Prevent duplicate issues from same user https://github.com/getsentry/raven-js/issues/530

filterThrottle.js

// @flow weak

function now() {
  return +new Date(); // timestamp in  ms
}

// Count the number of events sent over the last period of time.
const count = {
  minute: {
    slot: 0,
    budgetUsed: 0,
  },
  hour: {
    slot: 0,
    budgetUsed: 0,
  },
};

function filterThrottle(options) {
  const {
    maxBudgetMinute,
    maxBudgetHour,
    getDate = now,
  } = options;

  return () => {
    const timestamp = getDate();

    const minuteSlot = Math.round(timestamp / 1000 / 60);
    const hourSlot = Math.round(timestamp / 1000 / 60 / 60);

    // We are on a new minute slot.
    if (count.minute.slot !== minuteSlot) {
      count.minute.slot = minuteSlot;
      count.minute.budgetUsed = 0;
    }

    // We are on a new hour slot.
    if (count.hour.slot !== hourSlot) {
      count.hour.slot = hourSlot;
      count.hour.budgetUsed = 0;
    }

    // Check minute usage
    if (count.minute.budgetUsed < maxBudgetMinute) {
      count.minute.budgetUsed++;

      // Check hour usage
      if (count.hour.budgetUsed < maxBudgetHour) {
        count.hour.budgetUsed++;
        return true;
      }
    }

    return false;
  };
}

export default filterThrottle;

filterThrottle.test.js

// @flow weak

import {assert} from 'chai';
import filterThrottle from './filterThrottle';

describe.only('crashReporter/filterThrottle', () => {
  it('should work', () => {
    let hour = 0;
    let minute = 0;

    const shouldSendCallback = filterThrottle({
      maxBudgetMinute: 2,
      maxBudgetHour: 5,
      getDate: () => (hour * 60 + minute) * 60 * 1000, // timestamp ms
    });

    assert.strictEqual(shouldSendCallback(), true);
    assert.strictEqual(shouldSendCallback(), true);
    assert.strictEqual(shouldSendCallback(), false);

    minute++;

    assert.strictEqual(shouldSendCallback(), true);
    assert.strictEqual(shouldSendCallback(), true);
    assert.strictEqual(shouldSendCallback(), false);

    minute++;

    assert.strictEqual(shouldSendCallback(), true);
    assert.strictEqual(shouldSendCallback(), false);

    minute++;

    assert.strictEqual(shouldSendCallback(), false);

    minute++;
    hour++;

    assert.strictEqual(shouldSendCallback(), true);
  });
});