telegraf/plugins/inputs/kafka_consumer/kafka_consumer.go

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package kafka_consumer
import (
"log"
"strings"
"sync"
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"github.com/influxdata/influxdb/models"
"github.com/influxdata/telegraf/plugins/inputs"
"github.com/Shopify/sarama"
"github.com/wvanbergen/kafka/consumergroup"
)
type Kafka struct {
ConsumerGroup string
Topics []string
ZookeeperPeers []string
Consumer *consumergroup.ConsumerGroup
PointBuffer int
Offset string
sync.Mutex
// channel for all incoming kafka messages
in <-chan *sarama.ConsumerMessage
// channel for all kafka consumer errors
errs <-chan *sarama.ConsumerError
// channel for all incoming parsed kafka points
pointChan chan models.Point
done chan struct{}
// doNotCommitMsgs tells the parser not to call CommitUpTo on the consumer
// this is mostly for test purposes, but there may be a use-case for it later.
doNotCommitMsgs bool
}
var sampleConfig = `
# topic(s) to consume
topics = ["telegraf"]
# an array of Zookeeper connection strings
zookeeper_peers = ["localhost:2181"]
# the name of the consumer group
consumer_group = "telegraf_metrics_consumers"
# Maximum number of points to buffer between collection intervals
point_buffer = 100000
# Offset (must be either "oldest" or "newest")
offset = "oldest"
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`
func (k *Kafka) SampleConfig() string {
return sampleConfig
}
func (k *Kafka) Description() string {
return "Read line-protocol metrics from Kafka topic(s)"
}
func (k *Kafka) Start() error {
k.Lock()
defer k.Unlock()
var consumerErr error
config := consumergroup.NewConfig()
switch strings.ToLower(k.Offset) {
case "oldest", "":
config.Offsets.Initial = sarama.OffsetOldest
case "newest":
config.Offsets.Initial = sarama.OffsetNewest
default:
log.Printf("WARNING: Kafka consumer invalid offset '%s', using 'oldest'\n",
k.Offset)
config.Offsets.Initial = sarama.OffsetOldest
}
if k.Consumer == nil || k.Consumer.Closed() {
k.Consumer, consumerErr = consumergroup.JoinConsumerGroup(
k.ConsumerGroup,
k.Topics,
k.ZookeeperPeers,
config,
)
if consumerErr != nil {
return consumerErr
}
// Setup message and error channels
k.in = k.Consumer.Messages()
k.errs = k.Consumer.Errors()
}
k.done = make(chan struct{})
if k.PointBuffer == 0 {
k.PointBuffer = 100000
}
k.pointChan = make(chan models.Point, k.PointBuffer)
// Start the kafka message reader
go k.parser()
log.Printf("Started the kafka consumer service, peers: %v, topics: %v\n",
k.ZookeeperPeers, k.Topics)
return nil
}
// parser() reads all incoming messages from the consumer, and parses them into
// influxdb metric points.
func (k *Kafka) parser() {
for {
select {
case <-k.done:
return
case err := <-k.errs:
log.Printf("Kafka Consumer Error: %s\n", err.Error())
case msg := <-k.in:
points, err := models.ParsePoints(msg.Value)
if err != nil {
log.Printf("Could not parse kafka message: %s, error: %s",
string(msg.Value), err.Error())
}
for _, point := range points {
select {
case k.pointChan <- point:
continue
default:
log.Printf("Kafka Consumer buffer is full, dropping a point." +
" You may want to increase the point_buffer setting")
}
}
if !k.doNotCommitMsgs {
// TODO(cam) this locking can be removed if this PR gets merged:
// https://github.com/wvanbergen/kafka/pull/84
k.Lock()
k.Consumer.CommitUpto(msg)
k.Unlock()
}
}
}
}
func (k *Kafka) Stop() {
k.Lock()
defer k.Unlock()
close(k.done)
if err := k.Consumer.Close(); err != nil {
log.Printf("Error closing kafka consumer: %s\n", err.Error())
}
}
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func (k *Kafka) Gather(acc inputs.Accumulator) error {
k.Lock()
defer k.Unlock()
npoints := len(k.pointChan)
for i := 0; i < npoints; i++ {
point := <-k.pointChan
acc.AddFields(point.Name(), point.Fields(), point.Tags(), point.Time())
}
return nil
}
func init() {
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inputs.Add("kafka_consumer", func() inputs.Input {
return &Kafka{}
})
}