#include <rdkafkacpp.h>

Inheritance diagram for RdKafka::Consumer:

Collaboration diagram for RdKafka::Consumer:

Public Member Functions
virtual ErrorCode	start (Topic *topic, int32_t partition, int64_t offset)=0
	Start consuming messages for topic and `partition` at offset `offset` which may either be a proper offset (0..N) or one of the the special offsets: `OFFSET_BEGINNING` or `OFFSET_END`. More...

virtual ErrorCode	start (Topic topic, int32_t partition, int64_t offset, Queue queue)=0
	Start consuming messages for topic and `partition` on queue `queue`. More...

virtual ErrorCode	stop (Topic *topic, int32_t partition)=0
	Stop consuming messages for topic and `partition`, purging all messages currently in the local queue. More...

virtual ErrorCode	seek (Topic *topic, int32_t partition, int64_t offset, int timeout_ms)=0
	Seek consumer for topic+partition to `offset` which is either an absolute or logical offset. More...

virtual Message *	consume (Topic *topic, int32_t partition, int timeout_ms)=0
	Consume a single message from `topic` and `partition`. More...

virtual Message *	consume (Queue *queue, int timeout_ms)=0
	Consume a single message from the specified queue. More...

virtual int	consume_callback (Topic topic, int32_t partition, int timeout_ms, ConsumeCb consume_cb, void *opaque)=0
	Consumes messages from `topic` and `partition`, calling the provided callback for each consumed messsage. More...

virtual int	consume_callback (Queue queue, int timeout_ms, RdKafka::ConsumeCb consume_cb, void *opaque)=0
	Consumes messages from `queue`, calling the provided callback for each consumed messsage. More...

Public Member Functions inherited from RdKafka::Handle
virtual const std::string	name () const =0

virtual const std::string	memberid () const =0
	Returns the client's broker-assigned group member id. More...

virtual int	poll (int timeout_ms)=0
	Polls the provided kafka handle for events. More...

virtual int	outq_len ()=0
	Returns the current out queue length. More...

virtual ErrorCode	metadata (bool all_topics, const Topic only_rkt, Metadata *metadatap, int timeout_ms)=0
	Request Metadata from broker. More...

virtual ErrorCode	pause (std::vector< TopicPartition *> &partitions)=0
	Pause producing or consumption for the provided list of partitions. More...

virtual ErrorCode	resume (std::vector< TopicPartition *> &partitions)=0
	Resume producing or consumption for the provided list of partitions. More...

virtual ErrorCode	query_watermark_offsets (const std::string &topic, int32_t partition, int64_t low, int64_t high, int timeout_ms)=0
	Query broker for low (oldest/beginning) and high (newest/end) offsets for partition. More...

virtual ErrorCode	get_watermark_offsets (const std::string &topic, int32_t partition, int64_t low, int64_t high)=0
	Get last known low (oldest/beginning) and high (newest/end) offsets for partition. More...

Static Public Member Functions
static Consumer *	create (Conf *conf, std::string &errstr)
	Creates a new Kafka consumer handle. More...

static int64_t	OffsetTail (int64_t offset)
	Converts an offset into the logical offset from the tail of a topic. More...

Detailed Description

Simple Consumer (legacy)

A simple non-balanced, non-group-aware, consumer.

Member Function Documentation

◆ create()

static Consumer* RdKafka::Consumer::create	(	Conf *	conf,
		std::string &	errstr
	)

static

Creates a new Kafka consumer handle.

conf is an optional object that will be used instead of the default configuration. The conf object is reusable after this call.

Returns: the new handle on success or NULL on error in which case errstr is set to a human readable error message.

◆ start() [1/2]

virtual ErrorCode RdKafka::Consumer::start	(	Topic *	topic,
		int32_t	partition,
		int64_t	offset
	)

pure virtual

Start consuming messages for topic and partition at offset offset which may either be a proper offset (0..N) or one of the the special offsets: OFFSET_BEGINNING or OFFSET_END.

rdkafka will attempt to keep queued.min.messages (config property) messages in the local queue by repeatedly fetching batches of messages from the broker until the threshold is reached.

The application shall use one of the ..->consume*() functions to consume messages from the local queue, each kafka message being represented as a RdKafka::Message * object.

..->start() must not be called multiple times for the same topic and partition without stopping consumption first with ..->stop().

Returns: an ErrorCode to indicate success or failure.

