event

package
v1.65.3 Latest Latest
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 Go to latest Published: Jun 21, 2018 License: AGPL-3.0, MIT Imports: 7 Imported by: 0

README

EventBus

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Package EventBus is the little and lightweight eventbus with async compatibility for GoLang.

Installation

Make sure that Go is installed on your computer. Type the following command in your terminal:

go get github.com/asaskevich/EventBus

After it the package is ready to use.

Import package in your project

Add following line in your *.go file:

import "github.com/asaskevich/EventBus"

If you unhappy to use long EventBus, you can do something like this:

import (
	evbus "github.com/asaskevich/EventBus"
)
Example
func calculator(a int, b int) {
	fmt.Printf("%d\n", a + b)
}

func main() {
	bus := EventBus.New();
	bus.Subscribe("main:calculator", calculator);
	bus.Publish("main:calculator", 20, 40);
	bus.Unsubscribe("main:calculator", calculator);
}
Implemented methods
  • New()
  • Subscribe()
  • SubscribeOnce()
  • HasCallback()
  • Unsubscribe()
  • Publish()
  • SubscribeAsync()
  • SubscribeOnceAsync()
  • WaitAsync()
New()

New returns new EventBus with empty handlers.

bus := EventBus.New();
Subscribe(topic string, fn interface{}) error

Subscribe to a topic. Returns error if fn is not a function.

func Handler() { ... }
...
bus.Subscribe("topic:handler", Handler)
SubscribeOnce(topic string, fn interface{}) error

Subscribe to a topic once. Handler will be removed after executing. Returns error if fn is not a function.

func HelloWorld() { ... }
...
bus.SubscribeOnce("topic:handler", HelloWorld)
Unsubscribe(topic string) error

Remove callback defined for a topic. Returns error if there are no callbacks subscribed to the topic.

bus.Unsubscribe("topic:handler", HelloWord);
HasCallback(topic string) bool

Returns true if exists any callback subscribed to the topic.

Publish(topic string, args ...interface{})

Publish executes callback defined for a topic. Any addional argument will be tranfered to the callback.

func Handler(str string) { ... }
...
bus.Subscribe("topic:handler", Handler)
...
bus.Publish("topic:handler", "Hello, World!");
SubscribeAsync(topic string, fn interface{}, transactional bool)

Subscribe to a topic with an asyncrhonous callback. Returns error if fn is not a function.

func slowCalculator(a, b int) {
	time.Sleep(3 * time.Second)
	fmt.Printf("%d\n", a + b)
}

bus := EventBus.New()
bus.SubscribeAsync("main:slow_calculator", slowCalculator, false)
	
bus.Publish("main:slow_calculator", 20, 60)
	
fmt.Println("start: do some stuff while waiting for a result")
fmt.Println("end: do some stuff while waiting for a result") 
	
bus.WaitAsync() // wait for all async callbacks to complete
	
fmt.Println("do some stuff after waiting for result")

Transactional determines whether subsequent callbacks for a topic are run serially (true) or concurrently(false)

SubscribeOnceAsync(topic string, args ...interface{})

SubscribeOnceAsync works like SubscribeOnce except the callback to executed asynchronously

WaitAsync()

WaitAsync waits for all async callbacks to complete.

Cross Process Events

Works with two rpc services:

  • a client service to listen to remotely published events from a server
  • a server service to listen to client subscriptions

server.go

func main() {
    server := NewServer(":2010", "/_server_bus_", New())
    server.Start()
    // ...
    server.EventBus().Publish("main:calculator", 4, 6)
    // ...
    server.Stop()
}

client.go

func main() {
    client := NewClient(":2015", "/_client_bus_", New())
    client.Start()
    client.Subscribe("main:calculator", calculator, ":2010", "/_server_bus_")
    // ...
    client.Stop()
}
Notes

Documentation is available here: godoc.org. Full information about code coverage is also available here: EventBus on gocover.io.

Support

If you do have a contribution for the package feel free to put up a Pull Request or open Issue.

