How to Clear Redis Cache

Introduction

Redis is an open-source solution for data structure storage. It is primarily used as a key-value store, which allows it to work as a database, cache storage, and message broker.

In this tutorial we will cover different ways you can delete these key-values (keys) and clear Redis cache.

Prerequisites

• The latest version of Redis (see our guide on how to install Redis on Ubuntu, on Mac or run Redis on Docker)
• Access to the command line / terminal window

Clear Redis Cache With the redis-cli Command

The easiest way to clear Redis cache is to use the redis-cli command.

Databases in Redis are stored individually. Using the redis-cli command allows you to either clear the keys from all databases, or from a single specified database only.

redis-cli Command Syntax

The redis-cli command uses the following syntax:

redis-cli [database number] [option]

Where:

• [option] – Lets you choose between clearing all databases or one specific database of your choice.
• [database number] – Lets you specify which database you want to clear.

Deleting All Keys

To delete keys from all Redis databases, use the following command:

redis-cli flushall

As of version 4.0.0, Redis can clear keys in the background without blocking your server. To do this, use the flushall command with the async parameter:

redis-cli flushall async

Deleting Keys from a Specific Database

Use the following command to clear a specific database only:

redis-cli flushdb

Using the flushdb command without any parameters clears the currently selected database. Use the -n parameter with the database number to select a specific database you want to clear:

redis-cli -n [database number] flushdb

You can also use the async option when clearing keys from individual databases:

redis-cli -n [database number] flushdb async

Automating Cache Clearing Using Ansible

If you have a large number of Redis servers running, clearing the cache for each one manually takes time.

To speed this process up, use a tool like Ansible to clear the cache on all your Redis servers at the same time:

ansible all -m command -a '/usr/bin/redis-cli flushall '

Running this command applies the flushall command to every server in your Ansible inventory file:

• all – Lets you choose all the remote hosts in the Ansible inventory file.
• -m – Lets you choose a module to execute.
• -a – Provides an argument for the module. In this case, the command module runs the flushall command with redis-cli.

Conclusion

After going through this tutorial, you have learned how to use the redis-cli and flush commands to clear your Redis cache.

Next, learn more about Redis by exploring Redis Data Types.