func main() {
// Initialise our configuration from flags
var fbConnect = flag.String("forestbus", REQUIRED, "Connection string for Forest Bus cluster in ClusterID#Topic@host:port,host:port... format.")
var startIndex = flag.Int64("index", 1, "Index to start reading messages from")
var quantity = flag.Int("quantity", 1, "Target number of messages to retrieve. A larger or smaller number may be returned")
var waitForMessages = flag.Bool("wait", false, "Wait for messages to be available")
var enableDebug = flag.Bool("debug", false, "Enable debug logging")
var tail = flag.Bool("tail", false, "Keeps reading all available messages, implies -wait=true")
flag.Parse()
if flag.Lookup("help") != nil || flag.Lookup("h") != nil {
flag.PrintDefaults()
return
}
if *fbConnect == REQUIRED {
Print("forestbus connection string missing.\n")
flag.PrintDefaults()
return
}
clusterID, topic, peers := forestbus.ParseConnectionString(*fbConnect)
if len(peers) == 0 {
Print("At least one node name is required.\n")
}
if topic == "" {
fmt.Printf("Topic is missing.\n")
flag.PrintDefaults()
return
}
var client *forestbus.Client
if *enableDebug {
client = forestbus.NewClient(clusterID, peers, forestbus.ClientEnableDebug())
} else {
client = forestbus.NewClient(clusterID, peers)
}
maxMsgID, err := client.GetTopicMaxAvailableIndex(topic)
if err != nil {
Print("Error determining maximum available message ID: %v\n", err)
return
}
if maxMsgID == 0 {
Print("Commit index is zero due to a full cluster restart.)\n")
return
}
if *tail {
*waitForMessages = true
}
looping := true
recievedCount := 0
firstIndex := *startIndex
for looping {
msgs, nextID, err := client.GetMessages(topic, *startIndex, *quantity, *waitForMessages)
if err != nil {
Print("Error getting messages: %v\n", err)
return
}
if len(msgs) == 0 {
if nextID == 0 {
Print("Commit index is zero due to a full cluster restart.)\n")
return
} else if nextID == (*startIndex + 1) {
// Nothing came back - are we planning to wait for more?
if !*waitForMessages {
looping = false
}
} else if nextID == *startIndex {
// Index 1 not available due to clean up
firstIndex = nextID
}
}
for _, msg := range msgs {
os.Stdout.Write(msg)
os.Stdout.Write(NEWLINE)
recievedCount++
if recievedCount == *quantity && !*tail {
looping = false
break
}
}
*startIndex = nextID
}
maxMsgID, err = client.GetTopicMaxAvailableIndex(topic)
if err != nil {
Print("Error determining maximum available message ID: %v\n", err)
return
}
Print("Recieved %v messages from index %v\n", recievedCount, firstIndex)
Print("Maximum available message index: %v\n", maxMsgID)
}
