Implement blocking queries for /v1/job/evaluations

nomad/job_endpoint.go

@@ -570,26 +570,36 @@ func (j *Job) Evaluations(args *structs.JobSpecificRequest,
 	}
 	defer metrics.MeasureSince([]string{"nomad", "job", "evaluations"}, time.Now())
 
-	// Capture the evaluations
-	snap, err := j.srv.fsm.State().Snapshot()
-	if err != nil {
-		return err
-	}
-	reply.Evaluations, err = snap.EvalsByJob(args.JobID)
-	if err != nil {
-		return err
-	}
+	// Setup the blocking query
+	opts := blockingOptions{
+		queryOpts: &args.QueryOptions,
+		queryMeta: &reply.QueryMeta,
+		watch:     watch.NewItems(watch.Item{EvalJob: args.JobID}),
+		run: func() error {
+			// Capture the evals
+			snap, err := j.srv.fsm.State().Snapshot()
+			if err != nil {
+				return err
+			}
 
-	// Use the last index that affected the evals table
-	index, err := snap.Index("evals")
-	if err != nil {
-		return err
-	}
-	reply.Index = index
+			reply.Evaluations, err = snap.EvalsByJob(args.JobID)
+			if err != nil {
+				return err
+			}
 
-	// Set the query response
-	j.srv.setQueryMeta(&reply.QueryMeta)
-	return nil
+			// Use the last index that affected the evals table
+			index, err := snap.Index("evals")
+			if err != nil {
+				return err
+			}
+			reply.Index = index
+
+			// Set the query response
+			j.srv.setQueryMeta(&reply.QueryMeta)
+			return nil
+		}}
+
+	return j.srv.blockingRPC(&opts)
 }
 
 // Plan is used to cause a dry-run evaluation of the Job and return the results

nomad/job_endpoint_test.go

@@ -1421,6 +1421,59 @@ func TestJobEndpoint_Evaluations(t *testing.T) {
 	}
 }
 
+func TestJobEndpoint_Evaluations_Blocking(t *testing.T) {
+	s1 := testServer(t, nil)
+	defer s1.Shutdown()
+	codec := rpcClient(t, s1)
+	testutil.WaitForLeader(t, s1.RPC)
+
+	// Create the register request
+	eval1 := mock.Eval()
+	eval2 := mock.Eval()
+	eval2.JobID = "job1"
+	state := s1.fsm.State()
+
+	// First upsert an unrelated eval
+	time.AfterFunc(100*time.Millisecond, func() {
+		err := state.UpsertEvals(100, []*structs.Evaluation{eval1})
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+	})
+
+	// Upsert an eval for the job we are interested in later
+	time.AfterFunc(200*time.Millisecond, func() {
+		err := state.UpsertEvals(200, []*structs.Evaluation{eval2})
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+	})
+
+	// Lookup the jobs
+	get := &structs.JobSpecificRequest{
+		JobID: "job1",
+		QueryOptions: structs.QueryOptions{
+			Region:        "global",
+			MinQueryIndex: 50,
+		},
+	}
+	var resp structs.JobEvaluationsResponse
+	start := time.Now()
+	if err := msgpackrpc.CallWithCodec(codec, "Job.Evaluations", get, &resp); err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	if elapsed := time.Since(start); elapsed < 200*time.Millisecond {
+		t.Fatalf("should block (returned in %s) %#v", elapsed, resp)
+	}
+	if resp.Index != 200 {
+		t.Fatalf("Bad index: %d %d", resp.Index, 200)
+	}
+	if len(resp.Evaluations) != 1 || resp.Evaluations[0].JobID != "job1" {
+		t.Fatalf("bad: %#v", resp.Evaluations)
+	}
+}
+
 func TestJobEndpoint_Plan_WithDiff(t *testing.T) {
 	s1 := testServer(t, func(c *Config) {
 		c.NumSchedulers = 0 // Prevent automatic dequeue

nomad/state/state_store.go

@@ -638,6 +638,7 @@ func (s *StateStore) UpsertEvals(index uint64, evals []*structs.Evaluation) erro
 	jobs := make(map[string]string, len(evals))
 	for _, eval := range evals {
 		watcher.Add(watch.Item{Eval: eval.ID})
+		watcher.Add(watch.Item{EvalJob: eval.JobID})
 		if err := s.nestedUpsertEval(txn, index, eval); err != nil {
 			return err
 		}
@@ -734,8 +735,10 @@ func (s *StateStore) DeleteEval(index uint64, evals []string, allocs []string) e
 		if err := txn.Delete("evals", existing); err != nil {
 			return fmt.Errorf("eval delete failed: %v", err)
 		}
+		jobID := existing.(*structs.Evaluation).JobID
 		watcher.Add(watch.Item{Eval: eval})
-		jobs[existing.(*structs.Evaluation).JobID] = ""
+		watcher.Add(watch.Item{EvalJob: jobID})
+		jobs[jobID] = ""
 	}
 
 	for _, alloc := range allocs {
@@ -1729,6 +1732,7 @@ func (r *StateRestore) JobRestore(job *structs.Job) error {
 func (r *StateRestore) EvalRestore(eval *structs.Evaluation) error {
 	r.items.Add(watch.Item{Table: "evals"})
 	r.items.Add(watch.Item{Eval: eval.ID})
+	r.items.Add(watch.Item{EvalJob: eval.JobID})
 	if err := r.txn.Insert("evals", eval); err != nil {
 		return fmt.Errorf("eval insert failed: %v", err)
 	}

nomad/state/state_store_test.go

@@ -1227,7 +1227,8 @@ func TestStateStore_UpsertEvals_Eval(t *testing.T) {
 	notify := setupNotifyTest(
 		state,
 		watch.Item{Table: "evals"},
-		watch.Item{Eval: eval.ID})
+		watch.Item{Eval: eval.ID},
+		watch.Item{EvalJob: eval.JobID})
 
 	err := state.UpsertEvals(1000, []*structs.Evaluation{eval})
 	if err != nil {
@@ -1266,10 +1267,12 @@ func TestStateStore_Update_UpsertEvals_Eval(t *testing.T) {
 	notify := setupNotifyTest(
 		state,
 		watch.Item{Table: "evals"},
-		watch.Item{Eval: eval.ID})
+		watch.Item{Eval: eval.ID},
+		watch.Item{EvalJob: eval.JobID})
 
 	eval2 := mock.Eval()
 	eval2.ID = eval.ID
+	eval2.JobID = eval.JobID
 	err = state.UpsertEvals(1001, []*structs.Evaluation{eval2})
 	if err != nil {
 		t.Fatalf("err: %v", err)
@@ -1315,6 +1318,8 @@ func TestStateStore_DeleteEval_Eval(t *testing.T) {
 		watch.Item{Table: "allocs"},
 		watch.Item{Eval: eval1.ID},
 		watch.Item{Eval: eval2.ID},
+		watch.Item{EvalJob: eval1.JobID},
+		watch.Item{EvalJob: eval2.JobID},
 		watch.Item{Alloc: alloc1.ID},
 		watch.Item{Alloc: alloc2.ID},
 		watch.Item{AllocEval: alloc1.EvalID},

nomad/watch/watch.go

@@ -14,6 +14,7 @@ type Item struct {
 	AllocJob   string
 	AllocNode  string
 	Eval       string
+	EvalJob    string
 	Job        string
 	JobSummary string
 	Node       string