51Degrees Device Detection Node.js  4.4

51Degrees Device Detection for Node.js


This example illustrates various parameters that can be adjusted when using the on-premise device detection engine, and controls when a new data file is sought and when it is loaded by the device detection software.Three main aspects are demonstrated:

  • Update on Start-Up
  • Filesystem Watcher
  • Daily auto-update

License Key

In order to test this example you will need a 51Degrees Enterprise license which can be purchased from our pricing page. Look for our "Bigger" or "Biggest" options.

Data Files

You can find out more about data files, licenses etc. at our (FAQ page)[//51degrees.com/resources/faqs]

Enterprise Data File

Enterprise (fully-featured) data files are typically released by 51Degrees four days a week (Mon-Thu) and on-premise deployments can fetch and download those files automatically. Equally, customers may choose to download the files themselves and move them into place to be detected by the 51Degrees filesystem watcher.

Manual Download

If you prefer to download files yourself, you may do so here:


Lite Data File

Lite data files (free-to-use, limited capabilities, no license key required) are created roughly once a month and cannot be updated using auto-update, they may be downloaded from (Github)[href=https://github.com/51Degrees/device-detection-data] and are included with source distributions of this software.

Update on Start-Up

You can configure the pipeline builder to download an Enterprise data file on start-up.


  • a license key
  • a file location for the download
    • this may be an existing file - which will be overwritten
    • or if it does not exist must end in ".hash" and must be in an existing directory


  • the pipeline must be configured to use a temp file
    createTempDataCopy: true
  • a DataFileUpdateService must be supplied
    dataUpdateService.on('updateComplete', function(status, dataFile) {
    // do something with the result.
    dataFileUpdateService: dataUpdateService
  • update on start-up must be specified, which will cause pipeline creation to block until a file is downloaded
    updateOnStart: true

    File System Watcher

You can configure the pipeline builder to watch for changes to the currently loaded device detection data file, and to replace the file currently in use with the new one. This is useful, for example, if you wish to download and update the device detection file "manually" - i.e. you would download it then drop it into place with the same path as the currently loaded file. That location is checked periodically (by default every 30 mins) and this frequency can be configured.


  • a license key
  • the file location of the existing file


  • the pipeline must be configured to use a temp file
    createTempDataCopy: true
  • a DataFileUpdateService must be supplied
    dataUpdateService.on('updateComplete', function(status, dataFile) {
    // do something with the result.
    dataFileUpdateService: dataUpdateService
  • configure the frequency with which the location is checked, in seconds (10 mins as shown)
    pollingInterval: 10*60

    Daily auto-update

Enterprise data files are usually created four times a week. Each data file contains a date for when the next data file is expected. You can configure the pipeline so that it starts looking for a newer data file after that time, by connecting to the 51Degrees distributor to see if an update is available. If one is, then it is downloaded and will replace the existing device detection file, which is currently in use.


  • a license key
  • the file location of the existing file


  • the pipeline must be configured to use a temp file
    createTempDataCopy: true
  • a DataFileUpdateService must be supplied
    dataUpdateService.on('updateComplete', function(status, dataFile) {
    // do something with the result.
    dataFileUpdateService: dataUpdateService
  • Set the frequency in seconds that the pipeline should check for updates to data files. A recommended polling interval in a production environment is around 30 minutes.
    pollingInterval: 10*60
  • Set the max amount of time in seconds that should be added to the polling interval. This is useful in datacenter applications where multiple instances may be polling for updates at the same time. A recommended ammount in production environments is 600 seconds.
    updateTimeMaximumRandomisation: 10*60


This example is available in full on GitHub.

This example requires a subscription to 51Degrees Device Data, a subscription can be acquired from the 51Degrees pricing page.

Required npm Dependencies:

