Admin tips

What’s Redis?

Redis is an advanced key-value store. It is similar to memcached but the dataset is not volatile, and values can be strings, exactly like in memcached, but also lists, sets, and ordered sets. All this data types can be manipulated with atomic operations to push/pop elements, add/remove elements, perform server side union, intersection, difference between sets, and so forth. Redis supports different kind of sorting abilities.

Also it is really fast – 110000 SETs/second, 81000 GETs/second at Xeon X3320 2.5Ghz Linux 2.6.x server. I believe that everything should be monitored so I’ve written redis monitoring plugin for Munin. It allows to monitor some of the values such as:

• connected clients
• requests per second
• connections per second
• used memory

The plugin could be downloaded here.

Installation process:

1. Download the plugin to your plugins directory (e.g. /usr/share/munin/plugins)
2. Create 3 symlinks at the directory that us used by munin for plugins detection (e.g. /etc/munin/plugins): redis_connected_clients, redis_per_sec and and redis_used_memory
3. Edit plugin-conf.d/munin-node if it is needed (env.host and  env.port variables are accepted)
4. Restart munin-node service

As the result you’ll have something like this:

redis connected clients

redis requests/connections per second

redis used memory

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