I have Node.js service running on different computers and need to make this service self-updating, with opportunity to schedule different time for update for each computer. I tried to use GitHub Actions, it has on.schedule option for triggering, but the time that I can set here is constant.
Is it possible to change this time dynamically?
If you know some tools for self-updating Node.js application, please recommend them.
Thanks for help.
Related
I have a node.js app running in Azure as a webApp. On startup it connects to an external service using a websocket subscription. Specifically I'm using the reconnecting-websockets NPM package to wrap it to handle disconnects.
The problem I am having is that because there are 2 instances of the app running on Azure (horizontal scaling for failover) I end up with two subscriptions at any one time.
Is there an obvious way to solve this problem?
For extra context, this is a problem for 2 reasons:
I pay for each message received and am over quota
When messages are received I process then and do database updates, these are also being duplicated.
You basically want to have an AppService with potentially multiple instances, but you don't want your application to run in parallel. At least you don't want two have two subscriptions. Ideally you don't want to touch your application code.
An easy way to implement this would be to wrap your application into a continuous WebJob, and set its scale property to singleton.
Here is one tutorial on how to set up a nodejs webjob: https://morshemesh.medium.com/continuous-deployment-of-web-jobs-with-node-js-2308f95e63b1
You can then use a settings.job file to control that your webjob only runs on a single instance at any one time. Or you can use the Azure Portal to set the value when you manually deploy the Webjob.
{
"is_singleton": true
}
https://github.com/projectkudu/kudu/wiki/WebJobs-API#set-a-continuous-job-as-singleton
PS: Don't forget to enable Always On. It is also mentioned in the docs. But you probably already need that for your current deployment.
If you don't want your subscription to be duplicated then it stands to reason that you only want one process subscribing to the external websocket connection.
Since you mentioned that messages received will be updated in the db, then it makes sense that this would be an isolated backend process since you made it clear that you have multiple instances running for the frontend server (and whether or not a separate backend).
Of course if you want more redundancy, you could use a load balancer with simple distribution of messages to any number of instances behind. Perhaps some persistent queueing system if you feel that it's needed.
If you want these messages to be propagated to the client (not clear from the question), this will be a bit more annoying. If it's a one-way simple channel, then you could consider using SSE which is a rather simple protocol. If it's bilateral then I would myself probably consider running a STOMP server with intermediary broker (like RabbitMq) and connect directly from the client (i.e. the browser, not the server generating the frontend) to the service.
Not sure if you're well versed with Java, but I made some app that you could use for reference in case interested when we had to prepare some internal demos: https://github.com/kimgysen/zwoop-backend/tree/develop/stomp-api/src/main/java/be/zwoop
For all intents and purposes, I'm not sure if all this is worth the hustle for you, it sounds like you're on a tight budget and that you're looking for simple solutions without too much complexity. Have you considered giving up on load balancing the website (is the load really that high?), I don't have enough background knowledge on your project to judge, I believe. But proper caching optimization and initially scaling vertically may be sufficient at the start (?).
Personally I would start simple and gradually increase complexity when needed.
I'm just throwing ideas at you, hopefully it is helpful in any way to have a few considerations.
Btw, I don't understand why other answers on this question were all deleted (?).
I'm looking for some event/reactive online tools to make a card game in a browser.
I think JS is most appropriate here but I'm open to all propositions.
I already tried VueJS / Node with Socket.IO but I think it's very messy and not organized enough to make a project like this. So I was wondering if you guys knew some frameworks to make the job.
The projects is to make an online card game like poker.
Thanks !
You could try pixi.js or phaser 3+.
Also I've wright one of my card-games only using html+css+javascript.
For back-end you could use whatever you want. NodeJS + websockets is good choice!
If the main matter is the realtime database connection (for which you are looking for websockets), you could create the game and store it's data to firebase firestore, this way you could get everything synced in real time with a less pain than a node server setup, (for this purpose), if you need some backend functionality you could also work with firebase functions in order to achieve some backend stuff, also you could even store your project on firebase hosting, have an authentication ready platform with firebase auth and depending on your needs you would not even pay a penny (this really depends on the usage)
Hope this could at least be an option to consider.
