sarama_cluster

package
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 Go to latest Published: Jun 29, 2020 License: Apache-2.0, MIT Imports: 11 Imported by: 1

README

Consumer is a modified version of sarama-cluster using database as offset storage. etcd will be supported in future

Documentation

Overview

package kafka provides cluster extensions for Sarama, enabing users to consume topics across from multiple, balanced nodes.

It requires Kafka v0.9+ and follows the steps guide, described in: https://cwiki.apache.org/confluence/display/KAFKA/Kafka+0.9+Consumer+Rewrite+Design

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type BrokerOffsetStore 

type BrokerOffsetStore struct {
	// contains filtered or unexported fields
}

func (*BrokerOffsetStore) Close 

func (manager *BrokerOffsetStore) Close() error

func (*BrokerOffsetStore) CommitOffset 

func (manager *BrokerOffsetStore) CommitOffset(req *offsets.OffsetCommitRequest) (*offsets.OffsetCommitResponse, error)

func (*BrokerOffsetStore) FetchOffset 

func (manager *BrokerOffsetStore) FetchOffset(req *offsets.OffsetFetchRequest) (*offsets.OffsetFetchResponse, error)

type Client 

type Client struct {
	sarama.Client
	// contains filtered or unexported fields
}

Client is a group client

func NewClient 

func NewClient(addrs []string, config *Config) (*Client, error)

NewClient creates a new client instance

func (*Client) ClusterConfig 

func (c *Client) ClusterConfig() *Config

ClusterConfig returns the cluster configuration.

type Config 

type Config struct {
	sarama.Config

	// Group is the namespace for group management properties
	Group struct {

		// The strategy to use for the allocation of partitions to consumers (defaults to StrategyRange)
		PartitionStrategy Strategy

		// By default, messages and errors from the subscribed topics and partitions are all multiplexed and
		// made available through the consumer's Messages() and Errors() channels.
		//
		// Users who require low-level access can enable ConsumerModePartitions where individual partitions
		// are exposed on the Partitions() channel. Messages and errors must then be consumed on the partitions
		// themselves.
		Mode ConsumerMode

		Offsets struct {
			Retry struct {
				// The numer retries when committing offsets (defaults to 3).
				Max int
			}
			Synchronization struct {
				// The duration allowed for other clients to commit their offsets before resumption in this client, e.g. during a rebalance
				// NewConfig sets this to the Consumer.MaxProcessingTime duration of the Sarama configuration
				DwellTime time.Duration
			}
		}

		Session struct {
			// The allowed session timeout for registered consumers (defaults to 30s).
			// Must be within the allowed server range.
			Timeout time.Duration
		}

		Heartbeat struct {
			// Interval between each heartbeat (defaults to 3s). It should be no more
			// than 1/3rd of the Group.Session.Timout setting
			Interval time.Duration
		}

		// Return specifies which group channels will be populated. If they are set to true,
		// you must read from the respective channels to prevent deadlock.
		Return struct {
			// If enabled, rebalance notification will be returned on the
			// Notifications channel (default disabled).
			Notifications bool
		}

		Topics struct {
			// An additional whitelist of topics to subscribe to.
			Whitelist *regexp.Regexp
			// An additional blacklist of topics to avoid. If set, this will precede over
			// the Whitelist setting.
			Blacklist *regexp.Regexp
		}

		Member struct {
			// Custom metadata to include when joining the group. The user data for all joined members
			// can be retrieved by sending a DescribeGroupRequest to the broker that is the
			// coordinator for the group.
			UserData []byte
		}
	}
}

Config extends sarama.Config with Group specific namespace

func NewConfig 

func NewConfig() *Config

NewConfig returns a new configuration instance with sane defaults.

func (*Config) Validate 

func (c *Config) Validate() error

Validate checks a Config instance. It will return a sarama.ConfigurationError if the specified values don't make sense.

type Consumer 

type Consumer struct {
	// contains filtered or unexported fields
}

Consumer is a cluster group consumer

func NewConsumer 

func NewConsumer(addrs []string, groupID string, topics []string, config *Config, osf OffsetStoreFactory) (*Consumer, error)

NewConsumer initializes a new consumer

func NewConsumerFromClient 

func NewConsumerFromClient(client *Client, groupID string, topics []string, osf OffsetStoreFactory) (*Consumer, error)

NewConsumerFromClient initializes a new consumer from an existing client.

