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nats.go
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nats.go
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// Copyright 2019 The Go Cloud Development Kit 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
//
// https://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.
//
// natspubsub exposes the following types for use:
// - Connection: *nats.Conn
// - Subscription: *nats.Subscription
// - Message.BeforeSend: *nats.Msg for v2.
// - Message.AfterSend: None.
// - Message: *nats.Msg
//
// This implementation does not support nats version 1.0, actually from nats v2.2 onwards only.
//
//
package natspubsub
import (
"context"
"errors"
"fmt"
"github.com/nats-io/nats.go"
"github.com/nats-io/nats.go/jetstream"
"github.com/pitabwire/natspubsub/connections"
"net/url"
"regexp"
"slices"
"strconv"
"strings"
"sync"
"gocloud.dev/gcerrors"
"gocloud.dev/pubsub"
"gocloud.dev/pubsub/batcher"
"gocloud.dev/pubsub/driver"
)
var allowedParameters = []string{"subject", "stream_name", "stream_description", "stream_subjects",
"consumer_max_count", "consumer_request_batch", "consumer_request_max_batch_bytes", "consumer_durable",
"jetstream", "consumer_request_timeout_ms", "consumer_max_request_expires_ms", "consumer_max_waiting", "consumer_ack_wait_timeout_ms",
"consumer_max_ack_pending"}
var errInvalidUrl = errors.New("natspubsub: invalid connection url")
var errNotSubjectInitialized = errors.New("natspubsub: subject not initialized")
var errDuplicateParameter = errors.New("natspubsub: avoid specifying parameters more than once")
var errNotSupportedParameter = fmt.Errorf("natspubsub: invalid parameter used, "+
"only the parameters [ %s ] are supported and can be used",
strings.Join(allowedParameters, ", "))
func init() {
o := new(defaultDialer)
pubsub.DefaultURLMux().RegisterTopic(Scheme, o)
pubsub.DefaultURLMux().RegisterSubscription(Scheme, o)
}
// defaultDialer dials a NATS server based on the provided url
// see: https://docs.nats.io/using-nats/developer/connecting
// Guidance :
// - This dialer will only use the url formart nats://...
// - The dialer stores a map of unique nats connections without the parameters
type defaultDialer struct {
mutex sync.Mutex
openerMap sync.Map
}
// defaultConn
func (o *defaultDialer) defaultConn(_ context.Context, serverUrl *url.URL) (*URLOpener, error) {
o.mutex.Lock()
defer o.mutex.Unlock()
connectionUrl := strings.Replace(serverUrl.String(), serverUrl.RequestURI(), "", 1)
for param, values := range serverUrl.Query() {
paramName := strings.ToLower(param)
if !slices.Contains(allowedParameters, paramName) {
return nil, errNotSupportedParameter
}
if len(values) != 1 {
return nil, errDuplicateParameter
}
}
storedOpener, ok := o.openerMap.Load(connectionUrl)
if ok {
return storedOpener.(*URLOpener), nil
}
conn, err := o.createConnection(connectionUrl, serverUrl.Query().Has("jetstream"))
if err != nil {
return nil, err
}
opener := &URLOpener{
Connection: conn,
TopicOptions: connections.TopicOptions{},
SubscriptionOptions: connections.SubscriptionOptions{},
}
o.openerMap.Store(connectionUrl, opener)
return opener, nil
}
func (o *defaultDialer) createConnection(connectionUrl string, isJetstream bool) (connections.Connection, error) {
natsConn, err := nats.Connect(connectionUrl)
if err != nil {
return nil, fmt.Errorf("natspubsub: failed to dial server using %q: %v", connectionUrl, err)
}
sv, err := parseServerVersion(natsConn.ConnectedServerVersion())
if err != nil {
return nil, fmt.Errorf("failed to parse NATS server version %q: %v", natsConn.ConnectedServerVersion(), err)
}
// Check if the server version is at least 2.2.0.
