feat(metrics): add prometheus endpoint (#147)

Co-authored-by: Fabio Bonelli 
Co-authored-by: Nicola Squartini

charts/developers-italia-api/README.md

@@ -41,6 +41,12 @@ The API of Developers Italia
 | serviceAccount.annotations | object | `{}` |  |
 | serviceAccount.create | bool | `true` |  |
 | serviceAccount.name | string | `""` |  |
+| serviceMonitor.additionalLabels | object | `{}` |  |
+| serviceMonitor.enabled | bool | `false` | Create ServiceMonitor resource (requires corresponding Prometheus Operator CRD installed). |
+| serviceMonitor.interval | string | `nil` | Interval at which metrics should be scraped (uses Prometheus default if unspecified, details [here](https://prometheus-operator.dev/docs/operator/api/#monitoring.coreos.com/v1.Endpoint)) |
+| serviceMonitor.jobLabel | string | `nil` | Defaults to the name of the Kubernetes service (details [here](https://prometheus-operator.dev/docs/operator/api/#monitoring.coreos.com/v1.ServiceMonitor)). |
+| serviceMonitor.scrapeTimeout | string | `nil` | Timeout after which the scrape is ended (uses Prometheus default if unspecified, details [here](https://prometheus-operator.dev/docs/operator/api/#monitoring.coreos.com/v1.Endpoint)). |
+| serviceMonitor.targetLabels | list | `[]` |  |
 | tolerations | list | `[]` |  |
 | useExistingSecret | string | `nil` | Name of existing Kubernetes secret containing keys 'databaseDSN' and 'pasetoKey'. If not provided, a secret will be generated using values from 'databaseDSN' and 'pasetoKey'. |
 

charts/developers-italia-api/templates/servicemonitor.yaml

@@ -0,0 +1,35 @@
+{{- if .Values.serviceMonitor.enabled -}}
+apiVersion: monitoring.coreos.com/v1
+kind: ServiceMonitor
+metadata:
+  name: {{ include "developers-italia-api.fullname" . }}
+  labels:
+    {{- include "developers-italia-api.labels" . | nindent 4 }}
+  {{- if .Values.serviceMonitor.additionalLabels }}
+    {{- toYaml .Values.serviceMonitor.additionalLabels | nindent 4 }}
+  {{- end }}
+spec:
+  endpoints:
+    - port: http
+    {{- if .Values.serviceMonitor.interval }}
+      interval: {{ .Values.serviceMonitor.interval }}
+    {{- end }}
+    {{- if .Values.serviceMonitor.scrapeTimeout }}
+      scrapeTimeout: {{ .Values.serviceMonitor.scrapeTimeout }}
+    {{- end }}
+{{- if .Values.serviceMonitor.jobLabel }}
+  jobLabel: {{ .Values.serviceMonitor.jobLabel | quote }}
+{{- end }}
+  namespaceSelector:
+    matchNames:
+      - {{ .Release.Namespace }}
+{{- if .Values.serviceMonitor.targetLabels }}
+  targetLabels:
+  {{- range .Values.serviceMonitor.targetLabels }}
+    - {{ . }}
+  {{- end }}
+{{- end }}
+  selector:
+    matchLabels:
+      {{- include "developers-italia-api.selectorLabels" . | nindent 6 }}
+{{- end }}

charts/developers-italia-api/values.yaml

@@ -100,3 +100,15 @@ databaseDSN: ""
 
 # -- Base64 encoded Paseto Key.
 pasetoKey: ""
+
+serviceMonitor:
+  # -- Create ServiceMonitor resource (requires corresponding Prometheus Operator CRD installed).
+  enabled: false
+  additionalLabels: {}
+  # -- (string) Defaults to the name of the Kubernetes service (details [here](https://prometheus-operator.dev/docs/operator/api/#monitoring.coreos.com/v1.ServiceMonitor)).
+  jobLabel:
+  # -- (string) Interval at which metrics should be scraped (uses Prometheus default if unspecified, details [here](https://prometheus-operator.dev/docs/operator/api/#monitoring.coreos.com/v1.Endpoint))
+  interval:
+  # -- (string) Timeout after which the scrape is ended (uses Prometheus default if unspecified, details [here](https://prometheus-operator.dev/docs/operator/api/#monitoring.coreos.com/v1.Endpoint)).
+  scrapeTimeout:
+  targetLabels: []

go.mod

@@ -8,19 +8,32 @@ require (
 	github.com/go-playground/validator/v10 v10.11.0
 	github.com/go-testfixtures/testfixtures/v3 v3.8.0
 	github.com/gofiber/contrib/paseto v0.0.0-20220621082844-83549332c36e
-	github.com/gofiber/fiber/v2 v2.34.1
+	github.com/gofiber/fiber/v2 v2.36.0
 	github.com/jackc/pgerrcode v0.0.0-20220416144525-469b46aa5efa
 	github.com/stretchr/testify v1.7.5
 	gorm.io/driver/postgres v1.3.7
 	gorm.io/driver/sqlite v1.3.4
 	gorm.io/gorm v1.23.6
 )
 
-require golang.org/x/exp v0.0.0-20220827204233-334a2380cb91
+require (
+	github.com/ansrivas/fiberprometheus/v2 v2.4.1
+	golang.org/x/exp v0.0.0-20220827204233-334a2380cb91
+)
 
 require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.1.2 // indirect
+	github.com/gofiber/adaptor/v2 v2.1.25 // indirect
+	github.com/golang/protobuf v1.5.2 // indirect
 	github.com/mattn/go-sqlite3 v1.14.13 // indirect
+	github.com/matttproud/golang_protobuf_extensions v1.0.1 // indirect
+	github.com/prometheus/client_golang v1.12.2 // indirect
+	github.com/prometheus/client_model v0.2.0 // indirect
+	github.com/prometheus/common v0.32.1 // indirect
+	github.com/prometheus/procfs v0.7.3 // indirect
 	golang.org/x/net v0.0.0-20220722155237-a158d28d115b // indirect
+	google.golang.org/protobuf v1.26.0 // indirect
 )
 
 require (