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package EventBus
import (
"errors"
"fmt"
"net"
"net/http"
"net/rpc"
"sync"
)
const (
// PublishService - Client service method
PublishService = "ClientService.PushEvent"
)
// ClientArg - object containing event for client to publish locally
type ClientArg struct {
Args []interface{}
Topic string
}
// Client - object capable of subscribing to a remote event bus
type Client struct {
eventBus Bus
address string
path string
service *ClientService
}
// NewClient - create a client object with the address and server path
func NewClient(address, path string, eventBus Bus) *Client {
client := new(Client)
client.eventBus = eventBus
client.address = address
client.path = path
client.service = &ClientService{client, &sync.WaitGroup{}, false}
return client
}
// EventBus - returns the underlying event bus
func (client *Client) EventBus() Bus {
return client.eventBus
}
func (client *Client) doSubscribe(topic string, fn interface{}, serverAddr, serverPath string, subscribeType SubscribeType) {
defer func() {
if r := recover(); r != nil {
fmt.Println("Server not found -", r)
}
}()
rpcClient, err := rpc.DialHTTPPath("tcp", serverAddr, serverPath)
defer rpcClient.Close()
if err != nil {
fmt.Errorf("dialing: %v", err)
}
args := &SubscribeArg{client.address, client.path, PublishService, subscribeType, topic}
reply := new(bool)
err = rpcClient.Call(RegisterService, args, reply)
if err != nil {
fmt.Errorf("Register error: %v", err)
}
if *reply {
client.eventBus.Subscribe(topic, fn)
}
}
//Subscribe subscribes to a topic in a remote event bus
func (client *Client) Subscribe(topic string, fn interface{}, serverAddr, serverPath string) {
client.doSubscribe(topic, fn, serverAddr, serverPath, Subscribe)
}
//SubscribeOnce subscribes once to a topic in a remote event bus
func (client *Client) SubscribeOnce(topic string, fn interface{}, serverAddr, serverPath string) {
client.doSubscribe(topic, fn, serverAddr, serverPath, SubscribeOnce)
}
// Start - starts the client service to listen to remote events
func (client *Client) Start() error {
var err error
service := client.service
if !service.started {
server := rpc.NewServer()
server.Register(service)
server.HandleHTTP(client.path, "/debug"+client.path)
l, err := net.Listen("tcp", client.address)
if err == nil {
service.wg.Add(1)
service.started = true
go http.Serve(l, nil)
}
} else {
err = errors.New("Client service already started")
}
return err
}
// Stop - signal for the service to stop serving
func (client *Client) Stop() {
service := client.service
if service.started {
service.wg.Done()
service.started = false
}
}
// ClientService - service object listening to events published in a remote event bus
type ClientService struct {
client *Client
wg *sync.WaitGroup
started bool
}
// PushEvent - exported service to listening to remote events
func (service *ClientService) PushEvent(arg *ClientArg, reply *bool) error {
service.client.eventBus.Publish(arg.Topic, arg.Args...)
*reply = true
return nil
}
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