// Start a rebalance cycle
func (cg *ConsumerGroup) rebalance() (err error) {
var cids []string
var pids []int32
// Fetch a list of consumers and listen for changes
if cids, cg.zkchange, err = cg.zoo.Consumers(cg.name); err != nil {
cg.zkchange = nil
return
}
// Fetch a list of partition IDs
if pids, err = cg.client.Partitions(cg.topic); err != nil {
cg.zkchange = nil
return
}
// Get leaders for each partition ID
parts := make(PartitionSlice, len(pids))
for i, pid := range pids {
var broker *sarama.Broker
if broker, err = cg.client.Leader(cg.topic, pid); err != nil {
cg.zkchange = nil
return
}
defer broker.Close()
parts[i] = Partition{Id: pid, Addr: broker.Addr()}
}
if err = cg.makeClaims(cids, parts); err != nil {
cg.zkchange = nil
cg.releaseClaims()
return
}
return
}
// Connects to the broker that handles all produce and consume
// requests for the given chain (Partition Leader Replica)
func newBroker(brokers []string, cp ChainPartition) (Broker, error) {
var candidateBroker, connectedBroker, leaderBroker *sarama.Broker
// Connect to one of the given brokers
for _, hostPort := range brokers {
candidateBroker = sarama.NewBroker(hostPort)
if err := candidateBroker.Open(nil); err != nil {
logger.Warningf("Failed to connect to broker %s: %s", hostPort, err)
continue
}
if connected, err := candidateBroker.Connected(); !connected {
logger.Warningf("Failed to connect to broker %s: %s", hostPort, err)
continue
}
connectedBroker = candidateBroker
break
}
if connectedBroker == nil {
return nil, fmt.Errorf("Failed to connect to any of the given brokers (%v) for metadata request", brokers)
}
logger.Debugf("Connected to broker %s", connectedBroker.Addr())
// Get metadata for the topic that corresponds to this chain
metadata, err := connectedBroker.GetMetadata(&sarama.MetadataRequest{Topics: []string{cp.Topic()}})
if err != nil {
return nil, fmt.Errorf("Failed to get metadata for topic %s: %s", cp, err)
}
// Get the leader broker for this chain partition
if (cp.Partition() >= 0) && (cp.Partition() < int32(len(metadata.Topics[0].Partitions))) {
leaderBrokerID := metadata.Topics[0].Partitions[cp.Partition()].Leader
logger.Debugf("Leading broker for chain %s is broker ID %d", cp, leaderBrokerID)
for _, availableBroker := range metadata.Brokers {
if availableBroker.ID() == leaderBrokerID {
leaderBroker = availableBroker
break
}
}
}
if leaderBroker == nil {
return nil, fmt.Errorf("Can't find leader for chain %s", cp)
}
// Connect to broker
if err := leaderBroker.Open(nil); err != nil {
return nil, fmt.Errorf("Failed to connect ho Kafka broker: %s", err)
}
if connected, err := leaderBroker.Connected(); !connected {
return nil, fmt.Errorf("Failed to connect to Kafka broker: %s", err)
}
return &brokerImpl{broker: leaderBroker}, nil
}
func brokerAddress(b *sarama.Broker) string {
return strings.ToLower(b.Addr())
}