I am new to using loopback, and I'm using loopback4 (which I think is referred to as loopback-next)
I have set up my controllers, models & respositories in order to be able to support CRUD operations to mysql, and that is all fine.
I want my loopback application to also connect to an MQTT server, so that I can subscribe to messages from MQTT, and react to those messages by creating entities in my repositories. In addition, I want to be able to have existing controller methods drop messages onto the MQTT (publish)
I am struggling to understand the right way to do this in the loopback eco-system.
I don't think I want to create a Server - because the documentation describes a server as including a listen port. I don't want my loopback application to be a MQTT server. I just want it to interact with one.
Similarly, I don't think this would be an MQTT bridge, or a datasource.
I suspect, what I want is a service. But I'm not certain.
I would appreciate any advice on how to achieve this integration.
Thanks
LB4 is highly extensible and a very good choice for such integrations. What you need in this case is to have a MQTT connector component. You can refer to the documentation for how to create a component in LB4 here and here.
You can refer to an example component implementation for authorization as well for quicker understanding.
Related
At the moment i still only have about 2 months of experience in UI5. i developed a little sample-app, used sap gateway builder to pass my requests to sap backend.
Now my employer asked me to research the possibility to access two different backends (one sap, one nonsap) via odata from the same app. After a little reading and thinking i came to the conclusion that it would be best to access both backends from a single gateway.
Since ive already worked with sap gateway, i wonder if there is a way to access nonsap backends with sap gateway? Are the better options?
Or is my current approach complete wrong and i should think about a whole other way?
It depends on your approach and the non-sap-system:
Is the non-sap-system accesible via Webservices? Then use second data model (e.g. JSON/ODATA) within SAPUI5 by loading data via webservices after initial loadup of your application.
Is the non-sap-system connected to SAP? E.g. via RFC or another technology, then you can read data from the other system during calling your initial Gateway service and simply call your RFC function module in your method.
From my opinion you will not achieve an 'easy' way to read both via one single SAP NetWeaver Gateway.
Not sure why you would want to access a non-SAP oData service via SAP Gateway. On the other hand you may want a router of some sort so that all services are exposed on the same network location and then incoming requests are routed to the appropriate backend for action.
You may also want to "mash-up" the SAP and non-SAP services into some sort of new service. In that case maybe look to some of the API management tools like Apigee to help you achieve that.
I have implemented SignalR support for web application. It works great. The problem I'm dealing now is make it work in non-Azure web farm environment. SignalR supports Windows Azure Service Bus and Redis out of the box. Also there is RabbitMQ implementation on GitHub. All these solutions implement IMessageBus interface.
Based on our current situation we can't use Redis or RabbitMQ. So I have few questions:
1) Is there any alternative solution that uses SQL Server or MSMQ?
2) Is it difficult (possible) to implement your own solution for SQL Server or MSMQ? David's post on SignalR 0.5 (http://weblogs.asp.net/davidfowler/archive/2012/05/02/signalr-0-5.aspx) says they are going to support SQL Server QNS or Service Broker (not SQL Server DB itself) so maybe it's a wrong way at all?
3) Is there a way to work around until this support is implemented? For example, it sounds like the we need to handle state of the connections list between servers. If we know number of nodes and their IPs we can share this information between servers via Web Service calls instead. Does it make any sense?
Damian Edwards appears to have just started working on the SQL scaleout implementation. You can find the details of that implementation here on GitHub and the issue tracking this work can be followed here.
In a DELPHI 2007 application that I am developing some prospect clients just found interesting to be able to share data and information with each other.
They all have the same application.
All have independent Databases
But all have the same installed application and there are some data types that they might want to share (replicate) between their databases.
How can I enable them to share data with other users of the same application program, but not to everybody on the whole internet.
I would like this to be as automatic as possible, as I already have considered approaches that involve manually sending emails.
I know Datasnap is an option, is there any other.
UPDATE:
The idea is to enable companies that have the same application to be able to share data.
They should be able to select what partner and what to send.
I have been investigating datasnap, but would like to know if there is another way to do this
Another standard way to connect distributed applications and share data and information is through some Message-oriented middleware (MOM). There are many open source middleware products (message brokers) available, which can be used over Delphi client libraries, even in multithreaded Delphi server applications. (Disclaimer: I am the author of message broker client libraries for Delphi and Free Pascal)
There are many essential differences between web services and message brokers, like peer-to-peer and publish/subscribe communication models. They also play a key role in enterprise application integration patterns.
One standard way to connect applications to other applications is to make a web-service, and make a client that consumes that web-service, called a web-client. Technologies like SOAP and REST refer to such web service and web clients.
Your question is vague, perhaps due to english not being your language, but you should probably edit it and be more specific.
