func ExampleBroker_Consumer() {
broker := NewBroker()
msg := &proto.Message{Value: []byte("first")}
// mock server actions, pushing data through consumer
go func() {
consumer, _ := broker.Consumer(kafka.NewConsumerConf("my-topic", 0))
c := consumer.(*Consumer)
// it is possible to send messages through consumer...
c.Messages <- msg
// every consumer fetch call is blocking untill there is either message
// or error ready to return, this way we can test slow consumers
time.Sleep(time.Millisecond * 20)
// ...as well as push errors to mock failure
c.Errors <- errors.New("expected error is expected")
}()
// test broker never fails creating consumer
consumer, _ := broker.Consumer(kafka.NewConsumerConf("my-topic", 0))
m, err := consumer.Consume()
if err == nil {
fmt.Printf("Value: %q\n", m.Value)
}
if _, err = consumer.Consume(); err != nil {
fmt.Printf("Error: %s\n", err)
}
// output:
//
// Value: "first"
// Error: expected error is expected
}
// setup is the initial worker that initializes the claim structure. Until this is done,
// our internal state is inconsistent.
func (c *claim) setup() {
c.lock.Lock()
defer c.lock.Unlock()
// Of course, if the current offset is greater than the earliest, we must reset
// to the earliest known
if c.offsets.Current < c.offsets.Earliest {
log.Warningf("[%s:%d] consumer fast-forwarding from %d to %d",
c.topic, c.partID, c.offsets.Current, c.offsets.Earliest)
c.offsets.Current = c.offsets.Earliest
}
// Since it's claimed, we now want to heartbeat with the last seen offset
err := c.marshal.Heartbeat(c.topic, c.partID, c.offsets.Current)
if err != nil {
log.Errorf("[%s:%d] consumer failed to heartbeat: %s", c.topic, c.partID, err)
go c.Release()
return
}
c.lastHeartbeat = time.Now().Unix()
// Set up Kafka consumer
consumerConf := kafka.NewConsumerConf(c.topic, int32(c.partID))
consumerConf.StartOffset = c.offsets.Current
consumerConf.MaxFetchSize = c.marshal.cluster.options.MaxMessageSize
consumerConf.RequestTimeout = c.marshal.cluster.options.ConsumeRequestTimeout
// Do not retry. If we get back no data, we'll do our own retries.
consumerConf.RetryLimit = 0
kafkaConsumer, err := c.marshal.cluster.broker.Consumer(consumerConf)
if err != nil {
log.Errorf("[%s:%d] consumer failed to create Kafka Consumer: %s",
c.topic, c.partID, err)
go c.Release()
return
}
c.kafkaConsumer = kafkaConsumer
// Start our maintenance goroutines that keep this system healthy
go c.messagePump()
// Totally done, let the world know and move on
log.Infof("[%s:%d] consumer %s claimed at offset %d (is %d behind)",
c.topic, c.partID, c.marshal.clientID, c.offsets.Current, c.offsets.Latest-c.offsets.Current)
}
func TestProducerBrokenConnection(t *testing.T) {
IntegrationTest(t)
topics := []string{"Topic3", "Topic4"}
cluster := NewKafkaCluster("kafka-docker/", 4)
if err := cluster.Start(); err != nil {
t.Fatalf("cannot start kafka cluster: %s", err)
}
defer func() {
_ = cluster.Stop()
}()
bconf := kafka.NewBrokerConf("producer-broken-connection")
addrs, err := cluster.KafkaAddrs()
if err != nil {
t.Fatalf("cannot get kafka address: %s", err)
}
broker, err := kafka.Dial(addrs, bconf)
if err != nil {
t.Fatalf("cannot connect to cluster (%q): %s", addrs, err)
}
defer broker.Close()
// produce big message to enforce TCP buffer flush
m := proto.Message{
Value: []byte(strings.Repeat("producer broken connection message ", 1000)),
}
pconf := kafka.NewProducerConf()
producer := broker.Producer(pconf)
// send message to all topics to make sure it's working
for _, name := range topics {
if _, err := producer.Produce(name, 0, &m); err != nil {
t.Fatalf("cannot produce to %q: %s", name, err)
}
}
// close two kafka clusters and publish to all 3 topics - 2 of them should
// retry sending, because lack of leader makes the request fail
//
// request should not succeed until nodes are back - bring them back after
// small delay and make sure producing was successful
containers, err := cluster.Containers()
if err != nil {
t.Fatalf("cannot get containers: %s", err)
}
var stopped []*Container
for _, container := range containers {
if container.RunningKafka() {
if err := container.Kill(); err != nil {
t.Fatalf("cannot kill %q kafka container: %s", container.ID, err)
}
stopped = append(stopped, container)
}
if len(stopped) == 2 {
break
}
}
// bring stopped containers back
errc := make(chan error)
go func() {
time.Sleep(500 * time.Millisecond)
for _, container := range stopped {
if err := container.Start(); err != nil {
errc <- err
}
}
close(errc)
}()
// send message to all topics to make sure it's working
for _, name := range topics {
if _, err := producer.Produce(name, 0, &m); err != nil {
t.Errorf("cannot produce to %q: %s", name, err)
}
}
for err := range errc {
t.Errorf("cannot start container: %s", err)
}
// make sure data was persisted
for _, name := range topics {
consumer, err := broker.Consumer(kafka.NewConsumerConf(name, 0))
if err != nil {
t.Errorf("cannot create consumer for %q: %s", name, err)
continue
}
for i := 0; i < 2; i++ {
if _, err := consumer.Consume(); err != nil {
t.Errorf("cannot consume %d message from %q: %s", i, name, err)
}
}
}
}
// consumeFromKafka will start consuming messages from Kafka and writing them to the given
// channel forever. It is important that this method closes the "out" channel when it's done,
// as that instructs the downstream goroutine to exit.
