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// Copyright 2016-2018 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"
"fmt"
"log"
"os"
"os/signal"
"time"
"github.com/nats-io/go-nats-streaming"
"github.com/nats-io/go-nats-streaming/pb"
)
var usageStr = `
Usage: stan-sub [options] <subject>
Options:
-s, --server <url> NATS Streaming server URL(s)
-c, --cluster <cluster name> NATS Streaming cluster name
-id,--clientid <client ID> NATS Streaming client ID
Subscription Options:
--qgroup <name> Queue group
--seq <seqno> Start at seqno
--all Deliver all available messages
--last Deliver starting with last published message
--since <duration> Deliver messages in last interval (e.g. 1s, 1hr)
(for more information: https://golang.org/pkg/time/#ParseDuration)
--durable <name> Durable subscriber name
--unsubscribe Unsubscribe the durable on exit
`
// NOTE: Use tls scheme for TLS, e.g. stan-sub -s tls://demo.nats.io:4443 foo
func usage() {
log.Fatalf(usageStr)
}
func printMsg(m *stan.Msg, i int) {
log.Printf("[#%d] Received on [%s]: '%s'\n", i, m.Subject, m)
}
func main() {
var clusterID string
var clientID string
var showTime bool
var startSeq uint64
var startDelta string
var deliverAll bool
var deliverLast bool
var durable string
var qgroup string
var unsubscribe bool
var URL string
// defaultID := fmt.Sprintf("client.%s", nuid.Next())
flag.StringVar(&URL, "s", stan.DefaultNatsURL, "The nats server URLs (separated by comma)")
flag.StringVar(&URL, "server", stan.DefaultNatsURL, "The nats server URLs (separated by comma)")
flag.StringVar(&clusterID, "c", "test-cluster", "The NATS Streaming cluster ID")
flag.StringVar(&clusterID, "cluster", "test-cluster", "The NATS Streaming cluster ID")
flag.StringVar(&clientID, "id", "", "The NATS Streaming client ID to connect with")
flag.StringVar(&clientID, "clientid", "", "The NATS Streaming client ID to connect with")
flag.BoolVar(&showTime, "t", false, "Display timestamps")
// Subscription options
flag.Uint64Var(&startSeq, "seq", 0, "Start at sequence no.")
flag.BoolVar(&deliverAll, "all", false, "Deliver all")
flag.BoolVar(&deliverLast, "last", false, "Start with last value")
flag.StringVar(&startDelta, "since", "", "Deliver messages since specified time offset")
flag.StringVar(&durable, "durable", "", "Durable subscriber name")
flag.StringVar(&qgroup, "qgroup", "", "Queue group name")
flag.BoolVar(&unsubscribe, "unsubscribe", false, "Unsubscribe the durable on exit")
log.SetFlags(0)
flag.Usage = usage
flag.Parse()
args := flag.Args()
if clientID == "" {
log.Printf("Error: A unique client ID must be specified.")
usage()
}
if len(args) < 1 {
log.Printf("Error: A subject must be specified.")
usage()
}
sc, err := stan.Connect(clusterID, clientID, stan.NatsURL(URL),
stan.SetConnectionLostHandler(func(_ stan.Conn, reason error) {
log.Fatalf("Connection lost, reason: %v", reason)
}))
if err != nil {
log.Fatalf("Can't connect: %v.\nMake sure a NATS Streaming Server is running at: %s", err, URL)
}
log.Printf("Connected to %s clusterID: [%s] clientID: [%s]\n", URL, clusterID, clientID)
subj, i := args[0], 0
mcb := func(msg *stan.Msg) {
i++
printMsg(msg, i)
}
startOpt := stan.StartAt(pb.StartPosition_NewOnly)
if startSeq != 0 {
startOpt = stan.StartAtSequence(startSeq)
} else if deliverLast {
startOpt = stan.StartWithLastReceived()
} else if deliverAll {
log.Print("subscribing with DeliverAllAvailable")
startOpt = stan.DeliverAllAvailable()
} else if startDelta != "" {
ago, err := time.ParseDuration(startDelta)
if err != nil {
sc.Close()
log.Fatal(err)
}
startOpt = stan.StartAtTimeDelta(ago)
}
sub, err := sc.QueueSubscribe(subj, qgroup, mcb, startOpt, stan.DurableName(durable))
if err != nil {
sc.Close()
log.Fatal(err)
}
log.Printf("Listening on [%s], clientID=[%s], qgroup=[%s] durable=[%s]\n", subj, clientID, qgroup, durable)
if showTime {
log.SetFlags(log.LstdFlags)
}
// Wait for a SIGINT (perhaps triggered by user with CTRL-C)
// Run cleanup when signal is received
signalChan := make(chan os.Signal, 1)
cleanupDone := make(chan bool)
signal.Notify(signalChan, os.Interrupt)
go func() {
for range signalChan {
fmt.Printf("\nReceived an interrupt, unsubscribing and closing connection...\n\n")
// Do not unsubscribe a durable on exit, except if asked to.
if durable == "" || unsubscribe {
sub.Unsubscribe()
}
sc.Close()
cleanupDone <- true
}
}()
<-cleanupDone
}
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