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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,2 +1,2 @@ | ||
| // Package nats implements the NATS Streaming connector. | ||
| // Package nats provides NATS streaming connectors. | ||
| package nats |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,173 @@ | ||
| package nats | ||
|
|
||
| import ( | ||
| "context" | ||
| "log" | ||
|
|
||
| "github.com/nats-io/nats.go" | ||
| "github.com/reugn/go-streams" | ||
| "github.com/reugn/go-streams/flow" | ||
| ) | ||
|
|
||
| var ( | ||
| PullMaxWaiting = 128 | ||
| FetchBatchSize = 16 | ||
| ) | ||
|
|
||
| // JetStreamSource represents a NATS JetStream source connector. | ||
| // Uses a pull-based consumer. | ||
| type JetStreamSource struct { | ||
| conn *nats.Conn | ||
| jetStreamContext nats.JetStreamContext | ||
| subscription *nats.Subscription | ||
| out chan interface{} | ||
| ctx context.Context | ||
| } | ||
|
|
||
| // NewNatsSink returns a new JetStreamSource instance. | ||
| func NewJetStreamSource(ctx context.Context, subjectName, url string) (*JetStreamSource, error) { | ||
| nc, err := nats.Connect(url) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| // create JetStreamContext | ||
| js, err := nc.JetStream() | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| // create pull based consumer | ||
| sub, err := js.PullSubscribe(subjectName, "JetStreamSource", nats.PullMaxWaiting(PullMaxWaiting)) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| jetStreamSource := &JetStreamSource{ | ||
| conn: nc, | ||
| jetStreamContext: js, | ||
| subscription: sub, | ||
| out: make(chan interface{}), | ||
| ctx: ctx, | ||
| } | ||
|
|
||
| go jetStreamSource.init() | ||
| return jetStreamSource, nil | ||
| } | ||
|
|
||
| func (js *JetStreamSource) init() { | ||
| loop: | ||
| for { | ||
| select { | ||
| case <-js.ctx.Done(): | ||
| break loop | ||
| default: | ||
| } | ||
|
|
||
| messages, err := js.subscription.Fetch(FetchBatchSize, nats.Context(js.ctx)) | ||
| if err != nil { | ||
| log.Printf("JetStreamSource fetch error: %s", err) | ||
| break loop | ||
| } | ||
| for _, msg := range messages { | ||
| if err := msg.Ack(); err != nil { | ||
| log.Printf("Failed to Ack JetStream message: %s", err) | ||
| } | ||
| js.out <- msg | ||
| } | ||
| } | ||
|
|
||
| log.Printf("Closing JetStream consumer") | ||
| if err := js.subscription.Drain(); err != nil { | ||
| log.Printf("Failed to Drain JetStream subscription: %s", err) | ||
| } | ||
| close(js.out) | ||
| } | ||
|
|
||
| // Via streams data through the given flow | ||
| func (js *JetStreamSource) Via(_flow streams.Flow) streams.Flow { | ||
| flow.DoStream(js, _flow) | ||
| return _flow | ||
| } | ||
|
|
||
| // Out returns an output channel for sending data | ||
| func (js *JetStreamSource) Out() <-chan interface{} { | ||
| return js.out | ||
| } | ||
|
|
||
| // JetStreamSink represents a NATS JetStream sink connector. | ||
| type JetStreamSink struct { | ||
| conn *nats.Conn | ||
| jetStreamContext nats.JetStreamContext | ||
| subjectName string | ||
| in chan interface{} | ||
| } | ||
|
|
||
| // NewNatsSink returns a new JetStreamSource instance. | ||
| func NewJetStreamSink(streamName, subjectName, url string) (*JetStreamSink, error) { | ||
| nc, err := nats.Connect(url) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| // create JetStreamContext | ||
| js, err := nc.JetStream() | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| // check if the given stream already exists; if not, create it. | ||
| stream, _ := js.StreamInfo(streamName) | ||
| if stream == nil { | ||
| log.Printf("Creating JetStream %s with subject %s", streamName, subjectName) | ||
| _, err = js.AddStream(&nats.StreamConfig{ | ||
| Name: streamName, | ||
| Subjects: []string{subjectName}, | ||
| }) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| } else { | ||
| log.Printf("JetStream %s exists", streamName) | ||
| } | ||
|
|
||
| jetStreamSink := &JetStreamSink{ | ||
| conn: nc, | ||
| jetStreamContext: js, | ||
| subjectName: subjectName, | ||
| in: make(chan interface{}), | ||
| } | ||
|
|
||
| go jetStreamSink.init() | ||
| return jetStreamSink, nil | ||
| } | ||
|
|
||
| func (js *JetStreamSink) init() { | ||
| for msg := range js.in { | ||
| var err error | ||
| switch m := msg.(type) { | ||
| case *nats.Msg: | ||
| _, err = js.jetStreamContext.Publish(js.subjectName, m.Data) | ||
|
|
||
| case []byte: | ||
| _, err = js.jetStreamContext.Publish(js.subjectName, m) | ||
|
|
||
| default: | ||
| log.Printf("Unsupported message type %v", m) | ||
| } | ||
|
|
||
| if err != nil { | ||
| log.Printf("Error processing JetStream message: %s", err) | ||
| } | ||
| } | ||
|
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| log.Printf("Closing JetStream producer") | ||
| if err := js.conn.Drain(); err != nil { | ||
| log.Printf("Failed to Drain JetStream connection: %s", err) | ||
| } | ||
| } | ||
|
|
||
| // In returns an input channel for receiving data | ||
| func (js *JetStreamSink) In() chan<- interface{} { | ||
| return js.in | ||
| } |
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