recluster is a
clustering library with support for zero-downtime reloading.
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npm install recluster |
Delivering that 100% uptime for web apps can be a tricky business. Errors and new code rollouts are the things we have to deal with on a daily basis and if you run continuous integration, your app is probably restarting many times a day. What kind of experience this might be creating for your users?
recluster is among a few other
libraries that try to address this issue. It is:
- Cluster aware.
- Zero downtime errors and deploys.
- Does not run as daemon.
- Log agnostic.
- Simple, relatively easy to reason about.
Example
If server.js is your regular http server (e.g. express), create cluster.js and add:
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var recluster = require('recluster'), path = require('path');var cluster = recluster(path.join(__dirname, 'server.js'));cluster.run();process.on('SIGUSR2', function() { console.log('Got SIGUSR2, reloading cluster...'); cluster.reload();});console.log("spawned cluster, kill -s SIGUSR2", process.pid, "to reload"); |
then run it
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node cluster.js |
To hot-reload the server, simply run
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kill -s SIGUSR2 <cluster_pid> |
A server worker can gracefully exit by cleaning up in the ‘close’ event of its server:
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server.on('close', function() { // cleanup}); |
Non-server workers can listen for the disconnect command and shut down gracefully before the kill timeout:
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process.on('message', function(m) { if (m.cmd == 'disconnect') { // cleanup }}) |
For some fantastic insights on the subject, checkout Towards 100% Uptime with Node.js slides by William Bert @williamjohnbert and 10 steps to nodejs nirvana in production by Qasim Zaidi @kernelhacker.
Curious, how do you manage your node process?