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stream.go
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stream.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"
"encoding/json"
"errors"
"fmt"
"strconv"
"time"
"github.com/nats-io/nats.go"
"github.com/nats-io/nuid"
)
type (
// Stream contains CRUD methods on a consumer via [ConsumerManager], as well
// as operations on an existing stream. It allows fetching and removing
// messages from a stream, as well as purging a stream.
Stream interface {
ConsumerManager
// Info returns StreamInfo from the server.
Info(ctx context.Context, opts ...StreamInfoOpt) (*StreamInfo, error)
// CachedInfo returns ConsumerInfo currently cached on this stream.
// This method does not perform any network requests. The cached
// StreamInfo is updated on every call to Info and Update.
CachedInfo() *StreamInfo
// Purge removes messages from a stream. It is a destructive operation.
// Use with caution. See StreamPurgeOpt for available options.
Purge(ctx context.Context, opts ...StreamPurgeOpt) error
// GetMsg retrieves a raw stream message stored in JetStream by sequence number.
GetMsg(ctx context.Context, seq uint64, opts ...GetMsgOpt) (*RawStreamMsg, error)
// GetLastMsgForSubject retrieves the last raw stream message stored in
// JetStream on a given subject subject.
GetLastMsgForSubject(ctx context.Context, subject string) (*RawStreamMsg, error)
// DeleteMsg deletes a message from a stream.
// On the server, the message is marked as erased, but not overwritten.
DeleteMsg(ctx context.Context, seq uint64) error
// SecureDeleteMsg deletes a message from a stream. The deleted message
// is overwritten with random data. As a result, this operation is slower
// than DeleteMsg.
SecureDeleteMsg(ctx context.Context, seq uint64) error
}
// ConsumerManager provides CRUD API for managing consumers. It is
// available as a part of [Stream] interface. CreateConsumer,
// UpdateConsumer, CreateOrUpdateConsumer and Consumer methods return a
// [Consumer] interface, allowing to operate on a consumer (e.g. consume
// messages).
ConsumerManager interface {
// CreateOrUpdateConsumer creates a consumer on a given stream with
// given config. If consumer already exists, it will be updated (if
// possible). Consumer interface is returned, allowing to operate on a
// consumer (e.g. fetch messages).
CreateOrUpdateConsumer(ctx context.Context, cfg ConsumerConfig) (Consumer, error)
// CreateConsumer creates a consumer on a given stream with given
// config. If consumer already exists and the provided configuration
// differs from its configuration, ErrConsumerExists is returned. If the
// provided configuration is the same as the existing consumer, the
// existing consumer is returned. Consumer interface is returned,
// allowing to operate on a consumer (e.g. fetch messages).
CreateConsumer(ctx context.Context, cfg ConsumerConfig) (Consumer, error)
// UpdateConsumer updates an existing consumer. If consumer does not
// exist, ErrConsumerDoesNotExist is returned. Consumer interface is
// returned, allowing to operate on a consumer (e.g. fetch messages).
UpdateConsumer(ctx context.Context, cfg ConsumerConfig) (Consumer, error)
// OrderedConsumer returns an OrderedConsumer instance. OrderedConsumer
// are managed by the library and provide a simple way to consume
// messages from a stream. Ordered consumers are ephemeral in-memory
// pull consumers and are resilient to deletes and restarts.
OrderedConsumer(ctx context.Context, cfg OrderedConsumerConfig) (Consumer, error)
// Consumer returns an interface to an existing consumer, allowing processing
// of messages. If consumer does not exist, ErrConsumerNotFound is
// returned.
Consumer(ctx context.Context, consumer string) (Consumer, error)
// DeleteConsumer removes a consumer with given name from a stream.
// If consumer does not exist, ErrConsumerNotFound is returned.
DeleteConsumer(ctx context.Context, consumer string) error
// ListConsumers returns ConsumerInfoLister enabling iterating over a
// channel of consumer infos.
ListConsumers(context.Context) ConsumerInfoLister
// ConsumerNames returns a ConsumerNameLister enabling iterating over a
// channel of consumer names.
