confluent-kafka-go is Confluent's Golang client for Apache Kafka and the Confluent Platform.
Features:
High performance - confluent-kafka-go is a lightweight wrapper around librdkafka, a finely tuned C client.
Reliability - There are a lot of details to get right when writing an Apache Kafka client. We get them right in one place (librdkafka) and leverage this work across all of our clients (also confluent-kafka-python and confluent-kafka-dotnet).
Supported - Commercial support is offered by Confluent.
Future proof - Confluent, founded by the original creator/co-creator of Kafka, is building a streaming platform with Apache Kafka at its core. It's high priority for us that client features keep pace with core Apache Kafka and components of the Confluent Platform.
The Golang bindings provides a high-level Producer and Consumer with support for the balanced consumer groups of Apache Kafka 0.9 and above.
See the API documentation for more information.
For a step-by-step guide on using the client see Getting Started with Apache Kafka and Golang.
High-level balanced consumer
import (
"fmt"
"time"
"github.com/confluentinc/confluent-kafka-go/v2/kafka"
)
func main() {
c, err := kafka.NewConsumer(&kafka.ConfigMap{
"bootstrap.servers": "localhost",
"group.id": "myGroup",
"auto.offset.reset": "earliest",
})
if err != nil {
panic(err)
}
err = c.SubscribeTopics([]string{"myTopic", "^aRegex.*[Tt]opic"}, nil)
if err != nil {
panic(err)
}
// A signal handler or similar could be used to set this to false to break the loop.
run := true
for run {
msg, err := c.ReadMessage(time.Second)
if err == nil {
fmt.Printf("Message on %s: %s\n", msg.TopicPartition, string(msg.Value))
} else if !err.(kafka.Error).IsTimeout() {
// The client will automatically try to recover from all errors.
// Timeout is not considered an error because it is raised by
// ReadMessage in absence of messages.
fmt.Printf("Consumer error: %v (%v)\n", err, msg)
}
}
c.Close()
}
Producer
import (
"fmt"
"github.com/confluentinc/confluent-kafka-go/v2/kafka"
)
func main() {
p, err := kafka.NewProducer(&kafka.ConfigMap{"bootstrap.servers": "localhost"})
if err != nil {
panic(err)
}
defer p.Close()
// Delivery report handler for produced messages
go func() {
for e := range p.Events() {
switch ev := e.(type) {
case *kafka.Message:
if ev.TopicPartition.Error != nil {
fmt.Printf("Delivery failed: %v\n", ev.TopicPartition)
} else {
fmt.Printf("Delivered message to %v\n", ev.TopicPartition)
}
}
}
}()
// Produce messages to topic (asynchronously)
topic := "myTopic"
for _, word := range []string{"Welcome", "to", "the", "Confluent", "Kafka", "Golang", "client"} {
p.Produce(&kafka.Message{
TopicPartition: kafka.TopicPartition{Topic: &topic, Partition: kafka.PartitionAny},
Value: []byte(word),
}, nil)
}
// Wait for message deliveries before shutting down
p.Flush(15 * 1000)
}
More elaborate examples are available in the examples directory, including how to configure the Go client for use with Confluent Cloud.
Supports Go 1.17+ and librdkafka 2.11.0+.
You can use Go Modules to install confluent-kafka-go.
Import the kafka package from GitHub in your code:
import "github.com/confluentinc/confluent-kafka-go/v2/kafka"
Build your project:
If you are building for Alpine Linux (musl), -tags musl must be specified.
go build -tags musl ./...
A dependency to the latest stable version of confluent-kafka-go should be automatically added to your go.mod file.
Manual install:
go get -u github.com/confluentinc/confluent-kafka-go/v2/kafka
Golang import:
import "github.com/confluentinc/confluent-kafka-go/v2/kafka"
Prebuilt librdkafka binaries are included with the Go client and librdkafka does not need to be installed separately on the build or target system. The following platforms are supported by the prebuilt librdkafka binaries:
When building your application for Alpine Linux (musl libc) you must pass -tags musl to go get, go build, etc.
CGO_ENABLED must NOT be set to 0 since the Go client is based on the C library librdkafka.
If GSSAPI/Kerberos authentication support is required you will need to install librdkafka separately, see the Installing librdkafka chapter below, and then build your Go application with -tags dynamic.
If the bundled librdkafka build is not supported on your platform, or you need a librdkafka with GSSAPI/Kerberos support, you must install librdkafka manually on the build and target system using one of the following alternatives:
librdkafka-dev from the standard repositories or using Confluent's Deb repository.librdkafka-devel using Confluent's YUM repository.librdkafka from Homebrew. You may also need to brew install pkg-config if you don't already have it: brew install librdkafka pkg-config.apk add librdkafka-dev pkgconfBuild from source:
git clone https://github.com/confluentinc/librdkafka.git
cd librdkafka
./configure
make
sudo make install
After installing librdkafka you will need to build your Go application with -tags dynamic.
Note: If you use the master branch of the Go client, then you need to use the master branch of librdkafka.
confluent-kafka-go requires librdkafka v1.9.0 or later.
Since we are using cgo, Go builds a dynamically linked library even when using the prebuilt, statically-compiled librdkafka as described in the librdkafka chapter.
For glibc based systems, if the system where the client is being compiled is different from the target system, especially when the target system is older, there is a glibc version error when trying to run the compiled client.
Unfortunately, if we try building a statically linked binary, it doesn't solve the problem, since there is no way to have truly static builds using glibc. This is because there are some functions in glibc, like getaddrinfo which need the shared version of the library even when the code is compiled statically.
One way around this is to either use a container/VM to build the binary, or install an older version of glibc on the system where the client is being compiled.
The other way is using musl to create truly static builds for Linux. To do this, install it for your system.
Static compilation command, meant to be used alongside the prebuilt librdkafka bundle:
CC=/path/to/musl-gcc go build --ldflags '-linkmode external -extldflags "-static"' -tags musl
The recommended API strand is the Function-Based one, the Channel-Based one is documented in examples/legacy.
Messages, errors and events are polled through the consumer.Poll() function.
It has direct mapping to underlying librdkafka functionality.
Application calls producer.Produce() to produce messages. Delivery reports are emitted on the producer.Events() or specified private channel.
Warnings
Produce() is a non-blocking call, if the internal librdkafka queue is full the call will fail and can be retried.KAFKA is a registered trademark of The Apache Software Foundation and has been licensed for use by confluent-kafka-go. confluent-kafka-go has no affiliation with and is not endorsed by The Apache Software Foundation.
See kafka/README
Contributions to the code, examples, documentation, et.al, are very much appreciated.
Make your changes, run gofmt, tests, etc, push your branch, create a PR, and sign the CLA.
For a step-by-step guide on using the Golang client with Confluent Cloud see Getting Started with Apache Kafka and Golang on Confluent Developer.
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