Dynamic Sampler

This is a collection of samplers that can be used to provide sample rates when sending data to services like honeycomb

Usage

With defaults:

import { PerKeyThroughput } from "dynamic-sampler";
const sampler = new PerKeyThroughput();

const rate = sampler.getSampleRate("my key");

With options

import { PerKeyThroughput } from "dynamic-sampler";
const sampler = new PerKeyThroughput({
  clearFrequencySec: 100,
  perKeyThroughputSec: 2
});

Choosing a Sampler

TODO

Implementing New Samplers

The Sampler class includes:

• timer setup
• construction of initial state (Maps)
• getSampleRate returns the rate for a given key

You can extend it to create new samplers. updateMaps is the only function that needs to be defined, but it is often useful to collect additional configuration from the constructor:

import { Sampler } from "dynamic-sampler";

export class PerKey extends Sampler {
  constructor(opts = {}) {
    super(opts);
    this.perKeyThroughputSec = opts.perKeyThroughputSec || 5;
  }
  updateMaps() {
    if (this.currentCounts.size == 0) {
      //no traffic in the last 30s. clear the result Map
      this.savedSampleRates.clear();
      return;
    }
    const actualPerKeyRate = this.perKeyThroughputSec * this.clearFrequencySec;

    const newRates = new Map();
    this.currentCounts.forEach((val, key) => {
      newRates.set(key, Math.floor(Math.max(1, val / actualPerKeyRate)));
    });
    this.savedSampleRates = newRates;
  }
}

Modifying getSampleRate

Sometimes it makes sense to check additional state in getSampleRate and return a different result based on that. When overriding the function call super.getSampleRate.

class MySampler extends Sampler {
  constructor(opts = {}) {
    super(opts);
    this.hasReceivedTraffic = false;
  }
  updateMaps() {
    // other logic
    this.hasReceivedTraffic = true;
  }
  getSampleRate(key) {
    const superSampleRate = super.getSampleRate(key);
    if (!this.hasReceivedTraffic) {
      return this.goalSampleRate;
    } else {
      return superSampleRate;
    }
  }
}