package sarama import ( "math/rand" "sort" "sync" "time" ) // Client is a generic Kafka client. It manages connections to one or more Kafka brokers. // You MUST call Close() on a client to avoid leaks, it will not be garbage-collected // automatically when it passes out of scope. It is safe to share a client amongst many // users, however Kafka will process requests from a single client strictly in serial, // so it is generally more efficient to use the default one client per producer/consumer. type Client interface { // Config returns the Config struct of the client. This struct should not be // altered after it has been created. Config() *Config // Topics returns the set of available topics as retrieved from cluster metadata. Topics() ([]string, error) // Partitions returns the sorted list of all partition IDs for the given topic. Partitions(topic string) ([]int32, error) // WritablePartitions returns the sorted list of all writable partition IDs for // the given topic, where "writable" means "having a valid leader accepting // writes". WritablePartitions(topic string) ([]int32, error) // Leader returns the broker object that is the leader of the current // topic/partition, as determined by querying the cluster metadata. Leader(topic string, partitionID int32) (*Broker, error) // Replicas returns the set of all replica IDs for the given partition. Replicas(topic string, partitionID int32) ([]int32, error) // RefreshMetadata takes a list of topics and queries the cluster to refresh the // available metadata for those topics. If no topics are provided, it will refresh // metadata for all topics. RefreshMetadata(topics ...string) error // GetOffset queries the cluster to get the most recent available offset at the // given time on the topic/partition combination. Time should be OffsetOldest for // the earliest available offset, OffsetNewest for the offset of the message that // will be produced next, or a time. GetOffset(topic string, partitionID int32, time int64) (int64, error) // Coordinator returns the coordinating broker for a consumer group. It will // return a locally cached value if it's available. You can call // RefreshCoordinator to update the cached value. This function only works on // Kafka 0.8.2 and higher. Coordinator(consumerGroup string) (*Broker, error) // RefreshCoordinator retrieves the coordinator for a consumer group and stores it // in local cache. This function only works on Kafka 0.8.2 and higher. RefreshCoordinator(consumerGroup string) error // Close shuts down all broker connections managed by this client. It is required // to call this function before a client object passes out of scope, as it will // otherwise leak memory. You must close any Producers or Consumers using a client // before you close the client. Close() error // Closed returns true if the client has already had Close called on it Closed() bool } const ( // OffsetNewest stands for the log head offset, i.e. the offset that will be // assigned to the next message that will be produced to the partition. You // can send this to a client's GetOffset method to get this offset, or when // calling ConsumePartition to start consuming new messages. OffsetNewest int64 = -1 // OffsetOldest stands for the oldest offset available on the broker for a // partition. You can send this to a client's GetOffset method to get this // offset, or when calling ConsumePartition to start consuming from the // oldest offset that is still available on the broker. OffsetOldest int64 = -2 ) type client struct { conf *Config closer, closed chan none // for shutting down background metadata updater // the broker addresses given to us through the constructor are not guaranteed to be returned in // the cluster metadata (I *think* it only returns brokers who are currently leading partitions?) // so we store them separately seedBrokers []*Broker deadSeeds []*Broker brokers map[int32]*Broker // maps broker ids to brokers metadata map[string]map[int32]*PartitionMetadata // maps topics to partition ids to metadata coordinators map[string]int32 // Maps consumer group names to coordinating broker IDs // If the number of partitions is large, we can get some churn calling cachedPartitions, // so the result is cached. It is important to update this value whenever metadata is changed cachedPartitionsResults map[string][maxPartitionIndex][]int32 