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102 lines
2.9 KiB
102 lines
2.9 KiB
package rabbitmq
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import (
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"errors"
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"sync"
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"time"
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"github.com/streadway/amqp"
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)
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type channelManager struct {
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logger logger
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url string
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channel *amqp.Channel
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channelMux *sync.RWMutex
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notifyCancelOrClose chan error
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}
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func newChannelManager(url string, logging bool) (*channelManager, error) {
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ch, err := getNewChannel(url)
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if err != nil {
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return nil, err
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}
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chManager := channelManager{
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logger: logger{logging: logging},
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url: url,
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channel: ch,
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channelMux: &sync.RWMutex{},
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notifyCancelOrClose: make(chan error),
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}
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go chManager.startNotifyCancelOrClosed()
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return &chManager, nil
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}
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func getNewChannel(url string) (*amqp.Channel, error) {
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amqpConn, err := amqp.Dial(url)
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if err != nil {
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return nil, err
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}
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ch, err := amqpConn.Channel()
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if err != nil {
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return nil, err
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}
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return ch, err
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}
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// startNotifyCancelOrClosed listens on the channel's cancelled and closed
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// notifiers. When it detects a problem, it attempts to reconnect with an exponential
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// backoff. Once reconnected, it sends an error back on the manager's notifyCancelOrClose
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// channel
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func (chManager *channelManager) startNotifyCancelOrClosed() {
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notifyCloseChan := make(chan *amqp.Error)
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notifyCloseChan = chManager.channel.NotifyClose(notifyCloseChan)
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notifyCancelChan := make(chan string)
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notifyCancelChan = chManager.channel.NotifyCancel(notifyCancelChan)
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select {
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case err := <-notifyCloseChan:
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chManager.logger.Println("attempting to reconnect to amqp server after close")
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chManager.reconnectWithBackoff()
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chManager.logger.Println("successfully reconnected to amqp server after close")
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chManager.notifyCancelOrClose <- err
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case err := <-notifyCancelChan:
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chManager.logger.Println("attempting to reconnect to amqp server after cancel")
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chManager.reconnectWithBackoff()
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chManager.logger.Println("successfully reconnected to amqp server after cancel")
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chManager.notifyCancelOrClose <- errors.New(err)
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}
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close(notifyCancelChan)
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close(notifyCloseChan)
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}
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// reconnectWithBackoff continuously attempts to reconnect with an
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// exponential backoff strategy
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func (chManager *channelManager) reconnectWithBackoff() {
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backoffTime := time.Second
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for {
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chManager.logger.Printf("waiting %s seconds to attempt to reconnect to amqp server", backoffTime)
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time.Sleep(backoffTime)
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backoffTime *= 2
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err := chManager.reconnect()
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if err != nil {
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chManager.logger.Printf("error reconnecting to amqp server: %v", err)
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} else {
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return
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}
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}
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}
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// reconnect safely closes the current channel and obtains a new one
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func (chManager *channelManager) reconnect() error {
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chManager.channelMux.Lock()
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defer chManager.channelMux.Unlock()
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newChannel, err := getNewChannel(chManager.url)
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if err != nil {
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return err
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}
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chManager.channel.Close()
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chManager.channel = newChannel
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go chManager.startNotifyCancelOrClosed()
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return nil
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}
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