Goodbye node-forever, hello PM2
So far, we had been relying on the pretty nifty node-forever. Great tool, but a few things were missing:
- Limited monitoring and logging abilities,
- Poor support for process management configuration,
- No support for clusterization,
- Aging codebase (which meant frequent failures when upgrading Node).
This is what led us to write PM2 in the past couple months. We thought we’d give you a quick look at it while we’re nearing a production ready release.
So what’s in the box?
First things first, you can install it with
npm install -g pm2
Let’s open things up with the usual comparison table:
And now let me geek a tad more about the main features…
Node v0.6 introduced the cluster feature, allowing you to share a socket across multiple networked Node applications. Problem is, it doesn’t work out of the box and requires some tweaking to handle master and children processes.
PM2 handles this natively, without any extra code: PM2 itself will act as the master process and wrap your code into a special clustered process, as Nodejs does, to add some global variables to your files.
To start a clustered app using all the CPUs you just need to type something like that:
$ pm2 start app.js -i max
$ pm2 list
Which should display something like (ASCII UI FTW);
As you can see, your app is now forked into multiple processes depending on the number of CPUs available.
Monitoring a la termcaps-HTOP
It’s nice enough to have an overview of the running processes and their status with the
pm2 list command. But what about tracking their resources consumption? Fear not:
$ pm2 monit
You should get the CPU usage and memory consumption by process (and cluster).
Disclaimer: node-usage doesn’t support MacOS for now (feel free to PR). It works just fine on Linux though.
Now, what about checking on our clusters and GC cleaning of the memory stack? Let’s consider you already have an HTTP benchmark tool (if not, you should definitely check WRK):
$ express bufallo // Create an express app $ cd bufallo $ npm install $ pm2 start app.js -i max $ wrk -c 100 -d 100 http://localhost:3000/
In another terminal, launch the monitoring option:
$ pm2 monit
Realtime log aggregation
Now you have to manage multiple clustered processes: one who’s crawling data, another who is processing stuff, and so on so forth. That means logs, lots of it. You can still handle it the old fashioned way:
$ tail -f /path/to/log1 /path/to/log2 ...
But we’re nice, so we wrote the
$ pm2 logs
So things are nice and dandy, your processes are humming and you need to do a hard restart. What now? Well, first, dump things:
$ pm2 dump
From there, you should be able to resurrect things from file:
$ pm2 kill // let's simulate a pm2 stop $ pm2 resurect // All my processes are now up and running
API Health point
Let’s say you want to monitor all the processes managed by PM2, as well as the status of the machine they run on (and maybe even build a nice Angular app to consume this API…):
$ pm2 web
Point your browser at
http://localhost:9615, aaaaand… done!
And there’s more…
- Full tests,
- Generation of
pm2 startup), though still very alpha,
- Development mode with auto restart on file change (
pm2 dev), still very drafty too,
- Log flushing,
- Management of your applications fleet via JSON file,
- Log uncaught exceptions in error logs,
- Log of restart count and time,
- Automated killing of processes exiting too fast.
Well first, you could show your love on Github (we love stars): https://github.com/Unitech/pm2.
We developed PM2 to offer an advanced and complete solution for Node process management. We’re looking forward to getting more people helping us getting there: pull requests are more than welcome. A few things already on the roadmap that we’ll get right at once we have a stable core:
- Remote administration/status checking,
- Built-in inter-processes communication channel (message bus),
- V8 GC memory leak detection,
- Web interface,
- Persistent storage for monitoring data,
- Email notifications.