Table of Contents
- Getting Started
- Client libraries
rafka is a gateway service that exposes Kafka using simple semantics.
It implements a small subset of the Redis protocol, so that it can be used by leveraging existing Redis client libraries.
Using Kafka with languages that lack a reliable, solid client library can be a problem for mission-critical applications.
Using rafka we can:
- Hide Kafka low-level details from the application and provide sane defaults, backed by the excellent librdkafka.
- Use a Redis client instead of a Kafka client. This particularly useful in languages that lack a proper Kafka client library or do not provide concurrency primitives to implement buffering and other optimizations. Furthermore, writing a rafka client is much easier than writing a Kafka client. For a list of available client libraries see Client libraries.
Refer to "Introducing Kafka to a Rails application" for more background and how rafka is used in a production environment.
- librdkafka 0.11.5 or later
- A Kafka cluster
- Install librdkafka:
# debian $ sudo apt-get install librdkafka-dev # macOS $ brew install librdkafka
- Install rafka:
$ go get -u github.com/skroutz/rafka
- Run it:
$ rafka -c librdkafka.json.sample [rafka] 2017/06/26 11:07:23 Spawning Consumer Manager (librdkafka 0.11.0)... [server] 2017/06/26 11:07:23 Listening on 0.0.0.0:6380
rafka exposes a subset of the Redis protocol and tries to keep Redis semantics where possible.
We also try to design the protocol in a way that rafka can be replaced by a plain Redis instance so that it's easier to test client code and libraries.
In Kafka, each consumer represents a worker processing messages. That worker sends heartbeats and is de-pooled from its group when it misbehaves.
Those semantics are preserved in rafka by using stateful connections. In rafka, each connection is tied with a set of Kafka consumers. Consumers are not shared between connections and once the connection closes, the respective consumers are gracefully shut down too.
Each consumer must identify itself upon connection, by using
client setname <group.id>:<name>.
Then it can begin processing messages by issuing
blpop calls on the desired topics. Each message
should be explicitly acknowledged so it can be committed to Kafka. Acks are
rpushed to the
For more info refer to API - Consumer.
rafka periodically calls
under the hood. This means consumers must be configured accordingly:
enable.auto.commitmust be set to
enable.auto.offset.storemust be set to
For more info see https://github.com/edenhill/librdkafka/blob/master/CONFIGURATION.md.
- Each client connection is tied to a single Producer.
- Producers are not shared between connections and once the connection closes, its producer is also shutdown gracefully.
- Producers produce messages using
- Produced messages are buffered in rafka and are eventually flushed to Kafka. However,
DUMPcan be used to force a synchronous flush of any outstanding messages.
For more info refer to API - Producer.
There is currently is an upper message limit of 32MB to the messages that may be produced. It
is controlled by
RPUSHX topics:<topic> <message>produce a message
RPUSHX topics:<topic>:<key> <message>produce a message with a partition key. Messages with the same key will always be assigned to the same partition.
DUMP <timeoutMs>flush any outstanding messages to Kafka. This is a blocking operation; it returns until all buffered messages are flushed or the timeoutMs exceeds
Example using redis-cli:
127.0.0.1:6380> rpushx topics:greetings "hello there!" "OK"
CLIENT SETNAME <group.id>:<name>sets the consumer group and name
BLPOP topics:<topic>:<JSON-encoded consumer config> <timeoutMs>consume the next message from topic
RPUSH acks <topic>:<partition>:<offset>commit the offset for the given topic/partition
Example using redis-cli:
127.0.0.1:6380> client setname myapp:a-consumer "OK" 127.0.0.1:6380> blpop topics:greetings 1000 1) "topic" 2) "greetings" 3) "partition" 4) (integer) 2 5) "offset" 6) (integer) 10 7) "value" 8) "hello there!" # ... do some work with the greeting... 127.0.0.1:6380> rpush acks greetings:2:10 "OK"
HGETALL statsget monitoring statistics monitoring
KEYS topics:list all topics
DEL statsreset the monitoring statistics
- Ruby: rafka-rb
If this is your first time setting up development on rafka, ensure that you have all the build dependencies via dep:
$ dep ensure
To run all the tests (Go + end-to-end) do:
$ DIST=buster RDKAFKA_VERSION=v1.2.1 make test
rafka is released under the GNU General Public License version 3. See COPYING.