I've written two simple Node.js apps, each of which run a server on a port (1337 and 1338), and using PM2 (and Keymetrics) to keep them alive, but every few days all three Node.js apps (including PM2) crash simultaneously. I'm fairly new to Node.js and am not sure how to investigate the source of the problem.
DETAILS:
The two servers respond to incoming GET requests. One is to automatically do a GIT fetch/pull in response to a Bitbucket trigger, and the other converts a URL to PDF and sends the PDF back to the browser (using wkhtmltopdf). They both work fine while they're running.
I'm running Node.js v0.12.4.
When the three apps go down, my first indication is from my Uptime (https://github.com/fzaninotto/uptime) instance on OpenShift which emails me to say one of my Node.js servers is down, returning "connect ECONNREFUSED".
A couple of minutes later Keymetrics emails me saying "Agent is offline: Keymetrics Agent seems to be offline".
In other words, ALL my node.js stuff seems to go down at the same time; neither of the two apps nor even PM2 are running. I thought Node spawned a process for each app, so how could they all go down at once?
WHAT I'VE TRIED:
I've tried digging through the ~/.pm2/pm2.log but haven't been able to find anything useful in there. Maybe I just don't know what to look for.
$ pm2 resurrect always brings everything back to life just fine.
Please upgrade to latest PM2 version:
$ npm install pm2 -g
$ pm2 update
Related
I am using pm2 to keep a script running and making api calls in an interval. Sometimes the api calls fail, the script is running and not restarted but the calls just dont go out. I set up a health monitor in node.js to inform me whenever these api calls cease.
Now whenever I see downtime I go into the pm2 dashboard and restart my app. I would like to skip this step and have my health monitor just make a call to the pm2 instance that it should restart exactly like the dashboard is doing.
Is this possible? If so how can it be done? I see some pm2.restart options in the docs but Im not sure how this is supposed to occur from a different machine.
I'm newbie using GCP and his Compute Engine Service. I've deploy a Linux Ubuntu Image an it's running like a charm, but I have a issue running Node JS backend.
Let me explain it better:
I'm connecting using Web Browser SSH terminal or GCloud Shell ssh, and it way works running node app.js my backend starts working. But after a time, the sessions stop and my backend service stop working as well. At this time every time when I need to work have to re-activate the service each time.
How could I do for this service works in background and not depends that my ssh terminal are opened?
Thanks a lot in advance.
What actually happen is you are starting your nodejs application using an client which is parent process. So if after sometime the connection is lost of some xyz seconds the parent process dies killing your node application. Now what you can do is use screen. On ubuntu you would do something like this.
sudo apt-get install screen
after successful install run the screen command. Now you will be thrown a brand new terminal. Here you can run your nodejs code which will never die. Since screen runs your application in background. More information here
A good solution could be to use a startup script. To insert a startup script into your already created instance you need to go to this link [1]. When you have your startup script inserted in the metadata field you just need to restart your Instance and then should work perfectly without depending of the ssh session.
[1] https://cloud.google.com/compute/docs/startupscript#startupscriptrunninginstances
I've created this npm package, to make your node app run as a service on your linux machine. Please try it out.
It creates a systemctl service on your machine and runs it as a background service.
How to keep a node application running in windows even when user logs off?
Also how to keep running a node http-server even after user log-off?
You have 2 great options. One is as mentioned in comments above Forever.
The other is PM2 which is easy to install and offers an incredible amount of options. I use this in all projects, but I cannot attest to the Windows version as I am on Linux & Ubuntu servers and work on a Mac. You can daemonize your node process, follow logs, cluster it and make sure the process reboots even with a server shutdown (it is a service).
windows task scheduler: execute node.exe: start in project folder: and argument (app.js)
What is the easiest way to achieve zero downtime for my Node.js application?
I have an app that requires the following steps for redeployment:
npm install
node_modules/.bin/bower install
node_modules/.bin/gulp
The result of these operations is the ready-to-run application in the generated by the gulpfile.js directory named build. In this directory I have a currently-running instance of the same application (currently launched via forever like this -- forever start server.js).
As far as I know, it is not possible to achieve zero downtime via forever module, so I decided to choose another way to do it.
I saw pm2 but I found it very complex tbh (prove me wrong if you don't feel the same).
I also saw naught but I can't even start my application via naught start server.js -- it doesn't even print anything in stdout / stderr.
I also saw up-time but I didn't get the idea -- how will it handle situation when I run gulp that should replace files in the directory where currently-running instance work at the moment?
Regarding of handling replaced files during build: if these files is used by Node.js app then all changes will be applied upon process restart (since these files are loaded into memory), browser frontend files could also be cached in application memory to achieve similar behavior (changes applied only upon restart or/and cache invalidation).
We're using pm2 in cluster mode.
pm2 start app.js -i
The above command starts app.js in cluster mode on all available CPU cores.
zero downtime restart:
pm2 gracefulReload all
this command restarts all processes sequentially, so if you have more than one process up and running there is always at least one process that servers requests during restart.
If you have only one process of app.js you can start it in cluster mode and run pm2 scale app.js 2 (starts one more process) then pm2 gracefulReload all and then pm2 scale app.js 1 (removes previously started process).
Though I think app restarting is not main problem of zero downtime deployment, we've not managed to handle DB migrations, so full app shutdown is needed to apply DB changes. Also there could be an issue with browser frontend files when during deploy user obtained the new version of them, but AJAX request is processed by old version of server process, in this case sticky sessions and API versioning came to the rescue.
I am running a Node.JS + Angular JS application on a cloud server using the MEAN stack. The application is terminating every hour or sooner.
I have few thoughts and would like someone who can tell me which might a cause.
I am using SSH through root when I start the service using this command
NODE_ENV=production PORT=80 grunt serve:dist
Do I need forever to run this properly ?
Should I use a server user (similar to apache) that can run the application?
If yes how do I do this ?
We do not have a deployment engineer in our team but it is annoying to not being able to keep the app running on the server after developing the application. Please help diagnose the problem.
If you don't want to use a deployment service — MS azure, AWS, heroku, etc. (which would probably be a lot easier) — then yes, you would have to use something like forever to restart your sever every time it crashes. It's really odd that your app terminates after an hour though, it'd be helpful if you could describe why that's happening.