CODEWITHSUNDEEP
redis
royB
royB

Reputation: 12977

Redis expire on large set of keys

My problem is: i have a set of values that each of them has to have an expire value. code: 

set a:11111:22222 someValue
expire a:11111:22222 604800 \\usually equal a week

In a perfect world i would have put all those values in a hash and give each of them it's appropriate expire value, but redis does not allow expire on a hash fields.

problem is that i also have a process that need to get all those keys about once an hour

keys a:*

this command is really expensive and according to redis documentation can cause performance issues. I have about 25000-30000 keys at each given moment.

Does someone knows how can i solve such a problem? thumbs up it guarantee (-;
Roy

Upvotes: 5

Views: 20229

Answers (4)

Mahmoud.Eskandari
Mahmoud.Eskandari

Reputation: 1478

Also you can do complex commands with EVAL, like this:


EVAL "local keys = redis.call('keys',ARGV[1]) for _, key in ipairs(keys) do redis.call('EXPIRE', key, ARGV[2]) end return 1" 0 * 86400

It's a script * and 86400 at the end of command are pattern and expiration time

Upvotes: 0

kris.jeong
kris.jeong

Reputation: 99

Why don't you use a sorted set.

Here is some data creation sequence.

redis 127.0.0.1:6379> setex a:11111:22222 604800 someValue
OK
redis 127.0.0.1:6379> zadd user:index 1385112435 a:11111:22222   // 1384507635 + 604800
(integer) 1
redis 127.0.0.1:6379> setex a:11111:22223 604800 someValue2
OK
redis 127.0.0.1:6379> zadd user:index 1385113289 a:11111:22223  // 1384508489 + 604800
(integer) 1
redis 127.0.0.1:6379> zrangebyscore user:index 1385112435 1385113289
1) "a:11111:22222"
2) "a:11111:22223"

This is no select performance issue. but, It spends more memory and insert cost.

Upvotes: 0

Didier Spezia
Didier Spezia

Reputation: 73226

Let me propose an alternative solution.

Rather than asking Redis to scan all the keys, why not perform a background dump, and parse the dump to extract the keys? This way, there is zero impact on the Redis instance itself.

Parsing the dump file is not as scary as it sounds, because you can use the excellent redis-rdb-tools package:

https://github.com/sripathikrishnan/redis-rdb-tools

You can either convert the dump file into a json file, and then parse the json file, or use the Python API to extract the keys by yourself.

Upvotes: 11

RienNeVaPlu͢s
RienNeVaPlu͢s

Reputation: 7632

As you've already mentioned, using keys is not a good solution to get your keys:

Warning: consider KEYS as a command that should only be used in production environments with extreme care. It may ruin performance when it is executed against large databases. This command is intended for debugging and special operations, such as changing your keyspace layout. Don't use KEYS in your regular application code. If you're looking for a way to find keys in a subset of your keyspace, consider using sets.

Source: Redis docs for KEYS

As the docs are suggesting, you should build your own indices! A common way of building an index is to use a sorted set. You can read more on how it's working on my question over here.

Building references to your a:* keys using a sorted set, will also allow you to only select the required keys in relation to a date or any other int value, in case you're filtering the results!

And yes: it would be awesome if hashes could expire. Sadly it looks like its not going to happen, but there are in fact creative alternatives to take care about it by yourself.

Upvotes: 2

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