Special thanks to contributors

Documentation

Index

Constants

View Source 
const (
	// PublishService - Client service method
	PublishService = "ClientService.PushEvent"
)
View Source 
const (
	// RegisterService - Server subscribe service method
	RegisterService = "ServerService.Register"
)

Variables

This section is empty.

Functions

This section is empty.

Types

type Bus 

type Bus interface {
	BusController
	BusSubscriber
	BusPublisher
}

Bus englobes global (subscribe, publish, control) bus behavior

func Handler 

func Handler() Bus

Handler returns the global instance of the event bus

func New 

func New() Bus

New returns new EventBus with empty handlers.

type BusController 

type BusController interface {
	HasCallback(topic string) bool
	WaitAsync()
}

BusController defines bus control behavior (checking handler's presence, synchronization)

type BusPublisher 

type BusPublisher interface {
	Publish(topic string, args ...interface{})
}

BusPublisher defines publishing-related bus behavior

type BusSubscriber 

type BusSubscriber interface {
	Subscribe(topic string, fn interface{}) error
	SubscribeAsync(topic string, fn interface{}, transactional bool) error
	SubscribeOnce(topic string, fn interface{}) error
	SubscribeOnceAsync(topic string, fn interface{}) error
	Unsubscribe(topic string, handler interface{}) error
}

BusSubscriber defines subscription-related bus behavior

type Client 

type Client struct {
	// contains filtered or unexported fields
}

Client - object capable of subscribing to a remote event bus

func NewClient 

func NewClient(address, path string, eventBus Bus) *Client

NewClient - create a client object with the address and server path

func (*Client) EventBus 

func (client *Client) EventBus() Bus

EventBus - returns the underlying event bus

func (*Client) Start 

func (client *Client) Start() error

Start - starts the client service to listen to remote events

func (*Client) Stop 

func (client *Client) Stop()

Stop - signal for the service to stop serving

func (*Client) Subscribe 

func (client *Client) Subscribe(topic string, fn interface{}, serverAddr, serverPath string)

Subscribe subscribes to a topic in a remote event bus

func (*Client) SubscribeOnce 

func (client *Client) SubscribeOnce(topic string, fn interface{}, serverAddr, serverPath string)

SubscribeOnce subscribes once to a topic in a remote event bus

type ClientArg 

type ClientArg struct {
	Args  []interface{}
	Topic string
}

ClientArg - object containing event for client to publish locally

type ClientService 

type ClientService struct {
	// contains filtered or unexported fields
}

ClientService - service object listening to events published in a remote event bus

func (*ClientService) PushEvent 

func (service *ClientService) PushEvent(arg *ClientArg, reply *bool) error

PushEvent - exported service to listening to remote events

type EventBus 

type EventBus struct {
	// contains filtered or unexported fields
}

EventBus - box for handlers and callbacks.

func (*EventBus) HasCallback 

func (bus *EventBus) HasCallback(topic string) bool

HasCallback returns true if exists any callback subscribed to the topic.

func (*EventBus) Publish 

func (bus *EventBus) Publish(topic string, args ...interface{})

Publish executes callback defined for a topic. Any additional argument will be transferred to the callback.

func (*EventBus) Subscribe 

func (bus *EventBus) Subscribe(topic string, fn interface{}) error

Subscribe subscribes to a topic. Returns error if `fn` is not a function.

func (*EventBus) SubscribeAsync 

func (bus *EventBus) SubscribeAsync(topic string, fn interface{}, transactional bool) error

SubscribeAsync subscribes to a topic with an asynchronous callback Transactional determines whether subsequent callbacks for a topic are run serially (true) or concurrently (false) Returns error if `fn` is not a function.

func (*EventBus) SubscribeOnce 

func (bus *EventBus) SubscribeOnce(topic string, fn interface{}) error

SubscribeOnce subscribes to a topic once. Handler will be removed after executing. Returns error if `fn` is not a function.

