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https://github.com/mustafaturan/bus

🔊Minimalist message bus implementation for internal communication with zero-allocation magic on Emit
https://github.com/mustafaturan/bus

eventbus go go-library go-package message-broker message-bus pubsub zero-alloc zero-allocation

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🔊Minimalist message bus implementation for internal communication with zero-allocation magic on Emit

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# 🔊 Bus



[![GoDoc](https://godoc.org/github.com/mustafaturan/bus?status.svg)](https://godoc.org/github.com/mustafaturan/bus)

[![Build Status](https://travis-ci.org/mustafaturan/bus.svg?branch=main)](https://travis-ci.org/mustafaturan/bus)

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[![Go Report Card](https://goreportcard.com/badge/github.com/mustafaturan/bus)](https://goreportcard.com/report/github.com/mustafaturan/bus)

[![GitHub license](https://img.shields.io/github/license/mustafaturan/bus.svg)](https://github.com/mustafaturan/bus/blob/main/LICENSE)



Bus is a minimalist event/message bus implementation for internal communication.

It is heavily inspired from my [event_bus](https://github.com/otobus/event_bus)

package for Elixir language.



## API



The method names and arities/args are stable now. No change should be expected

on the package for the version `3.x.x` except any bug fixes.



## Installation



Via go packages:

```go get github.com/mustafaturan/bus/v3```



## Usage



### Configure



The package requires a unique id generator to assign ids to events. You can

write your own function to generate unique ids or use a package that provides

unique id generation functionality.



The `bus` package respect to software design choice of the packages/projects. It

supports both singleton and dependency injection to init a `bus` instance.



*Hint:*

Check the [demo project](https://github.com/mustafaturan/bus-sample-project) for

the singleton configuration.



Here is a sample initilization using `monoton` id generator:



```go

import (

    "github.com/mustafaturan/bus/v3"

    "github.com/mustafaturan/monoton/v2"

    "github.com/mustafaturan/monoton/v2/sequencer"

)



func NewBus() *bus.Bus {

    // configure id generator (it doesn't have to be monoton)

    node        := uint64(1)

    initialTime := uint64(1577865600000) // set 2020-01-01 PST as initial time

    m, err := monoton.New(sequencer.NewMillisecond(), node, initialTime)

    if err != nil {

        panic(err)

    }



    // init an id generator

    var idGenerator bus.Next = m.Next



    // create a new bus instance

    b, err := bus.NewBus(idGenerator)

    if err != nil {

        panic(err)

    }



    // maybe register topics in here

    b.RegisterTopics("order.received", "order.fulfilled")



    return b

}

```



### Register Event Topics



To emit events to the topics, topic names need to be registered first:



```go

// register topics

b.RegisterTopics("order.received", "order.fulfilled")

```



### Register Event Handlers



To receive topic events you need to register handlers; A handler basically

requires two vals which are a `Handle` function and topic `Matcher` regex

pattern.



```go

handler := bus.Handler{

    Handle: func(ctx context.Context, e bus.Event) {

        // do something

        // NOTE: Highly recommended to process the event in an async way

    },

    Matcher: ".*", // matches all topics

}

b.RegisterHandler("a unique key for the handler", handler)

```



### Emit Events



```go

// if txID val is blank, bus package generates one using the id generator

ctx := context.Background()

ctx = context.WithValue(ctx, bus.CtxKeyTxID, "some-transaction-id-if-exists")

// with optional source

ctx = context.WithValue(ctx, bus.CtxKeySource, "source-of-the-event")



// event topic name (must be registered before)

topic := "order.received"



// interface{} data for event

order := make(map[string]string)

order["orderID"]     = "123456"

order["orderAmount"] = "112.20"

order["currency"]    = "USD"



// emit the event

err := b.Emit(ctx, topic, order)



if err != nil {

    // report the err

    fmt.Println(err)

}



// emit the event with options

err := b.EmitWithOpts(ctx, topic, order, bus.WithTxID("some-tx-id"))



if err != nil {

    // report the err

    fmt.Println(err)

}

```



### Processing Events



When an event is emitted, the topic handlers receive the event synchronously.

It is highly recommended to process events asynchronous. Package leave the

decision to the packages/projects to use concurrency abstractions depending on

use-cases. Each handlers receive the same event as ref of `bus.Event` struct:



```go

// Event data structure

type Event struct {

    ID         string      // identifier

    TxID       string      // transaction identifier

    Topic      string      // topic name

    Source     string      // source of the event

    OccurredAt time.Time   // creation time in nanoseconds

    Data       interface{} // actual event data

}

```



### Sample Project



A [demo project](https://github.com/mustafaturan/bus-sample-project) with three

consumers which increments a `counter` for each event topic, `printer` consumer

which prints all events and lastly `calculator` consumer which sums amounts.



### Benchmarks



Command:

```

go test -benchtime 10000000x -benchmem -run=^$ -bench=. github.com/mustafaturan/bus/v3

```



Results:

```

goos: darwin

goarch: amd64

pkg: github.com/mustafaturan/bus/v3

cpu: Intel(R) Core(TM) i5-6267U CPU @ 2.90GHz

BenchmarkEmit-4                      	10000000	       180.5 ns/op	       8 B/op	       0 allocs/op

BenchmarkEmitWithoutTxID-4           	10000000	       244.6 ns/op	      72 B/op	       2 allocs/op

BenchmarkEmitWithOpts-4              	10000000	       280.8 ns/op	     112 B/op	       4 allocs/op

BenchmarkEmitWithOptsUnspecified-4   	10000000	       169.4 ns/op	       8 B/op	       0 allocs/op

PASS

ok  	github.com/mustafaturan/bus/v3	8.884s

```



## Contributing



All contributors should follow [Contributing Guidelines](CONTRIBUTING.md) before creating pull requests.



## Credits



[Mustafa Turan](https://github.com/mustafaturan)



## License



Apache License 2.0



Copyright (c) 2021 Mustafa Turan



Permission is hereby granted, free of charge, to any person obtaining a copy of

this software and associated documentation files (the "Software"), to deal in

the Software without restriction, including without limitation the rights to

use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of

the Software, and to permit persons to whom the Software is furnished to do so,

subject to the following conditions:



The above copyright notice and this permission notice shall be included in all

copies or substantial portions of the Software.



THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS

FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR

COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER

IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN

CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.