If all your applications are going to talk directly to each other that is called "peer to peer networking" and there are huge problems with enabling that kind of communication directly over the internet. It is much easier if you build a server that all these applications will connect to.
As a sample, consider the IRC Chat service, and consider writing a Web Service that will be the Chat Server, and consider all your clients to be "Chat clients". Sharing data could be the same idea as creating "rooms" or "channels" on a chat server.
I get the idea that you want something like a Peer to Peer Data Replication Service. I think that the closest you're going to get to that is something like "RSS Feeds" (used by blog syndication services). You subscribe to them via a simple web service, and pull down the new content on some periodic basis. Since that data has to be published to a central server, that means, that a peer to peer approach is out of the question. If you don't have your own web server running on a web hosting service, or on a "cloud", and you need a truly peer to peer solution, I am not aware of any way to do that, at least not without an incredible custom engineering effort.
I'm working on a rails app that will primarily be exposed by an api to various mobile clients (iOS, android etc). The application involves users submitting data to the server (via api calls), but what I want to include is the ability to push this data down to other clients. The general concept is similar to a messaging app, where I submit a message to the server from me client and the receiver is pushed the message from the server.
The only method I know of at the moment is to constantly poll the server, but there must be better tech solutions than this. Any ideas?
I would look at using a websocket within the page to push the updates.
You could implement this using Faye, which falls back to long polling and other work-arounds for browsers without websocket support. Faye has a pure-ruby implementation, so you could probably work out access to your model layer.
Edit:
Also, this is a project that combines Faye with Rails. It is fairly new, but might do what you want. Faye-Rails
You should check out http://www.pusher.com
Pusher is a hosted API for quickly, easily and securely adding scalable realtime functionality to web and mobile apps.
If you need self-hosted solution, then you should check out slanger gem https://github.com/stevegraham/slanger which is server implementation for pusher client libraries. When you feel you need hosted solution, you just change URL's.
Slanger is an open source server implementation of the Pusher protocol written in Ruby. It is designed to scale horizontally across N nodes and to be agnostic as to which Slanger node a subscriber is connected to, i.e subscribers to the same channel are NOT required to be connected to the same Slanger node. Multiple Slanger nodes can sit behind a load balancer with no special configuration. In essence it was designed to be very easy to scale.
Ruby has it's own event-processing library, implemented like a gem:
https://github.com/eventmachine/eventmachine
Maybe it helps you
I prefer event machine over any other solution. It is somewhat more complicated that faye but you can write way more sophisticated code using event machine.
You might wanna check this peepcode screencast on event machine
I have an existing complex website built using ASP.NET MVC, including a database backend, data layer, as well as the Web UI layer. Rebuilding this website in another language is not a feasible option.
There are some UI elements on some views (client side) which would benefit from live interactivity, involving both push and pull, so rather than implement some kind of custom long polling or websocket server in asp.net, I am looking to leverage node.js for Windows, and Socket.io.
My problem is that I need two way communication between both applications. Each user should only be able to receive data once they are authorised on the ASP.NET website, so I first need communication for this. Secondly, once certain events occur on the ASP.NET website I want to immediately push this data to the Node server, to be broadcast to specific users or groups of users. Thirdly, I would like any data sent to the node.js server to be pushed to the ASP.NET website for processing, as this is where all our business logic lies. The sole reason for adding Node.js is to have the possibility to push data directly to the client, I do not want to build any business logic into it (or as little as possible).
I would like to know what the fastest method of two-way push communication is between Node.Js and ASP.NET. The only good option I'm aware of so far is to create a special listener on a specific port on the node.js server and connect to that, but I was wondering if there's a more elegant or more efficient method? I also know that you could use a database inbetween but surely this would need to be polled and would be less efficient? Both servers will be running on the same server under a Visual Studio project.
Many thanks for any help you can provide.
I'm not an ASP.NET expert, but I think there are multiple ways you can achieve this:
1) As you said, you could make Node listen on a specific port for data and then react based on the data received (TCP)
2) You can make POST requests to Node.js (HTTP) and also send an auth-key in the process to be extra-secure. Like on 1) Node would react to the data you send.
3) Use something like Redis for pub-sub, send messages from ASP.NET (pub) and get them on the Node.js part (sub). This is even better if you want to scale your app across multiple machines etc.
The only good option I'm aware of so far is to create a special
listener on a specific port on the node.js server and connect to that,
but I was wondering if there's a more elegant or more efficient
method?
You can try to look at redis pub/sub model where ASP.NET MVC application and node.js would communicate through separate channels in order to achieve full-duplex communication. Or you can also try to use CouchDB change nofitications.
I also know that you could use a database inbetween but surely this
would need to be polled and would be less efficient?
Former techniques do not require you to poll for changes, but instead they will notify you when the changes happens or channel message arrives.