Issue 51: Assign on empty cluster sometime fails under high concurrency

load

Contributed by philoops

go/weed/master.go

@@ -14,6 +14,7 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 )
 
@@ -48,6 +49,7 @@ var (
 
 var topo *topology.Topology
 var vg *replication.VolumeGrowth
+var vgLock sync.Mutex
 
 func dirLookupHandler(w http.ResponseWriter, r *http.Request) {
 	vid := r.FormValue("volumeId")
@@ -97,12 +99,16 @@ func dirAssignHandler(w http.ResponseWriter, r *http.Request) {
 			writeJsonQuiet(w, r, map[string]string{"error": "No free volumes left!"})
 			return
 		} else {
+			vgLock.Lock()
+			defer vgLock.Unlock()
+			if topo.GetVolumeLayout(rt).GetActiveVolumeCount(dataCenter) <= 0 {
 				if _, err = vg.AutomaticGrowByType(rt, dataCenter, topo); err != nil {
 					writeJsonQuiet(w, r, map[string]string{"error": "Cannot grow volume group! " + err.Error()})
 					return
 				}
 			}
 		}
+	}
 	fid, count, dn, err := topo.PickForWrite(rt, c, dataCenter)
 	if err == nil {
 		writeJsonQuiet(w, r, map[string]interface{}{"fid": fid, "url": dn.Url(), "publicUrl": dn.PublicUrl, "count": count})