if sv.major < 2 && sv.minor < 2 {
return nil, fmt.Errorf("natspubsub: NATS server version %q is not supported", natsConn.ConnectedServerVersion())
}
var conn connections.Connection
if isJetstream {
js, err := jetstream.New(natsConn)
if err != nil {
return nil, fmt.Errorf("natspubsub: failed to convert server to jetstream : %v", err)
}
conn = connections.NewJetstream(js)
} else {
conn = connections.NewPlain(natsConn)
}
return conn, nil
}
func (o *defaultDialer) OpenTopicURL(ctx context.Context, u *url.URL) (*pubsub.Topic, error) {
opener, err := o.defaultConn(ctx, u)
if err != nil {
return nil, fmt.Errorf("open topic %v: failed to open default connection: %v", u, err)
}
return opener.OpenTopicURL(ctx, u)
}
func (o *defaultDialer) OpenSubscriptionURL(ctx context.Context, u *url.URL) (*pubsub.Subscription, error) {
opener, err := o.defaultConn(ctx, u)
if err != nil {
return nil, fmt.Errorf("open subscription %v: failed to open default connection: %v", u, err)
}
return opener.OpenSubscriptionURL(ctx, u)
}
var semVerRegexp = regexp.MustCompile(`\Av?([0-9]+)\.?([0-9]+)?\.?([0-9]+)?`)
func parseServerVersion(version string) (serverVersion, error) {
m := semVerRegexp.FindStringSubmatch(version)
if m == nil {
return serverVersion{}, errors.New("failed to parse server version")
}
var (
major, minor, patch int
err error
)
major, err = strconv.Atoi(m[1])
if err != nil {
return serverVersion{}, fmt.Errorf("failed to parse server version major number %q: %v", m[1], err)
}
minor, err = strconv.Atoi(m[2])
if err != nil {
return serverVersion{}, fmt.Errorf("failed to parse server version minor number %q: %v", m[2], err)
}
patch, err = strconv.Atoi(m[3])
if err != nil {
return serverVersion{}, fmt.Errorf("failed to parse server version patch number %q: %v", m[3], err)
}
return serverVersion{major: major, minor: minor, patch: patch}, nil
}
type serverVersion struct {
major, minor, patch int
}
// Scheme is the URL scheme natspubsub registers its URLOpeners under on pubsub.DefaultMux.
const Scheme = "nats"
// URLOpener opens NATS URLs like "nats://mysubject".
//
// The URL host+path is used as the subject.
//
// No query parameters are supported.
type URLOpener struct {
Connection connections.Connection
// TopicOptions specifies the options to pass to OpenTopic.
TopicOptions connections.TopicOptions
// SubscriptionOptions specifies the options to pass to OpenSubscription.
SubscriptionOptions connections.SubscriptionOptions
}
func cleanSubjectFromUrl(u *url.URL) (string, error) {
subject := u.Query().Get("subject")
// Clean the leading slash from the path
pathPart := strings.TrimPrefix(u.Path, "/")
if pathPart != "" {
if subject == "" {
subject = pathPart
} else {
subject += "." + pathPart
}
}
if subject == "" {
return "", errNotSubjectInitialized
}
return subject, nil
}
// OpenTopicURL opens a pubsub.Topic based on a url supplied.
//
// A topic can be specified in the subject and suffixed by the url path
// These definitions will yield the subject shown infront of them
//
// - nats://host:8934?subject=foo --> foo
// - nats://host:8934/bar?subject=foo --> foo/bar
// - nats://host:8934/bar --> /bar
// - nats://host:8934?no_subject=foo --> [this yields an error]
func (o *URLOpener) OpenTopicURL(ctx context.Context, u *url.URL) (*pubsub.Topic, error) {
opts := &o.TopicOptions
var err error
opts.Subject, err = cleanSubjectFromUrl(u)
if err != nil {
return nil, err
}
return OpenTopic(ctx, o.Connection, opts)
}
// OpenSubscriptionURL opens a pubsub.Subscription based on url supplied.
//
// A subscription also creates the required underlaying queue or streams
// There are many more parameters checked in this case compared to the publish topic section.
// If required, the list of parameters can be extended, but for now only a subset is defined and
// the remaining ones utilize the sensible defaults that nats come with.
