Backendjs Documentation

Table of contents

Backend library for Node.js

General purpose backend library. The primary goal is to have a scalable platform for running and managing Node.js servers for Web services implementation.

This project only covers the lower portion of the Web services ecosystem: Node.js processes, HTTP servers, basic API functionality, database access, caching, messaging between processes, metrics and monitoring, a library of tools for developing Node.js servers.

For the UI and presentation layer there are no restrictions what to use as long as it can run on top of the Express server.


Check out the Documentation for more details.


To install the module with all optional dependencies if they are available in the system

npm install backendjs

To install from the git

 npm install git+

or simply

 npm install vseryakov/backendjs


Only core required dependencies are installed but there are many modules which require a module to work correctly.

All optional dependencies are listed in the package.json under "modDependencies" so npm cannot use it, only manual install of required modules is supported or it is possible to install all optional dependencies for development purposes.

Here is the list of modules required for each internal feature:

The command below will show all core and optional dependencies, npm install will install only the core dependencies

 bkjs deps -dry-run -mods

Quick start and introduction

or the same using async/await, same methods with a prepended to the name

    > await db.aselect("bk_user", {});
    > await db.aadd("bk_user", { id: 'test2', login: 'test2', secret: 'test2', name' Test 2 name' });
    > await db.aselect("bk_user", { id: 'test2' });

To run an example


Almost everything in the backend is configurable using config files, a config database or DNS. The whole principle behind it is that once deployed in production, even quick restarts are impossible to do so there should be a way to push config changes to the processes without restarting.

Every module defines a set of config parameters that defines the behavior of the code, due to the single threaded nature of the Node.js. It is simple to update any config parameter to a new value so the code can operate differently. To achieve this the code must be written in a special way, like driven by configuration which can be changed at any time.

All configuration goes through the configuration process that checks all inputs and produces valid output which is applied to the module variables. Config file or database table with configuration can be loaded on demand or periodically, for example all local config files are watched for modification and reloaded automatically, the config database is loaded periodically which is defined by another config parameter.

Backend runtime

When the backendjs server starts it spawns several processes that perform different tasks.

There are 2 major tasks of the backend that can be run at the same time or in any combination:

These features can be run standalone or under the guard of the monitor which tracks all running processes and restarted any failed ones.

This is the typical output from the ps command on Linux server:

ec2-user    891  0.0  0.6 1071632 49504 ?  Ssl  14:33   0:01 bkjs: monitor
ec2-user    899  0.0  0.6 1073844 52892 ?  Sl   14:33   0:01 bkjs: master
ec2-user    908  0.0  0.8 1081020 68780 ?  Sl   14:33   0:02 bkjs: server
ec2-user    917  0.0  0.7 1072820 59008 ?  Sl   14:33   0:01 bkjs: web
ec2-user    919  0.0  0.7 1072820 60792 ?  Sl   14:33   0:02 bkjs: web
ec2-user    921  0.0  0.7 1072120 40721 ?  Sl   14:33   0:02 bkjs: worker

To enable any task a command line parameter must be provided, it cannot be specified in the config file. The bkjs utility supports several commands that simplify running the backend in different modes.

Application structure

The main purpose of the backendjs is to provide API to access the data, the data can be stored in the database or some other way but the access to that data will be over HTTP and returned back as JSON. This is default functionality but any custom application may return data in whatever format is required.

Basically the backendjs is a Web server with ability to perform data processing using local or remote jobs which can be scheduled similar to Unix cron.

The principle behind the system is that nowadays the API services just return data which Web apps or mobiles apps can render to the user without the backend involved. It does not mean this is simple gateway between the database, in many cases it is but if special processing of the data is needed before sending it to the user, it is possible to do and backendjs provides many convenient helpers and tools for it.

When the API layer is initialized, the api module contains app object which is an Express server.

Special module/namespace app is designated to be used for application development/extension. This module is available in the same way as api and core which makes it easy to refer and extend with additional methods and structures.

