[NEW] Introduce slot level metrics to Valkey cluster

@kyle-yh-kim

I’m revisiting the feature proposal we discussed in redis/redis#10472, which aims at providing metrics at the slot level. Despite the substantial effort and detailed discussions back then, we didn’t land this feature. I believe it’s worth reconsidering, given the potential benefits and previous interest.

@kyle-yh-kim @zuiderkwast @madolson

I fully agree!

I've also re-added my favorite creature comfort. @placeholderkv/core-team thoughts?

Sure, metrics seem fine. I don't have strong opinions about it, only that I think fixing the cluster consistency problems is more important than metrics.

redis/redis#11432

I think our big initial play should be cluster overhaul. I think a lot of us want it, and it makes the most compelling sense as the big "next major features".

Good to hear back on this thread, hope you all have been doing well.

Where we left-off

In total, there were 3 proposed metrics under CLUSTER SLOT-STATS command group;

key_count
cpu_usec
memory_bytes

Next steps

memory_bytes is the most complex of all, but this shouldn't stop us from implementing the first two metrics to gain some momentum.

I will open two PRs for key_count and cpu_usec in the coming days. These PRs will be based off of the already existing PRs for key_count and cpu_usec under Redis repository.

As for CLUSTER SLOT-STATS command format, below was the latest development we agreed upon. Lengthy discussion and rationale can be found here and here.

CLUSTER SLOT-STATS
[SLOTSRANGE start-slot end-slot [start-slot end-slot ...]]|
[ORDERBY column [LIMIT limit] [ASC|DESC]]

It is great, and I prefer to add this feature in CLUSTER INFO.

It is great, and I prefer to add this feature in CLUSTER INFO.

Why cluster info? It's a free form field I guess, it could be a new sub info field I suppose

Thanks for chiming in. Personally, I'm opposed to CLUSTER INFO. We could perhaps add aggregated information under CLUSTER INFO, but not for the slot level metrics themselves.

Imagine dumping ~16384 slot level metrics under CLUSTER INFO. This would unnecessarily bloat the info string, when the user may have only wanted to check cluster_state:ok.

A new command dedicated for slot level metrics querying, in this case, CLUSTER SLOT-STATS, is more suitable. For reference, below was the latest command format we agreed on.

CLUSTER SLOT-STATS
[SLOTSRANGE start-slot end-slot [start-slot end-slot ...]]|
[ORDERBY column [LIMIT limit] [ASC|DESC]]

I'll wait for the core team to finalize this decision, before opening the PRs.

@kyle-yh-kim

@kyle-yh-kim Yeah CLUSTER SLOT-STATS. We're a bit overloaded with the forking stuff, new core team, new project, etc. but I think we want this for our next release. There was already a lot of review done and I think it was almost ready to merge. Do you want to bring over your PR?

The four components for Valkey 8.0 are now merged. We will follow up with memory in Valkey 8.2.

Fix hashtablePauseAutoShrink and use it in hashtableScanDefrag (#2257)

Fix hashtablePauseAutoShrink and use it in hashtableScanDefrag (valke…

Fix hashtablePauseAutoShrink and use it in hashtableScanDefrag (#2257)

update artifactory repo (valkey-io#20)

Inline compression: drop dict-scoped retry guard (S2.3 superseded)

Inline compression: drop dict-scoped retry guard (S2.3 superseded) (#10)

feat(S1.2): training sampler + BIO_COMPRESSION_TRAIN job (valkey-io#20)

fix(S1.2): NULL-guard server.db[j] iteration in compressionTrainCron (v…

docs(plan): mark S1.2/S1.3/S1.4 complete (PR valkey-io#20, valkey-io#25…

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[NEW] Introduce slot level metrics to Valkey cluster #20

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madolson commented on Mar 25, 2024

madolson commented on Mar 25, 2024

zuiderkwast commented on Mar 25, 2024

zuiderkwast commented on Mar 25, 2024

madolson commented on Mar 25, 2024

kyle-yh-kim commented on Mar 26, 2024

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hwware commented on Mar 27, 2024

madolson commented on Mar 27, 2024

kyle-yh-kim commented on Mar 28, 2024

zuiderkwast commented on Apr 15, 2024

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madolson commented on Jul 26, 2024

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