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Cadence Web UI

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Cadence is a distributed, scalable, durable, and highly available orchestration engine we developed at Uber Engineering to execute asynchronous long-running business logic in a scalable and resilient way.

This web UI is used to view workflows from Cadence, see what's running, and explore and debug workflow executions.

Demo Usage

Getting Started


Set these environment variables if you need to change their defaults

Variable Description Default
CADENCE_TCHANNEL_PEERS Comma-delmited list of tchannel peers
CADENCE_TCHANNEL_SERVICE Name of the cadence tchannel service to call cadence-frontend
CADENCE_WEB_PORT HTTP port to serve on 8088
CADENCE_EXTERNAL_SCRIPTS Addtional JavaScript tags to serve in the UI
ENABLE_AUTH Enable auth feature false
AUTH_TYPE concurrently supports ADMIN_JWT ''
AUTH_ADMIN_JWT_PRIVATE_KEY JWT signing private key for ADMIN_JWT type ''

Running locally

cadence-web requires node v10.22.1 or greater to be able to run correctly. cadence-web uses all the standard npm scripts to install dependencies, run the server, and run tests.

To provide a consistent environment we recommend using docker in development. We provide a default configuration for remote containers using docker-compose.

Using VSCode Dev Containers

  1. Set up the Remote Containers plugin in VSCode.
  2. Open the cadence-web directory in VSCode.
  3. Use the Command Palette to select the 'Reopen folder in Container' option. npm install should run automatically in the container upon doing so.
  4. Run the app in the container with npm run dev.
  5. Open localhost:8088 (or the custom Cadence Web port you have defined) to load the webapp.

Using docker-compose to start the dev container

To start local server with live reload on code change you can run docker-compose up.

For development and contributing to cadence-web, please see the contributing guide.

You may also use docker by pulling ubercadence/web. It is also included in the Cadence server's local docker setup.


If you need to extend cadence-web to add middleware to the server, you can install cadence-web as a dependecy, and it will export the Koa web server that has not yet been started or configured. It includes an additional init function that will then compose the built-in middleware. This gives you an option to add middleware before or after you call init so it will add the middleware at the beginning or the end of the chain, respectively.


All options are optional.

useWebpack: If true, starts webpack and adds the middleware, otherwise if false, it assumes the UI bundle was already built and serves it statically. Defaults to process.env.NODE_ENV === 'production'.

logErrors: If true, thrown errors are logged to console.error. Defaults to true.

For example, here is how you would add a request count metric using uber-statsd-client:

var app = require('cadence-web');
var createStatsd = require('uber-statsd-client');
var sdc = createStatsd({
  host: '',

  .use(async function(ctx, next) {
    await next();

The webpack configuration is also exported as webpackConfig, and can be modified before calling init().


MIT License, please see LICENSE for details.