alerts: remove fiber csw example

Using rate with tnt_fiber_csw metric is incorrect.

Follows up #72

Author: DifferentialOrange

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 - Remove rate from fiber context switches panel
+- Remove fiber context switches alert example
 
 
 ## [1.1.0] - 2022-05-17

example_cluster/prometheus/alerts.yml

@@ -151,17 +151,6 @@ groups:
       description: "Instance '{{ $labels.alias }}' of job '{{ $labels.job }}' have
         high vinyl scheduler failed tasks rate."
 
-  # Alert for Tarantool low context switches rate.
-  - alert: LowFiberCSWRate
-    expr: rate(tnt_fiber_csw[2m]) < 10
-    for: 1m
-    labels:
-      severity: warning
-    annotations:
-      summary: "Instance '{{ $labels.alias }}' ('{{ $labels.job }}') has low fiber context switches rate"
-      description: "Instance '{{ $labels.alias }}' of job '{{ $labels.job }}' has low fiber context switches rate.
-        Some high loaded fiber has too little yields. It may be the reason of 'Too long WAL write' warnings."
-
   # Alert for high duration of event loop iteration in Tarantool.
   - alert: HighEVLoopTime
     expr: tnt_ev_loop_time > 0.1

example_cluster/prometheus/test_alerts.yml

@@ -349,25 +349,6 @@ tests:
                 high vinyl scheduler failed tasks rate."
 
 
-  - interval: 15s
-    input_series:
-      - series: tnt_fiber_csw{job="tarantool_app", instance="app:8081", alias="tnt_router"}
-        values: '15000+1x10'
-    alert_rule_test:
-      - eval_time: 2m
-        alertname: LowFiberCSWRate
-        exp_alerts:
-          - exp_labels:
-              severity: warning
-              instance: app:8081
-              alias: tnt_router
-              job: tarantool_app
-            exp_annotations:
-              summary: "Instance 'tnt_router' ('tarantool_app') has low fiber context switches rate"
-              description: "Instance 'tnt_router' of job 'tarantool_app' has low fiber context switches rate.
-                Some high loaded fiber has too little yields. It may be the reason of 'Too long WAL write' warnings."
-
-
   - interval: 15s
     input_series:
       - series: tnt_ev_loop_time{job="tarantool_app", instance="app:8081", alias="tnt_router"}