CODEWITHSUNDEEP
node.js
Dave
Dave

Reputation: 14178

node http-proxy least connections proxy

I'd like to use node http-proxy to create a "least connections" proxy. In other words it picks a backend that currently has the least connections. The proxy has an "end" event, but it doesn't pass you any information, so I'm not sure how I can increment/decrement a counter for each of my backends with the current number of concurrent requests.

Upvotes: 1

Views: 222

Answers (1)

robertklep
robertklep

Reputation: 203329

I think you can wait for the response to have been send to the client.

For example:

var backends = [
  { host : 'backend1', port: 80, active : 0 },
  { host : 'backend2', port: 80, active : 0 },
  { host : 'backend3', port: 80, active : 0 },
  { host : 'backend4', port: 80, active : 0 },
];

httpProxy.createServer(function (req, res, proxy) {
  var buffer = httpProxy.buffer(req);

  // Pick the backend with the least active requests (naive implementation).
  var backend = backends.sort(function(a, b) {
    return a.active - b.active;
  })[0];

  // Add a new active request.
  backend.active++;

  // Proxy the request.
  proxy.proxyRequest(req, res, {
    host    : backend.host,
    port    : backend.port,
    buffer  : buffer
  });

  // When the response is finished, decrease the count.
  res.on('finish', function() {
    backend.active--;
  });
}).listen(8000);

Upvotes: 2

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