lock sync.RWMutex // protects access to the maps that hold cluster state. } // NewClient creates a new Client. It connects to one of the given broker addresses // and uses that broker to automatically fetch metadata on the rest of the kafka cluster. If metadata cannot // be retrieved from any of the given broker addresses, the client is not created. func NewClient(addrs []string, conf *Config) (Client, error) { Logger.Println("Initializing new client") if conf == nil { conf = NewConfig() } if err := conf.Validate(); err != nil { return nil, err } if len(addrs) < 1 { return nil, ConfigurationError("You must provide at least one broker address") } client := &client{ conf: conf, closer: make(chan none), closed: make(chan none), brokers: make(map[int32]*Broker), metadata: make(map[string]map[int32]*PartitionMetadata), cachedPartitionsResults: make(map[string][maxPartitionIndex][]int32), coordinators: make(map[string]int32), } random := rand.New(rand.NewSource(time.Now().UnixNano())) for _, index := range random.Perm(len(addrs)) { client.seedBrokers = append(client.seedBrokers, NewBroker(addrs[index])) } // do an initial fetch of all cluster metadata by specifing an empty list of topics err := client.RefreshMetadata() switch err { case nil: break case ErrLeaderNotAvailable, ErrReplicaNotAvailable, ErrTopicAuthorizationFailed, ErrClusterAuthorizationFailed: // indicates that maybe part of the cluster is down, but is not fatal to creating the client Logger.Println(err) default: close(client.closed) // we haven't started the background updater yet, so we have to do this manually _ = client.Close() return nil, err } go withRecover(client.backgroundMetadataUpdater) Logger.Println("Successfully initialized new client") return client, nil } func (client *client) Config() *Config { return client.conf } func (client *client) Close() error { if client.Closed() { // Chances are this is being called from a defer() and the error will go unobserved // so we go ahead and log the event in this case. Logger.Printf("Close() called on already closed client") return ErrClosedClient } // shutdown and wait for the background thread before we take the lock, to avoid races close(client.closer) <-client.closed client.lock.Lock() defer client.lock.Unlock() Logger.Println("Closing Client") for _, broker := range client.brokers { safeAsyncClose(broker) } for _, broker := range client.seedBrokers { safeAsyncClose(broker) } client.brokers = nil client.metadata = nil return nil } func (client *client) Closed() bool { return client.brokers == nil } func (client *client) Topics() ([]string, error) { if client.Closed() { return nil, ErrClosedClient } client.lock.RLock() defer client.lock.RUnlock() ret := make([]string, 0, len(client.metadata)) for topic := range client.metadata { ret = append(ret, topic) } return ret, nil } func (client *client) Partitions(topic string) ([]int32, error) { if client.Closed() { return nil, ErrClosedClient } partitions := client.cachedPartitions(topic, allPartitions) if len(partitions) == 0 { err := client.RefreshMetadata(topic) if err != nil { return nil, err } partitions = client.cachedPartitions(topic, allPartitions) } if partitions == nil { return nil, ErrUnknownTopicOrPartition } return partitions, nil } func (client *client) WritablePartitions(topic string) ([]int32, error) { if client.Closed() { return nil, ErrClosedClient } partitions := client.cachedPartitions(topic, writablePartitions) // len==0 catches when it's nil (no such topic) and the odd case when every single // partition is undergoing leader election simultaneously. Callers have to be able to handle // this function returning an empty slice (which is a valid return value) but catching it // here the first time (note we *don't* catch it below where we return ErrUnknownTopicOrPartition) triggers // a metadata refresh as a nicety so callers can just try again and don't have to manually // trigger a refresh (otherwise they'd just keep getting a stale cached copy). if len(partitions) == 0 { err := client.RefreshMetadata(topic) if err != nil { return nil, err } partitions = client.cachedPartitions(topic, writablePartitions) } if partitions == nil { return nil, ErrUnknownTopicOrPartition } return partitions, nil } func (client *client) Replicas(topic string, partitionID int32) ([]int32, error) { if client.Closed() { return