Status
Current state: DISCARDED
Discussion thread: here
JIRA: KAFKA-3294
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
The goal is to add Kafka Rest Server to Kafka Repository. This will allow any language/tool that
can work with HTTP to produce and consume messages, and perform administrative actions with Kafka service.
There are already some open-source REST proxies are available. Confluent REST Proxy got comprehensive interface.
But we would like to add REST server that many users ask for under Apache Kafka repo.
We want to add Kafka Rest Server to Kafka for the following reasons.
1) Many data Infra tools comes up with Rest Interface. It is useful to have inbuilt Rest API support for Produce,
Consume messages and admin interface for integrating with external management and provisioning tools.
2) Shipping Kafka Rest Server as part of a normal Kafka release makes it immediately available to every user that downloads Kafka.
3) Helps to maintain the version compatibility between Kafka and Rest Server.
Some of the good practices and ideas will be borrowed from existing tools.
REST server accepts produce requests for specific topics or partitions. It internally uses java producer instance to write messages into Kafka.
REST Proxy uses the new consumer API to consume the messages from the subscribed topic on behalf of the
specified consumer group. Consumer instances are stateful and tied to a particular Rest server instance.
A full URL is provided when the instance is created and it should be used to construct any subsequent requests.
When a message is consumed on behalf of a consume group for the first time, then Kafka Consumer instance joins
the consumer group and subscribes to the topic. All Consumer instances that are currently members of that group
and subscribed to that topic divide topic partitions among themselves. If a Consumer instance has not consumed
from a particular topic on behalf of a particular consumer group for configured interval (normally large interval),
then it unsubscribes from the topic on behalf of that group. This is for cleaning unused consumer instances due to dead clients.
Offset commit can be either automatic or manual as requested by the user.
We can also retrieve the messages for a consumer, from a specific partition, starting with an offset.
This will be taken up as future work after the KIP-4 implementation.
POST /topics/:topic
Description : Produce messages to a given topic
Parameters:
Topic (String) - topic name
Request:
JSON Object contains array of produce records
Response:
JSON Object contains response objects
Status Codes:
404 Not Found
Error Code 40401 - topic Not Found
Error Code 40402 - Version Not Found
500 Internal Server Error
Error Code 50001 - Kafka Error
Example request:
POST /topics/test HTTP/1.1 Host:kafkarest.host.com Content-Type: application/vnd.kafka.binary.v1+json Accept: application/vnd.kafka.v1+json { "records": [ { "key": "a2V5", "value": "dmFsdWU=" }, { "value": "dmFsdWU=", "partition": 1 } ] } |
Example response:
HTTP/1.1 200 OK Content-Type: application/vnd.kafka.v1+json { "offsets": [ { "partition": 2, "offset": 1 }, { "partition": 1, "offset": 2 } ] } |
POST /topics/:topicName/partitions/:partition
Description : Produce messages to one partition of the topic
Parameters:
topicName (String) - topic name
partition (int) - partition number
Request:
JSON Object contains array of produce records
Response:
JSON Object contains response objects
Status Codes:
404 Not Found
Error Code 40401 - topic Not Found
Error Code 40402 - partition Not Found
500 Internal Server Error
Error Code 50001 - Kafka Error
Example request:
POST /topics/test/partitions/1 HTTP/1.1 Host:kafkarest.host.com Content-Type: application/vnd.kafka.binary.v1+json Accept: application/vnd.kafka.v1+json { "records": [ { "key": "a2V5", "value": "dmFsdWU=" }, { "value": "dmFsdWU=" } ] } |
Example response:
HTTP/1.1 200 OK Content-Type: application/vnd.kafka.v1+json { "offsets": [ { "partition": 1, "offset": 1, }, { "partition": 1, "offset": 2, } ] } |
Description : Create a new consumer instance in the consumer group.
POST /consumers/:group |
Parameters:
group (String) - group name
Request:
JSON Object contains name, dataformat, consumer properties.