ConsumerNames(context.Context) ConsumerNameLister
}
RawStreamMsg struct {
Subject string
Sequence uint64
Header nats.Header
Data []byte
Time time.Time
}
stream struct {
name string
info *StreamInfo
jetStream *jetStream
}
// StreamInfoOpt is a function setting options for [Stream.Info]
StreamInfoOpt func(*streamInfoRequest) error
streamInfoRequest struct {
apiPaged
DeletedDetails bool `json:"deleted_details,omitempty"`
SubjectFilter string `json:"subjects_filter,omitempty"`
}
consumerInfoResponse struct {
apiResponse
*ConsumerInfo
}
// StreamPurgeOpt is a function setting options for [Stream.Purge]
StreamPurgeOpt func(*StreamPurgeRequest) error
// StreamPurgeRequest is an API request body to purge a stream.
StreamPurgeRequest struct {
// Purge up to but not including sequence.
Sequence uint64 `json:"seq,omitempty"`
// Subject to match against messages for the purge command.
Subject string `json:"filter,omitempty"`
// Number of messages to keep.
Keep uint64 `json:"keep,omitempty"`
}
streamPurgeResponse struct {
apiResponse
Success bool `json:"success,omitempty"`
Purged uint64 `json:"purged"`
}
consumerDeleteResponse struct {
apiResponse
Success bool `json:"success,omitempty"`
}
// GetMsgOpt is a function setting options for [Stream.GetMsg]
GetMsgOpt func(*apiMsgGetRequest) error
apiMsgGetRequest struct {
Seq uint64 `json:"seq,omitempty"`
LastFor string `json:"last_by_subj,omitempty"`
NextFor string `json:"next_by_subj,omitempty"`
}
// apiMsgGetResponse is the response for a Stream get request.
apiMsgGetResponse struct {
apiResponse
Message *storedMsg `json:"message,omitempty"`
}
// storedMsg is a raw message stored in JetStream.
storedMsg struct {
Subject string `json:"subject"`
Sequence uint64 `json:"seq"`
Header []byte `json:"hdrs,omitempty"`
Data []byte `json:"data,omitempty"`
Time time.Time `json:"time"`
}
msgDeleteRequest struct {
Seq uint64 `json:"seq"`
NoErase bool `json:"no_erase,omitempty"`
}
msgDeleteResponse struct {
apiResponse
Success bool `json:"success,omitempty"`
}
// ConsumerInfoLister is used to iterate over a channel of consumer infos.
// Err method can be used to check for errors encountered during iteration.
// Info channel is always closed and therefore can be used in a range loop.
ConsumerInfoLister interface {
Info() <-chan *ConsumerInfo
Err() error
}
// ConsumerNameLister is used to iterate over a channel of consumer names.
// Err method can be used to check for errors encountered during iteration.
// Name channel is always closed and therefore can be used in a range loop.
ConsumerNameLister interface {
Name() <-chan string
Err() error
}
consumerLister struct {
js *jetStream
offset int
pageInfo *apiPaged
consumers chan *ConsumerInfo
names chan string
err error
}
consumerListResponse struct {
apiResponse
apiPaged
Consumers []*ConsumerInfo `json:"consumers"`
}
consumerNamesResponse struct {
apiResponse
apiPaged
Consumers []string `json:"consumers"`
}
)
// CreateOrUpdateConsumer creates a consumer on a given stream with
// given config. If consumer already exists, it will be updated (if
// possible). Consumer interface is returned, allowing to operate on a
// consumer (e.g. fetch messages).
func (s *stream) CreateOrUpdateConsumer(ctx context.Context, cfg ConsumerConfig) (Consumer, error) {
return upsertConsumer(ctx, s.jetStream, s.name, cfg, consumerActionCreateOrUpdate)
}
// CreateConsumer creates a consumer on a given stream with given
// config. If consumer already exists and the provided configuration
// differs from its configuration, ErrConsumerExists is returned. If the
// provided configuration is the same as the existing consumer, the
// existing consumer is returned. Consumer interface is returned,
// allowing to operate on a consumer (e.g. fetch messages).
func (s *stream) CreateConsumer(ctx context.Context, cfg ConsumerConfig) (Consumer, error) {
return upsertConsumer(ctx, s.jetStream, s.name, cfg, consumerActionCreate)
}
// UpdateConsumer updates an existing consumer. If consumer does not
// exist, ErrConsumerDoesNotExist is returned. Consumer interface is
// returned, allowing to operate on a consumer (e.g. fetch messages).
func (s *stream) UpdateConsumer(ctx context.Context, cfg ConsumerConfig) (Consumer, error) {
return upsertConsumer(ctx, s.jetStream, s.name, cfg, consumerActionUpdate)
}
// OrderedConsumer returns an OrderedConsumer instance. OrderedConsumer
// are managed by the library and provide a simple way to consume
// messages from a stream. Ordered consumers are ephemeral in-memory
// pull consumers and are resilient to deletes and restarts.
