Relay
If the Relay PHP extension is installed on your system, using it with Object Cache Pro is as easy as setting the client
configuration option.
There are however a few important things to know:
- Use compression and igbinary to reduce Relay memory usage
- Understand the multitenancy limitations
- Experiment with prefetching and
alloptions
splitting
Multitenancy limitations
With Relay enabled, running multiple WordPress sites using a single Redis instance has some limitations, which will cause unnecessary flushing of Relay’s memory.
To bypass most of them, it is vital to:
- Use a dedicated
database
for each WordPress site - As well as, a unique
prefix
for each WordPress site
Unfortunately, due to Redis’ design, Relay isn’t aware of the database index
when FLUSHDB
is called and thus will flush it’s entire memory.
If you’re curious, read the technical details.
Relay configuration
define('WP_REDIS_CONFIG', [
'token' => '...',
'host' => '127.0.0.1',
'port' => 6379,
// use `relay` extension
'client' => 'relay',
// avoid unnecessary flushing
// change `3` and `db3` for each site
'database' => 3,
'prefix' => 'db3',
// whether multiple WordPress sites use the Redis instance
'shared' => true,
// reduce memory usage
'compression' => 'zstd',
'serializer' => 'igbinary',
// experiment with these, some sites may benefits, so may not
'prefetch' => false,
'split_alloptions' => false,
// standard options
'timeout' => 0.5,
'read_timeout' => 0.5,
'retries' => 3,
'backoff' => 'smart',
// debug only
'debug' => false,
'save_commands' => false,
]);