profiler: Introduce a profiler package and use it in repo-updater (#16656)

* profiler: Introduce a profiler package and use it in repo-updater

This commit introduces a profiler package, similar to tracer and
logging, that is shim to Google Cloud Profiler, which we aim to use to
get continuous profiling information (every minute) on repo-updater.

Fixes #16655

* fixup! go mod tidy

Author: Tomás Senart

cmd/repo-updater/shared/main.go

@@ -34,6 +34,7 @@ import (
 	"github.com/sourcegraph/sourcegraph/internal/httpcli"
 	"github.com/sourcegraph/sourcegraph/internal/httpserver"
 	"github.com/sourcegraph/sourcegraph/internal/logging"
+	"github.com/sourcegraph/sourcegraph/internal/profiler"
 	"github.com/sourcegraph/sourcegraph/internal/ratelimit"
 	"github.com/sourcegraph/sourcegraph/internal/repos"
 	"github.com/sourcegraph/sourcegraph/internal/trace"
@@ -52,6 +53,11 @@ func Main(enterpriseInit EnterpriseInit) {
 	ctx := context.Background()
 	env.Lock()
 	env.HandleHelpFlag()
+
+	if err := profiler.Init(); err != nil {
+		log.Fatalf("failed to start profiler: %v", err)
+	}
+
 	logging.Init()
 	tracer.Init()
 	trace.Init(true)

go.mod

@@ -3,6 +3,7 @@ module github.com/sourcegraph/sourcegraph
 go 1.14
 
 require (
+	cloud.google.com/go v0.56.0
 	cloud.google.com/go/bigquery v1.6.0 // indirect
 	cloud.google.com/go/pubsub v1.3.1
 	cloud.google.com/go/storage v1.6.0

go.sum

@@ -531,6 +531,7 @@ github.com/golang/mock v1.3.1 h1:qGJ6qTW+x6xX/my+8YUVl4WNpX9B7+/l2tRsHGZ7f2s=
 github.com/golang/mock v1.3.1/go.mod h1:sBzyDLLjw3U8JLTeZvSv8jJB+tU5PVekmnlKIyFUx0Y=
 github.com/golang/mock v1.4.0/go.mod h1:UOMv5ysSaYNkG+OFQykRIcU/QvvxJf3p21QfJ2Bt3cw=
 github.com/golang/mock v1.4.1/go.mod h1:UOMv5ysSaYNkG+OFQykRIcU/QvvxJf3p21QfJ2Bt3cw=
+github.com/golang/mock v1.4.3 h1:GV+pQPG/EUUbkh47niozDcADz6go/dUwhVzdUQHIVRw=
 github.com/golang/mock v1.4.3/go.mod h1:UOMv5ysSaYNkG+OFQykRIcU/QvvxJf3p21QfJ2Bt3cw=
 github.com/golang/protobuf v1.3.5 h1:F768QJ1E9tib+q5Sc8MkdJi1RxLTbRcTf8LJV56aRls=
 github.com/golang/protobuf v1.3.5/go.mod h1:6O5/vntMXwX2lRkT1hjjk0nAC1IDOTvTlVgjlRvqsdk=

internal/profiler/profiler.go

@@ -0,0 +1,24 @@
+package profiler
+
+import (
+	"cloud.google.com/go/profiler"
+
+	"github.com/sourcegraph/sourcegraph/cmd/frontend/envvar"
+	"github.com/sourcegraph/sourcegraph/internal/env"
+	"github.com/sourcegraph/sourcegraph/internal/version"
+)
+
+// Init starts the Google Cloud Profiler when in sourcegraph.com mode.
+// https://cloud.google.com/profiler/docs/profiling-go
+func Init() error {
+	if !envvar.SourcegraphDotComMode() {
+		return nil
+	}
+
+	return profiler.Start(profiler.Config{
+		Service:        env.MyName,
+		ServiceVersion: version.Version(),
+		MutexProfiling: true,
+		AllocForceGC:   true,
+	})
+}