collectd-protocol

This is a NodeJS module for decoding and encoding Collectd's binary protocol collectd. It supports decoding/encoding binary protocol from versions 4 and 5 of collectd.

Custom binary protocol

This module allows to build a binary protocol based on Collectd's specification using custom string parts. This is useful when you need to send some kind of metadata with the metrics. It's not guaranteed that the custom protocol works with the protocol defined in the specification. Use at you own risk.

Configuring the custom parts

To exchange metrics with a custom tags part, both ends would have to support the following configuration:

var binaryData = encoder.encodeCustom(originalJsonData, { 0x0099: 'tags' });
var jsonData = decoder.decodeCustom(binaryData, { 0x0099: 'tags' });`

Would produce something like:

[
  {
    host: 'localhost',
    time: 1455098772,
    interval: 10,
    plugin: 'GenericJMX',
    plugin_instance: 'MemoryPool|Eden_Space',
    type: 'custom',
    type_instance: 'committed',
    dstypes: [ 'gauge' ],
    values: [ 152567808.92 ],
    dsnames: [ 'value' ],
    tags: 'host=localhost,cluster=dev'
  }
]

In the custom part configuration we have chosen the part type id 0x0099 because it's currently unused in the binary protocol specification. Note that future revisions of the binary protocol may use your custom part ids.

Installation

npm install collectd-protocol --save

Contributing

In lieu of a formal styleguide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code.

Running unit tests

grunt test

TODO

• Improve handling of large numbers encoding which Javascript can't handle with precision (numbers greater than Number.MAX_SAFE_INTEGER). It's ok for now since we convert high precision numbers to low precision every time, which makes the least significant bits irrelevant.
• Support async computations on message encoding (will break current encoding interface)
• Add logger support

Notes

Grouped metrics of the same type

The spec is vague about the way metrics of the same type are sent over the wire. Consider the following representation of a sequence of metrics of the same type, where some of the parts are omitted on subsequent metrics:

[--host-------------]
[--time_hr----------]
[--interval_hr------]
[--plugin-----------]
[--plugin_instance--]
[--type-------------]
[--type_instance----]
[--values-----------] <- ends
[--time_hr----------]
[--type_instance----]
[--values-----------] <- ends
[--time_hr----------]
[--type_instance----]
[--values-----------] <- ends

According to the network plugin source code, the value is always sent as the last part of a metric, so that's the way we're doing to understand when a metric ends. That's an assumption based on the current Collectd's network plugin implementation.

Release History

• 0.0.1

  • Fork from node-collectd
  • Removed the CollectD receiver to make this module a protocol
  • Changed the protocol to just use timer and interval properties whether is high resolution or not
  • Updated node-ctype dependency and removed unnecessary code
  • Added unit tests
  • Integration with Grunt
  • Integration with Travis
  • Created an encoder

• 0.0.2

  • Remove node_modules directory from npm_ignore

• 0.1.0

  • Add async support for decoding messages
  • Changed the decoding function to use Streams

• 0.1.1

  • Fix invalid header check

• 0.2.0

  • Add support the data-set specifications (types.db)

• 0.3.0

  • Add support for custom part encoding and decoding (not compliant with binary protocol)

• 0.3.1

  • Fix decoding of unknown values (not in types.db specification)

• 0.3.2

  • Fix decoding of a sequence of metrics from the same plugin

• 0.3.3

  • Fix decoding of a sequence of metrics from the same plugin (revisited)