SDK: span processor interface and simple span processor. (#117)

* SDK: SpanProcessor Interface.

* add simple span processor.

* rename span processor.

* fix logic to export or process span data.

sdk/trace/span_processor_test.go

@@ -0,0 +1,118 @@
+// Copyright 2019, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package trace_test
+
+import (
+	"context"
+	"testing"
+
+	apitrace "go.opentelemetry.io/api/trace"
+	sdktrace "go.opentelemetry.io/sdk/trace"
+)
+
+type testSpanProcesor struct {
+	spansStarted  []*sdktrace.SpanData
+	spansEnded    []*sdktrace.SpanData
+	shutdownCount int
+}
+
+func init() {
+	sdktrace.Register()
+	sdktrace.ApplyConfig(sdktrace.Config{DefaultSampler: sdktrace.AlwaysSample()})
+}
+
+func (t *testSpanProcesor) OnStart(s *sdktrace.SpanData) {
+	t.spansStarted = append(t.spansStarted, s)
+}
+
+func (t *testSpanProcesor) OnEnd(s *sdktrace.SpanData) {
+	t.spansEnded = append(t.spansEnded, s)
+}
+
+func (t *testSpanProcesor) Shutdown() {
+	t.shutdownCount++
+}
+
+func TestRegisterSpanProcessort(t *testing.T) {
+	name := "Register span processor before span starts"
+	sp := NewTestSpanProcessor()
+	sdktrace.RegisterSpanProcessor(sp)
+	defer sdktrace.UnregisterSpanProcessor(sp)
+	_, span := apitrace.GlobalTracer().Start(context.Background(), "OnStart")
+	span.Finish()
+	wantCount := 1
+	gotCount := len(sp.spansStarted)
+	if gotCount != wantCount {
+		t.Errorf("%s: started count: got %d, want %d\n", name, gotCount, wantCount)
+	}
+	gotCount = len(sp.spansEnded)
+	if gotCount != wantCount {
+		t.Errorf("%s: ended count: got %d, want %d\n", name, gotCount, wantCount)
+	}
+}
+
+func TestUnregisterSpanProcessor(t *testing.T) {
+	name := "Start span after unregistering span processor"
+	sp := NewTestSpanProcessor()
+	sdktrace.RegisterSpanProcessor(sp)
+	_, span := apitrace.GlobalTracer().Start(context.Background(), "OnStart")
+	span.Finish()
+	sdktrace.UnregisterSpanProcessor(sp)
+
+	// start another span after unregistering span processor.
+	_, span = apitrace.GlobalTracer().Start(context.Background(), "Start span after unregister")
+	span.Finish()
+
+	wantCount := 1
+	gotCount := len(sp.spansStarted)
+	if gotCount != wantCount {
+		t.Errorf("%s: started count: got %d, want %d\n", name, gotCount, wantCount)
+	}
+
+	gotCount = len(sp.spansEnded)
+	if gotCount != wantCount {
+		t.Errorf("%s: ended count: got %d, want %d\n", name, gotCount, wantCount)
+	}
+}
+
+func TestUnregisterSpanProcessorWhileSpanIsActive(t *testing.T) {
+	name := "Unregister span processor while span is active"
+	sp := NewTestSpanProcessor()
+	sdktrace.RegisterSpanProcessor(sp)
+	_, span := apitrace.GlobalTracer().Start(context.Background(), "OnStart")
+	sdktrace.UnregisterSpanProcessor(sp)
+
+	span.Finish()
+
+	wantCount := 1
+	gotCount := len(sp.spansStarted)
+	if gotCount != wantCount {
+		t.Errorf("%s: started count: got %d, want %d\n", name, gotCount, wantCount)
+	}
+
+	wantCount = 0
+	gotCount = len(sp.spansEnded)
+	if gotCount != wantCount {
+		t.Errorf("%s: ended count: got %d, want %d\n", name, gotCount, wantCount)
+	}
+}
+
+// TODO(rghetia): Add Shutdown test when it is implemented.
+func TestShutdown(t *testing.T) {
+}
+
+func NewTestSpanProcessor() *testSpanProcesor {
+	return &testSpanProcesor{}
+}