[optimization] cache prometheus : fix "loki_cache_request_duration_seconds_bucket" ‘status_code’ label always equals "200"

[liguozhong]

refer issue ：#4862
alert promql.

[stale]

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[jeschkies]

Thanks! I just cannot find where the error metric is increased or HTTP 5xx is returned.

[owen-d]

Nice work. I'm happy to merge this once the merge conflicts/etc are addressed.

[liguozhong]

Nice work. I'm happy to merge this once the merge conflicts/etc are addressed.

done,thanks

[owen-d]

One small suggestion, then LGTM. Thanks for all the great contributions!

[liguozhong]

thanks all，status_code = 500 now.

sum(rate(loki_cache_request_duration_seconds_count{status_code!="200"}[2m])) by (app,name,method,status_code)>0
alert

dadashboar