Confluent's Apache Kafka client for Golang

Confluent's Kafka client for Golang wraps the librdkafka C library, providing full Kafka protocol support with great performance and reliability.

The Golang bindings provides a high-level Producer and Consumer with support for the balanced consumer groups of Apache Kafka 0.9 and above.

License: Apache License v2.0

Beta information

The Go client is currently in beta and APIs are subject to (minor) change.

API strands

There are two main API strands: channel based or function based.

Channel based consumer

Messages, errors and events are posted on the consumer.Events channel for the application to read.

Pros:

• Possibly more Golang:ish
• Makes reading from multiple channels easy
• Fast

Cons:

• Outdated events and messages may be consumed due to the buffering nature of channels. The extent is limited, but not remedied, by the Events channel buffer size (go.events.channel.size).

See examples/consumer_channel_example

Function based consumer

Messages, errors and events are polled through the consumer.Poll() function.

Pros:

• More direct mapping to underlying librdkafka functionality.

Cons:

• Makes it harder to read from multiple channels, but a go-routine easily solves that (see Cons in channel based consumer above about outdated events).
• Slower than the channel consumer.

See examples/consumer_example

Channel based producer

Application writes messages to the producer.ProducerChannel. Delivery reports are emitted on the producer.Events or specified private channel.

Pros:

• Go:ish
• Proper channel backpressure if librdkafka internal queue is full.

Cons:

• Double queueing: messages are first queued in the channel (size is configurable) and then inside librdkafka.

See examples/producer_channel_example

Function based producer

Application calls producer.Produce() to produce messages. Delivery reports are emitted on the producer.Events or specified private channel.

Pros:

• Go:ish

Cons:

• Produce() is a non-blocking call, if the internal librdkafka queue is full the call will fail.
• Somewhat slower than the channel producer.

See examples/producer_example

Usage

See examples

Prerequisites

• librdkafka >= 0.9.2 (or master branch => 2016-08-16)

Build

$ cd kafka
$ go install

Static builds

NOTE: Requires pkg-config

To link your application statically with librdkafka append -tags static to your application's go build command, e.g.:

$ cd kafkatest/go_verifiable_consumer
$ go build -tags static

This will create a binary with librdkafka statically linked, do note however that any librdkafka dependencies (such as ssl, sasl2, lz4, etc, depending on librdkafka build configuration) will be linked dynamically and thus required on the target system.

To create a completely static binary append -tags static_all instead. This requires all dependencies to be available as static libraries (e.g., libsasl2.a). Static libraries are typically not installed by default but are available in the corresponding ..-dev or ..-devel packages (e.g., libsasl2-dev).

After a succesful static build verify the dependencies by running ldd ./your_program, librdkafka should not be listed.

Tests

See kafka/README

Getting started

Installing librdkafka

git clone https://github.com/edenhill/librdkafka.git
cd librdkafka
./configure --prefix /usr
make
sudo make install

Build the Go client

From the confluent-kafka-go directory which should reside in $GOPATH/src/github.com/confluentinc/confluent-kafka-go:

cd kafka
go install