Confluent REST APIs
The Confluent REST Proxy provides a RESTful interface to a Apache Kafka® cluster, making it easy to produce and consume messages, view
the state of the cluster, and perform administrative actions without using the native Kafka protocol or clients.
Some example use cases are:
- Reporting data to Kafka from any frontend app built in any language not supported by official Confluent clients
- Ingesting messages into a stream processing framework that doesn’t yet support Kafka
- Scripting administrative actions
There is a plugin available for Confluent REST Proxy that helps authenticate incoming
requests and propagates the authenticated principal to requests to Kafka. This
enables Confluent REST Proxy clients to utilize the multi-tenant security features of
the Kafka broker. For more information, see REST Proxy Security and
REST Proxy Security Plugins.
Eventually, the REST Proxy should be able to expose all of the functionality
of the Java producers, consumers, and command-line tools. Here is the list of
what is currently supported:
- Metadata - Most metadata about the cluster – brokers, topics,
partitions, and configs – can be read using
GET requests for the
- Producers - Instead of exposing producer objects, the API accepts produce
requests targeted at specific topics or partitions and routes them all through
a small pool of producers.
- Producer configuration - Producer instances are shared, so configs cannot
be set on a per-request basis. However, you can adjust settings globally by
passing new producer settings in the REST Proxy configuration. For example,
you might pass in the
compression.type option to enable site-wide
compression to reduce storage and network overhead.
- Consumers - Consumers are stateful and therefore tied to specific REST Proxy instances. Offset
commit can be either automatic or explicitly requested by the user. Currently limited to
one thread per consumer; use multiple consumers for higher throughput. The REST Proxy uses either the high level consumer (v1 api) or the
new 0.9 consumer (v2 api) to implement consumer-groups that can read from topics. Note: the v1 API has been marked for deprecation.
- Consumer configuration - Although consumer instances are not shared, they do
share the underlying server resources. Therefore, limited configuration
options are exposed via the API. However, you can adjust settings globally
by passing consumer settings in the REST Proxy configuration.
- Data Formats - The REST Proxy can read and write data using JSON, raw bytes
encoded with base64 or using JSON-encoded Avro, Protobuf, or JSON Schema. With Avro, Protobuf, or
JSON Schema, schemas are registered and validated against Schema Registry.
- REST Proxy Clusters and Load Balancing - The REST Proxy is designed to
support multiple instances running together to spread load and can safely be
run behind various load balancing mechanisms (e.g. round robin DNS, discovery
services, load balancers) as long as instances are
- Simple Consumer - The high-level consumer should generally be
preferred. However, it is occasionally useful to use low-level read
operations, for example to retrieve messages at specific offsets.
Just as important, here’s a list of features that aren’t yet supported:
- Multi-topic Produce Requests - Currently each produce request may only
address a single topic or topic-partition. Most use cases do not require
multi-topic produce requests, they introduce additional complexity into the
API, and clients can easily split data across multiple requests if necessary
- Most Producer/Consumer Overrides in Requests - Only a few key overrides are exposed in
the API (but global overrides can be set by the administrator). The reason is
two-fold. First, proxies are multi-tenant and therefore most user-requested
overrides need additional restrictions to ensure they do not impact other
users. Second, tying the API too much to the implementation restricts future
API improvements; this is especially important with the new upcoming consumer
Starting the Confluent REST Proxy service is simple once its dependencies are
# Start the REST Proxy. The default settings automatically work with the
# default settings for local |zk| and |ak| nodes.
If you installed Debian or RPM packages, you can simply run
as it will be on your
kafka-rest.properties file contains
configuration settings. The default configuration
included with the REST Proxy includes convenient defaults for a local testing setup
and should be modified for a production deployment. By default the server starts bound to port
8082, does not specify a unique instance ID (required to safely run multiple
proxies concurrently), and expects ZooKeeper to be available at
localhost:2181 and Schema Registry at
If you started the service in the background, you can use the following
command to stop it:
To build a development version, you may need a development versions of
installing these, you can build the Confluent REST Proxy
with Maven. All the standard lifecycle phases work. During development, use
mvn -f kafka-rest/pom.xml compile
mvn -f kafka-rest/pom.xml test
to run the unit and integration tests, and
to run an instance of the proxy against a local Kafka cluster (using the default
configuration included with Kafka).
To create a packaged version, optionally skipping the tests:
mvn -f kafka-rest/pom.xml package [-DskipTests]
This will produce a version ready for production in
target/kafka-rest-$VERSION-package containing a directory layout similar
to the packaged binary versions. You can also produce a standalone fat jar using the
mvn -f kafka-rest/pom.xml package -P standalone [-DskipTests]
target/kafka-rest-$VERSION-standalone.jar, which includes all the
dependencies as well.
To run a local ZooKeeper, Kafka and REST Proxy cluster, for testing: