wkafka

wkafka is a wrapper for kafka library to initialize and use for microservices.

go get github.com/worldline-go/wkafka

This library is using franz-go.

Usage

First set the connection config to create a new kafka client.
Main config struct that contains brokers, security settings and consumer validation.

brokers: # list of brokers, default is empty
  - localhost:9092
security:
  tls:
    enabled: false
    cert_file: ""
    key_file: ""
    ca_file: ""
  sasl: # SASL/SCRAM authentication could be multiple and will be used in order
    - plain:
        enabled: false
        user: ""
        pass: ""
      scram:
        enabled: false
        algorithm: "" # "SCRAM-SHA-256" or "SCRAM-SHA-512"
        user: ""
        pass: ""
consumer: # consumer validation and default values
  prefix_group_id: "" # add always a prefix to group id
  format_dlq_topic: "" # format dead letter topic name, ex: "finops_{{.AppName}}_dlq"
  validation:
    group_id: # validate group id
      enabled: false
      rgx_group_id: "" # regex to validate group id ex: "^finops_.*$"

Consumer

For creating a consumer we need to give additional consumer config when initializing the client.

topics: [] # list of topics to subscribe
group_id: "" # group id to subscribe, make is as unique as possible per service
# start offset to consume, 0 is the earliest offset, -1 is the latest offset and more than 0 is the offset number
# group_id has already committed offset then this will be ignored
start_offset: 0 # -1 to start end of the offsets
skip: # this is programatically skip, kafka will still consume the message
  # example skip topic and offset
  mytopic: # topic name to skip
    0: # partition number
      offsets: # list of offsets to skip
        - 31
        - 90
      before: 20 # skip all offsets before or equal to this offset
# max records to consume per poll, 0 is default value from kafka usually 500
# no need to touch most of the time, but batch consume's count max is max_poll_records
max_poll_records: 0 
# max records to consume per batch to give callback function, default is 100
# if this value is more than max_poll_records then max_poll_records will be used
batch_count: 100
dlq:
  disabled: false # disable dead letter queue
  topic: "" # dead letter topic name, it can be assigned in the kafka config's format_dlq_topic
  retry_interval: "10s" # retry time interval of the message if can't be processed, default is 10s
  start_offset: 0 # -1 to start end of the offsets
  skip: # same as skip but just for dead letter topic and not need to specify topic name
    # example skip offset
    0:
      offsets:
        - 31
      before: 20

Always give the client information so we can view in publish message's headers and kafka UI.

client, err := wkafka.New(
  ctx, kafkaConfig,
  wkafka.WithConsumer(consumeConfig),
  wkafka.WithClientInfo("testapp", "v0.1.0"),
)
if err != nil {
  return err
}

defer client.Close()

Now you need to run consumer with a callback function.
There is 2 options to run consumer, batch or single (WithCallbackBatch or WithCallback).
Default decoder is json, but you can change it with WithDecode option.
If you use []byte as data type then raw data will be passed to the callback function, batch consumer like [][]byte type.

// example single consumer
if err := client.Consume(ctx, wkafka.WithCallback(ProcessSingle)); err != nil {
  return fmt.Errorf("consume: %w", err)
}

Send record to dead letter queue, use WrapErrDLQ function with to wrap the error and it will be send to dead letter queue.

Check the aditional options for custom decode and precheck.

Skip Handler

Editing the skip map and use our handler to initialize server mux.

// import github.com/worldline-go/wkafka/handler

mux := http.NewServeMux()
mux.Handle(handler.New(client))

reflector := grpcreflect.NewStaticReflector(wkafkaconnect.WkafkaServiceName)

mux.Handle(grpcreflect.NewHandlerV1(reflector))
mux.Handle(grpcreflect.NewHandlerV1Alpha(reflector))

Handler Example

make env

# run the example
EXAMPLE=consumer_single_handler make example

Add messages in here to skip the message http://localhost:7071

Go to this side for grpcUI http://localhost:8082/#/grpc/wkafka

Producer

Use consumer client or create without consumer settings, New also try to connect to brokers.

client, err := wkafka.New(kafkaConfig)
if err != nil {
    return err
}
defer client.Close()

Create a producer based of client and specific data type.

WithHook, WithEncoder, WithHeaders options are optional.
Use WithHook to get metadata of the record and modify to produce record.

producer, err := wkafka.NewProducer[*Data](client, "test", wkafka.WithHook(ProduceHook))
if err != nil {
  return err
}

return producer.Produce(ctx, data)

Development

Initialize kafka and redpanda console with docker-compose.

# using "docker compose" command, if you use podman then add compose extension and link docker with podman binary
make env

Service	Description
localhost:9092	Kafka broker
localhost:7071	Redpanda console

Use examples with EXAMPLE env variable:

EXAMPLE=... make example