Add support for storing state in Redis

[ghimire]

This pull request introduces support for storing the persistent state of Flower in Redis, as an alternative to the existing file-based storage mechanism. This enhancement aims to improve the reliability, scalability, and performance of state management in Flower.

This removes the limitation that prevented running multiple instances of Flower concurrently by centralizing state management in Redis.

[ghimire]

cc: @mher

[iloveitaly]

This is a great idea. Makes it much easier to run flower in a containerized environment.

What needs to be done here to merge this in, @mher?

[iloveitaly]

This removes the limitation that prevented running multiple instances of Flower concurrently by centralizing state management in Redis.

the other big benefit here is state is not lost when the container restarts (if you don't have a persistent volume attached to your container).

Created a PR for rediss support here

[ghimire]

@Nusnus Bump

[Copilot]

Pull Request Overview

This PR adds Redis support as an alternative backend for storing Flower's persistent state, replacing the existing file-based storage mechanism. This enhancement enables running multiple instances of Flower concurrently by centralizing state management in Redis.

Key changes:

• Added Redis client initialization and state management logic
• Implemented Redis-based state loading and saving with pickle serialization
• Updated documentation to reflect Redis backend support

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
flower/events.py	Added Redis client initialization, state loading/saving logic with pickle serialization
docs/config.rst	Updated documentation to mention Redis backend support

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[ghimire]

@auvipy @Nusnus Bump

[auvipy]

this will also need unit tests to verify the proposed changes

[ghimire]

@auvipy Unit tests have been added for Redis events state storage in 0192efc.

[ghimire]

@auvipy @Nusnus

The flower/events.py:24:0: C0103: Variable name "PROMETHEUS_METRICS" doesn't conform to snake_case naming style (invalid-name) lint error is outside of the scope of this PR.

[mher]

Saving the entire state with a single redis_client.set is not scalable.

[ghimire]

Saving the entire state with a single redis_client.set is not scalable.

@mher Agreed, but Flower isn't scalable as it is, due to a file based state. I don't think having this Redis alternative makes it any worse. The flower database gets corrupted more frequently than one would hope. Fixing it in Redis is much easier, and it also means the Flower container doesn't need to be restarted.

Do you have any other plans or thoughts on moving the state out of filesystem to make it truly scalable?

I do think that this implementation is a start in that direction. Please share any suggestions you might have to improve the current implementation.