Redis: Show database size/size for keys

redis

My redis instance seems to being growing very large and I'd like to find out which of the multiple databases I have in there consumes how much memory. Redis' INFO command just shows me the total size and the number of keys per database which doesn't give me much insight… So any tools/ideas that give me more information when monitoring the redis server would be appreciated.

The Redis documentation doesn't show me any commands that can return the consumed memory of certain keys, so I guess if any buggy code would write a lot of "trash" to redis this could be really hard to find…

Best Answer

So my solution to my own problem: After playing around with redis-cli a bit longer I found out that DEBUG OBJECT <key> reveals something like the serializedlength of key, which was in fact something I was looking for...

For a whole database you need to aggregate all values for KEYS * which shouldn't be too difficult with a scripting language of your choice...

The bad thing is that redis.io doesn't really have a lot of information about DEBUG OBJECT.

Related Solutions

How to atomically delete keys matching a pattern using Redis

Execute in bash:

redis-cli KEYS "prefix:*" | xargs redis-cli DEL

UPDATE

Ok, i understood. What about this way: store current additional incremental prefix and add it to all your keys. For example:

You have values like this:

prefix_prefix_actuall = 2
prefix:2:1 = 4
prefix:2:2 = 10

When you need to purge data, you change prefix_actuall first (for example set prefix_prefix_actuall = 3), so your application will write new data to keys prefix:3:1 and prefix:3:2. Then you can safely take old values from prefix:2:1 and prefix:2:2 and purge old keys.

Redis command to get all available keys

Try to look at KEYS command. KEYS * will list all keys stored in redis.

EDIT: please note the warning at the top of KEYS documentation page:

Time complexity: O(N) with N being the number of keys in the database, under the assumption that the key names in the database and the given pattern have limited length.

UPDATE (V2.8 or greater): SCAN is a superior alternative to KEYS, in the sense that it does not block the server nor does it consume significant resources. Prefer using it.

Best Answer

Related Solutions

How to atomically delete keys matching a pattern using Redis

Redis command to get all available keys

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