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ordered.go
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ordered.go
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// Copyright 2022-2024 The NATS Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package jetstream
import (
"context"
"errors"
"fmt"
"strconv"
"sync"
"sync/atomic"
"time"
"github.com/nats-io/nats.go"
)
type (
orderedConsumer struct {
jetStream *jetStream
cfg *OrderedConsumerConfig
stream string
currentConsumer *pullConsumer
cursor cursor
namePrefix string
serial int
consumerType consumerType
doReset chan struct{}
resetInProgress uint32
userErrHandler ConsumeErrHandlerFunc
stopAfter int
stopAfterMsgsLeft chan int
withStopAfter bool
runningFetch *fetchResult
sync.Mutex
}
orderedSubscription struct {
consumer *orderedConsumer
opts []PullMessagesOpt
done chan struct{}
closed uint32
}
cursor struct {
streamSeq uint64
deliverSeq uint64
}
consumerType int
)
const (
consumerTypeNotSet consumerType = iota
consumerTypeConsume
consumerTypeFetch
)
var errOrderedSequenceMismatch = errors.New("sequence mismatch")
// Consume can be used to continuously receive messages and handle them
// with the provided callback function. Consume cannot be used concurrently
// when using ordered consumer.
//
// See [Consumer.Consume] for more details.
func (c *orderedConsumer) Consume(handler MessageHandler, opts ...PullConsumeOpt) (ConsumeContext, error) {
if (c.consumerType == consumerTypeNotSet || c.consumerType == consumerTypeConsume) && c.currentConsumer == nil {
err := c.reset()
if err != nil {
return nil, err
}
} else if c.consumerType == consumerTypeConsume && c.currentConsumer != nil {
return nil, ErrOrderedConsumerConcurrentRequests
}
if c.consumerType == consumerTypeFetch {
return nil, ErrOrderConsumerUsedAsFetch
}
c.consumerType = consumerTypeConsume
consumeOpts, err := parseConsumeOpts(true, opts...)
if err != nil {
return nil, fmt.Errorf("%w: %s", ErrInvalidOption, err)
}
c.userErrHandler = consumeOpts.ErrHandler
opts = append(opts, ConsumeErrHandler(c.errHandler(c.serial)))
if consumeOpts.StopAfter > 0 {
c.withStopAfter = true
c.stopAfter = consumeOpts.StopAfter
}
c.stopAfterMsgsLeft = make(chan int, 1)
if c.stopAfter > 0 {
opts = append(opts, consumeStopAfterNotify(c.stopAfter, c.stopAfterMsgsLeft))
}
sub := &orderedSubscription{
consumer: c,
done: make(chan struct{}, 1),
}
internalHandler := func(serial int) func(msg Msg) {
return func(msg Msg) {
// handler is a noop if message was delivered for a consumer with different serial
if serial != c.serial {
return
}
meta, err := msg.Metadata()
if err != nil {
sub, ok := c.currentConsumer.getSubscription("")
if !ok {
return
}
c.errHandler(serial)(sub, err)
return
}
dseq := meta.Sequence.Consumer
if dseq != c.cursor.deliverSeq+1 {
sub, ok := c.currentConsumer.getSubscription("")
if !ok {
return
}
c.errHandler(serial)(sub, errOrderedSequenceMismatch)
return
}
c.cursor.deliverSeq = dseq
c.cursor.streamSeq = meta.Sequence.Stream
handler(msg)
}
}
_, err = c.currentConsumer.Consume(internalHandler(c.serial), opts...)
if err != nil {
return nil, err
}
go func() {
for {
select {
case <-c.doReset:
if err := c.reset(); err != nil {
sub, ok := c.currentConsumer.getSubscription("")
if !ok {
return
}
c.errHandler(c.serial)(sub, err)
}
if c.withStopAfter {
select {
case c.stopAfter = <-c.stopAfterMsgsLeft:
default:
}
if c.stopAfter <= 0 {
sub.Stop()
return
}
}
if c.stopAfter > 0 {
opts = opts[:len(opts)-2]
} else {
opts = opts[:len(opts)-1]
}
// overwrite the previous err handler to use the new serial
opts = append(opts, ConsumeErrHandler(c.errHandler(c.serial)))
if c.withStopAfter {
opts = append(opts, consumeStopAfterNotify(c.stopAfter, c.stopAfterMsgsLeft))
}
if _, err := c.currentConsumer.Consume(internalHandler(c.serial), opts...); err != nil {
sub, ok := c.currentConsumer.getSubscription("")
if !ok {
return
}
c.errHandler(c.serial)(sub, err)
}
case <-sub.done:
return
case msgsLeft, ok := <-c.stopAfterMsgsLeft:
if !ok {
close(sub.done)
}
c.stopAfter = msgsLeft
return
}
}
}()
return sub, nil
}
func (c *orderedConsumer) errHandler(serial int) func(cc ConsumeContext, err error) {
return func(cc ConsumeContext, err error) {
c.Lock()
defer c.Unlock()
if c.userErrHandler != nil && !errors.Is(err, errOrderedSequenceMismatch) {
c.userErrHandler(cc, err)
}
if errors.Is(err, ErrNoHeartbeat) ||
errors.Is(err, errOrderedSequenceMismatch) ||
errors.Is(err, ErrConsumerDeleted) ||
errors.Is(err, ErrConsumerNotFound) {
// only reset if serial matches the current consumer serial and there is no reset in progress
if serial == c.serial && atomic.LoadUint32(&c.resetInProgress) == 0 {
atomic.StoreUint32(&c.resetInProgress, 1)
c.doReset <- struct{}{}
}
}
}
}
// Messages returns MessagesContext, allowing continuously iterating
// over messages on a stream. Messages cannot be used concurrently
// when using ordered consumer.