The typical structure of a single file backendjs application is the following:

    const bkjs = require('backendjs');
    const api = bkjs.api;
    const app =;
    const db = bkjs.db;

    app.listArg = [];

    // Define the module config parameters
    core.describeArgs('app', [
        { name: "list-arg", array: 1, type: "list", descr: "List of words" },
        { name: "int-arg", type: "int", descr: "An integer parameter" },

    // Describe the tables or data models, all DB pools will use it, the master or shell
    // process only creates new tables, workers just use the existing tables

     // Optionally customize the Express environment, setup MVC routes or else, `` is the Express server
    app.configureMiddleware = function(options, callback)

    // Register API endpoints, i.e. url callbacks
    app.configureWeb = function(options, callback)
    {'/some/api/endpoint', (req, res) => {
          // to return an error, the message will be translated with internal i18n module if locales
          // are loaded and the request requires it
          api.sendReply(res, err);

          // or with custom status and message, explicitely translated
          api.sendReply(res, 404, res.__({ phrase: "not found", locale: "fr" }));

          // with config check
          if (app.intArg > 5) ...
          if (app.listArg.indexOf( > -1) ...

          // to send data back with optional postprocessing hooks
          api.sendJSON(req, err, data);
          // or simply

    // Optionally register post processing of the returned data from the default calls
    api.registerPostProcess('', /^\/account\/([a-z\/]+)$/, (req, res, rows) => { ... });

    // Optionally register access permissions callbacks
    api.registerAccessCheck('', /^\/test\/list$/, (req, status, callback) => { ...  });
    api.registerPreProcess('', /^\/test\/list$/, (req, status, callback) => { ...  });

Another probably easier way to create single file apps is to use your namespace instead of app:

    const bkjs = require("backendjs");
    const api = bkjs.api;
    const db = bkjs.db;

    const mymod = {
        name: "mymod",
        args: [
            { name: "types", type: "list", descr: "Types allowed" },
            { name: "size", type: "int", descr: "Records in one page" },
        tables: {
            mytable: {
                id: { type: "int", primary: 1 },
                name: { primary: 2 },
                type: { type: "list" },
                descr: {}
    exports.module = mymod;

    mymod.configureWeb = function(options, callback)
    {"/mymod", async function(req, res) {
            if (! return api.sendReply(res, 400, "id is required");
            req.query.type = mod.types;

            const rows = await db.aselect("mymod", req.query, { ops: { type: "in" }, count: mod.size });
            api.sendJSON(req, null, rows);


Except the app.configureWeb and server.start() all other functions are optional, they are here for the sake of completeness of the example. Also because running the backend involves more than just running web server many things can be setup using the configuration options like common access permissions, configuration of the cron jobs so the amount of code to be written to have fully functioning production API server is not that much, basically only request endpoint callbacks must be provided in the application.

As with any Node.js application, node modules are the way to build and extend the functionality, backendjs does not restrict how the application is structured.


By default no system modules are loaded except bk_user, it must be configured by the -preload-modules config parameter to preload modules from the backendjs/modules/.

Another way to add functionality to the backend is via external modules specific to the backend, these modules are loaded on startup from the backend home subdirectory modules/. The format is the same as for regular Node.js modules and only top level .js files are loaded on the backend startup.

Once loaded they have the same access to the backend as the rest of the code, the only difference is that they reside in the backend home and can be shipped regardless of the npm, node modules and other env setup. These modules are exposed in the core.modules the same way as all other core submodules methods.

Let's assume the modules/ contains file facebook.js which implements custom FB logic:

    const bkjs = require("backendjs");
    const core = bkjs.core;
    const mod = {
        name: "facebook",
        args: [
            { name: "token", descr: "API token" },
    module.exports = mod;

    mod.configureWeb = function(options, callback) {

    mod.makeRequest = function(options, callback) {
         core.sendRequest({ url: options.path, query: { access_token: fb.token } }, callback);

This is the main app code:

    const bkjs = require("backendjs");
    const core = bkjs.core;

    // Using facebook module in the main app"/me", (req, res) => {

       core.modules.facebook.makeRequest({ path: "/me" }, (err, data) => {
          bkjs.api.sendJSON(req, err, data);


NPM packages as modules

In case different modules is better keep separately for maintenance or development purposes they can be split into separate NPM packages, the structure is the same, modules must be in the modules/ folder and the package must be loadable via require as usual. In most cases just empty index.js is enough. Such modules will not be loaded via require though but by the backendjs core.loadModule machinery, the NPM packages are just keep different module directories separate from each other.

