Add ordered consumer, FetchBytes and Next, rework options

Signed-off-by: Piotr Piotrowski <piotr@synadia.com>

examples/jsv2/js-ordered-messages/main.go

@@ -0,0 +1,82 @@
+// Copyright 2020-2023 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 main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"time"
+
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+)
+
+func main() {
+	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Minute)
+	defer cancel()
+
+	nc, err := nats.Connect("nats://127.0.0.1:4222")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	js, err := jetstream.New(nc)
+	if err != nil {
+		log.Fatal(err)
+	}
+	s, err := js.CreateStream(ctx, jetstream.StreamConfig{
+		Name:     "TEST_STREAM",
+		Subjects: []string{"FOO.*"},
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	cons, err := s.OrderedConsumer(ctx, jetstream.OrderedConsumerConfig{
+		MaxResetAttempts: 5,
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+	go endlessPublish(ctx, nc, js)
+
+	it, err := cons.Messages()
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer it.Stop()
+	for {
+		msg, err := it.Next()
+		if err != nil {
+			fmt.Println(err)
+		}
+		fmt.Println(string(msg.Data()))
+		msg.Ack()
+	}
+}
+
+func endlessPublish(ctx context.Context, nc *nats.Conn, js jetstream.JetStream) {
+	var i int
+	for {
+		time.Sleep(500 * time.Millisecond)
+		if nc.Status() != nats.CONNECTED {
+			continue
+		}
+		if _, err := js.Publish(ctx, "FOO.TEST1", []byte(fmt.Sprintf("msg %d", i))); err != nil {
+			fmt.Println("pub error: ", err)
+		}
+		i++
+	}
+}