//
// The list of parameters includes:
//
// - subject,
// - stream_name,
// - stream_description,
// - stream_subjects,
// - consumer_max_count,
// - consumer_queue
// - consumer_max_waiting
func (o *URLOpener) OpenSubscriptionURL(ctx context.Context, u *url.URL) (*pubsub.Subscription, error) {
opts := &o.SubscriptionOptions
subject, err := cleanSubjectFromUrl(u)
if err != nil {
return nil, err
}
opts.Subjects = []string{subject}
opts.Durable = u.Query().Get("consumer_durable")
opts.ConsumersMaxCount, err = strconv.Atoi(u.Query().Get("consumer_max_count"))
if err != nil {
opts.ConsumersMaxCount = 10
}
opts.ConsumerRequestBatch, err = strconv.Atoi(u.Query().Get("consumer_request_batch"))
if err != nil {
opts.ConsumerRequestBatch = 50
}
opts.ConsumerRequestMaxBatchBytes, err = strconv.Atoi(u.Query().Get("consumer_request_max_batch_bytes"))
if err != nil {
opts.ConsumerRequestMaxBatchBytes = 0
}
opts.ConsumerRequestTimeoutMs, err = strconv.Atoi(u.Query().Get("consumer_request_timeout_ms"))
if err != nil {
opts.ConsumerRequestTimeoutMs = 1000
}
opts.ConsumerMaxRequestExpiresMs, err = strconv.Atoi(u.Query().Get("consumer_max_request_expires_ms"))
if err != nil {
opts.ConsumerMaxRequestExpiresMs = 30000
}
opts.ConsumerMaxWaiting, err = strconv.Atoi(u.Query().Get("consumer_max_waiting"))
if err != nil {
opts.ConsumerMaxWaiting = 100
}
opts.ConsumerAckWaitTimeoutMs, err = strconv.Atoi(u.Query().Get("consumer_ack_wait_timeout_ms"))
if err != nil {
opts.ConsumerAckWaitTimeoutMs = 300000
}
opts.ConsumerMaxAckPending, err = strconv.Atoi(u.Query().Get("consumer_max_ack_pending"))
if err != nil {
opts.ConsumerMaxAckPending = 100
}
opts.StreamName = u.Query().Get("stream_name")
opts.StreamDescription = u.Query().Get("stream_description")
streamSubject := u.Query().Get("stream_subject")
if streamSubject != "" {
opts.Subjects = append(opts.Subjects, strings.Split(streamSubject, ",")...)
}
return OpenSubscription(ctx, o.Connection, opts)
}
type topic struct {
iTopic connections.Topic
}
// OpenTopic returns a *pubsub.Topic for use with NATS at least version 2.2.0.
// This changes the encoding of the message as, starting with version 2.2.0, NATS supports message headers.
// In previous versions the message headers were encoded along with the message content using gob.Encoder,
// which limits the subscribers only to Go clients.
// This implementation uses native NATS message headers, and native message content, which provides full support
// for non-Go clients.
func OpenTopic(ctx context.Context, conn connections.Connection, opts *connections.TopicOptions) (*pubsub.Topic, error) {
dt, err := openTopic(ctx, conn, opts)
if err != nil {
return nil, err
}
return pubsub.NewTopic(dt, nil), nil
}
// openTopic returns the driver for OpenTopic. This function exists so the test
// harness can get the driver interface implementation if it needs to.
func openTopic(ctx context.Context, conn connections.Connection, opts *connections.TopicOptions) (driver.Topic, error) {
if conn == nil {
return nil, errInvalidUrl
}
itopic, err := conn.CreateTopic(ctx, opts)
if err != nil {
return nil, err
}
return &topic{iTopic: itopic}, nil
}
// SendBatch implements driver.Connection.SendBatch.
func (t *topic) SendBatch(ctx context.Context, msgs []*driver.Message) error {
if t == nil || t.iTopic == nil {
return errNotSubjectInitialized
}
for _, m := range msgs {
err := ctx.Err()
if err != nil {
return err
}
err = t.sendMessage(ctx, m)
if err != nil {
return err
}
}
return nil
}
func (t *topic) sendMessage(ctx context.Context, m *driver.Message) error {
msg := encodeMessage(m, t.iTopic.Subject())
if m.BeforeSend != nil {
asFunc := func(i interface{}) bool {
if nm, ok := i.(**nats.Msg); ok {
*nm = msg
return true
}
return false
}
if err := m.BeforeSend(asFunc); err != nil {
return err
}
}
if _, err := t.iTopic.PublishMessage(ctx, msg); err != nil {
return err
}
if m.AfterSend != nil {
asFunc := func(i interface{}) bool { return false }
if err := m.AfterSend(asFunc); err != nil {
return err
}
}
return nil
}
// IsRetryable implements driver.Connection.IsRetryable.
func (*topic) IsRetryable(error) bool { return false }
// As implements driver.Connection.As.
func (t *topic) As(i interface{}) bool {
c, ok := i.(*connections.Topic)
if !ok {
return false
}
*c = t.iTopic
return true
}
// ErrorAs implements driver.Connection.ErrorAs
func (*topic) ErrorAs(error, interface{}) bool {
return false
}
// ErrorCode implements driver.Connection.ErrorCode
func (*topic) ErrorCode(err error) gcerrors.ErrorCode {
switch {
case err == nil:
return gcerrors.OK
case errors.Is(err, context.Canceled):
return gcerrors.Canceled
case errors.Is(err, errNotSubjectInitialized):
return gcerrors.NotFound
case errors.Is(err, nats.ErrBadSubject):
return gcerrors.FailedPrecondition
case errors.Is(err, nats.ErrAuthorization):
return gcerrors.PermissionDenied
case errors.Is(err, nats.ErrMaxPayload), errors.Is(err, nats.ErrReconnectBufExceeded):
return gcerrors.ResourceExhausted
}
return gcerrors.Unknown
}
// Close implements driver.Connection.Close.
func (*topic) Close() error { return nil }
type subscription struct {
queue connections.Queue
}
// OpenSubscription returns a *pubsub.Subscription representing a NATS subscription
// or NATS queue subscription for use with NATS at least version 2.2.0.
