What is Glue42 Core?

Core Concepts



The Glue42 Core Environment is a set of JS and JSON files which must be hosted at the same domain as your applications in order to have have access to the platform's functionality. This set of files (we call it environment) is not application-specific, it is domain-specific.

The environment consists of:

  • A shared worker used as a central point for all Glue42 Clients to connect to
  • A gateway which carries out the communication between all Glue42 Clients
  • Optional configuration file used to define Glue42 Core settings and defaults

The Glue42 Core environment requirements are:

  • All files must be hosted on the same domain as your applications
  • All files must be served from a path easily accessible by all Glue42 Clients.

Setting up environment

Setting up is much easier than it seems. We have created a CLI tool which makes the process of setting up your development environment and bundling the Glue42 Core environment for deployment easy and painless. We have prepared detailed guides for setting up the environment using the CLI for single application and multiple application projects.

Those of you who need fine-grained control over the development and deployment of their project, can head over to the Manual Setup section. There we have prepared a detailed guide for manually setting up the environment.

Configuration File

This is a simple JSON file containing general Glue42 Core settings, gateway settings and shared configuration used by all Glue42 Clients on this domain.

If this file is not present, then all Glue42 Clients will initialize using default settings (more on that in the Glue42 Client section) and will try to connect to the shared worker at the default location at /glue/worker.js. The shared worker will also try to connect to the gateway at the default location at /glue/gateway.js.

If you provide a configuration file, then it must be named glue.config.json. The interface of the config is:

interface Glue42CoreConfig {
    glue?: Glue42WebConfig;
    gateway?: GatewayConfig;


This is an optional configuration object which when defined will be used as a common setting when all Glue42 Clients on this domain initialize the Glue42 Web library. Every client can define it's own initialization options, which will overwrite the common settings in glue.config.json.

For more information on the Glue42WebConfig, head over to the Glue42 Web reference documentation.


This is an optional configuration object which defines settings used by the shared worker in order to initialize the gateway:

Property Type Description Default
location string Optional The location of the gateway script Defaults to: "./gateway.js"
logging object Optional Set the logging level and appender for the gateway -
logging.level `"trace" "debug" "info"
logging.appender object Optional Defines a custom log appender By default the gateway will log to the shared worker's console
logging.appender.location string The location of the appender script no default
logging.appender.name string The name of the appender function defined in the appender script No default

Gateway log appender

You can overwrite the default logging configuration of the gateway from glue.config.json. For most cases this is not needed, because the gateway logs internal messages sent back and forth from Glue42 Clients. However, if you really need to, you can define:

  • log level - accepts: "trace" | "debug" | "info" | "warn" | "error", defaults to: info
  • appender - a function that receives a LogInfo object. By default logs to the shared worker console, but your custom function can send those logs to a remote server, for example. The LogInfo object has a structure like this:
    time: 2017-06-22T15:38:34.230Z,
    file: 'C:\\Users\\dimd00d\\AppData\\Local\\Temp\\form-init8247674603237706851.clj',
    output: 'DEBUG [gateway.local-node.core:55] - Sending message {:domain "global", :type :error, :request_id nil, :peer_id nil, :reason_uri "global.errors.authentication.failure", :reason "Unknown authentication method "} to local peer',
    level: 'debug',
    line: 55,
    stacktrace: null,
    namespace: 'gateway.local-node.core',
    message: 'Sending message {:domain "global", :type :error, :request_id nil, :peer_id nil, :reason_uri "global.errors.authentication.failure", :reason "Unknown authentication method "} to local peer'

The output key contains a processed message for direct output where the rest of the keys hold the details.


    "glue": ...,
    "gateway": {
        "logging": {
            "level": "trace",
            "appender": {
                "location": "./gwLogAppender.js",
                "name": "log"
// ./gwLogAppender.js
self.log = (logInfo) => {
    // your custom log logic here

Shared Worker

The shared worker is a script, which is used to create a Shared Web Worker. This is the central point to which all Glue42 Clients connect when initializing the javascript glue library. It is responsible for configuring, initializing and linking Glue42 Clients to the gateway.

The shared worker will use the glue.config.json to get user-defined settings for the gateway.

Important! The shared worker will expect to find a configuration file at ./glue.config.json. Due to the current limitations of the Shared Web Worker interface, passing a different config file location is not an option. Therefore if this file is not found at that location, then the worker will proceed with default gateway settings.


The gateway is the backbone of the Glue42 Core environment. It facilitates all communication between all Glue42 Clients and is initialized by the shared worker. There are a few configuration options for the gateway, all exposed via the glue.config.json object.