nil, ErrClosedClient } metadata := client.cachedMetadata(topic, partitionID) if metadata == nil { err := client.RefreshMetadata(topic) if err != nil { return nil, err } metadata = client.cachedMetadata(topic, partitionID) } if metadata == nil { return nil, ErrUnknownTopicOrPartition } if metadata.Err == ErrReplicaNotAvailable { return nil, metadata.Err } return dupeAndSort(metadata.Replicas), nil } func (client *client) Leader(topic string, partitionID int32) (*Broker, error) { if client.Closed() { return nil, ErrClosedClient } leader, err := client.cachedLeader(topic, partitionID) if leader == nil { err = client.RefreshMetadata(topic) if err != nil { return nil, err } leader, err = client.cachedLeader(topic, partitionID) } return leader, err } func (client *client) RefreshMetadata(topics ...string) error { if client.Closed() { return ErrClosedClient } // Prior to 0.8.2, Kafka will throw exceptions on an empty topic and not return a proper // error. This handles the case by returning an error instead of sending it // off to Kafka. See: https://github.com/Shopify/sarama/pull/38#issuecomment-26362310 for _, topic := range topics { if len(topic) == 0 { return ErrInvalidTopic // this is the error that 0.8.2 and later correctly return } } return client.tryRefreshMetadata(topics, client.conf.Metadata.Retry.Max) } func (client *client) GetOffset(topic string, partitionID int32, time int64) (int64, error) { if client.Closed() { return -1, ErrClosedClient } offset, err := client.getOffset(topic, partitionID, time) if err != nil { if err := client.RefreshMetadata(topic); err != nil { return -1, err } return client.getOffset(topic, partitionID, time) } return offset, err } func (client *client) Coordinator(consumerGroup string) (*Broker, error) { if client.Closed() { return nil, ErrClosedClient } coordinator := client.cachedCoordinator(consumerGroup) if coordinator == nil { if err := client.RefreshCoordinator(consumerGroup); err != nil { return nil, err } coordinator = client.cachedCoordinator(consumerGroup) } if coordinator == nil { return nil, ErrConsumerCoordinatorNotAvailable } _ = coordinator.Open(client.conf) return coordinator, nil } func (client *client) RefreshCoordinator(consumerGroup string) error { if client.Closed() { return ErrClosedClient } response, err := client.getConsumerMetadata(consumerGroup, client.conf.Metadata.Retry.Max) if err != nil { return err } client.lock.Lock() defer client.lock.Unlock() client.registerBroker(response.Coordinator) client.coordinators[consumerGroup] = response.Coordinator.ID() return nil } // private broker management helpers // registerBroker makes sure a broker received by a Metadata or Coordinator request is registered // in the brokers map. It returns the broker that is registered, which may be the provided broker, // or a previously registered Broker instance. You must hold the write lock before calling this function. func (client *client) registerBroker(broker *Broker) { if client.brokers[broker.ID()] == nil { client.brokers[broker.ID()] = broker Logger.Printf("client/brokers registered new broker #%d at %s", broker.ID(), broker.Addr()) } else if broker.Addr() != client.brokers[broker.ID()].Addr() { safeAsyncClose(client.brokers[broker.ID()]) client.brokers[broker.ID()] = broker Logger.Printf("client/brokers replaced registered broker #%d with %s", broker.ID(), broker.Addr()) } } // deregisterBroker removes a broker from the seedsBroker list, and if it's // not the seedbroker, removes it from brokers map completely. func (client *client) deregisterBroker(broker *Broker) { client.lock.Lock() defer client.lock.Unlock() if len(client.seedBrokers) > 0 && broker == client.seedBrokers[0] { client.deadSeeds = append(client.deadSeeds, broker) client.seedBrokers = client.seedBrokers[1:] } else { // we do this so that our loop in `tryRefreshMetadata` doesn't go on forever, // but we really shouldn't have to; once that loop is made better this case can be // removed, and the function generally can be renamed from `deregisterBroker` to // `nextSeedBroker` or something Logger.Printf("client/brokers deregistered broker #%d at %s", broker.ID(), broker.Addr()) delete(client.brokers, broker.ID()) } } func (client *client) resurrectDeadBrokers() { client.lock.Lock() defer client.lock.Unlock() Logger.Printf("client/brokers resurrecting %d dead seed