Handle absense of mutation or query in GraphQL. Fix bugs in goroutine's...

Handle absense of mutation or query in GraphQL. Fix bugs in goroutine's variable access, and pointer assignment to mutationArray.

server/main.go

@@ -88,6 +88,7 @@ func mutationHandler(mu *gql.Mutation) error {
 		}
 	}
 	if err := worker.GetOrAssignUidsOverNetwork(&xidToUid); err != nil {
+		glog.WithError(err).Error("GetOrAssignUidsOverNetwork")
 		return err
 	}
 
@@ -143,7 +144,20 @@ func queryHandler(w http.ResponseWriter, r *http.Request) {
 		x.SetStatus(w, x.E_INVALID_REQUEST, err.Error())
 		return
 	}
-	mutationHandler(mu)
+
+	// If we have mutations, run them first.
+	if mu != nil && len(mu.Set) > 0 {
+		if err = mutationHandler(mu); err != nil {
+			glog.WithError(err).Error("While handling mutations.")
+			x.SetStatus(w, x.E_ERROR, err.Error())
+			return
+		}
+	}
+
+	if gq == nil || (gq.UID == 0 && len(gq.XID) == 0) {
+		x.SetStatus(w, x.E_OK, "Done")
+		return
+	}
 
 	sg, err := query.ToSubGraph(gq)
 	if err != nil {
@@ -204,6 +218,10 @@ func main() {
 
 	addrs := strings.Split(*workers, ",")
 	lenAddr := uint64(len(addrs))
+	if lenAddr == 0 {
+		// If no worker is specified, then we're it.
+		lenAddr = 1
+	}
 
 	posting.Init(clog)
 

worker/assign.go

 package worker
 
 import (
+	"fmt"
 	"sync"
 
 	"github.com/dgraph-io/dgraph/conn"
@@ -33,6 +34,10 @@ func createXidListBuffer(xids map[string]uint64) []byte {
 func getOrAssignUids(
 	xidList *task.XidList) (uidList []byte, rerr error) {
 
+	if xidList.XidsLength() == 0 {
+		return uidList, fmt.Errorf("Empty xid list")
+	}
+
 	wg := new(sync.WaitGroup)
 	uids := make([]uint64, xidList.XidsLength())
 	che := make(chan error, xidList.XidsLength())
@@ -40,15 +45,15 @@ func getOrAssignUids(
 		wg.Add(1)
 		xid := string(xidList.Xids(i))
 
-		go func() {
+		go func(idx int) {
 			defer wg.Done()
 			u, err := uid.GetOrAssign(xid, 0, 1)
 			if err != nil {
 				che <- err
 				return
 			}
-			uids[i] = u
-		}()
+			uids[idx] = u
+		}(i)
 	}
 	wg.Wait()
 	close(che)

worker/mutation.go

@@ -42,6 +42,7 @@ func mutate(m *Mutations, left *Mutations) error {
 			return fmt.Errorf("predicate fingerprint doesn't match this instance.")
 		}
 
+		glog.WithField("edge", edge).Debug("mutate")
 		key := posting.Key(edge.Entity, edge.Attribute)
 		plist := posting.GetOrCreate(key, dataStore)
 		if err := plist.AddMutation(edge, posting.Set); err != nil {
@@ -93,6 +94,7 @@ func MutateOverNetwork(
 		mu := mutationArray[idx]
 		if mu == nil {
 			mu = new(Mutations)
+			mutationArray[idx] = mu
 		}
 		mu.Set = append(mu.Set, edge)
 	}