Add a prometheus HTTP server per ignite-spawn process in an unix socket

cmd/ignite-spawn/ignite-spawn.go

@@ -3,8 +3,10 @@ package main
 import (
  "fmt"
  "os"
+ "path"
 
  "github.com/weaveworks/ignite/pkg/container"
+ "github.com/weaveworks/ignite/pkg/container/prometheus"
  "github.com/weaveworks/ignite/pkg/metadata/loader"
  "github.com/weaveworks/ignite/pkg/metadata/vmmd"
 )
@@ -43,6 +45,10 @@ func StartVM(co *options) error {
  return err
  }
 
+ // Serve metrics over an unix socket in the VM's own directory
+ metricsSocket := path.Join(co.vm.ObjectPath(), "prometheus.sock")
+ go prometheus.ServeMetrics(metricsSocket)
+
  // VM state handling
  if err := co.vm.SetState(vmmd.Running); err != nil {
  return fmt.Errorf("failed to update VM state: %v", err)

pkg/container/prometheus/server.go

@@ -0,0 +1,30 @@
+package prometheus
+
+import (
+ "net/http"
+ "net"
+
+ "github.com/prometheus/client_golang/prometheus"
+ "github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+func ServeMetrics(socketPath string) error {
+ // Create a registry to register metrics into
+ registry := prometheus.NewRegistry()
+ // Register the default collectors with this registry
+ registry.MustRegister(prometheus.NewBuildInfoCollector())
+ registry.MustRegister(prometheus.NewGoCollector())
+ registry.MustRegister(prometheus.NewProcessCollector(prometheus.ProcessCollectorOpts{}))
+
+ // Create a HTTP server to handle metrics requests
+ server := http.Server{
+ Handler: promhttp.HandlerFor(registry, promhttp.HandlerOpts{}),
+ }
+
+ // Listen on the unix socket and serve the web server
+ unixListener, err := net.Listen("unix", socketPath)
+ if err != nil {
+ panic(err)
+ }
+ return server.Serve(unixListener)
+}