func (*EventBus) SubscribeOnceAsync 

func (bus *EventBus) SubscribeOnceAsync(topic string, fn interface{}) error

SubscribeOnceAsync subscribes to a topic once with an asynchronous callback Handler will be removed after executing. Returns error if `fn` is not a function.

func (*EventBus) Unsubscribe 

func (bus *EventBus) Unsubscribe(topic string, handler interface{}) error

Unsubscribe removes callback defined for a topic. Returns error if there are no callbacks subscribed to the topic.

func (*EventBus) WaitAsync 

func (bus *EventBus) WaitAsync()

WaitAsync waits for all async callbacks to complete

type NetworkBus 

type NetworkBus struct {
	*Client
	*Server
	// contains filtered or unexported fields
}

NetworkBus - object capable of subscribing to remote event buses in addition to remote event busses subscribing to it's local event bus. Compoed of a server and cliet

func NewNetworkBus 

func NewNetworkBus(address, path string) *NetworkBus

NewNetworkBus - returns a new network bus object at the server address and path

func (*NetworkBus) EventBus 

func (networkBus *NetworkBus) EventBus() Bus

EventBus - returns wrapped event bus

func (*NetworkBus) Start 

func (networkBus *NetworkBus) Start() error

Start - helper method to serve a network bus service

func (*NetworkBus) Stop 

func (networkBus *NetworkBus) Stop()

Stop - signal for the service to stop serving

type NetworkBusService 

type NetworkBusService struct {
	// contains filtered or unexported fields
}

NetworkBusService - object capable of serving the network bus

type Server 

type Server struct {
	// contains filtered or unexported fields
}

Server - object capable of being subscribed to by remote handlers

func NewServer 

func NewServer(address, path string, eventBus Bus) *Server

NewServer - create a new Server at the address and path

func (*Server) EventBus 

func (server *Server) EventBus() Bus

EventBus - returns wrapped event bus

func (*Server) HasClientSubscribed 

func (server *Server) HasClientSubscribed(arg *SubscribeArg) bool

HasClientSubscribed - True if a client subscribed to this server with the same topic

func (*Server) Start 

func (server *Server) Start() error

Start - starts a service for remote clients to subscribe to events

func (*Server) Stop 

func (server *Server) Stop()

Stop - signal for the service to stop serving

type ServerService 

type ServerService struct {
	// contains filtered or unexported fields
}

ServerService - service object to listen to remote subscriptions

func (*ServerService) Register 

func (service *ServerService) Register(arg *SubscribeArg, success *bool) error

Register - Registers a remote handler to this event bus for a remote subscribe - a given client address only needs to subscribe once event will be republished in local event bus

type SubscribeArg 

type SubscribeArg struct {
	ClientAddr    string
	ClientPath    string
	ServiceMethod string
	SubscribeType SubscribeType
	Topic         string
}

SubscribeArg - object to hold subscribe arguments from remote event handlers

type SubscribeType 

type SubscribeType int

SubscribeType - how the client intends to subscribe 

const (
	// Subscribe - subscribe to all events
	Subscribe SubscribeType = iota
	// SubscribeOnce - subscribe to only one event
	SubscribeOnce
)

type Type 

type Type string

Type defines the format of event descriptors 

const (
	// TypeAddAccount for when account for user is created
	TypeAddAccount Type = "ACCOUNT_ADD"
	// TypeAddUser for when user is created
	TypeAddUser Type = "USER_ADD"
	// TypeRemoveUser for when user is deleted
	TypeRemoveUser Type = "USER_DELETE"
	// TypeAddDocument for when document created
	TypeAddDocument Type = "DOCUMENT_ADD"
	// TypeSystemLicenseChange for when global admin user updates license
	TypeSystemLicenseChange Type = "LICENSE_CHANGE"
	// TypeAddSpace for when space created
	TypeAddSpace Type = "SPACE_ADD"
	// TypeRemoveSpace for when space removed
	TypeRemoveSpace Type = "SPACE_REMOVE"
)

Valid event types for publication and subscription

Source Files

View all Source files

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