func (s *stream) OrderedConsumer(ctx context.Context, cfg OrderedConsumerConfig) (Consumer, error) {
oc := &orderedConsumer{
jetStream: s.jetStream,
cfg: &cfg,
stream: s.name,
namePrefix: nuid.Next(),
doReset: make(chan struct{}, 1),
}
if cfg.OptStartSeq != 0 {
oc.cursor.streamSeq = cfg.OptStartSeq - 1
}
err := oc.reset()
if err != nil {
return nil, err
}
return oc, nil
}
// Consumer returns an interface to an existing consumer, allowing processing
// of messages. If consumer does not exist, ErrConsumerNotFound is
// returned.
func (s *stream) Consumer(ctx context.Context, name string) (Consumer, error) {
return getConsumer(ctx, s.jetStream, s.name, name)
}
// DeleteConsumer removes a consumer with given name from a stream.
// If consumer does not exist, ErrConsumerNotFound is returned.
func (s *stream) DeleteConsumer(ctx context.Context, name string) error {
return deleteConsumer(ctx, s.jetStream, s.name, name)
}
// Info returns StreamInfo from the server.
func (s *stream) Info(ctx context.Context, opts ...StreamInfoOpt) (*StreamInfo, error) {
ctx, cancel := wrapContextWithoutDeadline(ctx)
if cancel != nil {
defer cancel()
}
var infoReq *streamInfoRequest
for _, opt := range opts {
if infoReq == nil {
infoReq = &streamInfoRequest{}
}
if err := opt(infoReq); err != nil {
return nil, err
}
}
var req []byte
var err error
var subjectMap map[string]uint64
var offset int
infoSubject := apiSubj(s.jetStream.apiPrefix, fmt.Sprintf(apiStreamInfoT, s.name))
var info *StreamInfo
for {
if infoReq != nil {
if infoReq.SubjectFilter != "" {
if subjectMap == nil {
subjectMap = make(map[string]uint64)
}
infoReq.Offset = offset
}
req, err = json.Marshal(infoReq)
if err != nil {
return nil, err
}
}
var resp streamInfoResponse
if _, err = s.jetStream.apiRequestJSON(ctx, infoSubject, &resp, req); err != nil {
return nil, err
}
if resp.Error != nil {
if resp.Error.ErrorCode == JSErrCodeStreamNotFound {
return nil, ErrStreamNotFound
}
return nil, resp.Error
}
info = resp.StreamInfo
var total int
if resp.Total != 0 {
total = resp.Total
}
if len(resp.StreamInfo.State.Subjects) > 0 {
for subj, msgs := range resp.StreamInfo.State.Subjects {
subjectMap[subj] = msgs
}
offset = len(subjectMap)
}
if total == 0 || total <= offset {
info.State.Subjects = nil
// we don't want to store subjects in cache
cached := *info
s.info = &cached
info.State.Subjects = subjectMap
break
}
}
return info, nil
}
// CachedInfo returns ConsumerInfo currently cached on this stream.
// This method does not perform any network requests. The cached
// StreamInfo is updated on every call to Info and Update.
func (s *stream) CachedInfo() *StreamInfo {
return s.info
}
// Purge removes messages from a stream. It is a destructive operation.
// Use with caution. See StreamPurgeOpt for available options.
func (s *stream) Purge(ctx context.Context, opts ...StreamPurgeOpt) error {
ctx, cancel := wrapContextWithoutDeadline(ctx)
if cancel != nil {
defer cancel()
}
var purgeReq StreamPurgeRequest
for _, opt := range opts {
if err := opt(&purgeReq); err != nil {
return err
}
}
var req []byte
var err error
req, err = json.Marshal(purgeReq)
if err != nil {
return err
}
purgeSubject := apiSubj(s.jetStream.apiPrefix, fmt.Sprintf(apiStreamPurgeT, s.name))
var resp streamPurgeResponse
if _, err = s.jetStream.apiRequestJSON(ctx, purgeSubject, &resp, req); err != nil {
return err
}
if resp.Error != nil {
return resp.Error
}
return nil
}
// GetMsg retrieves a raw stream message stored in JetStream by sequence number.
func (s *stream) GetMsg(ctx context.Context, seq uint64, opts ...GetMsgOpt) (*RawStreamMsg, error) {
req := &apiMsgGetRequest{Seq: seq}
for _, opt := range opts {
if err := opt(req); err != nil {
return nil, err
}
}
return s.getMsg(ctx, req)
}
// GetLastMsgForSubject retrieves the last raw stream message stored in
// JetStream on a given subject subject.
