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