added jenkins alert rules for jenkins metrics plugin (#268)

* added jenkins alert rules

* Update rules.yml

Co-authored-by: Samuel Berthe <dev@samuel-berthe.fr>

_data/rules.yml

@@ -2126,3 +2126,41 @@ groups:
                 query: sum by (job) (cortex_query_frontend_queue_length) > 0
                 severity: critical
                 for: 5m
+
+      - name: Jenkins
+        exporters:
+          - name: Metric plugin
+            doc_url: https://plugins.jenkins.io/prometheus/
+            rules:
+              - name: Jenkins offline
+                description: "Jenkins offline: `{{$labels.instance}}` in realm {{$labels.realm}}/{{$labels.env}} ({{$labels.region}})"
+                query: 'jenkins_node_offline_value > 1'
+                severity: critical
+              - name: Jenkins healthcheck
+                description: "Jenkins healthcheck score: {{$value}}. Healthcheck failure for `{{$labels.instance}}` in realm {{$labels.realm}}/{{$labels.env}} ({{$labels.region}})"
+                query: 'jenkins_health_check_score < 1'
+                severity: critical
+              - name: Jenkins builds health score
+                description: "Healthcheck failure for `{{$labels.instance}}` in realm {{$labels.realm}}/{{$labels.env}} ({{$labels.region}})"
+                query: 'default_jenkins_builds_health_score < 1'
+                severity: critical
+              - name: Jenkins run failure total
+                description: "Job run failures: ({{$value}}) {{$labels.jenkins_job}}. Healthcheck failure for `{{$labels.instance}}` in realm {{$labels.realm}}/{{$labels.env}} ({{$labels.region}})"
+                query: 'delta(jenkins_runs_failure_total[1h]) > 100'
+                severity: warning
+              - name: JenkinsBuildTestsFailing
+                description: "Last build tests failed: {{$labels.jenkins_job}}. Failed build Tests for job `{{$labels.jenkins_job}}` on {{$labels.instance}}/{{$labels.env}} ({{$labels.region}})"
+                query: 'default_jenkins_builds_last_build_tests_failing > 0'
+                severity: warning
+              - name: Jenkins last build failed
+                description: "Last build failed: {{$labels.jenkins_job}}. Failed build for job `{{$labels.jenkins_job}}` on {{$labels.instance}}/{{$labels.env}} ({{$labels.region}})"
+                query: 'default_jenkins_builds_last_build_result_ordinal == 2'
+                severity: warning
+                comments: |
+                  * RUNNING  -1 true  - The build had no errors.
+                  * SUCCESS   0 true  - The build had no errors.
+                  * UNSTABLE  1 true  - The build had some errors but they were not fatal. For example, some tests failed.
+                  * FAILURE   2 false - The build had a fatal error.
+                  * NOT_BUILT 3 false - The module was not built.
+                  * ABORTED   4 false - The build was manually aborted.
+