Please note that clients cannot be shared between consumers (due to Kafka internals), they can only be re-used which requires the user to call Close() on the first consumer before using this method again to initialize another one. Attempts to use a client with more than one consumer at a time will return errors.

func (*Consumer) Close 

func (c *Consumer) Close() (err error)

Close safely closes the consumer and releases all resources

func (*Consumer) CommitOffsets 

func (c *Consumer) CommitOffsets() error

CommitOffsets allows to manually commit previously marked offsets. By default there is no need to call this function as the consumer will commit offsets automatically using the Config.Consumer.Offsets.CommitInterval setting.

Please be aware that calling this function during an internal rebalance cycle may return broker errors (e.g. sarama.ErrUnknownMemberId or sarama.ErrIllegalGeneration).

func (*Consumer) Errors 

func (c *Consumer) Errors() <-chan error

Errors returns a read channel of errors that occur during offset management, if enabled. By default, errors are logged and not returned over this channel. If you want to implement any custom error handling, set your config's Consumer.Return.Errors setting to true, and read from this channel.

func (*Consumer) HighWaterMarks 

func (c *Consumer) HighWaterMarks() map[string]map[int32]int64

HighWaterMarks returns the current high water marks for each topic and partition Consistency between partitions is not guaranteed since high water marks are updated separately.

func (*Consumer) MarkOffset 

func (c *Consumer) MarkOffset(msg *sarama.ConsumerMessage, metadata string)

MarkOffset marks the provided message as processed, alongside a metadata string that represents the state of the partition consumer at that point in time. The metadata string can be used by another consumer to restore that state, so it can resume consumption.

Note: calling MarkOffset does not necessarily commit the offset to the backend store immediately for efficiency reasons, and it may never be committed if your application crashes. This means that you may end up processing the same message twice, and your processing should ideally be idempotent.

func (*Consumer) MarkOffsets 

func (c *Consumer) MarkOffsets(s *OffsetStash)

MarkOffsets marks stashed offsets as processed. See MarkOffset for additional explanation.

func (*Consumer) MarkPartitionOffset 

func (c *Consumer) MarkPartitionOffset(topic string, partition int32, offset int64, metadata string)

MarkPartitionOffset marks an offset of the provided topic/partition as processed. See MarkOffset for additional explanation.

func (*Consumer) Messages 

func (c *Consumer) Messages() <-chan *sarama.ConsumerMessage

Messages returns the read channel for the messages that are returned by the broker.

This channel will only return if Config.Group.Mode option is set to ConsumerModeMultiplex (default).

func (*Consumer) Notifications 

func (c *Consumer) Notifications() <-chan *Notification

Notifications returns a channel of Notifications that occur during consumer rebalancing. Notifications will only be emitted over this channel, if your config's Group.Return.Notifications setting to true.

func (*Consumer) OffsetStore 

func (c *Consumer) OffsetStore() OffsetStore

func (*Consumer) Partitions 

func (c *Consumer) Partitions() <-chan PartitionConsumer

Partitions returns the read channels for individual partitions of this broker.

This will channel will only return if Config.Group.Mode option is set to ConsumerModePartitions.