The config parameter allow-packages can be used to specify NPM package names to be loaded separated by comma, as with the default application structure all subfolders inside each NPM package will be added to the core:

If there is a config file present as etc/config it will be loaded as well, this way each package can maintain its default config parameters if necessary without touching other or global configuration. Although such config files will not be reloaded on changes, when NPM installs or updates packages it moves files around so watching the old config is no point because the updated config file will be different.

Database schema definition

The backend support multiple databases and provides the same db layer for access. Common operations are supported and all other specific usage can be achieved by using SQL directly or other query language supported by any particular database. The database operations supported in the unified way provide simple actions like db.get, db.put, db.update, db.del, The db.query method provides generic access to the database driver and executes given query directly by the db driver, it can be SQL or other driver specific query request.

Before the tables can be queried the schema must be defined and created, the backend db layer provides simple functions to do it:

           album: {
               id: { primary: 1 },                         // Primary key for an album
               name: { pub: 1 },                           // Album name, public column
               mtime: { type: "now" },                     // Modification timestamp
           photo: {
               album_id: { primary: 1 },                   // Combined primary key
               id: { primary: 1 },                         // consisting of album and photo id
               name: { pub: 1, index: 1 },                 // Photo name or description, public column with the index for faster search
               mtime: { type: "now" }

Each database may restrict how the schema is defined and used, the db layer does not provide an artificial layer hiding all specifics, it just provides the same API and syntax, for example, DynamoDB tables must have only hash primary key or combined hash and range key, so when creating table to be used with DynamoDB, only one or two columns can be marked with primary property while for SQL databases the composite primary key can consist of more than 2 columns.

The backendjs always creates several tables in the configured database pools by default, these tables are required to support default API functionality and some are required for backend operations. Refer below for the JavaScript modules documentation that described which tables are created by default. In the custom applications the db.describeTables method can modify columns in the default table and add more columns if needed.

For example, to make age and some other columns in the accounts table public and visible by other users with additional columns the following can be done in the api.initApplication method. It will extend the bk_user table and the application can use new columns the same way as the already existing columns. Using the birthday column we make 'age' property automatically calculated and visible in the result, this is done by the internal method api.processAccountRow which is registered as post process callback for the bk_user table. The computed property age will be returned because it is not present in the table definition and all properties not defined and configured are passed as is.

The cleanup of the public columns is done by the api.sendJSON which is used by all API routes when ready to send data back to the client. If any post-process hooks are registered and return data itself then it is the hook responsibility to cleanup non-public columns.

        bk_user: {
            birthday: {},
            ssn: {},
            salary: { type: "int" },
            occupation: {},
            home_phone: {},
            work_phone: {},

    app.configureWeb = function(options, callback)
       db.setProcessRow("post", "bk_user", this.processAccountRow);
    app.processAccountRow = function(req, row, options)
       if (row.birthday) row.age = Math.floor(( - core.toDate(row.birthday))/(86400000*365));

To define tables inside a module just provide a tables property in the module object, it will be picked up by database initialization automatically.

    const mod = {
        name: "billing",
        tables: {
            invoices: {
                id: { type: "int", primary: 1 },
                name: {},
                price: { type: "real" },
                mtime: { type: "now" }
    module.exports = mod;

    // Run db setup once all the DB pools are configured, for example produce dynamic icon property
    // for each record retrieved
    mod.configureModule = function(options, callback)
        db.setProcessRows("post", "invoices", function(req, row, opts) {
         if ( row.icon = "/images/" + + ".png";

Tables can have aliases

This is useful for easier naming conventions or switching to a different table name on the fly without changinbf the code, access to the table by it is real name is always available.

For example:

bksh -db-aliases-bk_user users

> await db.aget("bk_user", { login: "u1" })
> { login: "u1", name: "user", .... }

> await db.aget("users", { login: "u1" })
> { login: "u1", name: "user", .... }

API requests handling

All methods will put input parameters in the req.query, GET or POST.

One way to verify input values is to use lib.toParams, only specified parameters will be returned and converted according to the type or ignored.


   var params = {
      test1: { id: { type: "text" },
               count: { type: "int" },
               email: { regexp: /^[^@]+@[^@]+$/ }
   };"/endpoint/test1", function(req, res) {
      const query = lib.toParams(req.query, params.test1);
      if (typeof query == "string") return api.sendReply(res, 400, query);

Example of TODO application

Here is an example how to create simple TODO application using any database supported by the backend. It supports basic operations like add/update/delete a record, show all records.