func (c *KafkaCluster) consumeFromKafka(partID int, out chan message, startOldest bool) {
var err error
var alive bool
var offsetFirst, offsetNext int64
// Exit logic -- make sure downstream knows we exited.
defer func() {
log.Debugf("[%s] rationalize[%d]: terminating.", c.name, partID)
close(out)
}()
// Try to connect to Kafka. This might sleep a bit and retry since the broker could
// be down a bit.
retry := &backoff.Backoff{Min: 500 * time.Millisecond, Jitter: true}
for ; true; time.Sleep(retry.Duration()) {
// Figure out how many messages are in this topic. This can fail if the broker handling
// this partition is down, so we will loop.
offsetFirst, err = c.broker.OffsetEarliest(MarshalTopic, int32(partID))
if err != nil {
log.Errorf("[%s] rationalize[%d]: failed to get offset: %s", c.name, partID, err)
continue
}
offsetNext, err = c.broker.OffsetLatest(MarshalTopic, int32(partID))
if err != nil {
log.Errorf("[%s] rationalize[%d]: failed to get offset: %s", c.name, partID, err)
continue
}
log.Debugf("[%s] rationalize[%d]: offsets %d to %d",
c.name, partID, offsetFirst, offsetNext)
// TODO: Is there a case where the latest offset is X>0 but there is no data in
// the partition? does the offset reset to 0?
if offsetNext == 0 || offsetFirst == offsetNext {
alive = true
c.rationalizers.Done()
}
break
}
retry.Reset()
// Assume we're starting at the oldest offset for consumption
consumerConf := kafka.NewConsumerConf(MarshalTopic, int32(partID))
consumerConf.RetryErrLimit = 1 // Do not retry
consumerConf.StartOffset = kafka.StartOffsetOldest
consumerConf.RequestTimeout = c.options.MarshalRequestTimeout
consumerConf.RetryWait = c.options.MarshalRequestRetryWait
// Get the offsets of this partition, we're going to arbitrarily pick something that
// is ~100,000 from the end if there's more than that. This is only if startOldest is
// false, i.e., we didn't run into a "message too new" situation.
checkMessageTs := false
if !startOldest && offsetNext-offsetFirst > 100000 {
checkMessageTs = true
consumerConf.StartOffset = offsetNext - 100000
log.Infof("[%s] rationalize[%d]: fast forwarding to offset %d.",
c.name, partID, consumerConf.StartOffset)
}
consumer, err := c.broker.Consumer(consumerConf)
if err != nil {
// Unfortunately this is a termination error, as without being able to consume this
// partition we can't effectively rationalize.
log.Errorf("[%s] rationalize[%d]: Failed to create consumer: %s", c.name, partID, err)
c.Terminate()
return
}
// Consume messages forever, or until told to quit.
for !c.Terminated() {
msgb, err := consumer.Consume()
if err != nil {
// The internal consumer will do a number of retries. If we get an error here,
// we're probably in the middle of a partition handoff. We should pause so we
// don't hammer the cluster, but otherwise continue.
log.Warningf("[%s] rationalize[%d]: failed to consume: %s", c.name, partID, err)
time.Sleep(retry.Duration())
continue
}
retry.Reset()
msg, err := decode(msgb.Value)
if err != nil {
// Invalid message in the streac. This should never happen, but if it does, just
// continue on.
// TODO: We should probably think about this. If we end up in a situation where
// one version of this software has a bug that writes invalid messages, it could
// be doing things we don't anticipate. Of course, crashing all consumers
// reading that partition is also bad.
log.Errorf("[%s] rationalize[%d]: %s", c.name, partID, err)
// In the case where the first message is an invalid message, we need to
// to notify that we're alive now
if !alive {
alive = true
c.rationalizers.Done()
}
continue
}
// If we are on our first message, and we started at a non-zero offset, we need
// to check to make sure that the timestamp is older than a given threshold. If it's
// too new, that indicates our 100000 try didn't work, so let's go from the start.
// TODO: This could be a binary search or something.
if checkMessageTs {
if int64(msg.Timestamp()) > time.Now().Unix()-HeartbeatInterval*2 {
log.Warningf("[%s] rationalize[%d]: rewinding, fast-forwarded message was too new",
c.name, partID)
go c.consumeFromKafka(partID, out, true)
return // terminate self.
}
checkMessageTs = false
}
log.Debugf("[%s] rationalize[%d]: @%d: [%s]", c.name, partID, msgb.Offset, msg.Encode())
out <- msg
// This is a one-time thing that fires the first time the rationalizer comes up
// and makes sure we actually process all of the messages.
if !alive && msgb.Offset >= offsetNext-1 {
for len(out) > 0 {
time.Sleep(100 * time.Millisecond)
}
log.Infof("[%s] rationalize[%d]: reached offset %d, now alive",
c.name, partID, msgb.Offset)
alive = true
c.rationalizers.Done()
}
}
}