Bad performance after updating to v2.6.1

[timmipetit]

After updating to v2.6.1, which introduced #91, we've seen a enormous drop in performance for our collection script. This is interesting, because the merge request is meant to increase performance.

Here's a screenshot from the average response time of our prometheus collection script:

[LKaemmerling]

Hey @timmipetit,

can you try to downgrade to v2.6.0 just to make sure it is really related to the script? How many metrics do you expose? Might it be that the redis has a lot of keys?

[timmipetit]

Hi @LKaemmerling. We've downgraded back to v2.6.0, and performance is back to normal for us. We don't expose a lot of metrics, 6 histograms (with 16 buckets each) and 3 gauges (so no summaries). But our Redis instance is also used for sessions though, so we do have a lot of other keys (400k or so). The keys used for sessions have a different prefix. But since scan will iterate all keys, it will fetch all session keys (before discarding them again because they don't match)

[grogy]

I have to say the same from project https://supportbox.com/ - after upgrade to 2.6.1 so bad performance. Wipe storage (Redis) does not help.

[LKaemmerling]

Hello together,

i just released v2.6.2 with the revert of the given MR.

[LKaemmerling]

Hey @grogy & @timmipetit,

would it be possible that you test https://github.com/PromPHP/prometheus_client_php/pull/99/files against your workload (new StorageEngine RedisNG). This basically fixes the usage of KEYS and SCAN.

[timmipetit]

@LKaemmerling Thanks for the heads up. We'll test it

[timmipetit]

Tested on our workload, works fine!