Create a file named app.js with the code below.

    const bkjs = require('backendjs');
    const api = bkjs.api;
    const lib = bkjs.lib;
    const app =;
    const db = bkjs.db;

    // Describe the table to store todo records
       todo: {
           id: { type: "uuid", primary: 1 },  // Store unique task id
           due: {},                           // Due date
           name: {},                          // Short task name
           descr: {},                         // Full description
           mtime: { type: "now" }             // Last update time in ms

    // API routes
    app.configureWeb = function(options, callback)
    {^\/todo\/([a-z]+)$/, async function(req, res) {
           var options = api.getOptions(req);
           switch (req.params[0]) {
             case "get":
                if (! return api.sendReply(res, 400, "id is required");
                const rows = await db.aget("todo", { id: }, options);
                api.sendJSON(req, null, rows);

             case "select":
                options.noscan = 0; // Allow empty scan of the whole table if no query is given, disabled by default
                const rows = await db.aselect("todo", req.query, options);
                api.sendJSON(req, null, rows);

            case "add":
                if (! return api.sendReply(res, 400, "name is required");
                // By default due date is tomorrow
                if (req.query.due) req.query.due = lib.toDate(req.query.due, + 86400000).toISOString();
                db.add("todo", req.query, options, (err, rows) => {
                    api.sendJSON(req, err, rows);

            case "update":
                if (! return api.sendReply(res, 400, "id is required");
                const rows = await db.aupdate("todo", req.query, options);
                api.sendJSON(req, null, rows);

            case "del":
                if (! return api.sendReply(res, 400, "id is required");
                db.del("todo", { id: }, options, (err, rows) => {
                    api.sendJSON(req, err, rows);

Now run it with an option to allow API access without an account:

node app.js -log debug -web -api-allow-path /todo -db-create-tables

To use a different database, for example PostgresSQL(running localy) or DynamoDB(assuming EC2 instance), all config parametetrs can be stored in the etc/config as well

node app.js -log debug -web -api-allow-path /todo -db-pool dynamodb -db-dynamodb-pool default -db-create-tables
node app.js -log debug -web -api-allow-path /todo -db-pool pg -db-pg-pool default -db-create-tables

API commands can be executed in the browser or using curl:

curl 'http://localhost:8000/todo?name=TestTask1&descr=Descr1&due=2015-01-01`
curl 'http://localhost:8000/todo/select'

Backend directory structure

When the backend server starts and no -home argument passed in the command line the backend makes its home environment in the ~/.bkjs directory. It is also possible to set the default home using BKJS_HOME environment variable.

The backend directory structure is the following:

Cache configurations

Database layer support caching of the responses using db.getCached call, it retrieves exactly one record from the configured cache, if no record exists it will pull it from the database and on success will store it in the cache before returning to the client. When dealing with cached records, there is a special option that must be passed to all put/update/del database methods in order to clear local cache, so next time the record will be retrieved with new changes from the database and refresh the cache, that is { cached: true } can be passed in the options parameter for the db methods that may modify records with cached contents. In any case it is required to clear cache manually there is db.clearCache method for that.

Also there is a configuration option -db-caching to make any table automatically cached for all requests.


If no cache is configured the local driver is used, it keeps the cache on the master process in the LRU pool and any worker or Web process communicate with it via internal messaging provided by the cluster module. This works only for a single server.


Set ipc-client=redis://HOST[:PORT] that points to the server running Redis server.

The config option max_attempts defines maximum number of times to reconnect before giving up. Any other node-redis module parameter can be passed as well in the options or url, the system supports special parameters that start with bk-, it will extract them into options automatically.

For example:


PUB/SUB or Queue configurations

Redis system bus

If configured all processes subscribe to it and listen for system messages, it must support PUB/SUB and does not need to be reliable. Websockets in the API server also use the system bus to send broadcasts between multiple api instances.


Redis Queue

To configure the backend to use Redis for job processing set ipc-queue=redis://HOST where HOST is IP address or hostname of the single Redis server. This driver implements reliable Redis queue, with visibilityTimeout config option works similar to AWS SQS.