func (s *stream) GetLastMsgForSubject(ctx context.Context, subject string) (*RawStreamMsg, error) {
return s.getMsg(ctx, &apiMsgGetRequest{LastFor: subject})
}
func (s *stream) getMsg(ctx context.Context, mreq *apiMsgGetRequest) (*RawStreamMsg, error) {
ctx, cancel := wrapContextWithoutDeadline(ctx)
if cancel != nil {
defer cancel()
}
req, err := json.Marshal(mreq)
if err != nil {
return nil, err
}
var gmSubj string
// handle direct gets
if s.info.Config.AllowDirect {
if mreq.LastFor != "" {
gmSubj = apiSubj(s.jetStream.apiPrefix, fmt.Sprintf(apiDirectMsgGetLastBySubjectT, s.name, mreq.LastFor))
r, err := s.jetStream.apiRequest(ctx, gmSubj, nil)
if err != nil {
return nil, err
}
return convertDirectGetMsgResponseToMsg(s.name, r.msg)
}
gmSubj = apiSubj(s.jetStream.apiPrefix, fmt.Sprintf(apiDirectMsgGetT, s.name))
r, err := s.jetStream.apiRequest(ctx, gmSubj, req)
if err != nil {
return nil, err
}
return convertDirectGetMsgResponseToMsg(s.name, r.msg)
}
var resp apiMsgGetResponse
dsSubj := apiSubj(s.jetStream.apiPrefix, fmt.Sprintf(apiMsgGetT, s.name))
_, err = s.jetStream.apiRequestJSON(ctx, dsSubj, &resp, req)
if err != nil {
return nil, err
}
if resp.Error != nil {
if resp.Error.ErrorCode == JSErrCodeMessageNotFound {
return nil, ErrMsgNotFound
}
return nil, resp.Error
}
msg := resp.Message
var hdr nats.Header
if len(msg.Header) > 0 {
hdr, err = nats.DecodeHeadersMsg(msg.Header)
if err != nil {
return nil, err
}
}
return &RawStreamMsg{
Subject: msg.Subject,
Sequence: msg.Sequence,
Header: hdr,
Data: msg.Data,
Time: msg.Time,
}, nil
}
func convertDirectGetMsgResponseToMsg(name string, r *nats.Msg) (*RawStreamMsg, error) {
// Check for 404/408. We would get a no-payload message and a "Status" header
if len(r.Data) == 0 {
val := r.Header.Get(statusHdr)
if val != "" {
switch val {
case noMessages:
return nil, ErrMsgNotFound
default:
desc := r.Header.Get("Description")
if desc == "" {
desc = "unable to get message"
}
return nil, fmt.Errorf("nats: %s", desc)
}
}
}
// Check for headers that give us the required information to
// reconstruct the message.
if len(r.Header) == 0 {
return nil, fmt.Errorf("nats: response should have headers")
}
stream := r.Header.Get(StreamHeader)
if stream == "" {
return nil, fmt.Errorf("nats: missing stream header")
}
seqStr := r.Header.Get(SequenceHeader)
if seqStr == "" {
return nil, fmt.Errorf("nats: missing sequence header")
}
seq, err := strconv.ParseUint(seqStr, 10, 64)
if err != nil {
return nil, fmt.Errorf("nats: invalid sequence header '%s': %v", seqStr, err)
}
timeStr := r.Header.Get(TimeStampHeaer)
if timeStr == "" {
return nil, fmt.Errorf("nats: missing timestamp header")
}
tm, err := time.Parse(time.RFC3339Nano, timeStr)
if err != nil {
return nil, fmt.Errorf("nats: invalid timestamp header '%s': %v", timeStr, err)
}
subj := r.Header.Get(SubjectHeader)
if subj == "" {
return nil, fmt.Errorf("nats: missing subject header")
}
return &RawStreamMsg{
Subject: subj,
Sequence: seq,
Header: r.Header,
Data: r.Data,
Time: tm,
}, nil
}
// DeleteMsg deletes a message from a stream.
