How to delete all keys from redis cluster

Question

I want to delete all keys from redis cluster by using fast process. I know how to delete the keys by using "redis-cli FLUSHALL". But this command can be slow when the data set is large. I heard that all keys can be cleared from redis cache by re-starting the redis service. I am testing this process on my local mac laptop. I am performing following steps:-

1. Setting many number of keys on my local redis server by using example command redis-cli SET mykey1 "Hello"
2. Then Re-starting the redis service "brew services restart redis" in the hope that all keys will be deleted when the service will be back up
3. Then getting the keys by giving "redis-cli KEYS '*'" command

I still see the keys after step-3

The keys are gone only when I give this command--> redis-cli FLUSHALL? How I can clear the keys by re-starting the redis service locally on my mac laptop first then I will try on QA servers?

Answer 1

You see the keys after restart because there is either RDB or AOF persistence enabled. See https://redis.io/topics/persistence.

RDB is enabled by default. To disable persistence, you need to edit your redis.conf or start as redis-server --save "" --appendonly no

See Is there a way to flushall on a cluster so all keys from master and slaves are deleted from the db on how to use redis-cli to send the command to all cluster nodes.

As dizzyf indicates, use FLUSHALL ASYNC to have the deletion performed in the background. This will create fresh hash maps for each database, while the old ones are deleted (memory reclaimed) progressively by a background thread.

Answer 2

In redis 4.0 and greater, the FLUSHALL ASYNC command was introduced, as a way to delete all the keys in a non-blocking manner. Would this solve your issue?

https://redis.io/commands/flushall

Answer 3

Thank you for links. These were very helpful. I was able to achieve the result by making changes to my redis.conf file with--> redis-server --save "" and --appendonly no. So after these changes, when I now re-start redis service nothing is saved.