go-event-bus-gen

README

go-event-bus-gen

go-event-bus-gen is a Go code generator to build out event driven processing frameworks to fulfill the purpose of handling the boilerplate needed to establish and interact with messages on an event bus in a simliar fashion that you would get with your http style code generators.

go-event-bus-gen utilizes ProtoBuf specifications to build the underlying structs, publishing, and processing.

Installation

GO11MODULE=on go get github.com/rc1405/go-event-bus-gen

Example

A Protocol Buffer file such as Simple

syntax = "proto3";
import "google/protobuf/empty.proto";
package simple;

message HelloRequest {
    string name = 0;
}

message HelloReply {
  string message = 0;
}

service HelloService {
  rpc SayHello (HelloRequest) returns (HelloReply) {}
  rpc HelloWorld (HelloReply) returns (google.protobuf.Empty) {}
}

will generate the following Interface that needs to be satisfied

type Service interface {
	SayHello(HelloRequest) (HelloReply, error)
	HelloWorld(HelloReply) error
}

Running

bus := NewEventBus()
go bus.Run(context.Context, Service)

// waits for all subscriptions to be created and ready for processing
bus.Ready()

if err := bus.Publish(HelloRequest{Name: "Cheddar"}); err != nil {
    panic(err)
}

Code Generation

Inline comments

Use inline comments such as //go:generate go-event-bus-gen --in simple.proto --out bus.go which would take in the protobuf from simple.proto and generate code to bus.go. Or using a configuration file: //go:generate go-event-bus-gen --in external.proto --out bus.go --config config.yaml

Command Line

go-event-bus-gen --in simple.proto --out bus.go which would take in the protobuf from simple.proto and generate code to bus.go. Or using a configuration file: go-event-bus-gen --in external.proto --out bus.go --config config.yaml

Advanced Use

Foreign Inputs

Given the usecase where I would like to use structs not defined in the protobuf file, I would need to specify the needed imports through a config file.

imports:
  - github.com/aws/aws-lambda-go/events

In this case, the AWS Golang Events package will be added to imports and then can be used in the protobuf file, such as:

service HelloService {
  rpc HandleEvent (events.CloudWatchEvent) returns (google.protobuf.Empty) {}
}

Enums

Generating enums follows the same pattern as rpc code generation. i.e.

enum Status {
  SUCCESS = 0;
  FAILURE = 1;
}

message HelloReply {
  Status status  = 1;
}

Results in code generation such as

type StatusEnum int32

const (
	SUCCESS StatusEnum = 0
	FAILURE StatusEnum = 1
)

type HelloReply struct {
	Status    StatusEnum        `json:"status"`
}

Limitations

Multiple Services

Services within the same proto file are bundled into the same go interface. i.e.

service HelloService {
  rpc SayHello (HelloRequest) returns (HelloReply) {}
  rpc HelloWorld (HelloReply) returns (google.protobuf.Empty) {}
}

service ShadowService {
  rpc AnotherHello(HelloRequest) returns (google.protobuf.Empty) {}
}

bundles into the following interface

type Service interface {
	SayHello(HelloRequest) (HelloReply, error)
	HelloWorld(HelloReply) error
	AnotherHello(HelloRequest) error
}

Note: this also limits multiple services are unable to have a method with the same normalized name

Imports

Support for external proto imports is extremely limited. The ones supported are:

• google.protobuf.Timestamp: which will translate types to time.Time
• google.protobuf.Any: which will translate types to any
• google.protobuf.Empty: which modifies the return signature for the method from (Item, error) to error