CORAL WIKI
Actors
Getting started
Overview
KafkaConsumerActor
The KafkaConsumerActor (Kafka consumer actor) is a Coral Actor that can emits incoming Kafka messages as JSON message.
Creating a KafkaConsumerActor
The creation JSON of the KafkaConsumerActor (see Coral Actor) has "type": "kafka-consumer".
The params value is a JSON with the following field:
| field | type | required | description |
|---|---|---|---|
topic |
string | yes | the Kafka bus topic to read |
kafka |
map | yes | a set of kafka properties for the consumer |
The properties of the kafka attribute should include at least the following:
| field | type | required | description |
|---|---|---|---|
group.id |
string | yes | the unique identifier to read a stream (do not use the same name simultaneously for different instances) |
zookeeper.connect |
string | yes | the ip address(es) of the zookeeper node(s) to connect to |
Other properties may be supplied cf. the Kafka consumer properties.
Example
{
"data": {
"type": "actors",
"attributes": {
"type": "kafka-consumer",
"params": {
"topic": "clickstream",
"kafka": {
"zookeeper.connect": "localhost:2181",
"group.id": "mygroup"
}
}
}
}
}Trigger
The KafkaConsumerActor has no trigger.
Conceptually, the Kafka stream can be thought of as trigger.
Emit
The KafkaConsumerActor emits Kafka messages as JSON.
Message bodies are assumed to be in proper JSON format.
State
The KafkaConsumerActor keeps no state.
Collect
The KafkaConsumerActor does not collect state from other actors.
Timer
The KafkaConsumerActor does not provide timer actions.