brokers", len(client.deadSeeds)) client.seedBrokers = append(client.seedBrokers, client.deadSeeds...) client.deadSeeds = nil } func (client *client) any() *Broker { client.lock.RLock() defer client.lock.RUnlock() if len(client.seedBrokers) > 0 { _ = client.seedBrokers[0].Open(client.conf) return client.seedBrokers[0] } // not guaranteed to be random *or* deterministic for _, broker := range client.brokers { _ = broker.Open(client.conf) return broker } return nil } // private caching/lazy metadata helpers type partitionType int const ( allPartitions partitionType = iota writablePartitions // If you add any more types, update the partition cache in update() // Ensure this is the last partition type value maxPartitionIndex ) func (client *client) cachedMetadata(topic string, partitionID int32) *PartitionMetadata { client.lock.RLock() defer client.lock.RUnlock() partitions := client.metadata[topic] if partitions != nil { return partitions[partitionID] } return nil } func (client *client) cachedPartitions(topic string, partitionSet partitionType) []int32 { client.lock.RLock() defer client.lock.RUnlock() partitions, exists := client.cachedPartitionsResults[topic] if !exists { return nil } return partitions[partitionSet] } func (client *client) setPartitionCache(topic string, partitionSet partitionType) []int32 { partitions := client.metadata[topic] if partitions == nil { return nil } ret := make([]int32, 0, len(partitions)) for _, partition := range partitions { if partitionSet == writablePartitions && partition.Err == ErrLeaderNotAvailable { continue } ret = append(ret, partition.ID) } sort.Sort(int32Slice(ret)) return ret } func (client *client) cachedLeader(topic string, partitionID int32) (*Broker, error) { client.lock.RLock() defer client.lock.RUnlock() partitions := client.metadata[topic] if partitions != nil { metadata, ok := partitions[partitionID] if ok { if metadata.Err == ErrLeaderNotAvailable { return nil, ErrLeaderNotAvailable } b := client.brokers[metadata.Leader] if b == nil { return nil, ErrLeaderNotAvailable } _ = b.Open(client.conf) return b, nil } } return nil, ErrUnknownTopicOrPartition } func (client *client) getOffset(topic string, partitionID int32, time int64) (int64, error) { broker, err := client.Leader(topic, partitionID) if err != nil { return -1, err } request := &OffsetRequest{} request.AddBlock(topic, partitionID, time, 1) response, err := broker.GetAvailableOffsets(request) if err != nil { _ = broker.Close() return -1, err } block := response.GetBlock(topic, partitionID) if block == nil { _ = broker.Close() return -1, ErrIncompleteResponse } if block.Err != ErrNoError { return -1, block.Err } if len(block.Offsets) != 1 { return -1, ErrOffsetOutOfRange } return block.Offsets[0], nil } // core metadata update logic func (client *client) backgroundMetadataUpdater() { defer close(client.closed) if client.conf.Metadata.RefreshFrequency == time.Duration(0) { return } ticker := time.NewTicker(client.conf.Metadata.RefreshFrequency) defer ticker.Stop() for { select { case <-ticker.C: if err := client.RefreshMetadata(); err != nil { Logger.Println("Client background metadata update:", err) } case <-client.closer: return } } } func (client *client) tryRefreshMetadata(topics []string, attemptsRemaining int) error { retry := func(err error) error { if attemptsRemaining > 0 { Logger.Printf("client/metadata retrying after %dms... (%d attempts remaining)\n", client.conf.Metadata.Retry.Backoff/time.Millisecond, attemptsRemaining) time.Sleep(client.conf.Metadata.Retry.Backoff) return client.tryRefreshMetadata(topics, attemptsRemaining-1) } return err } for broker := client.any(); broker != nil; broker = client.any() { if len(topics) > 0 { Logger.Printf("client/metadata fetching metadata for %v from broker %s\n", topics, broker.addr) } else { Logger.Printf("client/metadata fetching metadata for all topics from broker %s\n", broker.addr) } response, err := broker.GetMetadata(&MetadataRequest{Topics: topics}) switch err.