//
// See [Consumer.Messages] for more details.
func (c *orderedConsumer) Messages(opts ...PullMessagesOpt) (MessagesContext, error) {
if (c.consumerType == consumerTypeNotSet || c.consumerType == consumerTypeConsume) && c.currentConsumer == nil {
err := c.reset()
if err != nil {
return nil, err
}
} else if c.consumerType == consumerTypeConsume && c.currentConsumer != nil {
return nil, ErrOrderedConsumerConcurrentRequests
}
if c.consumerType == consumerTypeFetch {
return nil, ErrOrderConsumerUsedAsFetch
}
c.consumerType = consumerTypeConsume
consumeOpts, err := parseMessagesOpts(true, opts...)
if err != nil {
return nil, fmt.Errorf("%w: %s", ErrInvalidOption, err)
}
opts = append(opts, WithMessagesErrOnMissingHeartbeat(true))
c.stopAfterMsgsLeft = make(chan int, 1)
if consumeOpts.StopAfter > 0 {
c.withStopAfter = true
c.stopAfter = consumeOpts.StopAfter
}
c.userErrHandler = consumeOpts.ErrHandler
if c.stopAfter > 0 {
opts = append(opts, messagesStopAfterNotify(c.stopAfter, c.stopAfterMsgsLeft))
}
_, err = c.currentConsumer.Messages(opts...)
if err != nil {
return nil, err
}
sub := &orderedSubscription{
consumer: c,
opts: opts,
done: make(chan struct{}, 1),
}
return sub, nil
}
func (s *orderedSubscription) Next() (Msg, error) {
for {
currentConsumer := s.consumer.currentConsumer
sub, ok := currentConsumer.getSubscription("")
if !ok {
return nil, ErrMsgIteratorClosed
}
msg, err := sub.Next()
if err != nil {
if errors.Is(err, ErrMsgIteratorClosed) {
s.Stop()
return nil, err
}
if s.consumer.withStopAfter {
select {
case s.consumer.stopAfter = <-s.consumer.stopAfterMsgsLeft:
default:
}
if s.consumer.stopAfter <= 0 {
s.Stop()
return nil, ErrMsgIteratorClosed
}
s.opts[len(s.opts)-1] = StopAfter(s.consumer.stopAfter)
}
if err := s.consumer.reset(); err != nil {
return nil, err
}
_, err := s.consumer.currentConsumer.Messages(s.opts...)
if err != nil {
return nil, err
}
continue
}
meta, err := msg.Metadata()
if err != nil {
s.consumer.errHandler(s.consumer.serial)(sub, err)
continue
}
serial := serialNumberFromConsumer(meta.Consumer)
dseq := meta.Sequence.Consumer
if dseq != s.consumer.cursor.deliverSeq+1 {
s.consumer.errHandler(serial)(sub, errOrderedSequenceMismatch)
continue
}
s.consumer.cursor.deliverSeq = dseq
s.consumer.cursor.streamSeq = meta.Sequence.Stream
return msg, nil
}
}
func (s *orderedSubscription) Stop() {
if !atomic.CompareAndSwapUint32(&s.closed, 0, 1) {
return
}
sub, ok := s.consumer.currentConsumer.getSubscription("")
if !ok {
return
}
s.consumer.currentConsumer.Lock()
defer s.consumer.currentConsumer.Unlock()
sub.Stop()
close(s.done)
}
func (s *orderedSubscription) Drain() {
if !atomic.CompareAndSwapUint32(&s.closed, 0, 1) {
return
}
sub, ok := s.consumer.currentConsumer.getSubscription("")
if !ok {
return
}
s.consumer.currentConsumer.Lock()
defer s.consumer.currentConsumer.Unlock()
sub.Drain()
close(s.done)
}
// Fetch is used to retrieve up to a provided number of messages from a
// stream. This method will always send a single request and wait until
// either all messages are retrieved or request times out.
