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main.go
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main.go
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// Copyright 2019-2020 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 (
"flag"
"log"
"github.com/nats-io/nats.go"
"github.com/nats-io/not.go"
"github.com/opentracing/opentracing-go"
"github.com/opentracing/opentracing-go/ext"
)
func usage() {
log.Fatalf("Usage: publish [-s server] [-creds file] <subject> <msg>")
}
func main() {
var urls = flag.String("s", nats.DefaultURL, "The nats server URLs (separated by comma)")
var userCreds = flag.String("creds", "", "User Credentials File")
log.SetFlags(0)
flag.Usage = usage
flag.Parse()
args := flag.Args()
if len(args) != 2 {
usage()
}
tracer, closer := not.InitTracing("NATS Publisher")
opentracing.SetGlobalTracer(tracer)
defer closer.Close()
// Connect Options.
opts := []nats.Option{nats.Name("NATS Sample Tracing Publisher")}
// Use UserCredentials.
if *userCreds != "" {
opts = append(opts, nats.UserCredentials(*userCreds))
}
// Connect to NATS.
nc, err := nats.Connect(*urls, opts...)
if err != nil {
log.Fatal(err)
}
defer nc.Close()
subj, msg := args[0], []byte(args[1])
// A NATS OpenTracing Message.
var t not.TraceMsg
// Setup a span for the operation to publish a message.
pubSpan := tracer.StartSpan("Published Message", ext.SpanKindProducer)
ext.MessageBusDestination.Set(pubSpan, subj)
defer pubSpan.Finish()
// Inject span context into our traceMsg.
if err := tracer.Inject(pubSpan.Context(), opentracing.Binary, &t); err != nil {
log.Fatalf("%v for Inject.", err)
}
// Add the payload.
t.Write(msg)
// Send the message over NATS.
nc.Publish(subj, t.Bytes())
if err := nc.LastError(); err != nil {
log.Fatal(err)
} else {
log.Printf("Published [%s] : '%s'\n", subj, msg)
}
}