Once configured, then all calls to jobs.submitJob will push jobs to be executed to the Redis queue, starting somewhere a backend master process with -jobs-workers 2 will launch 2 worker processes which will start pulling jobs from the queue and execute.

The naming convention is that any function defined as function(options, callback) can be used as a job to be executed in one of the worker processes.

An example of how to perform jobs in the API routes:

    core.describeArgs('app', [
        { name: "queue", descr: "Queue for jobs" },
    app.queue = "somequeue";

    app.processAccounts = function(options, callback) {"bk_user", { type: options.type || "user" }, (err, rows) => {

    api.all("/process/accounts", function(req, res) {
        jobs.submitJob({ job: { "app.processAccounts": { type: req.query.type } } }, { queueName: app.queue }, (err) => {
            api.sendReply(res, err);


To use AWS SQS for job processing set ipc-queue=, this queue system will poll SQS for new messages on a worker and after successful execution will delete the message. For long running jobs it will automatically extend visibility timeout if it is configured.


The local queue is implemented on the master process as a list, communication is done via local sockets between the master and workers. This is intended for a single server development purposes only.


To use NATS ( configure a queue like ipc-queue-nats=nats://HOST:PORT, it supports broadcasts and job queues only, visibility timeout is supported as well.


To configure the backend to use RabbitMQ for messaging set ipc-queue=amqp://HOST and optionally amqp-options=JSON with options to the amqp module. Additional objects from the config JSON are used for specific AMQP functions: { queueParams: {}, subscribeParams: {}, publishParams: {} }. These will be passed to the corresponding AMQP methods: amqp.queue, amqp.queue.subcribe, amqp.publish. See AMQP Node.js module for more info.

Security configurations

API only

This is default setup of the backend when all API requests except must provide valid signature and all HTML, JavaScript, CSS and image files are available to everyone. This mode assumes that Web development will be based on 'single-page' design when only data is requested from the Web server and all rendering is done using JavaScript. This is how the examples/api/api.html developers console is implemented, using JQuery-UI and Knockout.js.

To see current default config parameters run any of the following commands:

    bkjs bkhelp | grep api-allow

    node -e 'require("backendjs").core.showHelp()'

Secure Web site, client verification

This is a mode when the whole Web site is secure by default, even access to the HTML files must be authenticated. In this mode the pages must defined 'Backend.session = true' during the initialization on every html page, it will enable Web sessions for the site and then no need to sign every API request.

The typical client JavaScript verification for the html page may look like this, it will redirect to login page if needed, this assumes the default path '/public' still allowed without the signature:

   <link href="/css/bkjs.bundle.css" rel="stylesheet">
   <script src="/js/bkjs.bundle.js" type="text/javascript"></script>
    $(function () {
       bkjs.session = true;
       $(bkjs).on("bkjs.nologin", function() { window.location='/public/index.html'; });

Secure Web site, backend verification

On the backend side in your application app.js it needs more secure settings defined i.e. no html except /public will be accessible and in case of error will be redirected to the login page by the server. Note, in the login page bkjs.session must be set to true for all html pages to work after login without singing every API request.

  1. We disable all allowed paths to the html and registration:
   app.configureMiddleware = function(options, callback) {
       this.allow.splice(this.allow.indexOf('^/$'), 1);
       this.allow.splice(this.allow.indexOf('\\.html$'), 1);
  1. We define an auth callback in the app and redirect to login if the request has no valid signature, we check all html pages, all allowed html pages from the /public will never end up in this callback because it is called after the signature check but allowed pages are served before that:
   api.registerPreProcess('', /^\/$|\.html$/, function(req, status, callback) {
       if (status.status != 200) {
           status.status = 302;
           status.url = '/public/index.html';

WebSockets connections

The simplest way is to configure ws-port to the same value as the HTTP port. This will run WebSockets server along the regular Web server.

In the browser the connection config is stored in the bkjs.wsconf and by default it connects to the local server on port 8000.

