highcharts-export-server/lib/server/routes/health.js

Convert Highcharts.JS charts into static image files.

/*******************************************************************************

Highcharts Export Server

Copyright (c) 2016-2024, Highsoft

Licenced under the MIT licence.

Additionally a valid Highcharts license is required for use.

See LICENSE file in root for details.

*******************************************************************************/

import { readFileSync } from 'fs';
import { join as pather } from 'path';
import { log } from '../../logger.js';

import { version } from '../../cache.js';
import { addInterval } from '../../intervals.js';
import pool from '../../pool.js';
import { __dirname } from '../../utils.js';

const pkgFile = JSON.parse(readFileSync(pather(__dirname, 'package.json')));

const serverStartTime = new Date();

const successRates = [];
const recordInterval = 60 * 1000; // record every minute
const windowSize = 30; // 30 minutes

/**
 * Calculates moving average indicator based on the data from the successRates
 * array.
 *
 * @returns {number} - A moving average for success ratio of the server exports.
 */
function calculateMovingAverage() {
  const sum = successRates.reduce((a, b) => a + b, 0);
  return sum / successRates.length;
}

/**
 * Starts the interval responsible for calculating current success rate ratio
 * and gathers
 *
 * @returns {NodeJS.Timeout} id - Id of an interval.
 */
export const startSuccessRate = () =>
  setInterval(() => {
    const stats = pool.getStats();
    const successRatio =
      stats.exportAttempts === 0
        ? 1
        : (stats.performedExports / stats.exportAttempts) * 100;

    successRates.push(successRatio);
    if (successRates.length > windowSize) {
      successRates.shift();
    }
  }, recordInterval);

/**
 * Adds the /health and /success-moving-average routes
 * which output basic stats for the server.
 */
export default function addHealthRoutes(app) {
  if (!app) {
    return false;
  }

  // Start processing success rate ratio interval and save its id to the array
  // for the graceful clearing on shutdown with injected addInterval funtion
  addInterval(startSuccessRate());

  app.get('/health', (_, res) => {
    const stats = pool.getStats();
    const period = successRates.length;
    const movingAverage = calculateMovingAverage();

    log(4, '[health.js] GET /health [200] - returning server health.');

    res.send({
      status: 'OK',
      bootTime: serverStartTime,
      uptime:
        Math.floor(
          (new Date().getTime() - serverStartTime.getTime()) / 1000 / 60
        ) + ' minutes',
      version: pkgFile.version,
      highchartsVersion: version(),
      averageProcessingTime: stats.spentAverage,
      performedExports: stats.performedExports,
      failedExports: stats.droppedExports,
      exportAttempts: stats.exportAttempts,
      sucessRatio: (stats.performedExports / stats.exportAttempts) * 100,
      // eslint-disable-next-line import/no-named-as-default-member
      pool: pool.getPoolInfoJSON(),

      // Moving average
      period,
      movingAverage,
      message:
        isNaN(movingAverage) || !successRates.length
          ? 'Too early to report. No exports made yet. Please check back soon.'
          : `Last ${period} minutes had a success rate of ${movingAverage.toFixed(2)}%.`,

      // SVG/JSON attempts
      svgExportAttempts: stats.exportFromSvgAttempts,
      jsonExportAttempts: stats.performedExports - stats.exportFromSvgAttempts
    });
  });
}