Accumulated changes for message queue (#6600)

* rename

* set agent address

* refactor

* add agent sub

* pub messages

* grpc new client

* can publish records via agent

* send init message with session id

* fmt

* check cancelled request while waiting

* use sessionId

* handle possible nil stream

* subscriber process messages

* separate debug port

* use atomic int64

* less logs

* minor

* skip io.EOF

* rename

* remove unused

* use saved offsets

* do not reuse session, since always session id is new after restart

remove last active ts from SessionEntry

* simplify printing

* purge unused

* just proxy the subscription, skipping the session step

* adjust offset types

* subscribe offset type and possible value

* start after the known tsns

* avoid wrongly set startPosition

* move

* remove

* refactor

* typo

* fix

* fix changed path

weed/command/command.go

@@ -32,6 +32,7 @@ var Commands = []*Command{
 	cmdMaster,
 	cmdMasterFollower,
 	cmdMount,
+	cmdMqAgent,
 	cmdMqBroker,
 	cmdS3,
 	cmdScaffold,

weed/command/mq_agent.go

@@ -26,12 +26,12 @@ type MessageQueueAgentOptions struct {
 func init() {
 	cmdMqAgent.Run = runMqAgent // break init cycle
 	mqAgentOptions.brokersString = cmdMqAgent.Flag.String("broker", "localhost:17777", "comma-separated message queue brokers")
-	mqAgentOptions.ip = cmdMqAgent.Flag.String("ip", "localhost", "message queue agent host address")
+	mqAgentOptions.ip = cmdMqAgent.Flag.String("ip", "", "message queue agent host address")
 	mqAgentOptions.port = cmdMqAgent.Flag.Int("port", 16777, "message queue agent gRPC server port")
 }
 
 var cmdMqAgent = &Command{
-	UsageLine: "mq.agent [-port=6377] [-master=<ip:port>]",
+	UsageLine: "mq.agent [-port=16777] [-master=<ip:port>]",
 	Short:     "<WIP> start a message queue agent",
 	Long: `start a message queue agent
 
@@ -64,6 +64,7 @@ func (mqAgentOpt *MessageQueueAgentOptions) startQueueAgent() bool {
 	if err != nil {
 		glog.Fatalf("failed to listen on grpc port %d: %v", *mqAgentOpt.port, err)
 	}
+	glog.Infof("Start Seaweed Message Queue Agent on %s:%d", *mqAgentOpt.ip, *mqAgentOpt.port)
 	grpcS := pb.NewGrpcServer()
 	mq_agent_pb.RegisterSeaweedMessagingAgentServer(grpcS, agentServer)
 	reflection.Register(grpcS)