There are two ways to send messages via Websockets to the server from a browser:

    bkjs.wsConnect({ path: "/project/ws?id=1" });

    $(bkjs).on("", (msg) => {
        switch (msg.op) {
        case "/account/update":

        case "/project/update":
            for (const p in msg.project) app.project[p] = msg.project[p];

        case "/message/new":
            bkjs.showAlert("info", `New message: ${msg.msg}`);
    // Notify all clients who is using the project being updated"/project/ws", (req, res) => {
        switch (req.query.op) {
        case "/project/update":
           //  some code ....
           api.wsNotify({ query: { id: } }, { op: "/project/update", project: req.query.project });

In any case all Websocket messages sent from the server will arrive in the event handler and must be formatted properly in order to distinguish what is what, this is the application logic. If the server needs to send a message to all or some specific clients for example due to some updates in the DB, it must use the api.wsNotify function.

    // Received a new message for a user from external API service, notify all websocket clients by account id"/api/message", (req, res) => {
        ... processing logic
        api.wsNotify({ account_id: req.query.uid }, { op: "/message/new", msg: req.query.msg });


There is no ready to use support for different versions of API because there is no just one solution that satisfies all applications. But there are tools ready to use that will allow to implement such versioning system in the backend. Some examples are provided below:

    api.all(/\/domain\/(get|put|del)/, function(req, res) {
        var options = api.getOptions(req);
        var cmd = req.params[0];
        if (options.apiVersion) cmd += "/" + options.apiVersion;
        switch (cmd) {
        case "get":

        case "get/2015-01-01":

        case "put":

        case "put/2015-02-01":

        case "del"
    var options = api.getOptions(req);
    var version = lib.toVersion(options.appVersion);
    switch (req.params[0]) {
    case "get":
        if (version < lib.toVersion("1.2.5")) {
            res.json({ id: 1, name: "name", description: "descr" });
        if (version < lib.toVersion("1.1")) {
            res.json([id, name]);
        res.json({ id: 1, name: "name", descr: "descr" });

The actual implementation can be modularized, split into functions, controllers.... there are no restrictions how to build the working backend code, the backend just provides all necessary information for the middleware modules.

The backend provisioning utility: bkjs

The purpose of the bkjs shell script is to act as a helper tool in configuring and managing the backend environment and as well to be used in operations on production systems. It is not required for the backend operations and provided as a convenience tool which is used in the backend development and can be useful for others running or testing the backend.

Running without arguments will bring help screen with description of all available commands.

The tool is multi-command utility where the first argument is the command to be executed with optional additional arguments if needed. On Linux, when started the bkjs tries to load and source the following config files:


Any of the following config files can redefine any environment variable thus pointing to the correct backend environment directory or customize the running environment, these should be regular shell scripts using bash syntax.

Most common used commands are:

Web development notes

Then run the dev build script to produce web/js/bkjs.bundle.js and web/css/bkjs.bundle.css

    cd node_modules/backendjs && npm run devbuild

Now instead of including a bunch of .js or css files in the html pages it only needs /js/bkjs.bundle.js and /css/bkjs.bundle.css. The configuration is in the package.json file.

The list of files to be used in bundles is in the package.json under config.bundles.

To enable auto bundler in your project just add to the local config ~/.bkjs/etc/config.local a list of directories to be watched for changes. For example adding these lines to the local config will enable the watcher and bundle support

    build-web=bkjs web-bundle -dev

The simple script below allows to build the bundle and refresh Chrome tab automatically, saves several clicks:

    bkjs web-bundle -dev -file $2
    [ "$?" != "0" ] && exit
    osascript -e "tell application \"Google Chrome\" to reload (tabs of window 1 whose URL contains \"$1\")"

To use it call this script instead in the config.local: /website

NOTE: Because the rebuild happens while the watcher is running there are cases like the server is restarting or pulling a large update from the repository when the bundle build may not be called or called too early. To force rebuild run the command:

    bkjs web-bundle -dev -all -force

Deployment use cases

AWS instance setup with node and backendjs

NOTE: if running behind a Load balancer and actual IP address is needed set Express option in the command line -api-express-options {"trust%20proxy":1}. In the config file replacing spaces with %20 is not required.

AWS Provisioning examples

Note: on OS X laptop the -aws-sdk-profile uc when AWS credentials are in the ~/.aws/credentials.

