Periodically run GC in all dgraph commands. (#4032)

* Periodically run GC in all dgraph binaries.

Currently, only the bulk loader is making sure the garbage collector is
run periodically. This PR moves that logic to main.go so that it's run
by all dgraph commands.

* fix imports.

* Print glog.Infof

dgraph/cmd/bulk/run.go

@@ -28,11 +28,9 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
-	"time"
 
 	"github.com/dgraph-io/dgraph/tok"
 	"github.com/dgraph-io/dgraph/x"
-	"github.com/dustin/go-humanize"
 	"github.com/spf13/cobra"
 )
 
@@ -204,27 +202,6 @@ func run() {
 		defer os.RemoveAll(opt.TmpDir)
 	}
 
-	// Bulk loader can take up a lot of RAM. So, run GC often.
-	go func() {
-		ticker := time.NewTicker(10 * time.Second)
-		defer ticker.Stop()
-
-		var lastNum uint32
-		var ms runtime.MemStats
-		for range ticker.C {
-			runtime.ReadMemStats(&ms)
-			fmt.Printf("GC: %d. InUse: %s. Idle: %s\n", ms.NumGC, humanize.Bytes(ms.HeapInuse),
-				humanize.Bytes(ms.HeapIdle-ms.HeapReleased))
-			if ms.NumGC > lastNum {
-				// GC was already run by the Go runtime. No need to run it again.
-				lastNum = ms.NumGC
-			} else {
-				runtime.GC()
-				lastNum = ms.NumGC + 1
-			}
-		}
-	}()
-
 	loader := newLoader(opt)
 	if !opt.SkipMapPhase {
 		loader.mapStage()

dgraph/main.go

@@ -22,6 +22,8 @@ import (
 	"time"
 
 	"github.com/dgraph-io/dgraph/dgraph/cmd"
+	"github.com/dustin/go-humanize"
+	"github.com/golang/glog"
 )
 
 func main() {
@@ -30,5 +32,28 @@ func main() {
 	// improving throughput. The extra CPU overhead is almost negligible in comparison. The
 	// benchmark notes are located in badger-bench/randread.
 	runtime.GOMAXPROCS(128)
+
+	// Make sure the garbage collector is run periodically.
+	go func() {
+		ticker := time.NewTicker(10 * time.Second)
+		defer ticker.Stop()
+
+		var lastNum uint32
+		var ms runtime.MemStats
+		for range ticker.C {
+			runtime.ReadMemStats(&ms)
+			if ms.NumGC > lastNum {
+				// GC was already run by the Go runtime. No need to run it again.
+				lastNum = ms.NumGC
+			} else {
+				runtime.GC()
+				glog.V(2).Infof("GC: %d. InUse: %s. Idle: %s\n", ms.NumGC,
+					humanize.Bytes(ms.HeapInuse),
+					humanize.Bytes(ms.HeapIdle-ms.HeapReleased))
+				lastNum = ms.NumGC + 1
+			}
+		}
+	}()
+
 	cmd.Execute()
 }