godot

Godot is a streaming real-time event processor based on Riemann written in Node.js

• Usage
• Events
• Reactors
  • Primitives
• Producers
• Tests

Usage

Here is a simple example of a Reactor server that will send an email to user@host.com if the Producer server for app.server fails to send a heartbeat after 60 seconds.

  var godot = require('../lib/godot');

  //
  // Reactor server which will email `user@host.com`
  // whenever any service matching /.*\/health\/heartbeat/
  // fails to check in after 60 seconds.
  //
  godot.createServer({
    //
    // Defaults to UDP
    //
    type: 'udp',
    reactors: [
      godot.reactor()
        .where('service', '*/health/heartbeat')
        .expire(1000 * 60)
        .email({ to: 'user@host.com' })
    ]
  }).listen(1337);

  //
  // Producer client which sends events for the service
  // `app.server/health/heartbeat` every 15 seconds.
  //
  godot.createClient({
    //
    // Defaults to UDP
    //
    type: 'udp',
    producers: [
      godot.producer({
        host: 'app.server.com',
        service: 'app.server/health/heartbeat',
        ttl: 1000 * 15
      })
    ],
    //
    // Add Reconnect logic that uses node-backoff
    //
    reconnect: {
      type: 'exponential',
      maxTries: 2,
      initialDelay: 100,
      maxDelay: 300
    }
  }).connect(1337);

Events

Similar to Riemann, events in godot are simply JSON sent over UDP or TCP. Each event has these optional fields:

  {
    host:         "A hostname, e.g. 'api1', 'foo.com'"
    service:      "e.g. 'API port 8000 reqs/sec'",
    state:        "Any string less than 255 bytes, e.g. 'ok', 'warning', 'critical'",
    time:         "The time of the event, in unix epoch seconds",
    description:  "Freeform text",
    tags:         "Freeform list of strings, e.g. ['rate', 'fooproduct', 'transient']",
    meta:         "Freeform set of key:value pairs e.g. { 'ewma': 12345 }",
    metric:       "A number associated with this event, e.g. the number of reqs/sec.",
    ttl:          "A floating-point time, in seconds, that this event is considered valid for."
  }

Reactors

Reactors in Godot are readable and writable Stream instances which consume Events and produce actions or aggregate data flow.

Primitives

There are several core Reactor primitives available in godot which can be composed to create more complex behavior:

• .aggregate(): Aggregates metric property on events
• .change(key {from: x, to: y}): Emits events when the key is changed, accepts optional from and to options for more specific changes.
• .email(options): Sends an email to the specified options.
• .expire(ttl): Emits an event when no data is received after ttl milliseconds.
• .forward(options): Forwards all events to a remote server located at options.host and options.port.
• .sms(options): Sends an sms to the specified options.
• .where(key, value)|.where(filters): Filters events based on a single key:value pair or a set of key:value filters.
• .rollup(interval, limit)|.rollup(options): Rollup a limit amount of events to emit every interval. interval can also be a function to allow you to create varying intervals (see below).

Rollup

Here are two possible rollup examples:

//
// Rolls up 10,0000 events every 5 minute interval
//
var rollup =
  reactor()
    .rollup(1000 * 60 * 5, 10000)

//
// Scaling Rollup, rolls up 10,000 events every 5min interval for 1 hour,
// then rolls up 10,000 events every 30mins
//

var scalingRollup =
  reactor()
    .rollup(function (period) {
      if(period < 12) {
        return 1000 * 60 * 5;
      }
      return 1000 * 60 * 30;
    }, 10000)

Producers

Producers in Godot are readable Stream instances which produce Events. Events will be emitted by a given Producer every ttl milliseconds.

Tests

All tests are written in vows and can be run with npm:

  npm test

Copyright (C) 2012. Nodejitsu Inc.