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worker.go
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/
worker.go
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package gbus
import (
"context"
"database/sql"
"errors"
"fmt"
"runtime/debug"
"sync"
"time"
"github.com/Rican7/retry"
"github.com/Rican7/retry/backoff"
"github.com/Rican7/retry/strategy"
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 func(tx *sql.Tx, poision amqp.Delivery) error
isTxnl bool
b *DefaultBus
serializer Serializer
txProvider TxProvider
amqpErrors chan *amqp.Error
stop chan bool
}
func (worker *worker) Start() error {
worker.log().Info("starting worker")
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
worker.stop = make(chan bool)
go worker.consumeMessages()
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() {
//TODO:Handle panics due to tx errors so the consumption of messages will continue
for {
var isRPCreply bool
var delivery amqp.Delivery
var shouldProceed bool
select {
case <-worker.stop:
worker.log().Info("stopped consuming messages")
return
case msgDelivery, ok := <-worker.messages:
if ok {
shouldProceed = true
}
delivery = msgDelivery
isRPCreply = false
case rpcDelivery, ok := <-worker.rpcMessages:
if ok {
shouldProceed = true
}
delivery = rpcDelivery
isRPCreply = true
}
/*
as the bus shuts down and amqp connection is killed the messages channel (b.msgs) gets closed
and delivery is a zero value so in order not to panic down the road we return if bus is shutdown
*/
if shouldProceed {
worker.processMessage(delivery, isRPCreply)
} else {
worker.log().WithField("message id", delivery.MessageId).Warn("no proceed")
}
}
}
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"
}
worker.log().WithField("message name", bm.PayloadFQN).Info("")
if bm.PayloadFQN == "" || bm.Semantics == "" {
//TODO: Log poision pill message
worker.log().WithFields(log.Fields{"fqn": 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", delivery).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()
worker.log().WithFields(log.Fields{"number of handlers": len(worker.registrations)}).Info("found message handlers")
for _, registration := range worker.registrations {
if registration.Matches(delivery.Exchange, delivery.RoutingKey, bm.PayloadFQN) {
handlers = append(handlers, registration.Handler)
}
}
worker.handlersLock.Unlock()
}
return handlers
}
func (worker *worker) Ack(delivery amqp.Delivery) error {
ack := func() error { return delivery.Ack(false /*multiple*/) }
return worker.SafeWithRetries(ack, MaxRetryCount)
}
func (worker *worker) Reject(requeue bool, delivery amqp.Delivery) error {
reject := func() error { return delivery.Reject(requeue /*multiple*/) }
return worker.SafeWithRetries(reject, MaxRetryCount)
}
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.Ack(delivery)
return
}
deadErr := worker.deadletterHandler(tx, delivery)
if deadErr != nil {
worker.SafeWithRetries(tx.Rollback, MaxRetryCount)
} else {
worker.SafeWithRetries(tx.Commit, MaxRetryCount)
}
}
func (worker *worker) processMessage(delivery amqp.Delivery, isRPCreply bool) {
worker.log().WithFields(log.Fields{"Worker": worker.consumerTag, "MessageId": delivery.MessageId}).Info("GOT MSG")
// worker.log("%v GOT MSG - Worker %v - MessageId %v", worker.svcName, worker.consumerTag, delivery.MessageId)
/*TODO:FIX Opentracing
spCtx, _ := amqptracer.Extract(delivery.Headers)
sp := opentracing.StartSpan(
"processMessage",
opentracing.FollowsFrom(spCtx),
)
if sp != nil {
defer sp.Finish()
}
*/
// Update the context with the span for the subsequent reference.
//handle a message that originated from a deadletter exchange
if worker.isDead(delivery) {
worker.log().Info("invoking deadletter handler")
worker.invokeDeadletterHandler(delivery)
return
}
bm, err := worker.extractBusMessage(delivery)
if err != nil {
//reject poison message
worker.Reject(false, delivery)
return
}
//TODO:Dedup message
handlers := worker.resolveHandlers(isRPCreply, bm, delivery)
if len(handlers) == 0 {
worker.log().
WithFields(
log.Fields{"Message Name": bm.PayloadFQN,
"Message Type": bm.Semantics}).
Warn("Message received but 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
}
var tx *sql.Tx
var txErr error
if worker.isTxnl {
//TODO:Add retries, and reject message with requeue=true
tx, txErr = worker.txProvider.New()
if txErr != nil {
worker.log().WithError(txErr).Error("failed to create transaction")
//reject the error and reuqueu so it can be processed once we can create transactions
worker.Reject(true, delivery)
return
}
}
var ackErr, commitErr, rollbackErr, rejectErr error
invkErr := worker.invokeHandlers(context.Background(), handlers, bm, &delivery, tx)
// if all handlers executed with out errors then commit the transactional if the bus is transactional
// if the tranaction committed successfully then ack the message.
// if the bus is not transactional then just ack the message
if invkErr == nil {
if worker.isTxnl {
commitErr = worker.SafeWithRetries(tx.Commit, MaxRetryCount)
if commitErr == nil {
worker.log().Info("bus transaction committed successfully ")
//ack the message
ackErr = worker.Ack(delivery)
if ackErr != nil {
// if this fails then the message will be eventually redeilvered by RabbitMQ
//sp handlers should be idempotent.
worker.log().Info("failed to send ack to the broker ")
}
} else {
worker.log().WithError(commitErr).Error("failed committing transaction")
//if the commit failed we will reject the message
worker.Reject(false, delivery)
}
} else { /*if the bus in not transactional just try acking the message*/
ackErr = worker.Ack(delivery)
if ackErr != nil {
worker.log().Info("failed to send ack to the broker ")
}
}
//else there was an error in the invokation then try rollingback the transaction and reject the message
} else {
worker.log().WithError(invkErr).WithFields(log.Fields{"message name": bm.PayloadFQN, "semantics": bm.Semantics}).Error("Failed to consume message due to failure of one or more handlers.\n Message rejected as poison")
if worker.isTxnl {
worker.log().Warn("rolling back transaction")
rollbackErr = worker.SafeWithRetries(tx.Rollback, MaxRetryCount)
if rollbackErr != nil {
worker.log().WithError(rollbackErr).Error("failed to rollback transaction")
}
}
rejectErr = worker.Reject(false, delivery)
if rejectErr != nil {
worker.log().WithError(rejectErr).Error("failed to reject message")
}
}
}
func (worker *worker) invokeHandlers(sctx context.Context, handlers []MessageHandler, message *BusMessage, delivery *amqp.Delivery, tx *sql.Tx) (err error) {
action := func(attempts uint) (actionErr error) {
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)
}
}()
for _, handler := range handlers {
ctx := &defaultInvocationContext{
invocingSvc: delivery.ReplyTo,
bus: worker.b,
inboundMsg: message,
tx: tx,
ctx: sctx,
exchange: delivery.Exchange,
routingKey: delivery.RoutingKey}
e := handler(ctx, message)
if e != nil {
return e
}
}
return nil
}
//retry for MaxRetryCount, back off by a Fibonacci series 50, 50, 100, 150, 250 ms
return retry.Retry(action,
strategy.Limit(MaxRetryCount),
strategy.Backoff(backoff.Fibonacci(50*time.Millisecond)))
}
func (worker *worker) log() *log.Entry {
return log.WithFields(log.Fields{
"Service": worker.svcName})
}