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mqtt.go
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mqtt.go
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// ------------------------------------------------------------
// Copyright (c) Microsoft Corporation and Dapr Contributors.
// Licensed under the MIT License.
// ------------------------------------------------------------
package mqtt
import (
"context"
"crypto/tls"
"crypto/x509"
"encoding/pem"
"fmt"
"net/url"
"os"
"os/signal"
"strconv"
"syscall"
"time"
"github.com/cenkalti/backoff/v4"
mqtt "github.com/eclipse/paho.mqtt.golang"
"github.com/dapr/components-contrib/bindings"
"github.com/dapr/kit/logger"
"github.com/dapr/kit/retry"
)
const (
// Keys.
mqttURL = "url"
mqttTopic = "topic"
mqttQOS = "qos"
mqttRetain = "retain"
mqttClientID = "consumerID"
mqttCleanSession = "cleanSession"
mqttCACert = "caCert"
mqttClientCert = "clientCert"
mqttClientKey = "clientKey"
mqttBackOffMaxRetries = "backOffMaxRetries"
// errors.
errorMsgPrefix = "mqtt binding error:"
// Defaults.
defaultQOS = 0
defaultRetain = false
defaultWait = 3 * time.Second
defaultCleanSession = true
)
// MQTT allows sending and receiving data to/from an MQTT broker.
type MQTT struct {
producer mqtt.Client
consumer mqtt.Client
metadata *metadata
logger logger.Logger
ctx context.Context
cancel context.CancelFunc
backOff backoff.BackOff
}
// NewMQTT returns a new MQTT instance.
func NewMQTT(logger logger.Logger) *MQTT {
return &MQTT{logger: logger}
}
// isValidPEM validates the provided input has PEM formatted block.
func isValidPEM(val string) bool {
block, _ := pem.Decode([]byte(val))
return block != nil
}
func parseMQTTMetaData(md bindings.Metadata) (*metadata, error) {
m := metadata{}
// required configuration settings
if val, ok := md.Properties[mqttURL]; ok && val != "" {
m.url = val
} else {
return &m, fmt.Errorf("%s missing url", errorMsgPrefix)
}
if val, ok := md.Properties[mqttTopic]; ok && val != "" {
m.topic = val
} else {
return &m, fmt.Errorf("%s missing topic", errorMsgPrefix)
}
// optional configuration settings
m.qos = defaultQOS
if val, ok := md.Properties[mqttQOS]; ok && val != "" {
qosInt, err := strconv.Atoi(val)
if err != nil {
return &m, fmt.Errorf("%s invalid qos %s, %s", errorMsgPrefix, val, err)
}
m.qos = byte(qosInt)
}
m.retain = defaultRetain
if val, ok := md.Properties[mqttRetain]; ok && val != "" {
var err error
m.retain, err = strconv.ParseBool(val)
if err != nil {
return &m, fmt.Errorf("%s invalid retain %s, %s", errorMsgPrefix, val, err)
}
}
if val, ok := md.Properties[mqttClientID]; ok && val != "" {
m.clientID = val
} else {
return &m, fmt.Errorf("%s missing consumerID", errorMsgPrefix)
}
m.cleanSession = defaultCleanSession
if val, ok := md.Properties[mqttCleanSession]; ok && val != "" {
var err error
m.cleanSession, err = strconv.ParseBool(val)
if err != nil {
return &m, fmt.Errorf("%s invalid clean session %s, %s", errorMsgPrefix, val, err)
}
}
if val, ok := md.Properties[mqttCACert]; ok && val != "" {
if !isValidPEM(val) {
return &m, fmt.Errorf("%s invalid ca certificate", errorMsgPrefix)
}
m.tlsCfg.caCert = val
}
if val, ok := md.Properties[mqttClientCert]; ok && val != "" {
if !isValidPEM(val) {
return &m, fmt.Errorf("%s invalid client certificate", errorMsgPrefix)
}
m.tlsCfg.clientCert = val
}
if val, ok := md.Properties[mqttClientKey]; ok && val != "" {
if !isValidPEM(val) {
return &m, fmt.Errorf("%s invalid client certificate key", errorMsgPrefix)
}
m.tlsCfg.clientKey = val
}
if val, ok := md.Properties[mqttBackOffMaxRetries]; ok && val != "" {
backOffMaxRetriesInt, err := strconv.Atoi(val)
if err != nil {
return &m, fmt.Errorf("%s invalid backOffMaxRetries %s, %s", errorMsgPrefix, val, err)
}
m.backOffMaxRetries = backOffMaxRetriesInt
}
return &m, nil
}
// Init does MQTT connection parsing.