//
// It is not efficient to use Fetch with on an ordered consumer, as it will
// reset the consumer for each subsequent Fetch call.
// Consider using [Consumer.Consume] or [Consumer.Messages] instead.
func (c *orderedConsumer) Fetch(batch int, opts ...FetchOpt) (MessageBatch, error) {
if c.consumerType == consumerTypeConsume {
return nil, ErrOrderConsumerUsedAsConsume
}
c.currentConsumer.Lock()
if c.runningFetch != nil {
if !c.runningFetch.done {
c.currentConsumer.Unlock()
return nil, ErrOrderedConsumerConcurrentRequests
}
c.cursor.streamSeq = c.runningFetch.sseq
}
c.currentConsumer.Unlock()
c.consumerType = consumerTypeFetch
err := c.reset()
if err != nil {
return nil, err
}
msgs, err := c.currentConsumer.Fetch(batch, opts...)
if err != nil {
return nil, err
}
c.runningFetch = msgs.(*fetchResult)
return msgs, nil
}
// FetchBytes is used to retrieve up to a provided bytes from the
// stream. This method will always send a single request and wait until
// provided number of bytes is exceeded or request times out.
//
// It is not efficient to use FetchBytes with on an ordered consumer, as it will
// reset the consumer for each subsequent Fetch call.
// Consider using [Consumer.Consume] or [Consumer.Messages] instead.
func (c *orderedConsumer) FetchBytes(maxBytes int, opts ...FetchOpt) (MessageBatch, error) {
if c.consumerType == consumerTypeConsume {
return nil, ErrOrderConsumerUsedAsConsume
}
if c.runningFetch != nil {
if !c.runningFetch.done {
return nil, ErrOrderedConsumerConcurrentRequests
}
c.cursor.streamSeq = c.runningFetch.sseq
}
c.consumerType = consumerTypeFetch
err := c.reset()
if err != nil {
return nil, err
}
msgs, err := c.currentConsumer.FetchBytes(maxBytes, opts...)
if err != nil {
return nil, err
}
c.runningFetch = msgs.(*fetchResult)
return msgs, nil
}
// FetchNoWait is used to retrieve up to a provided number of messages
// from a stream. This method will always send a single request and
// immediately return up to a provided number of messages or wait until
// at least one message is available or request times out.
//
// It is not efficient to use FetchNoWait with on an ordered consumer, as it will
// reset the consumer for each subsequent Fetch call.
// Consider using [Consumer.Consume] or [Consumer.Messages] instead.
func (c *orderedConsumer) FetchNoWait(batch int) (MessageBatch, error) {
if c.consumerType == consumerTypeConsume {
return nil, ErrOrderConsumerUsedAsConsume
}
if c.runningFetch != nil && !c.runningFetch.done {
return nil, ErrOrderedConsumerConcurrentRequests
}
c.consumerType = consumerTypeFetch
err := c.reset()
if err != nil {
return nil, err
}
return c.currentConsumer.FetchNoWait(batch)
}
// Next is used to retrieve the next message from the stream. This
// method will block until the message is retrieved or timeout is
// reached.
//
// It is not efficient to use Next with on an ordered consumer, as it will
// reset the consumer for each subsequent Fetch call.
// Consider using [Consumer.Consume] or [Consumer.Messages] instead.
func (c *orderedConsumer) Next(opts ...FetchOpt) (Msg, error) {
res, err := c.Fetch(1, opts...)
