Add Kafka Consumer Plugin

The Kafka consumer plugin polls a specified Kafka topic and adds messages to
InfluxDB. The plugin assumes messages follow the line protocol. Consumer Group
is used to talk to the Kafka cluster so multiple instances of telegraf can read
from the same topic in parallel.

plugins/kafka_consumer/kafka_consumer_test.go

@@ -0,0 +1,95 @@
+package kafka_consumer
+
+import (
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/influxdb/telegraf/testutil"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gopkg.in/Shopify/sarama.v1"
+)
+
+const testMsg = "cpu_load_short,direction=in,host=server01,region=us-west value=23422.0 1422568543702900257"
+
+func TestReadFromKafkaBatchesMsgsOnBatchSize(t *testing.T) {
+	halt := make(chan bool, 1)
+	metricChan := make(chan []byte, 1)
+	kafkaChan := make(chan *sarama.ConsumerMessage, 10)
+	for i := 0; i < 10; i++ {
+		kafkaChan <- saramaMsg(testMsg)
+	}
+
+	expectedBatch := strings.Repeat(testMsg+"\n", 9) + testMsg
+	readFromKafka(kafkaChan, metricChan, 10, func(msg *sarama.ConsumerMessage) error {
+		batch := <-metricChan
+		assert.Equal(t, expectedBatch, string(batch))
+
+		halt <- true
+
+		return nil
+	}, halt)
+}
+
+func TestReadFromKafkaBatchesMsgsOnTimeout(t *testing.T) {
+	halt := make(chan bool, 1)
+	metricChan := make(chan []byte, 1)
+	kafkaChan := make(chan *sarama.ConsumerMessage, 10)
+	for i := 0; i < 3; i++ {
+		kafkaChan <- saramaMsg(testMsg)
+	}
+
+	expectedBatch := strings.Repeat(testMsg+"\n", 2) + testMsg
+	readFromKafka(kafkaChan, metricChan, 10, func(msg *sarama.ConsumerMessage) error {
+		batch := <-metricChan
+		assert.Equal(t, expectedBatch, string(batch))
+
+		halt <- true
+
+		return nil
+	}, halt)
+}
+
+func TestEmitMetricsSendMetricsToAcc(t *testing.T) {
+	k := &Kafka{}
+	var acc testutil.Accumulator
+	testChan := make(chan []byte, 1)
+	testChan <- []byte(testMsg)
+
+	err := emitMetrics(k, &acc, testChan)
+	require.NoError(t, err)
+
+	assert.Equal(t, 1, len(acc.Points), "there should be a single point")
+
+	point := acc.Points[0]
+	assert.Equal(t, "cpu_load_short", point.Measurement)
+	assert.Equal(t, map[string]interface{}{"value": 23422.0}, point.Values)
+	assert.Equal(t, map[string]string{
+		"host":      "server01",
+		"direction": "in",
+		"region":    "us-west",
+	}, point.Tags)
+
+	assert.Equal(t, time.Unix(0, 1422568543702900257), point.Time)
+}
+
+func TestEmitMetricsTimesOut(t *testing.T) {
+	k := &Kafka{}
+	var acc testutil.Accumulator
+	testChan := make(chan []byte)
+
+	err := emitMetrics(k, &acc, testChan)
+	require.NoError(t, err)
+
+	assert.Equal(t, 0, len(acc.Points), "there should not be a any points")
+}
+
+func saramaMsg(val string) *sarama.ConsumerMessage {
+	return &sarama.ConsumerMessage{
+		Key:       nil,
+		Value:     []byte(val),
+		Offset:    0,
+		Partition: 0,
+	}
+}