heartbeat

A good heartbeat timer

Installation

npm install jasonkuhrt-heartbeat

Example

var tcp = require('net');
var heartbeat = require('heartbeat');

tcp.createServer(9000, function(socket){
  /* If we the socket ever doesn't send data for ten
  consecutive seconds, consider it dead.*/
  var thump = heartbeat(onFlatline, 10000);
  socket.on('data', thump);

  function onFlatline(){
    log.warn('Socket timed out, destroying socket.');
    socket.removeListener('data', thump);
    socket.removeListener('end', onCleanDisconnect);
    socket.destroy();
  }

  /* On a clean disconnect destroy the heartbeat.*/

  socket.once('end', onCleanDisconnect);

  function onCleanDisconnect(){
    socket.removeListener('data', thump);
    heartbeat.clear(thump);
  }
});

> npm start
...
... (some time passes, your app does stuff, then maybe...)
...
Socket timed out, destroying socket.

API

Heartbeat → .setHeartbeat

.setHeartbeat(onFlatline, intervalMs)

Heartbeat h; Int i;  :: ( -> ), i -> h

Returns a heartbeat instance. A heartbeat instance is a function. Invoke it to keep the heartbeat going. The identifier is typically thump (see guide).

• onFlatline is invoked when/if thump is not invoked during an interval.

• intervalMs sets the time between thump checks.

.clear(heartbeat)

Heartbeat a :: a -> undefined

Destroy a heartbeat instance. Analagous to clearInterval/clearTimeout.

Only use clearHeartbeat if you need to abort a heartbeat before onFlatline.

Guide

https://github.com/jasonkuhrt/heartbeat/blob/master/test/index.js