kafka::ConsumerComponent Class Reference

#include <userver/kafka/consumer_component.hpp>

Detailed Description

Apache Kafka Consumer client component.

Static configuration example:

        # yaml
        kafka-consumer:                  # Kafka consumer component name must start with kafka-consumer
            group_id: test-group         # Consumers group current consumer will join on start
            topics:                      # List of topics consumer starts to listen
              - test-topic-1
              - test-topic-2
            auto_offset_reset: smallest  # Strategy for reading topics without committed offsets
            max_batch_size: 5            # Number of messages consumers waits until user-callback is called
            security_protocol: PLAINTEXT # Broker connection settings

Secdist format

A Kafka alias in secdist is described as a JSON object kafka_settings, containing credentials of Kafka brokers.

@pytest.fixture(scope='session')
def service_env(kafka_secdist) -> dict:
    """
    Note: kafka_secist fixture generates the secdist config
 
    Expected secdist format is:
    "kafka_settings": {
        "<kafka-component-name>": {
            "brokers": "<brokers comma-separated endpoint list>",
            "username": "SASL2 username (may be empty if use PLAINTEXT)",
            "password": "SASL2 password (may be empty if use PLAINTEXT)"
        }
    }
    """
 
    return {'SECDIST_CONFIG': kafka_secdist}

Static options:

Name	Description	Default value
client_id	Client identifier. May be an arbitrary string	userver
group_id	consumer group id (name)	–
topics	list of topics consumer subscribes	–
max_batch_size	maximum number of messages consumer waits for new message before calling a callback	1
poll_timeout	maximum amount of time consumer waits for messages for new messages before calling a callback	1s
max_callback_duration	duration user callback must fit not to be kicked from the consumer group	5m
restart_after_failure_delay	time consumer suspends execution if user-callback fails	10s
auto_offset_reset	action to take when there is no initial offset in offset store	smallest
env_pod_name	environment variable to substitute {pod_name} substring in group_id	none
security_protocol	protocol used to communicate with brokers	–
sasl_mechanisms	SASL mechanism to use for authentication	none
ssl_ca_location	File or directory path to CA certificate(s) for verifying the broker's key	none
topic_metadata_refresh_interval	period of time at which topic and broker metadata is refreshed	5m
metadata_max_age	metadata cache max age	15
rd_kafka_custom_options	a map of librdkafka library additional options	'{}'

Examples

samples/kafka_service/main.cpp.

Definition at line 59 of file consumer_component.hpp.

Inheritance diagram for kafka::ConsumerComponent:

Public Member Functions
	ConsumerComponent (const components::ComponentConfig &config, const components::ComponentContext &context)
ConsumerScope	GetConsumer ()
	Returns consumer instance.
ComponentHealth	GetComponentHealth () const override
void	OnLoadingCancelled () override
void	OnAllComponentsLoaded () override
void	OnAllComponentsAreStopping () override

Static Public Member Functions
static yaml_config::Schema	GetStaticConfigSchema ()

Static Public Attributes
static constexpr std::string_view	kName {"kafka-consumer"}
	The default name of kafka::ConsumerComponent component.

Protected Types
using	LoggableComponentBase = ComponentBase
	Legacy alias, use ComponentBase instead.

Member Typedef Documentation

LoggableComponentBase

using components::ComponentBase::LoggableComponentBase = ComponentBase

protectedinherited

Legacy alias, use ComponentBase instead.

Definition at line 67 of file component_base.hpp.

Member Function Documentation

GetComponentHealth()

ComponentHealth components::ComponentBase::GetComponentHealth ( ) const

inlineoverridevirtualinherited

Override this function to inform the world of the state of your component.

Warning

The function is called concurrently from multiple threads.

Reimplemented from components::RawComponentBase.

Reimplemented in server::handlers::Restart.

Definition at line 35 of file component_base.hpp.

GetConsumer()

ConsumerScope kafka::ConsumerComponent::GetConsumer

(

)

Returns consumer instance.

See also

kafka::ConsumerScope

OnAllComponentsAreStopping()

void components::ComponentBase::OnAllComponentsAreStopping ( )

inlineoverridevirtualinherited

Component may use this function to stop doing work before the stop of the components that depend on it.

Base components may override it and make final to do some work before the derived object constructor is called. Don't use it otherwise.

Reimplemented from components::RawComponentBase.

Reimplemented in urabbitmq::ConsumerComponentBase, and components::Server.

Definition at line 58 of file component_base.hpp.

OnAllComponentsLoaded()

void components::ComponentBase::OnAllComponentsLoaded ( )

inlineoverridevirtualinherited

Component may use this function to finalize registration of other components that depend on it (for example, handler components register in server component, and the latter uses OnAllComponentsLoaded() to start processing requests).

Base components may override it and make final to do some work after the derived object constructor is called. Don't use it otherwise.

Reimplemented from components::RawComponentBase.

Reimplemented in urabbitmq::ConsumerComponentBase, components::Server, and server::handlers::Ping.

Definition at line 51 of file component_base.hpp.

OnLoadingCancelled()

void components::ComponentBase::OnLoadingCancelled ( )

inlineoverridevirtualinherited

Called once if the creation of any other component failed. If the current component expects some other component to take any action with the current component, this call is a signal that such action may never happen due to components loading was cancelled. Application components might not want to override it.

Reimplemented from components::RawComponentBase.

Definition at line 42 of file component_base.hpp.

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

• userver/kafka/consumer_component.hpp