net-cluster

a drop-in replacement for node's net module that works in a sane way when clustered

npm install net-cluster
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net-cluster

a drop-in replacement for node's net module that works in a sane way when clustered

Build Status

listening on a random port

server.listen(0)

http://nodejs.org/api/cluster.html

from the documentation:

Normally, this will case servers to listen on a random port. However, in a cluster, each worker will receive the same "random" port each time they do listen(0). In essence, the port is random the first time, but predictable thereafter. If you want to listen on a unique port, generate a port number based on the cluster worker ID.

2 problems with this functionality

  • listen(0) should always bind to a random port
  • the listen(cluster.workerId) is unreliable
    • you can't gurantee that the port cluster.workerId is available

how net-cluster operates

listen(0) always binds to a random port

usage

net-cluster strictly implements node's net module.

/**
 * uses net-cluster instead of net to create a server
 * 
 * Note: 2 servers will be created and they will be listening
 * on 2 distinct random ports. Try using node's net module instead
 * of net-cluster and see what happens.
 */
var cluster = require('cluster')
  , net = require('net-cluster')
  ;

if (cluster.isMaster) {
  cluster.fork();
  cluster.fork();
} else if (cluster.isWorker) {
  var server = net.createServer();
  server.listen(function() {
    var port = server.address().port;
    console.log('listening on port: ' + port);
  });
}

use cases

  • network application that needs to open multiple non-pre-determined ports
  • if you provide a module that listens on port 0
    • this is a difficult bug for people using your module. Not only will every instance of your module code be sharing the same socket, but ANY other piece of code using listen(0) will be sharing the same socket (other modules or even the user's code)

The MIT License

Copyright (c)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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