i have a nodejs application, which using express.
My problem:
The app working well on localhost, until i stop that
I bought a shared hosting on Namecheap.com and deployed my app
Everything working, except one thing, this is the 24/7 availability
After half hour of idle (When server does not get request(s)) application shuts down, until it gets new request, and this causes high load time
There are no errors
My question is, is there anything that i can do to prevent this?
Like a custom code that does not let server to go idle?
Application uses: Express, MySql, Express-session, nodecache, Body and cookie parser, gz compression, nodemailer, path, fs
I am using pm2.
Code is long so i won't paste here, if you have suggestions i'll check and provide you more info!
(App registered in cPanel Application Manager powered by Phusion Passanger, NodeEnv=Production)
Related
Introduction
So I made a discord bot and hosted it on Heroku server. The bot is basic, it just listens to new messages and responds to them.
I am using a free tier of heroku and discovered that there are so called "free dyno hours". When it is end of the month, all the free hours are consumed and my bot will go offline until next month.
I own a Raspberry pi and so I thought it would be a good idea to host it there as well in case Heroku goes offline.
What I want to achieve
Host discord bot on hosting platform(Heroku).
use my Raspberry pi as a failover server.
Ensure that only one instance of the bot is running at a time.
If both servers are online Heroku(chosen as the main server) has priority.
If the application on Heroku somehow crashes or goes offline the bot on my Raspberry gets activated.
And vice versa.
How would that work if I had 3 and more servers?
How would I approach this if I had the bot connected to database?
This is just an example I would appreciate if more general solution would be provided.
NginX(load balancer)
When searching for help, I came across load balancers and NginX.
If I am right, it basically functions like a gateway, all requests go to the server NginX is hosted on and then they get redirected to one of many servers(depending on how loaded they are etc.).
I have few problems with this:
my bot doesn't receive any requests, it just listens to the discord api.
if the server with Nginx fails it all falls apart?
My solution 1
My first approach was to let the bot running on both Heroku and Raspberry at the same time.
It guarantees that the bot runs on at least one server if the other one fails.
But it is not ideal as the bot responds 2 times when both servers are up.
My solution 2
Heroku:
I added a simple Rest api endpoint with express.js to the bot app.
This way I can check if the bot on Heroku is running.
Raspberry pi:
I wrapped the bot app with this Node program that basically functions like a switch.
Link to a git repo: https://github.com/Matyanson/secondary-node-server.git
Every 3 minutes the program calls the endpoint and then by looking at the status code it checks whether the app is down.
Then it either starts the app or shuts down the app on raspberry(using pm2).
This kinda works but I am sure there is a better solution!
There is also a problem with Heroku(you can skip this):
Heroku uses Dynos(containers) to run the apps. There are different configurations of dynos including 'Web' and 'Worker'.
Worker is used for background job and never is never put to sleep.
Web dyno is the only dyno to receive HTTP traffic. It is put to sleep after 30min of receiving no web traffic.
I can switch on/off either of these.
both: there are 2 instances of my bot.
Worker: Can't connect to the endpoint.
Web: have to 'ping' the api at least every 30min or the bot sleeps.
Why am I asking?
Not because I need to solve this exact problem but because I want to learn a good way of doing this to use it in the future projects.
I also think this would be a good way to not 100% rely on external Hosting providers.
I want to practice creating my own RESTful API service to go along with a client-side application that I've created. My plan is to use Node and Express to create a server. On my local machine, I know how to set up a local server, but I would like to be able to host my application (client and server) online as part of my portfolio.
The data that my client application would send to the server would not be significant in size, so there wouldn't be a need for a database. It would be sufficient to just have my server save received data dynamically in an array, and I wouldn't care about having that data persist if the user exits the webpage.
Is it possible to use a service like Netlify in order to host both a client and server for my purposes? I'm picturing something similar to how I can start up a local dev server on my computer so that the front-end can interface with it. Except now I want everything hosted online for others to view. I plan to create the Express server in the same repo as the front-end code.
No, Netlify doesn't allow you to run a server or backend. However, they do allow you to run serverless functions in the cloud. These can run for up to 10 sec. at a time. Furthermore Netlify also have a BETA solution called "background functions" That can run for up to 15 minutes. But honestly for a RESTful API there sure would be better solutions out there?
