Merge pull request #297 from jetstack/add-prometheus

Add prometheus server

Author: Oluwole Fadeyi

cmd/agent.go

@@ -124,4 +124,11 @@ func init() {
 		false,
 		"Enables the pprof profiling server on the agent (port: 6060).",
 	)
+	agentCmd.PersistentFlags().BoolVarP(
+		&agent.Prometheus,
+		"enable-metrics",
+		"",
+		false,
+		"Enables Prometheus metrics server on the agent (port: 8081).",
+	)
 }

go.mod

@@ -24,6 +24,7 @@ require (
 	github.com/maxatome/go-testdeep v1.11.0
 	github.com/pkg/errors v0.9.1
 	github.com/pmylund/go-cache v2.1.0+incompatible
+	github.com/prometheus/client_golang v1.9.0
 	github.com/sirupsen/logrus v1.8.1
 	github.com/spf13/cobra v1.4.0
 	github.com/spf13/pflag v1.0.5

pkg/agent/run.go

@@ -23,6 +23,7 @@ import (
 	"github.com/jetstack/preflight/pkg/datagatherer"
 	dgerror "github.com/jetstack/preflight/pkg/datagatherer/error"
 	"github.com/jetstack/preflight/pkg/version"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/spf13/cobra"
 )
 
@@ -56,6 +57,9 @@ var APIToken string
 // Profiling flag enabled pprof endpoints to run on the agent
 var Profiling bool
 
+// Prometheus flag enabled Prometheus metrics endpoint to run on the agent
+var Prometheus bool
+
 // schema version of the data sent by the agent.
 // The new default version is v2.
 // In v2 the agent posts data readings using api.gathereredResources
@@ -79,6 +83,17 @@ func Run(cmd *cobra.Command, args []string) {
 			}
 		}()
 	}
+	if Prometheus {
+		log.Printf("Prometheus was enabled.\nRunning prometheus server on port :8081")
+		go func() {
+			metricsServer := http.NewServeMux()
+			metricsServer.Handle("/metrics", promhttp.Handler())
+			err := http.ListenAndServe(":8081", metricsServer)
+			if err != nil && !errors.Is(err, http.ErrServerClosed) {
+				log.Fatalf("failed to run prometheus server: %s", err)
+			}
+		}()
+	}
 
 	dataGatherers := map[string]datagatherer.DataGatherer{}
 	var wg sync.WaitGroup