The Partitions() channel must be listened to for the life of this consumer; when a rebalance happens old partitions will be closed (naturally come to completion) and new ones will be emitted. The returned channel will only close when the consumer is completely shut down.

func (*Consumer) Subscriptions 

func (c *Consumer) Subscriptions() map[string][]int32

Subscriptions returns the consumed topics and partitions

type ConsumerMode 

type ConsumerMode uint8
const (
	ConsumerModeMultiplex ConsumerMode = iota
	ConsumerModePartitions
)

type DefaultOffsetStoreFactory 

type DefaultOffsetStoreFactory struct {
}

func (*DefaultOffsetStoreFactory) GenOffsetStore 

func (f *DefaultOffsetStoreFactory) GenOffsetStore(c *Consumer) OffsetStore

type Error 

type Error struct {
	Ctx string
	// contains filtered or unexported fields
}

Error instances are wrappers for internal errors with a context and may be returned through the consumer's Errors() channel

type Notification 

type Notification struct {
	// Type exposes the notification type
	Type NotificationType

	// Claimed contains topic/partitions that were claimed by this rebalance cycle
	Claimed map[string][]int32

	// Released contains topic/partitions that were released as part of this rebalance cycle
	Released map[string][]int32

	// Current are topic/partitions that are currently claimed to the consumer
	Current map[string][]int32
}

Notification are state events emitted by the consumers on rebalance

type NotificationType 

type NotificationType uint8

NotificationType defines the type of notification 

const (
	UnknownNotification NotificationType = iota
	RebalanceStart
	RebalanceOK
	RebalanceError
)

func (NotificationType) String 

func (t NotificationType) String() string

String describes the notification type

type OffsetStash 

type OffsetStash struct {
	// contains filtered or unexported fields
}

OffsetStash allows to accumulate offsets and mark them as processed in a bulk

func NewOffsetStash 

func NewOffsetStash() *OffsetStash

NewOffsetStash inits a blank stash

func (*OffsetStash) MarkOffset 

func (s *OffsetStash) MarkOffset(msg *sarama.ConsumerMessage, metadata string)

MarkOffset stashes the provided message offset

func (*OffsetStash) MarkPartitionOffset 

func (s *OffsetStash) MarkPartitionOffset(topic string, partition int32, offset int64, metadata string)

MarkPartitionOffset stashes the offset for the provided topic/partition combination

func (*OffsetStash) Offsets 

func (s *OffsetStash) Offsets() map[string]int64

Offsets returns the latest stashed offsets by topic-partition

type OffsetStore 

type OffsetStore interface {
	CommitOffset(req *offsets.OffsetCommitRequest) (*offsets.OffsetCommitResponse, error)
	FetchOffset(req *offsets.OffsetFetchRequest) (*offsets.OffsetFetchResponse, error)
	Close() error
}

type OffsetStoreFactory 

type OffsetStoreFactory interface {
	GenOffsetStore(c *Consumer) OffsetStore
}

type PartitionConsumer 

type PartitionConsumer interface {
	// Close stops the PartitionConsumer from fetching messages. It will initiate a shutdown, drain
	// the Messages channel, harvest any errors & return them to the caller and trigger a rebalance.
	Close() error

	// Messages returns the read channel for the messages that are returned by
	// the broker.
	Messages() <-chan *sarama.ConsumerMessage

	// HighWaterMarkOffset returns the high water mark offset of the partition,
	// i.e. the offset that will be used for the next message that will be produced.
	// You can use this to determine how far behind the processing is.
	HighWaterMarkOffset() int64

	// Topic returns the consumed topic name
	Topic() string

	// Partition returns the consumed partition
	Partition() int32
}

PartitionConsumer allows code to consume individual partitions from the cluster.

See docs for Consumer.Partitions() for more on how to implement this.

type Strategy 

type Strategy string

Strategy for partition to consumer assignement 

const (
	// StrategyRange is the default and assigns partition ranges to consumers.
	// Example with six partitions and two consumers:
	//   C1: [0, 1, 2]
	//   C2: [3, 4, 5]
	StrategyRange Strategy = "range"

	// StrategyRoundRobin assigns partitions by alternating over consumers.
	// Example with six partitions and two consumers:
	//   C1: [0, 2, 4]
	//   C2: [1, 3, 5]
	StrategyRoundRobin Strategy = "roundrobin"
)

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