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1.0.2 • Public • Published


The component observes a number specified models and notifies about the changes by SSE.

The main difference with Loopback /change-stream channels is that this implementation creates only two observers (after save and after delete) per model and then streams the changes to keep-alive registered connections. In contrast Loopback creates two same observers for each connection.

Install and Setup

Install the company: npm install --save loopback-component-changestreamer

Important! Disable compression middleware in middleware.json files like this:

  "compression": {

Add the following configuration to component-config.json:

  "loopback-component-changestreamer": {
    "mountPath": "/api/updates",
    "reconnectTimeout": 3000,
    "responseTimeout": 120000,
    "models": [
    "headers": [

See e2e/ directory as an example for how to make project configuration.

The configuration parameters:

  • mountPath - base URL to subscribe for updates;
  • reconnectTimeout - instruct Browser to reconnect after this timeout if connection is lost;
  • responseTimeout - the response socket will be closed after this timeout;
  • models - array of model names to observe.
    • headers - headers and values to embed in the stream metadata.

The component configuration above adds 3 middleware rules:

  • GET "/api/updates" to connect some SourceEvent listener;
  • GET "/api/updates/stat" to see a statistics about number of current connections;
  • DELETE "/api/updates" to close all registered connections.

The following snippet can be used on client side to connect:

var src = new EventSource('//<host>:<port>/api/updates');
src.addEventListener('message', function(message) {


npm i loopback-component-changestreamer

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