# README
Tackle
An opinionated RabbitMQ message processing and publishing library, ideal for async communicaton between microservices.
Installation
go get github.com/renderedtext/go-tackle
Publishing messages to a RabbitMQ exchange (simple)
To publish a message to a RabbitMQ exchange, use the tackle.PublishMessage
function. For example, if you are writting a user managment service and want
to publish that a user was created, use the following snippet.
package main
import (
tackle "github.com/renderedtext/go-tackle"
)
func main() {
publishParams := tackle.PublishParams{
Body: []byte(`{"user_id": "123"}`),
RoutingKey: "user-created",
Exchange: "user-exchange",
AmqpURL: "guest@localhost:5467",
}
err := tackle.PublishMessage(&publishParams)
if err != nil {
log.Info("something went wrong while publishing %v", err)
}
}
Publishing messages to a RabbitMQ exchange (advanced)
In the simple publishing mechanism, tackle will open and close a connection every time it sends a message. This is fine for sending one or two messages, however, if you plan to publish large batches of messages, it will be more efficient to create a dedicated publisher that keeps the connection open for a longer duration.
tackle.NewPublisher creates a publisher that will lazily create the connection,
re-connecting if the current connection is closed for some reason.
package main
import (
tackle "github.com/renderedtext/go-tackle"
)
func main() {
publisher := tackle.NewPublisher("guest@localhost:5467")
defer publisher.Close()
publishParams := tackle.PublishParams{
Body: []byte(`{"user_id": "123"}`),
RoutingKey: "user-created",
Exchange: "user-exchange",
}
err := publisher.PublishWithContext(context.Background(), &publishParams)
if err != nil {
log.Info("something went wrong while publishing %v", err)
}
}
Consuming messages from RabbitMQ
To consume messages from rabbit mq, you need to set up a consumer. Here is an example consumer for the above example messages:
package main
import (
tackle "github.com/renderedtext/go-tackle"
)
func main() {
consumer := tackle.NewConsumer()
options := tackle.Options{
URL: "amqp://guest:guest@rabbitmq:5672",
RemoteExchange: "user-exchange",
Service: "user-persister",
RoutingKey: "user-created",
}
consumer.Start(&options, func(delivery Delivery) {
fmt.Printf("Received message from the consumer: %s", delivery.Body())
delivery.Ack()
})
}
Let's brake down what happens here: We are connecting to the remote exchange "user-exchange" and consuming those messages in our local "user-persister" queue.
Visually this looks like this:
+--------------------+
| Publishing Service |
+--------------------+
|
| Publish
| "user-created"
|
+---|---RabbitMQServer-------------------------------------------------------+
| v |
| +---------------+ * defined by publishing service * |
| | user-exchange | |
| +---------------+ |
| | |
| | key = user-created |
| | |
|---|------------------------------------------------------------------------|
| | |
| | * defined by subscriber service * |
| v |
| +-------------------------+ |
| | user-persister-exchange | <-+ |
| +------*------------------+ | |
| | | after N secs |
| v | |
| +----------------+ +----------------------+ +--------------------+ |
| | user-persister | | user-persister-delay | | user-perister-dead | |
| +------*---------+ +----------------------+ +--------------------+ |
| | ^ ^ |
+---------|-------------------------------|-----------------|----------------+
| | |
v | |
+-------------------+ ----(on err)----+ |
| Consuming Service | |
+-------------------+ ------------------- (after N err)-+