External changes to distributed cache

[ajbeaven]

I've been reviewing the following docs to answer this question, but am unfortunately still unclear:

https://github.com/ZiggyCreatures/FusionCache/blob/main/docs/Backplane.md#%EF%B8%8F-external-changes-be-careful

I'm using L1+L2 cache (Redis) with a backplane. I'm wanting to know what happens in the event I manually delete a key from Redis and whether that change somehow flows through to the L1 caches. I understand the backplane is responsible for updating the nodes, but I want to confirm that if I make a change to the L2 distributed cache externally (e.g. log in to Redis and delete a key), does the backplane sees this and propagate this to the L1 caches in all nodes?

From the docs above:

Just to reiterate, because it's very important: when using the backplane without a distributed cache, any change not manually published by us would result in different nodes not being synched.

In my case I am making an external change, but I am using a distributed cache. I took from this then that the nodes would be synced. ChatGPT thinks otherwise so I wanted to confirm here.

[jodydonetti]

Hi @ajbeaven , sorry for the delay, I was away for a week.

I've been reviewing the following docs to answer this question, but am unfortunately still unclear:

https://github.com/ZiggyCreatures/FusionCache/blob/main/docs/Backplane.md#%EF%B8%8F-external-changes-be-careful

I'm using L1+L2 cache (Redis) with a backplane. I'm wanting to know what happens in the event I manually delete a key from Redis and whether that change somehow flows through to the L1 caches.
I understand the backplane is responsible for updating the nodes, but I want to confirm that if I make a change to the L2 distributed cache externally (e.g. log in to Redis and delete a key), does the backplane sees this and propagate this to the L1 caches in all nodes?

Short answer: no, it will not flow.

Longer answer: the backplane is used to send notifications to all the connected nodes. But if no nodes actively send one, nothing will be sent automatically based on a manual change in the key-value store.

From the docs above:

Just to reiterate, because it's very important: when using the backplane without a distributed cache, any change not manually published by us would result in different nodes not being synched.

This passage was about a particular edge case: using a backplane without an L2, which is something technically doable but overall risky and honestly not suggested.

Hope this helps, let me know.

[ajbeaven]

Got it - thanks for the confirmation!

[bryancrosby]

I have wondered the same thing @ajbeaven , thank you for asking this question.

@jodydonetti is this technically impossible or just something that hasn't been implemented?

Once again, thank you for your fantastic library and documentation! 😄