Xenforo Plugin Redis Cache By Xon v2.16.1

License Information :

Compatible XF 2.x versions 2.1 2.2
Additional requirements php 7.0+
Redis (v3.0.0 or better)
phpredis (for performance) Developer Xon

This add-on uses Credis with a custom cache provider for Redis (based off Cm_Cache_Backend_Redis). For best performance, install the php extension: phpredis

You must have a Redis instance installed, this is likely not possible with shared hosting

While XenForo 2 has a redis connector, it requires phpredis. This add-on does not.

Feature overview

• A pure php redis connector
• High availability support
• Exposes redis cache object for use for use by other add-ons
• Implements some minor caching of forum thread counts
• Redirect's XenForo's individual css template caching to hit redis as otherwise it causes unexpected write & deadlocking on the xf_css_cache table

Troubleshooting

Please be aware that Redis is very sensitive to latency in a virtual environment. If repeated connection failures or protocol errors are experienced disable any Redis Persistence options.

Options
By default, forum thread counts are cached. In general, this is observable when moving large number of threads from one forum to another, and the total page counts are wrong.



Redis Statistics
Admincp dash board is extended with basic redis statistics:



Read Scaling
With the $config['cache']['config']['load_from_slave'] option, reads can be deferred to a singular slave instance. This takes all the options of 'config' (except the slave config)
See the FAQ for configuration samples.
High availability
The Zend component support master/slave setups with Redis Sentinel support. It does not support Redis multi-master clustering.

• Additionally, this add-on implement caching of thread counts in a forum.
• Redis Sentinel support for high-availability (see FAQ for details).

Licencing
Components licenced under; New BSD

• Credis

Components licenced under; MIT Licence

• XenForo Add-on code

Contributing features or bug fixes
Please create a GitHub Pull request via the "More Information" link.

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FAQ

Q: There are a lot of the errors; "CredisException: read error on connection" or "CredisException: protocol error, got 'xxx' as reply type byte" being logged
A: Please be aware that Redis is very sensitive to latency in a virtual environment. If repeated connection failures or protocol errors are experienced disable any Redis Persistence options. Additionally, check CPU steal as this can also cause latency issues.
Additionally, check the redis log file ( /var/log/redis/redis.log ) for any warnings. Key things to look for:

• WARNING you have Transparent Huge Pages (THP) support enabled in your kernel

• WARNING /proc/sys/net/core/somaxconn is set to the lower value of 128

You may require to adjust "net.ipv4.tcp_max_syn_backlog" to be larger!

• WARNING overcommit_memory is set to 0! Background save may fail under low memory condition

(All 'fixes' require restarting redis to apply).
You may need to increase tcp-backlog from the stock 511, please ensure net.core.somaxconn is adjusted as well!
This server configuration advise is best effort, and not guarantied as it is well outside the scope of this add-on.
Q. CPU Steal is mentioned as causing latency issue, how do I check this.
A. On Linux, run:


screen
iostat -c -t 30 > /tmp/cpu_stats.log


Then after a day or so; check your max CPU steal:


cat /tmp/cpu_stats.log | grep -v iowait | awk '{print $5;}' | sort -rn | more


Q: Support for earlier versions of XenForo
A: See Zend Redis cache add-on for XenForo 1.4+ support
Q: Redis Configuration
A: Please see the Redis Documenatation.
Alternatively, you can use @eva2000's How to install Redis server on Centmin Mod LEMP stack Guide.
Q:Make Redis behave like Memcache
A: See Using Redis as an LRU cache, and make sure to set maxmemory!


maxmemory 256mb
maxmemory-policy allkeys-lru


ou may wish to disable the periodic 'save' directives which can cause latency on high-usage websites in virtual environments.
Q: Sample XenForo Configuration using TCP
A: Please see https://xenforo.com/xf2-docs/manual/cache/ for details on setting up the general XenForo Cache.
The minimum configuration is:


$config['cache']['enabled'] = true;
$config['cache']['provider'] = 'SV\RedisCache\Redis';
$config['cache']['config'] = [
'server' => '127.0.0.1',
'port' => 6379,
];


Q: Sample XenForo Configuration using a socket
A: Please see https://xenforo.com/help/cache/ for details on setting up the general XenForo Cache.
The minimum configuration is:


$config['cache']['enabled'] = true;
$config['cache']['provider'] = 'SV\RedisCache\Redis';
$config['cache']['config'] = [
'server' => 'unix:///tmp/redis.sock',
];


Q: Sample XenForo Configuration using username/password
Redis supports username/password authentication.
This is most common in cloud environments which use redis 6 (ie with a username), while older redis only supports just a password


$config['cache']['config']['username'] = 'myUsername'; // requires redis 6+, or for cloud redis installations
$config['cache']['config']['password'] = '....';


Q. Sample XenForo Configuration using SSL/TLS support


$config['cache']['config']['server'] = 'ssl://127.0.0.1';
// See https://www.php.net/manual/en/context.ssl.php for details
$config['cache']['config']['tlsOptions'] = [
'SNI_enabled' => true,
];


Q. When trying to use a socket, an exception with "No such file or directory" is thrown
A. There are a few reasons this could happen;
After confirming that the socket path is correct, try the following suggestions:

• selinux is preventing php from accessing the socket.
• open_basedir is preventing php from accessing the socket.
• chroot is preventing php from accessing the socket.
• permissions are preventing php from reading/writing to the socket.

Q: Sample Single Redis Slave Configuration
A:
The minimum configuration is:


$config['cache']['enabled'] = true;
$config['cache']['provider'] = 'SV\RedisCache\Redis';
$config['cache']['config'] = [
'server' => '127.0.0.1',
'port' => 6379,
];
$config['cache']['config']['load_from_slave'] = array(
'server' => '127.0.0.1',
'port' => 6378,
];


Q: Sample Redis Sentinel Configuration
A:
Redis Sentinel support for high-availability. See http://redis.io/topics/sentinel for more information.
Enable with:


$config['cache']['config']['sentinel_master'] = 'mymaster';
$config['cache']['config']['server'] = 'tcp://127.0.0.1:26379';


'server' now points to a comma delimited list of sentinel servers to find the master. Note; the port must be explicitly listed
To load data from slaves use;


$config['cache']['config']['load_from_slaves'] = true;


By default, a local slave is preferred, this can be changed by setting:


$config['cache']['config']['slave_select_callable'] = function (array $slaves) {
$slaveKey = array_rand($slaves, 1);
return $slaves[$slaveKey];
};


Setting to false (or some non-callable) will fall back to a random slave.
Q: Performance - Redis
A: See:

• phpredis PECL extension
• Benchmarking
• Latency troubleshooting

Q: phpredis supports persistent connection, are these recommended?
A: I do not recommend using persistent connections, as they appear to be quite buggy.