// This changes the encoding of the message as, starting with version 2.2.0, NATS supports message headers.
// In previous versions the message headers were encoded along with the message content using gob.Encoder,
// which limits the subscribers only to Go clients.
// This implementation uses native NATS message headers, and native message content, which provides full support
// for non-Go clients.
func OpenSubscription(ctx context.Context, conn connections.Connection, opts *connections.SubscriptionOptions) (*pubsub.Subscription, error) {
ds, err := openSubscription(ctx, conn, opts)
if err != nil {
return nil, err
}
maxConsumerCount := opts.ConsumersMaxCount
if maxConsumerCount <= 0 {
maxConsumerCount = 1
}
maxBatchSize := opts.ConsumerRequestBatch
if maxBatchSize <= 0 {
maxBatchSize = 1
}
maxBatchBytesSize := opts.ConsumerRequestMaxBatchBytes
var recvBatcherOpts = &batcher.Options{
MaxHandlers: maxConsumerCount, // max concurrency for receives
MaxBatchSize: maxBatchSize,
MaxBatchByteSize: maxBatchBytesSize,
}
return pubsub.NewSubscription(ds, recvBatcherOpts, nil), nil
}
func openSubscription(ctx context.Context, conn connections.Connection, opts *connections.SubscriptionOptions) (driver.Subscription, error) {
if opts == nil {
return nil, errors.New("natspubsub: subscription options missing")
}
queue, err := conn.CreateSubscription(ctx, opts)
if err != nil {
return nil, err
}
return &subscription{queue: queue}, nil
}
// ReceiveBatch implements driver.ReceiveBatch.
func (s *subscription) ReceiveBatch(ctx context.Context, batchCount int) ([]*driver.Message, error) {
if s == nil || s.queue == nil {
return nil, nats.ErrBadSubscription
}
return s.queue.ReceiveMessages(ctx, batchCount)
}
// SendAcks implements driver.Subscription.SendAcks.
func (s *subscription) SendAcks(ctx context.Context, ids []driver.AckID) error {
// Ack is a no-op.
return s.queue.Ack(ctx, ids)
}
// CanNack implements driver.CanNack.
func (s *subscription) CanNack() bool { return s != nil && s.queue != nil && s.queue.IsQueueGroup() }
// SendNacks implements driver.Subscription.SendNacks
func (s *subscription) SendNacks(ctx context.Context, ids []driver.AckID) error {
return s.queue.Nack(ctx, ids)
}
// IsRetryable implements driver.Subscription.IsRetryable.
func (s *subscription) IsRetryable(error) bool { return false }
// As implements driver.Subscription.As.
func (s *subscription) As(i interface{}) bool {
if p, ok := i.(*connections.Queue); ok {
*p = s.queue
return true
}
return false
}
// ErrorAs implements driver.Subscription.ErrorAs
func (*subscription) ErrorAs(error, interface{}) bool {
return false
}
// ErrorCode implements driver.Subscription.ErrorCode
func (*subscription) ErrorCode(err error) gcerrors.ErrorCode {
switch {
case err == nil:
return gcerrors.OK
case errors.Is(err, context.Canceled):
return gcerrors.Canceled
case errors.Is(err, errNotSubjectInitialized), errors.Is(err, nats.ErrBadSubscription):
return gcerrors.NotFound
case errors.Is(err, nats.ErrBadSubject), errors.Is(err, nats.ErrTypeSubscription):
return gcerrors.FailedPrecondition
case errors.Is(err, nats.ErrAuthorization):
return gcerrors.PermissionDenied
case errors.Is(err, nats.ErrMaxMessages), errors.Is(err, nats.ErrSlowConsumer):
return gcerrors.ResourceExhausted
case errors.Is(err, nats.ErrTimeout):
return gcerrors.DeadlineExceeded
}
return gcerrors.Unknown
}
// Close implements driver.Subscription.Close.
func (*subscription) Close() error { return nil }
func encodeMessage(dm *driver.Message, sub string) *nats.Msg {
var header nats.Header
if dm.Metadata != nil {
header = nats.Header{}
for k, v := range dm.Metadata {
header[url.QueryEscape(k)] = []string{url.QueryEscape(v)}
}
}
return &nats.Msg{
Subject: sub,
Data: dm.Body,
Header: header,
}
}