func (m *MQTT) Init(metadata bindings.Metadata) error {
mqttMeta, err := parseMQTTMetaData(metadata)
if err != nil {
return err
}
m.metadata = mqttMeta
// mqtt broker allows only one connection at a given time from a clientID.
producerClientID := fmt.Sprintf("%s-producer", m.metadata.clientID)
p, err := m.connect(producerClientID)
if err != nil {
return err
}
m.ctx, m.cancel = context.WithCancel(context.Background())
// TODO: Make the backoff configurable for constant or exponential
b := backoff.NewConstantBackOff(5 * time.Second)
m.backOff = backoff.WithContext(b, m.ctx)
m.producer = p
m.logger.Debug("mqtt message bus initialization complete")
return nil
}
func (m *MQTT) Operations() []bindings.OperationKind {
return []bindings.OperationKind{bindings.CreateOperation}
}
func (m *MQTT) Invoke(req *bindings.InvokeRequest) (*bindings.InvokeResponse, error) {
// MQTT client Publish() has an internal race condition in the default autoreconnect config.
// To mitigate sporadic failures on the Dapr side, this implementation retries 3 times at
// a fixed 200ms interval. This is not configurable to keep this as an implementation detail
// for this component, as the additional public config metadata required could be replaced
// by the more general Dapr APIs for resiliency moving forwards.
cbo := backoff.NewConstantBackOff(200 * time.Millisecond)
bo := backoff.WithMaxRetries(cbo, 3)
bo = backoff.WithContext(bo, m.ctx)
return nil, retry.NotifyRecover(func() error {
m.logger.Debugf("mqtt publishing topic %s with data: %v", m.metadata.topic, req.Data)
token := m.producer.Publish(m.metadata.topic, m.metadata.qos, m.metadata.retain, req.Data)
if !token.WaitTimeout(defaultWait) || token.Error() != nil {
return fmt.Errorf("mqtt error from publish: %v", token.Error())
}
return nil
}, bo, func(err error, _ time.Duration) {
m.logger.Debugf("Could not publish MQTT message. Retrying...: %v", err)
}, func() {
m.logger.Debug("Successfully published MQTT message after it previously failed")
})
}
func (m *MQTT) handleMessage(handler func(*bindings.ReadResponse) ([]byte, error), mqttMsg mqtt.Message) error {
msg := bindings.ReadResponse{Data: mqttMsg.Payload()}
// paho.mqtt.golang requires that handlers never block or it can deadlock on client.Disconnect.
// To ensure that the Dapr runtime does not hang on teardown on of the component, run the app's
// handling code in a goroutine so that this handler function is always cancellable on Close().
ch := make(chan error)
go func(m *bindings.ReadResponse) {
defer close(ch)
_, err := handler(m)
ch <- err
}(&msg)
select {
case handlerErr := <-ch:
if handlerErr != nil {
return handlerErr
}
mqttMsg.Ack()
return nil
case <-m.ctx.Done():
m.logger.Infof("Read context cancelled: %v", m.ctx.Err())
return m.ctx.Err()
}
}
func (m *MQTT) Read(handler func(*bindings.ReadResponse) ([]byte, error)) error {
sigterm := make(chan os.Signal, 1)
signal.Notify(sigterm, os.Interrupt, syscall.SIGTERM)
// reset synchronization
if m.consumer != nil {
m.logger.Warnf("re-initializing the subscriber")
m.consumer.Disconnect(0)
m.consumer = nil
}
// mqtt broker allows only one connection at a given time from a clientID.