Make an AMI

On the running machine which will be used for an image:

    bksh -aws-create-image -no-reboot

Use an instance by tag for an image:

    bksh -aws-create-image -no-reboot -instance-id `bkjs ec2-show -tag api -fmt id | head -1`

Launch instances when not using AutoScaling Groups

When launching from an EC2 instance no need to specify any AWS credentials.

Copy Autoscaling launch templates after new AMI is created

bksh -aws-create-launch-template-version -name jobs -aws-sdk-profile uc -dry-run
bksh -aws-create-launch-template-version -name api -aws-sdk-profile uc -dry-run

Update Route53 with all IPs from running instances

bksh -aws-set-route53 -name -filter elasticsearch

Proxy mode

By default the Web proceses spawned by the server are load balanced using default cluster module which relies on the OS to do scheduling. On Linux with node 0.10 this is proven not to work properly due to the kernel keeping the context switches to a minimum thus resulting in one process to be very busy while the others idle. Node versions 4 and above perform round-robin by default.

For such case the Backendjs implements the proxy mode by setting proxy-port config parameter to any number above 1000, this will be the initial port for the web processes to listen for incoming requests, for example if use -proxy-port 3000 and launch 2 web processes they will listen on ports 3000 and 3001. The main server process will start internal HTTP proxy and will perform round-robin load balancing the incoming requests between the web processes by forwarding them to the web processes over TCP and then returning the responses back to the clients.

Configure HTTP port

The first thing when deploying the backend into production is to change API HTTP port, by default is is 8000, but we would want port 80 so regardless how the environment is setup it is ultimately 2 ways to specify the port for HTTP server to use:

Backend library development (Mac OS X, developers)

Design considerations

While creating Backendjs there were many questions and issues to be considered, some I was able to implement, some still not. Below are the thoughts that might be useful when designing, developing or choosing the API platform:

API endpoints provided by the backend

All API endpoints are optional and can be disabled or replaced easily. By default the naming convention is:


Any HTTP methods can be used because its the command in the URL that defines the operation. The payload can be url-encoded query parameters or JSON or any other format supported by any particular endpoint. This makes the backend universal and usable with any environment, not just a Web browser. Request signature can be passed in the query so it does not require HTTP headers at all.

Authentication and sessions


All requests to the API server must be signed with account login/secret pair.

The resulting signature is sent as HTTP header bk-signature or in the header specified by the api-signature-name config parameter.

For JSON content type, the method must be POST and no query parameters specified, instead everything should be inside the JSON object which is placed in the body of the request. For additional safety, SHA1 checksum of the JSON payload can be calculated and passed in the signature, this is the only way to ensure the body is not modified when not using query parameters.

See web/js/bkjs.js function bkjs.createSignature or api.js function api.createSignature for the JavaScript implementations.

There is also native iOS implementation Bkjs.m.

Authentication API

    $.ajax({ url: "/login?login=test123&secret=test123&_session=1",
        success: function(json, status, xhr) { console.log(json) }

    > { id: "XXXX...", name: "Test User", login: "test123", ...}


The accounts API manages accounts and authentication, it provides basic user account features with common fields like email, name, address.

Health enquiry

When running with AWS load balancer there should be a url that a load balancer polls all the time and this must be very quick and lightweight request. For this purpose there is an API endpoint /ping that just responds with status 200. It is open by default in the default api-allow-path config parameter.


The data API is a generic way to access any table in the database with common operations, as oppose to the any specific APIs above this API only deals with one table and one record without maintaining any other features like auto counters, cache...

Because it exposes the whole database to anybody who has a login it is a good idea to disable this endpoint in the production or provide access callback that verifies who can access it.

This is implemented by the data module from the core.

System API

The system API returns information about the backend statistics, allows provisioning and configuration commands and other internal maintenance functions. By default is is open for access to all users but same security considerations apply here as for the Data API.

This is implemented by the system module from the core. To enable this functionality specify -preload-modules=bk_system.


Vlad Seryakov

Check out the Documentation for more details.

Configuration parameters

Module: API

Module: APP

Module: AUTH

Module: AWS

Module: CORE

Module: DB

Module: EVENTS


Module: INDEX

Module: IPC

Module: JOBS

Module: LIB

Module: LOGGER


Module: MSG

Module: POOL

Module: SERVER

Module: SHELL

Module: BK_DATA


Module: BK_USER