publish-subscribe

问题 Is there any way to implement request-response pattern with mosca MQTT to "check reply from the client and re publish if i dont receive expected reply within expected time". I believe this is possible in Mqtt 5, but as of now, I have to use Mosca broker with QoS 1(which support until Mqtt 3.1.1) I am looking for a Node js workaround to achieve this. 回答1: As per my comment you can implement a request-response pattern with any MQTT broker but, prior to v5, you need to implement this yourself

问题 Is there any way to implement request-response pattern with mosca MQTT to "check reply from the client and re publish if i dont receive expected reply within expected time". I believe this is possible in Mqtt 5, but as of now, I have to use Mosca broker with QoS 1(which support until Mqtt 3.1.1) I am looking for a Node js workaround to achieve this. 回答1: As per my comment you can implement a request-response pattern with any MQTT broker but, prior to v5, you need to implement this yourself

问题 Let below is a component which I will be extending in various other components ti reuse some code.. import { Component } from '@angular/core'; @Component ({ selector: 'my-app', template: ` <div> <h1>{{appTitle}}</h1> <div>To Tutorials Point</div> </div> `, }) export class AppComponent { appTitle: string = 'Welcome'; ngOnInit(){ this.registerSomeSubscriptions(); } registerSomeSubscriptions(){ this.subscribeSomething.subscribe((data)=>{ performSomeAction(); }) } } I can extend it like below

问题 I'm able to display data from two topics but I can't do use and compute data in real time from these two topics in ROS (written in Python code). Have you got any idea to stock this data and compute in real time ? Thanks ;) #!/usr/bin/env python import rospy import string from std_msgs.msg import String from std_msgs.msg import Float64MultiArray from std_msgs.msg import Float64 import numpy as np class ListenerVilma: def __init__(self): self.orientation = rospy.Subscriber('/orientation',

问题 I'm able to display data from two topics but I can't do use and compute data in real time from these two topics in ROS (written in Python code). Have you got any idea to stock this data and compute in real time ? Thanks ;) #!/usr/bin/env python import rospy import string from std_msgs.msg import String from std_msgs.msg import Float64MultiArray from std_msgs.msg import Float64 import numpy as np class ListenerVilma: def __init__(self): self.orientation = rospy.Subscriber('/orientation',

问题 I am using publishOn vs subscribeOn both on the same flux as follows: System.out.println("*********Calling Concurrency************"); List<Integer> elements = new ArrayList<>(); Flux.just(1, 2, 3, 4) .map(i -> i * 2) .log() .publishOn(Schedulers.elastic()) .subscribeOn(Schedulers.parallel()) .subscribe(elements::add); System.out.println("-------------------------------------"); Although, when i use both, nothing is printed in logs. But when i use only publishOn, i got the following info logs:

问题 I have an admin dashboard where I want an alert to be fired whenever a user is created (on a separate page). The code below works, however, there's a race condition. If 2 users are created very close together, it will only fire once. class User < ApplicationRecord after_commit :notify_creation, on: :create def notify_creation ActiveRecord::Base.connection_pool.with_connection do |connection| self.class.execute_query(connection, ["NOTIFY user_created, '?'", id]) end end def self.listen_to

问题 I am using PubNub for notifications transfer across my Js code. I am unable to figure out how to reconnect in PubNub once internet disconnects and comes back up. having restore: true in my init and doing this.listeners = { message: msgEvent => { console.log(msgEvent); }, status: statusEvent => { if (statusEvent.category === "PNNetworkUpCategory") { this.pubnub.reconnect(); }}}; Doesn't work for me. full code: this.pubnub = new PubNub({ subscribeKey: this.serverDetails.authInfo.subscribeKey,

问题 How does AMQP overcome the difficulties of using TCP directly when sending messages? Or more specifically in a pub/sub scenario? 回答1: In AMQP there is a broker, that broker receives the messages and then does the hard part about routing them to exchanges and queues. You can also setup durable queues which save the messages for clients even when they are disconnected. You could certainly do all this yourself, but it's a tremendous amount of work to do correctly. RabbitMQ in particular has been

问题 How does AMQP overcome the difficulties of using TCP directly when sending messages? Or more specifically in a pub/sub scenario? 回答1: In AMQP there is a broker, that broker receives the messages and then does the hard part about routing them to exchanges and queues. You can also setup durable queues which save the messages for clients even when they are disconnected. You could certainly do all this yourself, but it's a tremendous amount of work to do correctly. RabbitMQ in particular has been