Providers Reference

Configuration reference for all herald providers.

Kafka

import "github.com/zoobz-io/herald/kafka"

Constructor

func New(topic string, opts ...Option) *Provider

Options

Option	Description
`WithWriter(w Writer)`	Set Kafka writer for publishing
`WithReader(r Reader)`	Set Kafka reader for subscribing

Interfaces

type Writer interface {
    WriteMessages(ctx context.Context, msgs ...kafka.Message) error
    Close() error
}

type Reader interface {
    FetchMessage(ctx context.Context) (kafka.Message, error)
    CommitMessages(ctx context.Context, msgs ...kafka.Message) error
    Close() error
}

NATS

import "github.com/zoobz-io/herald/nats"

Constructor

func New(subject string, opts ...Option) *Provider

Options

Option	Description
`WithConn(c *nats.Conn)`	Set NATS connection

Note: NATS core does not support headers. Metadata is ignored.

JetStream

import "github.com/zoobz-io/herald/jetstream"

Constructor

func New(subject string, opts ...Option) *Provider

Options

Option	Description
`WithJetStream(js jetstream.JetStream)`	Set JetStream context
`WithConsumer(c jetstream.Consumer)`	Set consumer for subscribing
`WithStream(name string)`	Set stream name for publishing

Google Pub/Sub

import "github.com/zoobz-io/herald/pubsub"

Constructor

func New(opts ...Option) *Provider

Unlike other providers, Pub/Sub requires no identifier in the constructor. Topic and subscription are configured via options.

Options

Option	Description
`WithTopic(t *pubsub.Topic)`	Set topic for publishing
`WithSubscription(s *pubsub.Subscription)`	Set subscription for consuming

Redis Streams

import "github.com/zoobz-io/herald/redis"

Constructor

func New(stream string, opts ...Option) *Provider

Options

Option	Description
`WithClient(c *redis.Client)`	Set Redis client
`WithGroup(name string)`	Set consumer group name
`WithConsumer(name string)`	Set consumer name within group
`WithMaxLen(n int64)`	Set stream max length

AWS SQS

import "github.com/zoobz-io/herald/sqs"

Constructor

func New(queueURL string, opts ...Option) *Provider

Options

Option	Description
`WithClient(c *sqs.Client)`	Set SQS client
`WithWaitTimeSeconds(n int32)`	Long polling wait time
`WithMaxMessages(n int32)`	Max messages per receive
`WithVisibilityTimeout(n int32)`	Visibility timeout seconds

RabbitMQ/AMQP

import "github.com/zoobz-io/herald/amqp"

Constructor

func New(exchange string, opts ...Option) *Provider

Options

Option	Description
`WithChannel(ch *amqp.Channel)`	Set AMQP channel
`WithQueue(name string)`	Set queue name for consuming
`WithRoutingKey(key string)`	Set routing key for publishing
`WithConsumerTag(tag string)`	Set consumer tag

AWS SNS

import "github.com/zoobz-io/herald/sns"

Constructor

func New(topicARN string, opts ...Option) *Provider

Options

Option	Description
`WithClient(c *sns.Client)`	Set SNS client

Note: SNS is publish-only. Subscribe returns closed channel.

BoltDB

import "github.com/zoobz-io/herald/bolt"

Constructor

func New(bucket string, opts ...Option) *Provider

Options

Option	Description
`WithDB(db *bbolt.DB)`	Set BoltDB database
`WithPollInterval(d time.Duration)`	Polling interval (default 100ms)
`WithBatchSize(n int)`	Messages per poll (default 10)

Note: BoltDB does not support metadata. Metadata is ignored.

Firestore

import "github.com/zoobz-io/herald/firestore"

Constructor

func New(collection string, opts ...Option) *Provider

Options

Option	Description
`WithClient(c *firestore.Client)`	Set Firestore client
`WithPollInterval(d time.Duration)`	Polling interval
`WithBatchSize(n int)`	Documents per poll

io

import "github.com/zoobz-io/herald/io"

Constructor

func New(opts ...Option) *Provider

Options

Option	Description
`WithWriter(w io.Writer)`	Set writer for publishing
`WithReader(r io.Reader)`	Set reader for subscribing
`WithDelimiter(b byte)`	Message delimiter (default newline)

Useful for testing with bytes.Buffer or os.Stdout.

Feature Matrix

Provider	Publish	Subscribe	Metadata	Ack/Nack
Kafka	✓	✓	✓	✓
NATS	✓	✓	✗	✗
JetStream	✓	✓	✓	✓
Pub/Sub	✓	✓	✓	✓
Redis	✓	✓	✓	✓
SQS	✓	✓	✓	✓
AMQP	✓	✓	✓	✓
SNS	✓	✗	✓	N/A
BoltDB	✓	✓	✗	✓
Firestore	✓	✓	✓	✓
io	✓	✓	✗	✗