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worker.go
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worker.go
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package gbus
import (
"context"
"errors"
"fmt"
"math/rand"
"runtime/debug"
"sync"
"time"
"github.com/wework/grabbit/gbus/metrics"
"github.com/Rican7/retry"
"github.com/Rican7/retry/backoff"
"github.com/Rican7/retry/jitter"
"github.com/Rican7/retry/strategy"
"github.com/opentracing-contrib/go-amqp/amqptracer"
"github.com/opentracing/opentracing-go"
slog "github.com/opentracing/opentracing-go/log"
"github.com/sirupsen/logrus"
"github.com/streadway/amqp"
)
type worker struct {
*Safety
channel *amqp.Channel
messages <-chan amqp.Delivery
rpcMessages <-chan amqp.Delivery
q amqp.Queue
rpcq amqp.Queue
consumerTag string
svcName string
rpcLock *sync.Mutex
handlersLock *sync.Mutex
registrations []*Registration
rpcHandlers map[string]MessageHandler
deadletterHandler DeadLetterMessageHandler
b *DefaultBus
serializer Serializer
txProvider TxProvider
amqpErrors chan *amqp.Error
stop chan bool
span opentracing.Span
}
func (worker *worker) Start() error {
worker.log().Info("starting worker")
worker.stop = make(chan bool)
worker.channel.NotifyClose(worker.amqpErrors)
var (
messages, rpcmsgs <-chan amqp.Delivery
err error
)
if messages, err = worker.createMessagesChannel(worker.q, worker.consumerTag); err != nil {
return err
}
if rpcmsgs, err = worker.createMessagesChannel(worker.rpcq, worker.consumerTag+"_rpc"); err != nil {
return err
}
worker.messages = messages
worker.rpcMessages = rpcmsgs
go worker.consumeMessages()
go worker.consumeRPC()
return nil
}
func (worker *worker) Stop() error {
worker.log().Info("stopping worker")
close(worker.stop) // worker.stop <- true
return nil
}
func (worker *worker) createMessagesChannel(q amqp.Queue, consumerTag string) (<-chan amqp.Delivery, error) {
msgs, e := worker.channel.Consume(q.Name, /*queue*/
consumerTag, /*consumer*/
false, /*autoAck*/
false, /*exclusive*/
false, /*noLocal*/
false, /*noWait*/
nil /*args* amqp.Table*/)
if e != nil {
return nil, e
}
return msgs, nil
}
func (worker *worker) consumeMessages() {
for msg := range worker.messages {
if msg.Body == nil || len(msg.Body) == 0 {
continue
}
worker.processMessage(msg, false)
}
}
func (worker *worker) consumeRPC() {
for msg := range worker.rpcMessages {
if msg.Body == nil || len(msg.Body) == 0 {
continue
}
worker.processMessage(msg, true)
}
}
func (worker *worker) extractBusMessage(delivery amqp.Delivery) (*BusMessage, error) {
bm := NewFromAMQPHeaders(delivery.Headers)
bm.ID = delivery.MessageId
bm.CorrelationID = delivery.CorrelationId
if delivery.Exchange != "" {
bm.Semantics = EVT
} else {
bm.Semantics = CMD
}
if bm.PayloadFQN == "" || bm.Semantics == "" {
//TODO: Log poison pill message
worker.log().WithFields(logrus.Fields{"message_name": bm.PayloadFQN, "semantics": bm.Semantics}).Warn("message received but no headers found...rejecting message")
return nil, errors.New("missing critical headers")
}
var decErr error
bm.Payload, decErr = worker.serializer.Decode(delivery.Body, bm.PayloadFQN)
if decErr != nil {
worker.log().WithError(decErr).WithField("message_name", bm.PayloadFQN).Error("failed to decode message. rejected as poison")
return nil, decErr
}
return bm, nil
}
func (worker *worker) resolveHandlers(isRPCreply bool, bm *BusMessage, delivery amqp.Delivery) []MessageHandler {
handlers := make([]MessageHandler, 0)
if isRPCreply {
rpcID, rpcHeaderFound := delivery.Headers[RpcHeaderName].(string)
if !rpcHeaderFound {
worker.log().Warn("rpc message received but no rpc header found...rejecting message")
return handlers
}
worker.rpcLock.Lock()
rpcHandler := worker.rpcHandlers[rpcID]
worker.rpcLock.Unlock()
if rpcHandler == nil {
worker.log().Warn("rpc message received but no rpc header found...rejecting message")
return handlers
}
handlers = append(handlers, rpcHandler)
} else {
worker.handlersLock.Lock()
defer worker.handlersLock.Unlock()
for _, registration := range worker.registrations {
