Performance refactor of running_output buffers

closes #914
closes #967

internal/buffer/buffer_test.go

@@ -0,0 +1,94 @@
+package buffer
+
+import (
+	"testing"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/testutil"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var metricList = []telegraf.Metric{
+	testutil.TestMetric(2, "mymetric1"),
+	testutil.TestMetric(1, "mymetric2"),
+	testutil.TestMetric(11, "mymetric3"),
+	testutil.TestMetric(15, "mymetric4"),
+	testutil.TestMetric(8, "mymetric5"),
+}
+
+func BenchmarkAddMetrics(b *testing.B) {
+	buf := NewBuffer(10000)
+	m := testutil.TestMetric(1, "mymetric")
+	for n := 0; n < b.N; n++ {
+		buf.Add(m)
+	}
+}
+
+func TestNewBufferBasicFuncs(t *testing.T) {
+	b := NewBuffer(10)
+
+	assert.True(t, b.IsEmpty())
+	assert.Zero(t, b.Len())
+	assert.Zero(t, b.Drops())
+	assert.Zero(t, b.Total())
+
+	m := testutil.TestMetric(1, "mymetric")
+	b.Add(m)
+	assert.False(t, b.IsEmpty())
+	assert.Equal(t, b.Len(), 1)
+	assert.Equal(t, b.Drops(), 0)
+	assert.Equal(t, b.Total(), 1)
+
+	b.Add(metricList...)
+	assert.False(t, b.IsEmpty())
+	assert.Equal(t, b.Len(), 6)
+	assert.Equal(t, b.Drops(), 0)
+	assert.Equal(t, b.Total(), 6)
+}
+
+func TestDroppingMetrics(t *testing.T) {
+	b := NewBuffer(10)
+
+	// Add up to the size of the buffer
+	b.Add(metricList...)
+	b.Add(metricList...)
+	assert.False(t, b.IsEmpty())
+	assert.Equal(t, b.Len(), 10)
+	assert.Equal(t, b.Drops(), 0)
+	assert.Equal(t, b.Total(), 10)
+
+	// Add 5 more and verify they were dropped
+	b.Add(metricList...)
+	assert.False(t, b.IsEmpty())
+	assert.Equal(t, b.Len(), 10)
+	assert.Equal(t, b.Drops(), 5)
+	assert.Equal(t, b.Total(), 15)
+}
+
+func TestGettingBatches(t *testing.T) {
+	b := NewBuffer(20)
+
+	// Verify that the buffer returned is smaller than requested when there are
+	// not as many items as requested.
+	b.Add(metricList...)
+	batch := b.Batch(10)
+	assert.Len(t, batch, 5)
+
+	// Verify that the buffer is now empty
+	assert.True(t, b.IsEmpty())
+	assert.Zero(t, b.Len())
+	assert.Zero(t, b.Drops())
+	assert.Equal(t, b.Total(), 5)
+
+	// Verify that the buffer returned is not more than the size requested
+	b.Add(metricList...)
+	batch = b.Batch(3)
+	assert.Len(t, batch, 3)
+
+	// Verify that buffer is not empty
+	assert.False(t, b.IsEmpty())
+	assert.Equal(t, b.Len(), 2)
+	assert.Equal(t, b.Drops(), 0)
+	assert.Equal(t, b.Total(), 10)
+}