Check the firebase documentation: FIREBASE
Even if you wish to work with Unity instead of VueJS you can also use firebase for all this matters.
I have recently deployed my Angular 2 application to Firebase hosting successfully and am really enjoying this set up so far, particularly on how easy it is to deploy using CI as well.
At the moment, I am looking at adding a universal server rendering support to my app, but I'm not sure if this is handled by Firebase Hosting, as it says it is static file only.
However, what made me think that this could be a potential feature that I am missing is that Firebase offers support for single page applications, hence I decided to ask.
If there isn't support for such apps, can we expect it in the future?
At the moment this is not possible. However since Angular 2, Google and Firebase go hand in hand I would say this it is just a matter of time.
In the meantime you can create a Node.js-based server, where you install Angular Universal, and have it connect to Firebase with the Firebase Node SDK.
Next, you simply communicate with that Node-backend from your Angular 2 application.
If you're using angularfire2, that will break universal either way. There's something in the package that calls "window" which doesn't exist on the server. Unless something changes with universal or angularfire this is a ways off
At the end of that video David East mentions that one can use Google Cloud Functions with Angular Universal and such: https://www.youtube.com/watch?v=R3v8EcYzf_M
The video itself is quite useful for firebase users. But the topic starts at approximately 23:30.
A different approach is to skip universal altogether and do something like this.
Rendertron is a headless chrome that can be launched. Similar to phantomjs. But universal gives speed.
I am writing a real time web app with pouchdb. I am currently using vanilla pouchdb on top of backbone.
That being said, I have been running into quite a bit of conflicts and was wondering if you have any suggestions as to how to handle pouchdb conflicts in the context of a real time web app?
Also, I've noticed this plugin:
https://github.com/redgeoff/delta-pouch. How would this plugin assist with real time web apps?
delta-pouch will give you a setup where there are no conflicts at all, as long as you can express every change as a delta (i.e. a change that is not dependent on a previous state, such as a transaction to a bank account that adds $50).
You can also use this project to assist in resolving conflicts: https://github.com/jo/pouch-resolve-conflicts Or read the guide to conflicts: http://pouchdb.com/guides/conflicts.html
I need to run my app always on top of the android system, while the user will be able to exit the app only with his own password. I was told that in order to do that i need to setup and run a Service of my own.
My question is can and how it is done using Phonegap and Jquery. How do i define and run my own service? Thanks for your help.
First, don't do that. I know that doesn't sound like an answer, but trust me, it actually is the answer. What I mean is, no, you don't want your app to be "always on top of the android system." Use the actual Android lifecycle and participate as a good citizen, don't abuse it and try to keep your app always running. I know you may have a use case that makes you think you need to do that, but you most likely don't.
Second, you can write a native service (not JS) and keep it running in the background. This is a a standard Android service. You'll need to create a PhoneGap plugin to hook into your app via the service (or you can create this yourself outside PhoneGap, either way). Then you can either do work in the background, or bring your app to the foreground via the service.
This answer may help: Creating an Android Service with Phonegap? (Have phonegap app run even when closed)
Third, again, don't do that. Most long running services are a bad idea (not all mind you, some use cases require it, a music player, etc, but most do not). It's a much better idea to create an IntentService and schedule an alarm (via AlarmManager) to launch it in the background periodically if you just need to do some occasional background work (fetch data, etc). Regardless of the use case though, a long running background service will consume a lot of resources and make users justifiably wary of your app.
I don't think Phonegap will let you create a service solely in javascript. To be able to make a service, you will have to write at least some native code. See https://stackoverflow.com/a/10427975/1721527.
I've never used Phonegap, but I think you can create a native plugin to talk to the javascript. See http://docs.phonegap.com/en/2.1.0/guide_plugin-development_index.md.html.
See Android documentation on services at http://developer.android.com/guide/components/services.html.