feat(mastodon): Extend mastodon SLO with response speeds

apps/k8s01/mastodon/slo.yaml

@@ -8,7 +8,7 @@ spec:
   slos:
     - name: "requests-availability"
       objective: 98
-      description: "Mastodon SLO based on availability for HTTP request responses."
+      description: "Mastodon: SLO based on availability for HTTP request responses."
       sli:
         events:
           errorQuery: sum(rate(nginx_ingress_controller_requests{exported_namespace="mastodon",ingress="mastodon",status=~"(5..|429)"}[{{.window}}]))
@@ -19,3 +19,23 @@ spec:
           category: "availability"
         annotations:
           summary: "High error rate on 'mastodon' requests responses"
+    - name: "requests-latency"
+      objective: 98
+      description: "Mastodon: SLO based on latency for HTTP request responses. Warns if requests take longer than 250ms. When responses are slower than 200ms they become noticable slow."
+      labels:
+        category: latency
+      sli:
+        events:
+          errorQuery: |
+            (
+              sum(rate(nginx_ingress_controller_request_duration_seconds_count{exported_namespace="mastodon",ingress="mastodon",method!="WATCH"}[{{.window}}]))
+              -
+              sum(rate(nginx_ingress_controller_request_duration_seconds_bucket{exported_namespace="mastodon",ingress="mastodon",le="0.25",verb!="WATCH"}[{{.window}}]))
+            )
+          totalQuery: sum(rate(nginx_ingress_controller_request_duration_seconds_count{exported_namespace="mastodon",ingress="mastodon",method!="WATCH"}[{{.window}}]))
+      alerting:
+        name: MastodonLatencyAlert
+        labels:
+          category: "latency"
+        annotations:
+          summary: "Slow responses on 'mastodon' requests responses. More than 1% take more than 250ms."
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