lobby/nats_driver/main.go

134 lines
3.5 KiB
Go
Raw Normal View History

package nats_driver
import (
"encoding/json"
"fmt"
"log"
"strings"
"time"
"github.com/by-cx/lobby/common"
"github.com/by-cx/lobby/server"
"github.com/nats-io/nats.go"
)
// NATS drivers is used to send discovery packet to other nodes into the group via NATS messenging protocol.
type Driver struct {
NATSUrl string
NATSDiscoveryChannel string
LogChannel chan string
nc *nats.Conn
subscribeListener common.Listener
unsubscribeListener common.Listener
}
// handler is called asynchronously so and because it cannot log directly to stderr there
// is channel called LogChannel that can be used to log error messages from this
func (d *Driver) handler(m *nats.Msg) {
message := discoveryEnvelope{}
err := json.Unmarshal(m.Data, &message)
if err != nil && d.LogChannel != nil {
d.LogChannel <- fmt.Errorf("decoding message error: %v", err).Error()
}
err = message.Discovery.Validate()
if err != nil && d.LogChannel != nil {
d.LogChannel <- fmt.Errorf("validation error: %v", err).Error()
}
if message.Message == "hi" {
d.subscribeListener(message.Discovery)
} else if message.Message == "goodbye" {
d.unsubscribeListener(message.Discovery)
} else {
if d.LogChannel != nil {
d.LogChannel <- "incompatible message"
}
}
}
func (d *Driver) Init() error {
if d.LogChannel == nil {
return fmt.Errorf("please initiate LogChannel variable")
}
for {
nc, err := nats.Connect(d.NATSUrl)
if err != nil {
log.Printf("Can't connect to the NATS server, waiting for 5 seconds before I try it again. (%v)\n", err)
time.Sleep(time.Second * 5)
continue
}
d.nc = nc
break
}
_, err := d.nc.Subscribe(d.NATSDiscoveryChannel, d.handler)
if err != nil {
return fmt.Errorf("subscribe error: %v", err)
}
return nil
}
// Close is called when all is done.
func (d *Driver) Close() error {
return d.nc.Drain()
}
// RegisterSubscribeFunction sets the function that will process the incoming messages
func (d *Driver) RegisterSubscribeFunction(listener common.Listener) {
d.subscribeListener = listener
}
// RegisterUnsubscribeFunction sets the function that will process the goodbye incoming messages
func (d *Driver) RegisterUnsubscribeFunction(listener common.Listener) {
d.unsubscribeListener = listener
}
// SendDiscoveryPacket send discovery packet to the group.
func (d *Driver) SendDiscoveryPacket(discovery server.Discovery) error {
envelope := discoveryEnvelope{
Discovery: discovery,
Message: "hi",
}
data, err := envelope.Bytes()
if err != nil {
return fmt.Errorf("sending discovery formating message error: %v", err)
}
err = d.nc.Publish(d.NATSDiscoveryChannel, data)
// In case the connection is down we will try to reconnect
if err != nil && strings.Contains(err.Error(), "connection closed") {
d.nc.Close()
err = d.Init()
if err != nil {
return fmt.Errorf("sending discovery reconnect error: %v", err)
}
} else if err != nil {
return fmt.Errorf("sending discovery error: %v", err)
}
return nil
}
// SendGoodbyePacket deregister node from the group. It tells everybody that it's going to die.
func (d *Driver) SendGoodbyePacket(discovery server.Discovery) error {
envelope := discoveryEnvelope{
Discovery: discovery,
Message: "goodbye",
}
data, err := envelope.Bytes()
if err != nil {
return fmt.Errorf("sending discovery formating message error: %v", err)
}
err = d.nc.Publish(d.NATSDiscoveryChannel, data)
if err != nil {
return fmt.Errorf("sending discovery error: %v", err)
}
return nil
}