if registration.Matches(delivery.Exchange, delivery.RoutingKey, bm.PayloadFQN) {
handlers = append(handlers, registration.Handler)
}
}
}
worker.log().WithFields(logrus.Fields{"number_of_handlers": len(handlers)}).Info("found message handlers")
return handlers
}
func (worker *worker) ack(delivery amqp.Delivery) error {
ack := func(attempts uint) error { return delivery.Ack(false /*multiple*/) }
worker.log().WithField("message_id", delivery.MessageId).Debug("acking message")
err := retry.Retry(ack,
strategy.Wait(100*time.Millisecond))
if err != nil {
worker.log().WithError(err).Error("could not ack the message")
worker.span.LogFields(slog.Error(err))
} else {
worker.log().WithField("message_id", delivery.MessageId).Debug("message acked")
}
return err
}
func (worker *worker) reject(requeue bool, delivery amqp.Delivery) error {
reject := func(attempts uint) error { return delivery.Reject(requeue /*multiple*/) }
worker.log().WithFields(logrus.Fields{"message_id": delivery.MessageId, "requeue": requeue}).Info("rejecting message")
err := retry.Retry(reject,
strategy.Wait(100*time.Millisecond))
if err != nil {
worker.log().WithError(err).Error("could not reject the message")
worker.span.LogFields(slog.Error(err))
}
worker.log().WithFields(logrus.Fields{"message_id": delivery.MessageId, "requeue": requeue}).Info("message rejected")
return err
}
func (worker *worker) isDead(delivery amqp.Delivery) bool {
if xDeath := delivery.Headers["x-death"]; xDeath != nil {
return true
}
return false
}
func (worker *worker) invokeDeadletterHandler(delivery amqp.Delivery) {
tx, txCreateErr := worker.txProvider.New()
if txCreateErr != nil {
worker.log().WithError(txCreateErr).Error("failed creating new tx")
worker.span.LogFields(slog.Error(txCreateErr))
_ = worker.reject(true, delivery)
return
}
err := metrics.RunHandlerWithMetric(func() error {
return worker.deadletterHandler(tx, delivery)
}, worker.deadletterHandler.Name(), worker.log())
var reject bool
if err != nil {
worker.log().WithError(err).Error("failed handling deadletter")
worker.span.LogFields(slog.Error(err))
err = worker.SafeWithRetries(tx.Rollback, MaxRetryCount)
reject = true
} else {
err = worker.SafeWithRetries(tx.Commit, MaxRetryCount)
}
if err != nil {
worker.log().WithError(err).Error("Rollback/Commit deadletter handler message")
worker.span.LogFields(slog.Error(err))
reject = true
}
if reject {
_ = worker.reject(true, delivery)
} else {
_ = worker.ack(delivery)
}
}
func (worker *worker) processMessage(delivery amqp.Delivery, isRPCreply bool) {
var ctx context.Context
var spanOptions []opentracing.StartSpanOption
spCtx, err := amqptracer.Extract(delivery.Headers)
if err != nil {
worker.log().WithError(err).Debug("could not extract SpanContext from headers")
} else {
spanOptions = append(spanOptions, opentracing.FollowsFrom(spCtx))
}
worker.span, ctx = opentracing.StartSpanFromContext(context.Background(), "processMessage", spanOptions...)
//catch all error handling so goroutine will not crash
defer func() {
if r := recover(); r != nil {
logEntry := worker.log().WithField("worker", worker.consumerTag)
if err, ok := r.(error); ok {
worker.span.LogFields(slog.Error(err))
logEntry = logEntry.WithError(err)
} else {
logEntry = logEntry.WithField("panic", r)
}
worker.span.LogFields(slog.String("panic", "failed to process message"))
logEntry.Error("failed to process message")
}
worker.span.Finish()
}()
worker.log().WithFields(logrus.Fields{"worker": worker.consumerTag, "message_id": delivery.MessageId}).Info("GOT MSG")
//handle a message that originated from a deadletter exchange
if worker.isDead(delivery) {
worker.span.LogFields(slog.Error(errors.New("handling dead-letter delivery")))
worker.log().Info("invoking deadletter handler")
worker.invokeDeadletterHandler(delivery)
return
}
bm, err := worker.extractBusMessage(delivery)
if err != nil {
worker.span.LogFields(slog.Error(err), slog.String("grabbit", "message is poison"))
//reject poison message
_ = worker.reject(false, delivery)
return
}
worker.span.LogFields(bm.GetTraceLog()...)