◆ start() [2/2]

virtual ErrorCode RdKafka::Consumer::start	(	Topic *	topic,
		int32_t	partition,
		int64_t	offset,
		Queue *	queue
	)

pure virtual

Start consuming messages for topic and partition on queue queue.

See also: RdKafka::Consumer::start()

◆ stop()

virtual ErrorCode RdKafka::Consumer::stop	(	Topic *	topic,
		int32_t	partition
	)

pure virtual

Stop consuming messages for topic and partition, purging all messages currently in the local queue.

The application needs to be stop all consumers before destroying the Consumer handle.

Returns: an ErrorCode to indicate success or failure.

◆ seek()

virtual ErrorCode RdKafka::Consumer::seek	(	Topic *	topic,
		int32_t	partition,
		int64_t	offset,
		int	timeout_ms
	)

pure virtual

Seek consumer for topic+partition to offset which is either an absolute or logical offset.

If timeout_ms is not 0 the call will wait this long for the seek to be performed. If the timeout is reached the internal state will be unknown and this function returns ERR__TIMED_OUT. If timeout_ms is 0 it will initiate the seek but return immediately without any error reporting (e.g., async).

This call triggers a fetch queue barrier flush.

Returns: an ErrorCode to indicate success or failure.

◆ consume() [1/2]

virtual Message* RdKafka::Consumer::consume	(	Topic *	topic,
		int32_t	partition,
		int	timeout_ms
	)

pure virtual

Consume a single message from topic and partition.

timeout_ms is maximum amount of time to wait for a message to be received. Consumer must have been previously started with ..->start().

Returns: a Message object, the application needs to check if message is an error or a proper message RdKafka::Message::err() and checking for ERR_NO_ERROR.

The message object must be destroyed when the application is done with it.

Errors (in RdKafka::Message::err()):

ERR__TIMED_OUT - timeout_ms was reached with no new messages fetched.
ERR__PARTITION_EOF - End of partition reached, not an error.

◆ consume() [2/2]

virtual Message* RdKafka::Consumer::consume	(	Queue *	queue,
		int	timeout_ms
	)

pure virtual

Consume a single message from the specified queue.

timeout_ms is maximum amount of time to wait for a message to be received. Consumer must have been previously started on the queue with ..->start().

Returns: a Message object, the application needs to check if message is an error or a proper message Message->err() and checking for ERR_NO_ERROR.

The message object must be destroyed when the application is done with it.

Errors (in RdKafka::Message::err()):

ERR__TIMED_OUT - timeout_ms was reached with no new messages fetched

Note that Message->topic() may be nullptr after certain kinds of errors, so applications should check that it isn't null before dereferencing it.

◆ consume_callback() [1/2]

virtual int RdKafka::Consumer::consume_callback	(	Topic *	topic,
		int32_t	partition,
		int	timeout_ms,
		ConsumeCb *	consume_cb,
		void *	opaque
	)

pure virtual

Consumes messages from topic and partition, calling the provided callback for each consumed messsage.

consume_callback() provides higher throughput performance than consume().

timeout_ms is the maximum amount of time to wait for one or more messages to arrive.

The provided consume_cb instance has its consume_cb function called for every message received.

The opaque argument is passed to the consume_cb as opaque.

Returns: the number of messages processed or -1 on error.

See also: RdKafka::Consumer::consume()

◆ consume_callback() [2/2]

virtual int RdKafka::Consumer::consume_callback	(	Queue *	queue,
		int	timeout_ms,
		RdKafka::ConsumeCb *	consume_cb,
		void *	opaque
	)

pure virtual

Consumes messages from queue, calling the provided callback for each consumed messsage.

See also: RdKafka::Consumer::consume_callback()

◆ OffsetTail()

static int64_t RdKafka::Consumer::OffsetTail ( int64_t offset )

static

Converts an offset into the logical offset from the tail of a topic.

offset is the (positive) number of items from the end.

Returns: the logical offset for message offset from the tail, this value may be passed to Consumer::start, et.al.

Remarks: The returned logical offset is specific to librdkafka.

The documentation for this class was generated from the following file:

src-cpp/rdkafkacpp.h

Public Member Functions

Static Public Member Functions

Detailed Description

Member Function Documentation

◆ create()

◆ start() [1/2]

◆ start() [2/2]

◆ stop()

◆ seek()

◆ consume() [1/2]

◆ consume() [2/2]

◆ consume_callback() [1/2]

◆ consume_callback() [2/2]

◆ OffsetTail()