adds Recorder.Finish() method

in order to reduce the number of `InfluxDBStore.Collect()` calls for
performance reasons

aggregate_test.go

@@ -32,6 +32,7 @@ func TestAggregateStore(t *testing.T) {
 			E: time.Now(),
 		}
 		rec.Event(e)
+		rec.Finish()
 		if errs := rec.Errors(); len(errs) > 0 {
 			t.Fatal(errs)
 		}
@@ -103,6 +104,7 @@ func TestAggregateStoreNSlowest(t *testing.T) {
 				E: now.Add(times[i]),
 			}
 			rec.Event(e)
+			rec.Finish()
 			if errs := rec.Errors(); len(errs) > 0 {
 				t.Fatal(errs)
 			}
@@ -218,6 +220,7 @@ func TestAggregateStoreMinEvictAge(t *testing.T) {
 			E: time.Now(),
 		}
 		rec.Event(e)
+		rec.Finish()
 		if errs := rec.Errors(); len(errs) > 0 {
 			t.Fatal(errs)
 		}
@@ -238,6 +241,7 @@ func TestAggregateStoreMinEvictAge(t *testing.T) {
 	// Trigger the eviction by making any sort of collection.
 	rec := NewRecorder(NewRootSpanID(), as)
 	rec.Name("collect")
+	rec.Finish()
 	if errs := rec.Errors(); len(errs) > 0 {
 		t.Fatal(errs)
 	}

httptrace/client.go

@@ -158,6 +158,7 @@ func (t *Transport) RoundTrip(original *http.Request) (*http.Response, error) {
 		e.Response.StatusCode = -1
 	}
 	child.Event(e)
+	child.Finish()
 	return resp, err
 }
 

httptrace/server.go

@@ -103,6 +103,7 @@ func Middleware(c appdash.Collector, conf *MiddlewareConfig) func(rw http.Respon
 			rec.Name(r.URL.Host + r.URL.Path)
 		}
 		rec.Event(e)
+		rec.Finish()
 	}
 }
 

recorder.go

@@ -1,15 +1,22 @@
 package appdash
 
 import (
+	"errors"
 	"fmt"
 	"sync"
 	"time"
 )
 
+var (
+	errMultipleFinishCalls = errors.New("multiple Recorder.Finish calls")
+)
+
 // A Recorder is associated with a span and records annotations on the
 // span by sending them to a collector.
 type Recorder struct {
-	SpanID // the span ID that annotations are about
+	SpanID                   // the span ID that annotations are about
+	annotations []Annotation // SpanID's annotations to be collected
+	finished    bool         // finished is whether Recorder.Finish was called
 
 	collector Collector // the collector to send to
 
@@ -65,7 +72,23 @@ func (r *Recorder) Event(e Event) {
 		r.error("Event", err)
 		return
 	}
-	r.Annotation(as...)
+	r.annotations = append(r.annotations, as...)
+}
+
+// Finish finishes recording and saves the recorded information to the
+// underlying collector. If Finish is not called, then no data will be written
+// to the underlying collector.
+// Finish must be called once, otherwise r.error is called, this constraint
+// ensures that collector is called once per Recorder, in order to avoid
+// for performance reasons extra operations(span look up & span's annotations update)
+// within the collector.
+func (r *Recorder) Finish() {
+	if r.finished {
+		r.error("Finish", errMultipleFinishCalls)
+		return
+	}
+	r.finished = true
+	r.Annotation(r.annotations...)
 }
 
 // Annotation records raw annotations on the span.

recorder_test.go

@@ -26,17 +26,18 @@ func TestRecorder(t *testing.T) {
 	r := NewRecorder(id, c)
 
 	r.Msg("msg")
-	if calledCollect != 1 {
-		t.Errorf("got calledCollect %d, want 1", calledCollect)
+	r.Name("name")
+
+	if calledCollect != 0 {
+		t.Errorf("got calledCollect %d, want 0", calledCollect)
 	}
+
+	r.Finish()
+
 	if diff := diffAnnotationsFromEvent(anns, Msg("msg")); len(diff) > 0 {
 		t.Errorf("got diff annotations for Msg event:\n%s", strings.Join(diff, "\n"))
 	}
 
-	r.Name("name")
-	if calledCollect != 2 {
-		t.Errorf("got calledCollect %d, want 1", calledCollect)
-	}
 	if diff := diffAnnotationsFromEvent(anns, spanName{"name"}); len(diff) > 0 {
 		t.Errorf("got diff annotations for spanName event:\n%s", strings.Join(diff, "\n"))
 	}
@@ -53,9 +54,10 @@ func TestRecorder_Errors(t *testing.T) {
 	r := NewRecorder(SpanID{}, c)
 
 	r.Msg("msg")
-	if calledCollect != 2 {
-		t.Errorf("got calledCollect %d, want 1", calledCollect)
+	if calledCollect != 0 {
+		t.Errorf("got calledCollect %d, want 0", calledCollect)
 	}
+	r.Finish()
 	errs := r.Errors()
 	if want := []error{collectErr}; !reflect.DeepEqual(errs, want) {
 		t.Errorf("got errors %v, want %v", errs, want)
@@ -64,6 +66,11 @@ func TestRecorder_Errors(t *testing.T) {
 	if errs := r.Errors(); len(errs) != 0 {
 		t.Errorf("got len(errs) == %d, want 0 (after call to Errors)", len(errs))
 	}
+
+	r.Finish()
+	if errs := r.Errors(); len(errs) != 1 && errs[0] != errMultipleFinishCalls {
+		t.Errorf("got %d errors, want 1", len(errs))
+	}
 }
 
 func diffAnnotationsFromEvent(anns Annotations, e Event) (diff []string) {