consumerClientID := fmt.Sprintf("%s-consumer", m.metadata.clientID)
c, err := m.connect(consumerClientID)
if err != nil {
return err
}
m.consumer = c
m.logger.Debugf("mqtt subscribing to topic %s", m.metadata.topic)
token := m.consumer.Subscribe(m.metadata.topic, m.metadata.qos, func(client mqtt.Client, mqttMsg mqtt.Message) {
b := m.backOff
if m.metadata.backOffMaxRetries >= 0 {
b = backoff.WithMaxRetries(m.backOff, uint64(m.metadata.backOffMaxRetries))
}
if err := retry.NotifyRecover(func() error {
m.logger.Debugf("Processing MQTT message %s/%d", mqttMsg.Topic(), mqttMsg.MessageID())
return m.handleMessage(handler, mqttMsg)
}, b, func(err error, d time.Duration) {
m.logger.Errorf("Error processing MQTT message: %s/%d. Retrying...", mqttMsg.Topic(), mqttMsg.MessageID())
}, func() {
m.logger.Infof("Successfully processed MQTT message after it previously failed: %s/%d", mqttMsg.Topic(), mqttMsg.MessageID())
}); err != nil {
m.logger.Errorf("Failed processing MQTT message: %s/%d: %v", mqttMsg.Topic(), mqttMsg.MessageID(), err)
}
})
if err := token.Error(); err != nil {
m.logger.Errorf("mqtt error from subscribe: %v", err)
return err
}
<-sigterm
return nil
}
func (m *MQTT) connect(clientID string) (mqtt.Client, error) {
uri, err := url.Parse(m.metadata.url)
if err != nil {
return nil, err
}
opts := m.createClientOptions(uri, clientID)
client := mqtt.NewClient(opts)
token := client.Connect()
for !token.WaitTimeout(defaultWait) {
}
if err := token.Error(); err != nil {
return nil, err
}
return client, nil
}
func (m *MQTT) newTLSConfig() *tls.Config {
tlsConfig := new(tls.Config)
if m.metadata.clientCert != "" && m.metadata.clientKey != "" {
cert, err := tls.X509KeyPair([]byte(m.metadata.clientCert), []byte(m.metadata.clientKey))
if err != nil {
m.logger.Warnf("unable to load client certificate and key pair. Err: %v", err)
return tlsConfig
}
tlsConfig.Certificates = []tls.Certificate{cert}
}
if m.metadata.caCert != "" {
tlsConfig.RootCAs = x509.NewCertPool()
if ok := tlsConfig.RootCAs.AppendCertsFromPEM([]byte(m.metadata.caCert)); !ok {
m.logger.Warnf("unable to load ca certificate.")
}
}
return tlsConfig
}
func (m *MQTT) createClientOptions(uri *url.URL, clientID string) *mqtt.ClientOptions {
opts := mqtt.NewClientOptions()
opts.SetClientID(clientID)
opts.SetCleanSession(m.metadata.cleanSession)
// URL scheme backward compatibility
scheme := uri.Scheme
switch scheme {
case "mqtt":
scheme = "tcp"
case "mqtts", "tcps", "tls":
scheme = "ssl"
}
opts.AddBroker(scheme + "://" + uri.Host)
opts.SetUsername(uri.User.Username())
password, _ := uri.User.Password()
opts.SetPassword(password)
// tls config
opts.SetTLSConfig(m.newTLSConfig())
return opts
}
func (m *MQTT) Close() error {
// Cancel any read callback handlers before Disconnect to prevent deadlocks.
m.cancel()
if m.consumer != nil {
m.consumer.Disconnect(1)
}
m.producer.Disconnect(1)
return nil
}