Trace sdk (#65)

* trace sdk initial commit.

* fix imports and comments.

* remove tracestate

* split trace.go

* add attribute over limit test.

* add comments and restructure span.go and tracer.go

* refactor MessageEvent

* defer unlock

* some more cleanup in span.go

* rename *MessageEvent* to *Event*

* cleanup comments in trace_test.go

* fix typos.

* return full string ID for traceID and spanID.

sdk/trace/evictedqueue_test.go

@@ -0,0 +1,65 @@
+// 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
+
+import (
+	"reflect"
+	"testing"
+)
+
+func init() {
+}
+
+func TestAdd(t *testing.T) {
+	q := newEvictedQueue(3)
+	q.add("value1")
+	q.add("value2")
+	if wantLen, gotLen := 2, len(q.queue); wantLen != gotLen {
+		t.Errorf("got queue length %d want %d", gotLen, wantLen)
+	}
+}
+
+func (eq *evictedQueue) queueToArray() []string {
+	arr := make([]string, 0)
+	for _, value := range eq.queue {
+		arr = append(arr, value.(string))
+	}
+	return arr
+}
+
+func TestDropCount(t *testing.T) {
+	q := newEvictedQueue(3)
+	q.add("value1")
+	q.add("value2")
+	q.add("value3")
+	q.add("value1")
+	q.add("value4")
+	if wantLen, gotLen := 3, len(q.queue); wantLen != gotLen {
+		t.Errorf("got queue length %d want %d", gotLen, wantLen)
+	}
+	if wantDropCount, gotDropCount := 2, q.droppedCount; wantDropCount != gotDropCount {
+		t.Errorf("got drop count %d want %d", gotDropCount, wantDropCount)
+	}
+	wantArr := []string{"value3", "value1", "value4"}
+	gotArr := q.queueToArray()
+
+	if wantLen, gotLen := len(wantArr), len(gotArr); gotLen != wantLen {
+		t.Errorf("got array len %d want %d", gotLen, wantLen)
+	}
+
+	if !reflect.DeepEqual(gotArr, wantArr) {
+		t.Errorf("got array = %#v; want %#v", gotArr, wantArr)
+	}
+}