): _load_textdomain_just_in_time()
#6 /home/www/cc.cz/subdomains/www/wp-includes/l10n.php(185): get_translations_for_domain()
#7 /home/www/cc.cz/subdomains/www/wp-includes/l10n.php(297): translate()
#8 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(2922): __()
#9 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(2890): WP_Object_Cache->show_error_and_die()
#10 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(566): WP_Object_Cache->handle_exception()
#11 /home/www/cc.cz/subdomains/www/wp-content/object-cache.php(256): WP_Object_Cache->__construct()
#12 /home/www/cc.cz/subdomains/www/wp-includes/load.php(856): wp_cache_init()
#13 /home/www/cc.cz/subdomains/www/wp-settings.php(131): wp_start_object_cache()
#14 /home/www/cc.cz/subdomains/www/wp-config.php(114): require_once('...')
#15 /home/www/cc.cz/subdomains/www/wp-load.php(50): require_once('...')
#16 /home/www/cc.cz/subdomains/www/wp-blog-header.php(13): require_once('...')
#17 /home/www/cc.cz/subdomains/www/index.php(17): require('...')
#18 {main}
  thrown in /home/www/cc.cz/subdomains/www/wp-content/object-cache.php on line 193

[tillkruss]

These are really helpful.

[tillkruss]

I'm gonna move these here:
rhubarbgroup/redis-cache#508
rhubarbgroup/redis-cache#507