Add prometheus /metrics endpoint.

This just exposes the default go metrics for now. We can use middleware to expose
more custom metrics for our API.

cmd/server/app/serve.go

@@ -18,6 +18,7 @@ package app
 
 import (
 	"flag"
+	"net/http"
 
 	"github.com/go-openapi/loads"
 	"github.com/projectrekor/rekor/pkg/api"
@@ -29,6 +30,7 @@ import (
 	rpm_v001 "github.com/projectrekor/rekor/pkg/types/rpm/v0.0.1"
 
 	"github.com/projectrekor/rekor/pkg/generated/restapi"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
 )
@@ -75,6 +77,12 @@ var serveCmd = &cobra.Command{
 
 		api.ConfigureAPI()
 		server.ConfigureAPI()
+
+		http.Handle("/metrics", promhttp.Handler())
+		go func() {
+			_ = http.ListenAndServe(":2112", nil)
+		}()
+
 		if err := server.Serve(); err != nil {
 			log.Logger.Fatal(err)
 		}

config/README.md

@@ -44,3 +44,14 @@ Install nginx-ingress with: kubectl apply -f nginx.yaml
 This was taken from https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v0.43.0/deploy/static/provider/cloud/deploy.yaml
 
 Local modification was to scale replicas to 3.
+Install nginx-ingress with: kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v0.43.0/deploy/static/provider/cloud/deploy.yaml
+
+## Prometheus
+
+Installed Prometheus Chart with:
+
+```
+helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
+helm repo add kube-state-metrics https://kubernetes.github.io/kube-state-metrics
+helm install prometheus prometheus-community/prometheus --namespace=prometheus
+```

config/prometheus/values.yaml

+
+server:
+  sidecarContainers:
+    sidecar:
+      image: gcr.io/stackdriver-prometheus/stackdriver-prometheus-sidecar:0.8.2
+      imagePullPolicy: Always
+      args:
+      - "--stackdriver.project-id=project-rekor"
+      - "--prometheus.wal-directory=/data/wal"
+      - "--stackdriver.kubernetes.location=us-central1"
+      - "--stackdriver.kubernetes.cluster-name=rekor-dev"
+      ports:
+      - name: sidecar
+        containerPort: 9091
+      volumeMounts:
+      - name: storage-volume
+        mountPath: /data

config/rekor.yaml

@@ -13,12 +13,17 @@ spec:
     metadata:
       labels:
         app: rekor-server
+      annotations:
+        prometheus.io/scrape: "true"
+        prometheus.io/path: /metrics
+        prometheus.io/port: "2112"
     spec:
       containers:
       - name: rekor-server
         image: ko://github.com/projectrekor/rekor/cmd/server
         ports:
         - containerPort: 3000
+        - containerPort: 2112 # metrics
         args: [
           "serve",
           "--trillian_log_server.address=trillian-server",

docker-compose.yml

@@ -67,6 +67,7 @@ services:
     restart: always # keep the server running
     ports:
       - "3000:3000"
+      - "2112:2112"
     depends_on:
       - mysql
       - redis-server

go.mod

@@ -21,7 +21,6 @@ require (
 	github.com/go-openapi/validate v0.20.1
 	github.com/golang/protobuf v1.4.3
 	github.com/google/certificate-transparency-go v1.1.0 // indirect
-	github.com/google/go-cmp v0.5.2
 	github.com/google/rpmpack v0.0.0-20210107155803-d6befbf05148
 	github.com/google/trillian v1.3.10
 	github.com/jedisct1/go-minisign v0.0.0-20210106175330-e54e81d562c7
@@ -30,6 +29,7 @@ require (
 	github.com/mitchellh/go-homedir v1.1.0
 	github.com/mitchellh/mapstructure v1.4.1
 	github.com/pelletier/go-toml v1.8.1 // indirect
+	github.com/prometheus/client_golang v1.9.0
 	github.com/rs/cors v1.7.0
 	github.com/spf13/afero v1.5.1 // indirect
 	github.com/spf13/cast v1.3.1 // indirect