Remove flaky PromscaleCacheTooSmall alert

This commit removes the alert PromscaleCacheTooSmall which is flaky and fires during same cause as `PromscaleCacheHighNumberOfEvictions`.

Fixes #1356.

Signed-off-by: Arunprasad Rajkumar <ar.arunprasad@gmail.com>

CHANGELOG.md

@@ -26,6 +26,7 @@ We use the following categories for changes:
 - Refine check for existence of `prom_schema_migrations` table [#1452]
 - Do not run rules-manager in `-db.read-only` mode [#1451]
 - Fix underlying metric(`promscale_sql_database_chunks_count`) which leads to false positive firing of PromscaleCompressionLow alert [#1494]
+- Remove flaky PromscaleCacheTooSmall alert  [#1498]
 
 ## [0.12.1] - 2022-06-29
 

docs/mixin/alerts/alerts.yaml

@@ -172,37 +172,16 @@ groups:
   - alert: PromscaleCacheHighNumberOfEvictions
     expr: |
       (
-        sum by (job, instance, name, type) (
-          rate(promscale_cache_evictions_total[5m])
-        )
-      /
-        sum by (job, instance, name, type) (
-          promscale_cache_capacity_elements
-        )
+        rate(promscale_cache_evictions_total[5m])
+        /
+        promscale_cache_capacity_elements
       ) > 0.2
     labels:
       severity: warning
     annotations:
       summary: High cache eviction in Promscale.
       description: "Promscale {{ $labels.name }} is evicting at {{ $value }} entries a second."
       runbook_url: https://github.com/timescale/promscale/blob/master/docs/runbooks/PromscaleCacheHighNumberOfEvictions.md
-  - alert: PromscaleCacheTooSmall
-    expr: |
-      (
-        sum by (job, instance, type, name) (
-          rate(promscale_cache_query_hits_total[5m])
-        )
-      /
-        sum by (job, instance, type, name) (
-          rate(promscale_cache_queries_total[5m])
-        )
-      ) < 0.9
-    labels:
-      severity: warning
-    annotations:
-      summary: High cache eviction in Promscale.
-      description: "Promscale {{ $labels.name }} has a hit ratio of {{ $value | humanizePercentage }}."
-      runbook_url: https://github.com/timescale/promscale/blob/master/docs/runbooks/PromscaleCacheTooSmall.md
 - name: promscale-database-connection
   rules:
   - alert: PromscaleDBHighErrorRate