grabbit
A lightweight transactional message bus on top of RabbitMQ supporting:
- Supported Messaging Styles
- One Way (Fire and forget)
- Publish/Subscribe
- Aync Command/Reply
- Blocking Command/Reply (RPC)
- Transactional message processing
- Message Orchestration via the Saga pattern
- At least once reliable messaging via Transaction Outbox and Publisher Confirms
- Retry and backoffs
- Structured logging
- Reporting Metrics via Prometheus
- Distributed Tracing via OpenTracing
- Extensible serialization with default support for gob, protobuf and avro
Stable release
the v1.x branch contains the latest stable releases of grabbit and one should track that branch to get point and minor release updates.
Supported transactional resources
- MySql > 8.0 (InnoDB)
Basic Usage
- For a complete sample application see the vacation booking sample app in the examples directory
The following outlines the basic usage of grabbit. For a complete view of how you would use grabbit including how to write saga's and handle deadlettering refer to grabbit/tests package
import (
"github.com/wework/grabbit/gbus"
"github.com/wework/grabbit/gbus/builder"
)
Define a message
type SomeMessage struct {}
func(SomeMessage) SchemaName() string{
return "some.unique.namespace.somemessage"
}
Creating a transactional GBus instance
gb := builder.
New().
Bus("connection string to RabbitMQ").
Txnl("mysql", "connection string to mysql").
WithConfirms().
Build("name of your service")
Register a command handler
handler := func(invocation gbus.Invocation, message *gbus.BusMessage) error{
cmd, ok := message.Payload.(*SomeCommand)
if ok {
fmt.Printf("handler invoked with message %v", cmd)
return nil
}
return fmt.Errorf("failed to handle message")
}
gb.HandleMessage(SomeCommand{}, handler)
Register an event handler
eventHandler := func(invocation gbus.Invocation, message *gbus.BusMessage) {
evt, ok := message.Payload.(*SomeEvent)
if ok {
fmt.Printf("handler invoked with event %v", evt)
return nil
}
return fmt.Errorf("failed to handle event")
}
gb.HandleEvent("name of exchange", "name of topic", SomeEvent{}, eventHandler)
Start the bus
gb.Start()
defer gb.Shutdown()
Send a command
gb.Send(context.Background(), "name of service you are sending the command to", gbus.NewBusMessage(SomeCommand{}))
Publish an event
gb.Publish(context.Background(), "name of exchange", "name of topic", gbus.NewBusMessage(SomeEvent{}))
RPC style call
request := gbus.NewBusMessage(SomeRPCRequest{})
reply := gbus.NewBusMessage(SomeRPCReply{})
timeOut := 2 * time.Second
reply, e := gb.RPC(context.Background(), "name of service you are sending the request to", request, reply, timeOut)
if e != nil{
fmt.Printf("rpc call failed with error %v", e)
} else{
fmt.Printf("rpc call returned with reply %v", reply)
}
Testing
- ensure that you have the dependencies installed:
go get -v -t -d ./... - make sure to first:
docker-compose up -V -d - then to run the tests:
go test ./...
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