if err != nil {
return nil, err
}
msg := <-res.Messages()
if msg != nil {
return msg, nil
}
if res.Error() == nil {
return nil, nats.ErrTimeout
}
return nil, res.Error()
}
func serialNumberFromConsumer(name string) int {
if len(name) == 0 {
return 0
}
serial, err := strconv.Atoi(name[len(name)-1:])
if err != nil {
return 0
}
return serial
}
func (c *orderedConsumer) reset() error {
c.Lock()
defer c.Unlock()
defer atomic.StoreUint32(&c.resetInProgress, 0)
if c.currentConsumer != nil {
sub, ok := c.currentConsumer.getSubscription("")
c.currentConsumer.Lock()
if ok {
sub.Stop()
}
consName := c.currentConsumer.CachedInfo().Name
c.currentConsumer.Unlock()
var err error
for i := 0; ; i++ {
if c.cfg.MaxResetAttempts > 0 && i == c.cfg.MaxResetAttempts {
return fmt.Errorf("%w: maximum number of delete attempts reached: %s", ErrOrderedConsumerReset, err)
}
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
err = c.jetStream.DeleteConsumer(ctx, c.stream, consName)
cancel()
if err != nil {
if errors.Is(err, ErrConsumerNotFound) {
break
}
if errors.Is(err, nats.ErrTimeout) || errors.Is(err, context.DeadlineExceeded) {
continue
}
return err
}
break
}
}
seq := c.cursor.streamSeq + 1
c.cursor.deliverSeq = 0
consumerConfig := c.getConsumerConfigForSeq(seq)
var err error
var cons Consumer
for i := 0; ; i++ {
if c.cfg.MaxResetAttempts > 0 && i == c.cfg.MaxResetAttempts {
return fmt.Errorf("%w: maximum number of create consumer attempts reached: %s", ErrOrderedConsumerReset, err)
}
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
cons, err = c.jetStream.CreateOrUpdateConsumer(ctx, c.stream, *consumerConfig)
if err != nil {
if errors.Is(err, ErrConsumerNotFound) {
cancel()
break
}
if errors.Is(err, nats.ErrTimeout) || errors.Is(err, context.DeadlineExceeded) {
cancel()
continue
}
cancel()
return err
}
cancel()
break
}
c.currentConsumer = cons.(*pullConsumer)
return nil
}
func (c *orderedConsumer) getConsumerConfigForSeq(seq uint64) *ConsumerConfig {
c.serial++
name := fmt.Sprintf("%s_%d", c.namePrefix, c.serial)
cfg := &ConsumerConfig{
Name: name,
DeliverPolicy: DeliverByStartSequencePolicy,
OptStartSeq: seq,
AckPolicy: AckNonePolicy,
InactiveThreshold: 5 * time.Minute,
Replicas: 1,
HeadersOnly: c.cfg.HeadersOnly,
MemoryStorage: true,
}
if len(c.cfg.FilterSubjects) == 1 {
cfg.FilterSubject = c.cfg.FilterSubjects[0]
} else {
cfg.FilterSubjects = c.cfg.FilterSubjects
}
if seq != c.cfg.OptStartSeq+1 {
return cfg
}
// initial request, some options may be modified at that point
cfg.DeliverPolicy = c.cfg.DeliverPolicy
if c.cfg.DeliverPolicy == DeliverLastPerSubjectPolicy ||
c.cfg.DeliverPolicy == DeliverLastPolicy ||
c.cfg.DeliverPolicy == DeliverNewPolicy ||
c.cfg.DeliverPolicy == DeliverAllPolicy {
cfg.OptStartSeq = 0
}
if cfg.DeliverPolicy == DeliverLastPerSubjectPolicy && len(c.cfg.FilterSubjects) == 0 {
cfg.FilterSubjects = []string{">"}
}
if c.cfg.OptStartTime != nil {
cfg.OptStartSeq = 0
cfg.DeliverPolicy = DeliverByStartTimePolicy
cfg.OptStartTime = c.cfg.OptStartTime
}
if c.cfg.InactiveThreshold != 0 {
cfg.InactiveThreshold = c.cfg.InactiveThreshold
}
return cfg
}
func consumeStopAfterNotify(numMsgs int, msgsLeftAfterStop chan int) PullConsumeOpt {
return pullOptFunc(func(opts *consumeOpts) error {
opts.StopAfter = numMsgs
opts.stopAfterMsgsLeft = msgsLeftAfterStop
return nil
})
}
func messagesStopAfterNotify(numMsgs int, msgsLeftAfterStop chan int) PullMessagesOpt {
return pullOptFunc(func(opts *consumeOpts) error {
opts.StopAfter = numMsgs
opts.stopAfterMsgsLeft = msgsLeftAfterStop
return nil
})
}
// Info returns information about the ordered consumer.
// Note that this method will fetch the latest instance of the
// consumer from the server, which can be deleted by the library at any time.
func (c *orderedConsumer) Info(ctx context.Context) (*ConsumerInfo, error) {
c.Lock()
defer c.Unlock()
if c.currentConsumer == nil {
return nil, ErrOrderedConsumerNotCreated
}
infoSubject := apiSubj(c.jetStream.apiPrefix, fmt.Sprintf(apiConsumerInfoT, c.stream, c.currentConsumer.name))
var resp consumerInfoResponse
if _, err := c.jetStream.apiRequestJSON(ctx, infoSubject, &resp); err != nil {
return nil, err
}
if resp.Error != nil {
if resp.Error.ErrorCode == JSErrCodeConsumerNotFound {
return nil, ErrConsumerNotFound
}
return nil, resp.Error
}
if resp.Error == nil && resp.ConsumerInfo == nil {
return nil, ErrConsumerNotFound
}
c.currentConsumer.info = resp.ConsumerInfo
return resp.ConsumerInfo, nil
}
// CachedInfo returns cached information about the consumer currently
// used by the ordered consumer. Cached info will be updated on every call
// to [Consumer.Info] or on consumer reset.
func (c *orderedConsumer) CachedInfo() *ConsumerInfo {
c.Lock()
defer c.Unlock()
if c.currentConsumer == nil {
return nil
}
return c.currentConsumer.info
}