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Mcrouter is a memcache protocol routing layer. It abstracts request routing, connection pooling, failover, and many other features from the client, which can simply talk to mcrouter over a TCP connection using the memcache protocol.

Typically, minimal or no client changes are needed to make use of mcrouter's features, which is set up as a drop-in proxy between the client and memcached hosts.

At Facebook, mcrouter is a core component of a distributed cache infrastructure that spans over a large number of individual memcached boxes.

To install Mcrouter, see Installation.

Quick start

Assuming you have a memcached instance on the local host running on port 5001, the simplest Mcrouter setup is (::1 is IPv6 loopback address; IPv6 addresses must be specified in square brackets. You can also use "127.0.0.1:5001" or "localhost:5001"):

./mcrouter --config-str='{"pools":{"A":{"servers":["[::1]:5001"]}},"route":"PoolRoute|A"}' -p 5000

To test it works one can send a request to port 5000. For example, using Netcat (http://netcat.sourceforge.net/):

echo -ne "get key\r\n" | nc 0 5000

For a complete list of command line arguments, check ./mcrouter --help.

Next steps

Essentially, Mcrouter takes in a memcache request, applies rules defined by the configs, and sends it on. The complexity resides in defining and subscribing to the configuration rules properly. Configuration allows for flexible specification of special handling and failover behavior.

Mcrouter supports typical memcache protocol commands like get, set, delete, etc. and specific commands to access stats, version and so on. See Routing for more.

See Configuration for information about how Mcrouter is configured. Mcrouter config is JSON file(s) primarily consisting of pool and route information.