(type) { case nil: // valid response, use it if shouldRetry, err := client.updateMetadata(response); shouldRetry { Logger.Println("client/metadata found some partitions to be leaderless") return retry(err) // note: err can be nil } else { return err } case PacketEncodingError: // didn't even send, return the error return err default: // some other error, remove that broker and try again Logger.Println("client/metadata got error from broker while fetching metadata:", err) _ = broker.Close() client.deregisterBroker(broker) } } Logger.Println("client/metadata no available broker to send metadata request to") client.resurrectDeadBrokers() return retry(ErrOutOfBrokers) } // if no fatal error, returns a list of topics that need retrying due to ErrLeaderNotAvailable func (client *client) updateMetadata(data *MetadataResponse) (retry bool, err error) { client.lock.Lock() defer client.lock.Unlock() // For all the brokers we received: // - if it is a new ID, save it // - if it is an existing ID, but the address we have is stale, discard the old one and save it // - otherwise ignore it, replacing our existing one would just bounce the connection for _, broker := range data.Brokers { client.registerBroker(broker) } for _, topic := range data.Topics { delete(client.metadata, topic.Name) delete(client.cachedPartitionsResults, topic.Name) switch topic.Err { case ErrNoError: break case ErrInvalidTopic, ErrTopicAuthorizationFailed: // don't retry, don't store partial results err = topic.Err continue case ErrUnknownTopicOrPartition: // retry, do not store partial partition results err = topic.Err retry = true continue case ErrLeaderNotAvailable: // retry, but store partial partition results retry = true break default: // don't retry, don't store partial results Logger.Printf("Unexpected topic-level metadata error: %s", topic.Err) err = topic.Err continue } client.metadata[topic.Name] = make(map[int32]*PartitionMetadata, len(topic.Partitions)) for _, partition := range topic.Partitions { client.metadata[topic.Name][partition.ID] = partition if partition.Err == ErrLeaderNotAvailable { retry = true } } var partitionCache [maxPartitionIndex][]int32 partitionCache[allPartitions] = client.setPartitionCache(topic.Name, allPartitions) partitionCache[writablePartitions] = client.setPartitionCache(topic.Name, writablePartitions) client.cachedPartitionsResults[topic.Name] = partitionCache } return } func (client *client) cachedCoordinator(consumerGroup string) *Broker { client.lock.RLock() defer client.lock.RUnlock() if coordinatorID, ok := client.coordinators[consumerGroup]; ok { return client.brokers[coordinatorID] } return nil } func (client *client) getConsumerMetadata(consumerGroup string, attemptsRemaining int) (*ConsumerMetadataResponse, error) { retry := func(err error) (*ConsumerMetadataResponse, error) { if attemptsRemaining > 0 { Logger.Printf("client/coordinator retrying after %dms... (%d attempts remaining)\n", client.conf.Metadata.Retry.Backoff/time.Millisecond, attemptsRemaining) time.Sleep(client.conf.Metadata.Retry.Backoff) return client.getConsumerMetadata(consumerGroup, attemptsRemaining-1) } return nil, err } for broker := client.any(); broker != nil; broker = client.any() { Logger.Printf("client/coordinator requesting coordinator for consumergroup %s from %s\n", consumerGroup, broker.Addr()) request := new(ConsumerMetadataRequest) request.ConsumerGroup = consumerGroup response, err := broker.GetConsumerMetadata(request) if err != nil { Logger.Printf("client/coordinator request to broker %s failed: %s\n", broker.Addr(), err) switch err.(type) { case PacketEncodingError: return nil, err default: _ = broker.Close() client.deregisterBroker(broker) continue } } switch response.Err { case ErrNoError: Logger.Printf("client/coordinator coordinator for consumergroup %s is #%d (%s)\n", consumerGroup, response.Coordinator.ID(), response.Coordinator.Addr()) return response, nil case ErrConsumerCoordinatorNotAvailable: Logger.Printf("client/coordinator coordinator for consumer group %s is not available\n", consumerGroup) // This is very ugly, but this scenario will only happen once per cluster. // The __consumer_offsets topic only has to be created one time. // The number of partitions not configurable, but partition 0 should always exist. if _, err := client.Leader("__consumer_offsets", 0); err != nil { Logger.Printf("client/coordinator the __consumer_offsets topic is not initialized completely yet. Waiting 2 seconds...\n") time.Sleep(2 * time.Second) } return retry(ErrConsumerCoordinatorNotAvailable) default: return nil, response.Err } } Logger.Println("client/coordinator no available broker to send consumer metadata request to") client.resurrectDeadBrokers() return retry(ErrOutOfBrokers) }