If you are still looking for the Netlify for Backend you can consider Qovery. They explained here why it is a good fit for their users.
I have a Facebook Messenger bot written with Node.JS. Currently, it initializes the database (and cache) before initializing Express and receiving requests. I wonder if some requests are sent during initialization, will they get lost?
I'm using Heroku, it that matters.
For free or hobby dyno in heroku there is no zero-downtime setup or preboot as a feature available. While deployment, your Node.js dyno will not serve
the incoming request from the point it restarts the process on that dyno till your server is running successfully on the specified port.
If you have zero-downtime setup already, then your requests will be served by
previous deployed instance unless the new one is spawn and ready to serve.
here is reference link for more info. on zero-downtime heroku
I have deployed a node js web application on app service in azure. Issue is that my application occasionally getting killed for unknown reason. I have done exhaustive search through all the log fines using kudu.
If I restart app service, application starts working.
Is there any way I can restart my node application once it has crashed. Kind of run for ever no matter what. For example if any error happens in an asp.net code deployed in IIS, IIS never crashes, its keeps of serving other incoming request.
Something like using forever/pm2 in azure app service.
node.js in Azure App Services is powered by IISNode, which takes care of everything you described, including monitoring your process for failures and restarting it.
Consider the following POC:
var http = require('http');
http.createServer(function (req, res) {
if (req.url == '/bad') {
throw 'bad';
}
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('bye');
}).listen(process.env.PORT || 1337);
If I host this in a Web App and issue the following sequence of requests:
GET /
GET /bad
GET /
Then the first will yield HTTP 200, the second will throw on the server and yield HTTP 500, and the third will yield HTTP 200 without me having to do anything. IISNode will just detect the crash and restart the process.
So you shouldn't need PM2 or similar solution because this is built in with App Services. However, if you really want to, they now have App Services Preview on Linux, which is powered by PM2 and lets you configure PM2. More on this here. But again you get this out of the box already.
Another thing to consider is Always On setting which is on by default:
By default, web apps are unloaded if they are idle for some period of time. This lets the system conserve resources. In Basic or Standard mode, you can enable Always On to keep the app loaded all the time. If your app runs continuous web jobs, you should enable Always On, or the web jobs may not run reliably.
This is another possible root cause for your issue and the solution is to disable Always On for your Web App (see the link above).
I really want to thank itaysk for your support for this issue.
Issue was not what I was suspecting. Actually the node server was getting restarted on failure correctly.
There was a different issue. Why my website was getting non responsive is for a different reason. Here is what was happening-
We have used rethinkdbdash to connect to rethinkdb database and we was using connection pool. There was a coding/design issue. We have around 15 change feeds implemented with along with socket.io. And the change feed was getting initialised for every user logged in. This was increasing number of active connections in the pool. And rethinkdbdash has default limit of 1000 connection in the pool and as there were lots of live connections, all the available connection in the pool was getting exhausted resulting no more available connection. So, request was waiting for an open connection and it was not getting any available, hence waiting for ever blocking any new requests to be served.
Consider this scenario:
Socket.io app went down (or restarted) for some reason and took about 2 seconds before it started again (considering the use of production manager app ie: PM2).
Within the 3 second down time a client tried to request the client socket.io.js script (localhost:xxxx/socket.io/socket.io.js) and resulted as a failed request (error 500, 404, or net::ERR_CONNECTION_REFUSED) before the server got started again.
After the three second downtime the server file is available again.
So now i have no other way but to inform the user to refresh to resume real time transactions.
I cannot retry to reconnect to the socket.io server because i do not have the client script.
But if it is served somewhere else, perhaps at the same dir where jQuery is, i could just listen if io is available again by writing a simple retry function that fires for every few seconds.
In general, it's a good idea to use the version served by Socket.IO, as you'll have guaranteed compatibility. However, as long as you stay on top of making sure you deploy the right versions, it's perfectly fine to host that file somewhere else. In fact, it's even preferred since you're taking the static load off your application servers and putting it elsewhere.
An easy way to do what you want is to configure Nginx or similar to cache that file and serve a stale copy when the upstream server (your Node.js with Socket.IO server) is down. https://serverfault.com/q/357541/52951