// On the server, the message is marked as erased, but not overwritten.
func (s *stream) DeleteMsg(ctx context.Context, seq uint64) error {
return s.deleteMsg(ctx, &msgDeleteRequest{Seq: seq, NoErase: true})
}
// SecureDeleteMsg deletes a message from a stream. The deleted message
// is overwritten with random data. As a result, this operation is slower
// than DeleteMsg.
func (s *stream) SecureDeleteMsg(ctx context.Context, seq uint64) error {
return s.deleteMsg(ctx, &msgDeleteRequest{Seq: seq})
}
func (s *stream) deleteMsg(ctx context.Context, req *msgDeleteRequest) error {
ctx, cancel := wrapContextWithoutDeadline(ctx)
if cancel != nil {
defer cancel()
}
r, err := json.Marshal(req)
if err != nil {
return err
}
subj := apiSubj(s.jetStream.apiPrefix, fmt.Sprintf(apiMsgDeleteT, s.name))
var resp msgDeleteResponse
if _, err = s.jetStream.apiRequestJSON(ctx, subj, &resp, r); err != nil {
return err
}
if !resp.Success {
return fmt.Errorf("%w: %s", ErrMsgDeleteUnsuccessful, err)
}
return nil
}
// ListConsumers returns ConsumerInfoLister enabling iterating over a
// channel of consumer infos.
func (s *stream) ListConsumers(ctx context.Context) ConsumerInfoLister {
l := &consumerLister{
js: s.jetStream,
consumers: make(chan *ConsumerInfo),
}
go func() {
defer close(l.consumers)
ctx, cancel := wrapContextWithoutDeadline(ctx)
if cancel != nil {
defer cancel()
}
for {
page, err := l.consumerInfos(ctx, s.name)
if err != nil && !errors.Is(err, ErrEndOfData) {
l.err = err
return
}
for _, info := range page {
select {
case <-ctx.Done():
l.err = ctx.Err()
return
default:
}
if info != nil {
l.consumers <- info
}
}
if errors.Is(err, ErrEndOfData) {
return
}
}
}()
return l
}
func (s *consumerLister) Info() <-chan *ConsumerInfo {
return s.consumers
}
func (s *consumerLister) Err() error {
return s.err
}
// ConsumerNames returns a ConsumerNameLister enabling iterating over a
// channel of consumer names.
func (s *stream) ConsumerNames(ctx context.Context) ConsumerNameLister {
l := &consumerLister{
js: s.jetStream,
names: make(chan string),
}
go func() {
defer close(l.names)
ctx, cancel := wrapContextWithoutDeadline(ctx)
if cancel != nil {
defer cancel()
}
for {
page, err := l.consumerNames(ctx, s.name)
if err != nil && !errors.Is(err, ErrEndOfData) {
l.err = err
return
}
for _, info := range page {
select {
case l.names <- info:
case <-ctx.Done():
l.err = ctx.Err()
return
}
}
if errors.Is(err, ErrEndOfData) {
return
}
}
}()
return l
}
func (s *consumerLister) Name() <-chan string {
return s.names
}
// consumerInfos fetches the next ConsumerInfo page
func (s *consumerLister) consumerInfos(ctx context.Context, stream string) ([]*ConsumerInfo, error) {
if s.pageInfo != nil && s.offset >= s.pageInfo.Total {
return nil, ErrEndOfData
}
req, err := json.Marshal(
apiPagedRequest{Offset: s.offset},
)
if err != nil {
return nil, err
}
slSubj := apiSubj(s.js.apiPrefix, fmt.Sprintf(apiConsumerListT, stream))
var resp consumerListResponse
_, err = s.js.apiRequestJSON(ctx, slSubj, &resp, req)
if err != nil {
return nil, err
}
if resp.Error != nil {
return nil, resp.Error
}
s.pageInfo = &resp.apiPaged
s.offset += len(resp.Consumers)
return resp.Consumers, nil
}
// consumerNames fetches the next consumer names page
func (s *consumerLister) consumerNames(ctx context.Context, stream string) ([]string, error) {
if s.pageInfo != nil && s.offset >= s.pageInfo.Total {
return nil, ErrEndOfData
}
req, err := json.Marshal(
apiPagedRequest{Offset: s.offset},
)
if err != nil {
return nil, err
}
slSubj := apiSubj(s.js.apiPrefix, fmt.Sprintf(apiConsumerNamesT, stream))
var resp consumerNamesResponse
_, err = s.js.apiRequestJSON(ctx, slSubj, &resp, req)
if err != nil {
return nil, err
}
if resp.Error != nil {
return nil, resp.Error
}
s.pageInfo = &resp.apiPaged
s.offset += len(resp.Consumers)
return resp.Consumers, nil
}