//TODO:Dedup message
handlers := worker.resolveHandlers(isRPCreply, bm, delivery)
if len(handlers) == 0 {
worker.log().
WithFields(
logrus.Fields{"message-name": bm.PayloadFQN,
"message-type": bm.Semantics}).
Warn("Message received but no handlers found")
worker.span.LogFields(slog.String("grabbit", "no handlers found"))
// worker.log("Message received but no handlers found\nMessage name:%v\nMessage Type:%v\nRejecting message", bm.PayloadFQN, bm.Semantics)
//remove the message by acking it and not rejecting it so it will not be routed to a deadletter queue
_ = worker.ack(delivery)
return
}
err = worker.invokeHandlers(ctx, handlers, bm, &delivery)
if err == nil {
_ = worker.ack(delivery)
} else {
_ = worker.reject(false, delivery)
metrics.ReportRejectedMessage()
}
}
func (worker *worker) invokeHandlers(sctx context.Context, handlers []MessageHandler, message *BusMessage, delivery *amqp.Delivery) (err error) {
//this is the action that will get retried
// each retry should run a new and separate transaction which should end with a commit or rollback
action := func(attempt uint) (actionErr error) {
tx, txCreateErr := worker.txProvider.New()
if txCreateErr != nil {
worker.log().WithError(txCreateErr).Error("failed creating new tx")
worker.span.LogFields(slog.Error(txCreateErr))
return txCreateErr
}
worker.span, sctx = opentracing.StartSpanFromContext(sctx, "invokeHandlers")
worker.span.LogFields(slog.Uint64("attempt", uint64(attempt+1)))
defer func() {
if p := recover(); p != nil {
pncMsg := fmt.Sprintf("%v\n%s", p, debug.Stack())
worker.log().WithField("stack", pncMsg).Error("recovered from panic while invoking handler")
actionErr = errors.New(pncMsg)
rbkErr := tx.Rollback()
if rbkErr != nil {
worker.log().WithError(rbkErr).Error("failed rolling back transaction when recovering from handler panic")
}
worker.span.LogFields(slog.Error(actionErr))
}
worker.span.Finish()
}()
var handlerErr error
var hspan opentracing.Span
var hsctx context.Context
for _, handler := range handlers {
hspan, hsctx = opentracing.StartSpanFromContext(sctx, handler.Name())
ctx := &defaultInvocationContext{
invocingSvc: delivery.ReplyTo,
bus: worker.b,
inboundMsg: message,
tx: tx,
ctx: hsctx,
exchange: delivery.Exchange,
routingKey: delivery.RoutingKey,
deliveryInfo: DeliveryInfo{
Attempt: attempt,
MaxRetryCount: MaxRetryCount,
},
}
ctx.SetLogger(worker.log().WithField("handler", handler.Name()))
handlerErr = metrics.RunHandlerWithMetric(func() error {
return handler(ctx, message)
}, handler.Name(), worker.log())
if handlerErr != nil {
hspan.LogFields(slog.Error(handlerErr))
break
}
hspan.Finish()
}
if handlerErr != nil {
hspan.LogFields(slog.Error(handlerErr))
rbkErr := tx.Rollback()
if rbkErr != nil {
worker.log().WithError(rbkErr).Error("failed rolling back transaction when recovering from handler error")
}
hspan.Finish()
return handlerErr
}
cmtErr := tx.Commit()
if cmtErr != nil {
worker.log().WithError(cmtErr).Error("failed committing transaction after invoking handlers")
return cmtErr
}
return nil
}
//retry for MaxRetryCount, back off by a jittered strategy
seed := time.Now().UnixNano()
random := rand.New(rand.NewSource(seed))
return retry.Retry(action,
strategy.Limit(MaxRetryCount),
strategy.BackoffWithJitter(
backoff.BinaryExponential(BaseRetryDuration),
jitter.Deviation(random, 0.5),
))
}
func (worker *worker) log() logrus.FieldLogger {
return worker.b.Log()
}
func (worker *worker) AddRegistration(registration *Registration) {
worker.handlersLock.Lock()
defer worker.handlersLock.Unlock()
worker.registrations = append(worker.registrations, registration)
}