Response:
JSON Object contains response objects.
Response includes a URL including the host since the consumer is stateful and tied to a specific REST proxy instance
Status Codes:
404 Not Found
Error Code 40401 - topic Not Found
Error Code 40402 - partition Not Found
500 Internal Server Error
Error Code 50001 - Kafka Error
Example request:
POST /consumers/group/ HTTP/1.1 Accept: application/vnd.kafka.v1+json, application/vnd.kafka+json, application/json { "name": "Instance1", "format": "binary", "auto.offset.reset": "smallest", "auto.commit.enable": "false" } |
Example response:
HTTP/1.1 200 OK Content-Type: application/vnd.kafka.v1+json { "id": "Instance1", "url": "http://kafkarest1.com/consumers/group/instances/Instance1" } |
Description : consumes a message from the specified topic on behalf of the specified consumer group
GET /consumers/:group/:instance/:topic |
Parameters:
topic (String) - topic name
group (String) - consumer group id
Instance (string) - consumer instance name
Response:
JSON Object contains response objects
Status Codes:
404 Not Found
Error Code 4040X - topic Not Found
Error Code 4040Y - group Not Found
Error Code 4040Z - instance Not Found
500 Internal Server Error
Error Code 50001 - Kafka Error
Example request:
GET /consumers/group/instance1/topic HTTP/1.1 Accept: application/vnd.kafka.binary.v1+json |
Example response:
HTTP/1.1 200 OK Content-Type: application/vnd.kafka.binary.v1+json [ { "key": "a2V5", "value": "dmFsdWU=", "partition": 1, "offset": 1, }, { "key": "a2V5", "value": "dmFsdWU=", "partition": 1, "offset": 2, } ] |
Description : Commit offsets for the consumer instance associated with group.
POST /consumers/:group/:instance/offsets |
Parameters:
group (String) - consumer group id
Instance (String) - consumer instance name
Response:
JSON Object contains response objects
Status Codes:
404 Not Found
Error Code 40401 - group Not Found
Error Code 40402 - consumer instance Not Found
500 Internal Server Error
Error Code 50001 - Kafka Error
Example request:
POST /consumers/group/instance1/offsets HTTP/1.1 Accept: application/vnd.kafka.v1+json |
Example response:
HTTP/1.1 200 OK Content-Type: application/vnd.kafka.v1+json [ { "topic": "test", "partition": 1, "committed": 100 }, { "topic": "test", "partition": 2, "committed": 200 }, { "topic": "test2", "partition": 1, "committed": 50 } ] |
GET /topics/:topic_name/partitions/:partition?offset=(int)
Description : Consume messages from one partition of the topic.
Parameters:
topic_name (String) - topic name
partition (int) - partition number
offset (int) - offset to fetch
Response:
JSON Object contains response objects
Status Codes:
404 Not Found
Error Code 40401 - topic Not Found
Error Code 40402 - partition Not Found
500 Internal Server Error
Error Code 50001 - Kafka Error
Example request:
GET /consume/test/partitions/1?offset=1 HTTP/1.1 Accept: application/vnd.kafka.binary.v1+json |
Example response:
HTTP/1.1 200 OK Content-Type: application/vnd.kafka.binary.v1+json [ { "key": "a2V5", "value": "dmFsdWU=", "partition": 1, "offset": 1, }, { "key": "a2V5", "value": "dmFsdWU=", "partition": 1, "offset": 2, } ] |
Main Reason for this KIP is to add Rest Server to Kafka. Shipping Kafka Rest Server as part of a normal Kafka release
makes it immediately available to every user that downloads Kafka. Also helps to maintain the version compatibility
between Kafka clients and Rest Server.
End clients can register for the listening of events. This can be implemented used Web socket push notifications.
But This is against kafka consumer's pull model. It is good maintain Kafka consumer's semantics.