Samples for synthetic monitors

This document describes the templates and sample code that are available to help you create synthetic monitors. The sample functions are available on the Google Cloud/synthetics-sdk-nodjs repository.

If you write tests and don't rely on a template, then ensure that your test passes unless an Error is thrown. We recommend that you use the Assert library to ensure that when failures occur, they are attributed to the proper line of code.

Generic templates

The generic templates are configured to collect trace and log data for outbound HTTP requests. The solution leverages the OpenTelemetry auto-instrumentation-node module and the winston logger. Due to the dependency on open source products, you should expect changes in the structure of trace and log data. Therefore, the collected trace and log data should be used only for debugging purposes.

You can implement your own approach to collect trace and log data for outbound HTTP requests. For an example of a custom approach, see the class SyntheticAutoInstrumentation.

Generic Node.js sample

The generic-synthetic-nodejs sample illustrates how to query a URL. This sample contains the same as the default function displayed by the Google Cloud console.

const { instantiateAutoInstrumentation, runSyntheticHandler } = require('@google-cloud/synthetics-sdk-api');
// Run instantiateAutoInstrumentation before any other code runs, to get automatic logs and traces
instantiateAutoInstrumentation();
const functions = require('@google-cloud/functions-framework');
const axios = require('axios');
const assert = require('node:assert');

functions.http('SyntheticFunction', runSyntheticHandler(async ({logger, executionId}) => {
  /*
   * This function executes the synthetic code for testing purposes.
   * If the code runs without errors, the synthetic test is considered successful.
   * If an error is thrown during execution, the synthetic test is considered failed.
   */
  logger.info('Making an http request using synthetics, with execution id: ' + executionId);
  const url = 'https://www.google.com/'; // URL to send the request to
  return await assert.doesNotReject(axios.get(url));
}));

TypeScript sample

The generic-synthetic-typescript sample illustrates how to query a URL.

import {runSyntheticHandler, instantiateAutoInstrumentation} from '@google-cloud/synthetics-sdk-api'
// Run instantiateAutoInstrumentation before any other code runs, to get automatic logs and traces
instantiateAutoInstrumentation();
import * as ff from '@google-cloud/functions-framework';
import axios from 'axios';
import assert from 'node:assert';
import {Logger} from 'winston';

ff.http('SyntheticFunction', runSyntheticHandler(async ({logger, executionId}: {logger: Logger, executionId: string|undefined}) => {
  /*
   * This function executes the synthetic code for testing purposes.
   * If the code runs without errors, the synthetic test is considered successful.
   * If an error is thrown during execution, the synthetic test is considered failed.
   */
  logger.info('Making an http request using synthetics, with execution id: ' + executionId);
  const url = 'https://www.google.com/'; // URL to send the request to
  return await assert.doesNotReject(axios.get(url));
}));

Puppeteer template

If you use Puppeteer, then consider starting with the generic-puppeteer-nodejs sample. This sample illustrates how to use Puppeteer with your Cloud Function.

const { instantiateAutoInstrumentation, runSyntheticHandler } = require('@google-cloud/synthetics-sdk-api');
// Run instantiateAutoInstrumentation before any other code runs, to get automatic logs and traces
instantiateAutoInstrumentation();
const functions = require('@google-cloud/functions-framework');
const axios = require('axios');
const assert = require('node:assert');
const puppeteer = require('puppeteer');


functions.http('CustomPuppeteerSynthetic', runSyntheticHandler(async ({logger, executionId}) => {
 /*
  * This function executes the synthetic code for testing purposes.
  * If the code runs without errors, the synthetic test is considered successful.
  * If an error is thrown during execution, the synthetic test is considered failed.
  */

 // Launch a headless Chrome browser and open a new page
 const browser = await puppeteer.launch({ headless: 'new', timeout: 0});
 const page = await browser.newPage();

 // Navigate to the target URL
 const result = await page.goto('https://www.example.com', {waitUntil: 'load'});

 // Confirm successful navigation
 await assert.equal(result.status(), 200);

 // Print the page title to the console
 const title = await page.title();
 logger.info(`My Page title: ${title} ` + executionId);

 // Close the browser
 await browser.close();
}));

Mocha template

If you write tests that rely on the Mocha template, then consider whether a sequence of tests should continue, or stop, when a failure occurs. To stop a sequence of tests after a failure, you must set the bail flag.

For an end-to-end example which includes deploying an API, a sample Mocha test suite for the API endpoints, and how to configure the synthetic monitor, see the blog Google Cloud Synthetic Monitoring Tutorial.

The mocha-url-ok sample illustrates how a Cloud Function can invoke a Mocha test suite, and it provides a sample test suite.


const functions = require('@google-cloud/functions-framework');
const GcmSynthetics = require('@google-cloud/synthetics-sdk-mocha');

/*
 * This is the server template that is required to run a synthetic monitor in
 * Google Cloud Functions.
 */

functions.http('SyntheticMochaSuite', GcmSynthetics.runMochaHandler({
  spec: `${__dirname}/mocha_tests.spec.js`
}));

/*
 * This is the file may be interacted with to author mocha tests. To interact
 * with other GCP products or services, users should add dependencies to the
 * package.json file, and require those dependencies here A few examples:
 *  - @google-cloud/secret-manager:
 *        https://www.npmjs.com/package/@google-cloud/secret-manager
 *  - @google-cloud/spanner: https://www.npmjs.com/package/@google-cloud/spanner
 *  - Supertest: https://www.npmjs.com/package/supertest
 */

const {expect} = require('chai');
const fetch = require('node-fetch');

it('pings my website', async () => {
  const url = 'https://google.com/'; // URL to send the request to
  const externalRes = await fetch(url);
  expect(externalRes.ok).to.be.true;
});

The broken-links-ok sample illustrates how to configure a broken-link checker. For this template, you only specify the values of the options object. This object specifies the URI to be tested, and the parameters of the test. For details, see the following code:


const functions = require('@google-cloud/functions-framework');
const GcmSynthetics = require('@google-cloud/synthetics-sdk-broken-links');

const options = {
  origin_uri: "https://example.com",
  // link_limit: 10,
  // query_selector_all: "a", // https://developer.mozilla.org/en-US/docs/Web/API/Document/querySelectorAll
  // get_attributes: ['href'], // https://developer.mozilla.org/en-US/docs/Web/API/Element/getAttribute
  // link_order: "FIRST_N", // "FIRST_N" or "RANDOM"
  // link_timeout_millis: 30000, // timeout per link
  // max_retries: 0, // number of retries per link if it failed for any reason
  // wait_for_selector: '', // https://pptr.dev/api/puppeteer.page.waitforselector
  // per_link_options: {}
    /*
    // example:
      per_link_options: {
        'http://fake-link1': { expected_status_code: "STATUS_CLASS_4XX" },
        'http://fake-link2': { expected_status_code: 304 },
        'http://fake-link3': { link_timeout_millis: 10000 },
        'http://fake-link4': {
          expected_status_code: "STATUS_CLASS_3XX",
          link_timeout_millis: 10,
        },
      },
    */
};

functions.http('BrokenLinkChecker', GcmSynthetics.runBrokenLinksHandler(options));

What's next