  • fiftyone.pipeline.core
  • fiftyone.pipeline.engines
  • fiftyone.pipeline.engines.fiftyone
  • fiftyone.devicedetection.onpremise
/* *********************************************************************
* This Original Work is copyright of 51 Degrees Mobile Experts Limited.
* Copyright 2022 51 Degrees Mobile Experts Limited, Davidson House,
* Forbury Square, Reading, Berkshire, United Kingdom RG1 3EU.
* This Original Work is licensed under the European Union Public Licence
* (EUPL) v.1.2 and is subject to its terms as set out below.
* If a copy of the EUPL was not distributed with this file, You can obtain
* one at https://opensource.org/licenses/EUPL-1.2.
* The 'Compatible Licences' set out in the Appendix to the EUPL (as may be
* amended by the European Commission) shall be deemed incompatible for
* the purposes of the Work and the provisions of the compatibility
* clause in Article 5 of the EUPL shall not apply.
* If using the Work as, or as part of, a network application, by
* including the attribution notice(s) required under Article 5 of the EUPL
* in the end user terms of the application under an appropriate heading,
* such notice(s) shall fulfill the requirements of that article.
* ********************************************************************* */
const fs = require('fs');
const path = require('path');
const os = require('os');
const DataFileUpdateService = require('fiftyone.pipeline.engines').DataFileUpdateService;
const AutoUpdateStatus = require('fiftyone.pipeline.engines').AutoUpdateStatus;
require(path.join(__dirname, '/../../../deviceDetectionOnPremisePipelineBuilder'));
const ExampleUtils = require(path.join(__dirname, '/../exampleUtils')).ExampleUtils;
const ExampleConstants = require('fiftyone.devicedetection.shared').exampleConstants;
const KeyUtils = require('fiftyone.devicedetection.shared').keyUtils;
os.homedir() + path.sep + ExampleConstants.fileNames.enterpriseDataFileName;
const run = async function (dataFilePath, licenseKey, interactive, output) {
output.write('Starting example\n');
// try to find a license key
if (!licenseKey) {
licenseKey = KeyUtils.getNamedKey(UPDATE_EXAMPLE_LICENSE_KEY_NAME);
if (!licenseKey || KeyUtils.isInvalidKey(licenseKey)) {
console.error('In order to test this example you will need a 51Degrees Enterprise ' +
'license which can be obtained on a trial basis or purchased from our\n' +
'pricing page http://51degrees.com/pricing. You must supply the license ' +
'key as an argument to this program, or as an environment or system variable ' +
throw new Error('No license key available');
// work out where the downloaded file will be put, directory must exist
if (dataFilePath) {
try {
dataFilePath = ExampleUtils.findFile(dataFilePath);
} catch (e) {
if (fs.existsSync(path.dirname(dataFilePath))) {
console.error('The directory must exist when specifying a location for a new ' +
`file to be downloaded. Path specified was '${dataFilePath}'`);
throw new Error('Directory for new file must exist');
console.warn(`File ${dataFilePath} not found, a file will be downloaded to that location on ` +
// no filename specified use the default
if (!dataFilePath) {
console.warn(`No filename specified. Using default '${dataFilePath}' which will be downloaded to ` +
'that location on start-up, if it does not exist already');
const copyDataFile = dataFilePath + '.bak';
if (fs.existsSync(dataFilePath)) {
// let's check this file out
dataFile: dataFilePath,
performanceProfile: 'LowMemory',
shareUsage: false,
autoUpdate: false,
updateOnStart: false,
fileSystemWatcher: false
// and output the results
ExampleUtils.checkDataFile(pipeline, dataFilePath);
if (ExampleUtils.getDataTier(pipeline) === 'Lite') {
console.error('Will not download an "Enterprise" data file over the top of ' +
'a "Lite" data file, please supply another location.');
throw new Error('File supplied has wrong data tier');
output.write('Existing data file will be replaced with downloaded data file\n');
output.write(`Existing data file will be copied to ${copyDataFile}\n`);
// do we really want to do this
if (interactive) {
const buffer = Buffer.alloc(1);
output.write('Please note - this example will use available downloads ' +
'in your licensed allocation.\n');
output.write('Do you wish to continue with this example (y)? ');
fs.readSync(0, buffer, 0, 1);
const input = buffer.toString('utf8');
if ((input === os.EOL || input.toLowerCase().startsWith('y')) === false) {
output.write('Stopping example without download\n');
output.write('Checking file exists\n');
if (fs.existsSync(dataFilePath)) {
fs.copyFileSync(dataFilePath, copyDataFile);
output.write(`Existing data file copied to ${copyDataFile}\n`);
output.write('Creating pipeline and initiating update on start-up - please wait for that ' +
'to complete\n');
// create update service and add listener
const dataUpdateService = new DataFileUpdateService();
new Promise(resolve => {
dataUpdateService.once('updateComplete', function (status, dataFile) {
// thread blocks till update checking is complete - or if there is an
// exception we don't get this far
output.write(`Update on start-up complete - status: ${status}\n`);
if (status !== AutoUpdateStatus.AUTO_UPDATE_SUCCESS) {
output.write('Auto update was not successful, abandoning example\n');
throw new Error('Auto update failed: ' + status);
.then(() => {
output.write('Modifying downloaded file to trigger reload - please wait for that' +
' to complete\n');
// In this example we set a timeout to make sure node waits for the promise
// to complete. Without this, node exits without waiting for the promise.
// This is not a neat way of achieving this, but for now it makes the
// example run as intended.
const timeoutId = setTimeout(() => {
output.write('Update on file modification timed out\n');
}, 60 * 1000);
return new Promise(resolve => {
dataUpdateService.once('updateComplete', function (status, dataFile) {
output.write(`Update on file modification complete - status: ${status}\n`);
try {
// it's the same file but changing the file metadata will trigger reload,
// demonstrating that if you download a new file and replace the
// existing one, then it will be loaded
const time = new Date();
fs.utimesSync(dataFilePath, time, time);
} catch (err) {
throw new Error('Could not modify file time - abandoning ' +
.then(() => {
output.write('Finished example\n');
// Build the device detection pipeline and pass in the desired settings to configure
// automatic updates.
dataFileUpdateService: dataUpdateService,
// specify the filename for the data file. When using update on start-up
// the file need not exist, but the directory it is in must exist.
// Any file that is present is overwritten. Because the file will be
// overwritten the pipeline must be configured to copy the supplied
// file to a temporary file (createTempDataCopy parameter == true.
dataFile: dataFilePath,
createTempDataCopy: true,
// Enable automatic updates once the pipeline has started
autoUpdate: true,
// For automatic updates to work you will need to provide a license key.
// A license key can be obtained with a subscription from https://51degrees.com/pricing
licenceKeys: licenseKey,
// Enable update on startup, the auto update system
// will be used to check for an update before the
// device detection engine is created. This will block
// creation of the pipeline.
updateOnStart: true,
// Watch the data file on disk and refresh the engine
// as soon as that file is updated.
dataFileSystemWatcher: true,
// for the purposes of this example we are setting the time
// between checks to see if the file has changed to 1 second
// by default this is 30 mins
pollingInterval: 1
// build the pipeline
// Don't run the server if under TEST
if (process.env.JEST_WORKER_ID === undefined) {
const args = process.argv.slice(2);
// Use the supplied path for the data file or find the lite
// file that is included in the repository.
const licenseKey = args.length > 0 ? args[0] : null;
const dataFilePath = args.length > 1 ? args[1] : null;
run(dataFilePath, licenseKey, true, process.stdout);
module.exports = { run };