kafka
A Kafka source receives events to be processed by GDP stream workers from a topic with a partition for a Kafka cluster. The events received can be in the TEXT, JSON, or Binary format. If the topic is not already created in the Kafka cluster, the Kafka sink creates the default partition for the given topic.
Syntax
CREATE SOURCE <NAME> WITH (type="kafka", map.type="<STRING>", bootstrap.servers="<STRING>", topic.list="<STRING>", group.id="<STRING>", threading.option="<STRING>", partition.no.list="<STRING>", seq.enabled="<BOOL>", is.binary.message="<BOOL>", topic.offsets.map="<STRING>", enable.offsets.commit="<BOOL>", optional.configuration="<STRING>")
Query Parameters
| Name | Description | Default Value | Possible Data Types | Optional | Dynamic |
|---|---|---|---|---|---|
| bootstrap.servers | This specifies the list of Kafka servers to which the Kafka source must listen. This list can be provided as a set of comma-separated values. e.g., localhost:9092,localhost:9093 | STRING | No | No | |
| topic.list | This specifies the list of topics to which the source must listen. This list can be provided as a set of comma-separated values. e.g., topic_one,topic_two | STRING | No | No | |
| group.id | This is an ID to identify the Kafka source group. The group ID ensures that sources with the same topic and partition that are in the same group do not receive the same event. | STRING | No | No | |
| threading.option | This specifies whether the Kafka source is to be run on a single thread, or in multiple threads based on a condition. Possible values are as follows: single.thread: To run the Kafka source on a single thread. topic.wise: To use a separate thread per topic. partition.wise: To use a separate thread per partition. | STRING | No | No | |
| partition.no.list | The partition number list for the given topic. This is provided as a list of comma-separated values. e.g., 0,1,2,. | 0 | STRING | Yes | No |
| seq.enabled | If this parameter is set to true, the sequence of the events received via the source is taken into account. Therefore, each event should contain a sequence number as an attribute value to indicate the sequence. | false | BOOL | Yes | No |
| is.binary.message | In order to receive binary events via the Kafka source,it is required to setthis parameter to True. | false | BOOL | Yes | No |
| topic.offsets.map | This parameter specifies reading offsets for each topic and partition. The value for this parameter is specified in the following format: <topic>=<offset>,<topic>=<offset>, When an offset is defined for a topic, the Kafka source skips reading the message with the number specified as the offset as well as all the messages sent previous to that message. If the offset is not defined for a specific topic it reads messages from the beginning. e.g., stocks=100,trades=50 reads from the 101th message of the stocks topic, and from the 51st message of the trades topic. | null | STRING | Yes | No |
| enable.offsets.commit | This parameter specifies whether to commit offsets. If the manual asynchronous offset committing is needed, enable.offsets.commit should be true and enable.auto.commit should be false. If periodical committing is needed enable.offsets.commit should be true and enable.auto.commit should be true. If committing is not needed, enable.offsets.commit should be false. Note: enable.auto.commit is an optional.configuration property. If it is set to true, Source will periodically(default: 1000ms. Configurable with auto.commit.interval.ms property as an optional.configuration) commit its current offset (defined as the offset of the next message to be read) for the partitions it is reading from back to Kafka. To guarantee at-least-once processing, we recommend you to enable Stream App Periodic State Persistence when enable.auto.commit property is set to true. During manual committing, it might introduce a latency during consumption. | true | BOOL | Yes | No |
| optional.configuration | This parameter contains all the other possible configurations that the consumer is created with. e.g., ssl.keystore.type:JKS,batch.size:200. | null | STRING | Yes | No |
Example 1
@App:name('TestExecutionPlan')
CREATE STREAM BarStream (symbol string, price float, volume long);
CREATE SOURCE FooStream WITH (type='kafka', topic.list='kafka_topic,kafka_topic2', group.id='test', threading.option='partition.wise', bootstrap.servers='localhost:9092', partition.no.list='0,1', map.type='json') (symbol string, price float, volume long);
@info(name = 'query1')
insert into BarStream
from FooStream select symbol, price, volume;
This kafka source configuration listens to the kafka_topic and kafka_topic2 topics with 0 and 1 partitions. A thread is created
for each topic and partition combination. The events are received in the JSON format, mapped to a stream worker event, and sent to a stream named FooStream.
Example 2
@App:name('TestExecutionPlan')
CREATE STREAM BarStream (symbol string, price float, volume long);
CREATE SOURCE FooStream WITH (type='kafka', topic.list='kafka_topic', group.id='test', threading.option='single.thread', bootstrap.servers='localhost:9092', map.type='json') (symbol string, price float, volume long);
@info(name = 'query1')
insert into BarStream
from FooStream select symbol, price, volume;
This Kafka source configuration listens to the kafka_topic topic for the default partition because no partition.no.list is defined. Only one thread is created for the topic. The events are received in the JSON format, mapped to a stream worker event, and sent to a stream named FooStream.