kafka-http-proxy

A proxy that allows applications to use Kafka via HTTP... written in NodeJS.

But why...?

Native clients for Kafka are tricky. The protocol is moving fast and there is a lot to manage. This project gives applications a bridge so that languages that aren't "supported" can still use Kafka.

The inspiration for this project came from the Confluent REST Proxy. We found that project to be too heavy for what we wanted and introduce a lot of lag between messages going from producer to consumer. We have tried to keep the API consistent with that so clients already using it can easily switch over, but wanted to simplify as much as possible.

Getting started

Get the source...

git clone https://github.com/hoppity/kafka-http-proxy
npm install
export ZOOKEEPER_CONNECT=127.0.0.1:2181,127.0.0.2:2181,127.0.0.3:2181
node server.js

Or using docker...

docker run
    -p 8085:8085 `
    -e "ZOOKEEPER_CONNECT=127.0.0.1:2181,127.0.0.2:2181,127.0.0.3:2181" `
    --name kafka-http-proxy
    hoppity/kafka-http-proxy

Configuration

Most configuration is contained in config/default.json.

• kafka
• zkConnect - the Zookeeper connection string
• clientId - the client identifier for the application
• logging
• logName - ?
• level - the level of logging to output
• accessLogPath - the path to an Apache standard compliant access log
• port - the port to expose the application on
• consumer
• timeoutMs - the number of milliseconds to wait between polls before a consumer is deemed inactive and timed-out.

This can be changed or overriden by placing values in another file in the config directory and setting the NODE_ENV variable (e.g. production.json and export NODE_ENV=production).

API

TODO: Write about standard errors.

/topics

PUT /topics/{topic}

Creates a topic with the name specified using the default topic creation settings. This will fail if automatic topic creation is disabled in Kafka.

Input

• params
• topic - the name of the topic to create

Output

• JSON Response
• message - "All created"

E.g.

$ curl -X PUT http://localhost:8085/topics/test-topic

{"message":"All created"}

POST /topics/{topic}

Publishes a message to the specified topic.

Input

• params
• topic - the name of the topic to publish to
• JSON body
• records - array of messages to publish
• key
• value
• partition

E.g.

$ curl -X POST \
    -H 'Content-Type: application/kafka.binary.v1+json' \
    -d '{"records":[{"value":"1234"}]}' \
    http://localhost:8085/topics/test-topic

{"offsets":[{"partition":"0","offset":0}]}

/consumers

POST /consumers/{group}

Create a consumer with the specified group name.

Input

• params
• group - the name of the consumer group
• JSON body
• auto.offset.reset - the point to automatically reset the offset to if the consumer group does not exist. Options: smallest, largest. Default: largest
• auto.commit.enable - enable/disable the consumer to autocommit on the server side. When true, the server will commit the offset after every get request. When false, you must commit manually (as below). Default: true.
• value.encode - enable/disable base64 encoded messages to be returned from the consumer. Default: true
• request.max.messages - the number of messages to return in a single get request. Configurable in config.consumer.requestMaxMessages. Default: 100.

Output

• JSON response
• instance_id - the identifier of the consumer instance
• base_uri - the base URI for consumers to use when polling for messages

E.g.

$ curl -X POST http://localhost:8085/consumers/test-group

{
    "instance_id":"3bae5d25-b0bc-4e4a-b937-bdc75ceece39",
    "base_uri":"http://localhost:8085/consumers/test-group/instances/3bae5d25-b0bc-4e4a-b937-bdc75ceece39"
}

GET /consumers/{group}/instances/{instance_id}/topics/{topic}

Consumes messages from the topic on the specified consumer. The URI should be formed by concatenating the base_uri returned when creating the consumer and /topics/{topic}.

Input

• params
• group - the name of the consumer group
• instance_id - the consumer instance id
• topic - the name of the topic to consume

Output

• JSON response
• Array of message
• topic
• partition
• offset
• key
• value

E.g.

$ curl http://localhost:8085/consume/test-group/instances/3bae5d25-b0bc-4e4a-b937-bdc75ceece39

[
    {
        "topic":"test-topic",
        "partition":0,
        "offset":0,
        "key":"",
        "value":"1234"
    }
]

POST /consumers/{group}/instances/{instance_id}/offsets

Commit the current offset of the consumer instance. The URI should be formed by concatenating the base_uri returned when creating the consumer and /offsets.

Input

• params
• group - the name of the consumer group
• instance_id - the consumer instance id

Output

• JSON Response
• Empty array

E.g.

$ curl -X POST http://localhost:8085/consume/test-group/instances/3bae5d25-b0bc-4e4a-b937-bdc75ceece39/offsets

[]

DELETE /consumers/{group}/instances/{instance_id}

Shut down a consumer instance. The URI should the base_uri returned when creating the consumer.

Input

• params
• group - the name of the consumer group
• instance_id - the consumer instance id

Output

• JSON Response
• Empty object

E.g.

$ curl -X DELETE http://localhost:8085/consume/test-group/instances/3bae5d25-b0bc-4e4a-b937-bdc75ceece39

{}