cadence_001

Cadence Web UI

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.

Getting Started

Configuration

Set these environment variables if you need to change their defaults

Variable	Description	Default
CADENCE_TCHANNEL_PEERS	Comma-delmited list of tchannel peers	127.0.0.1:7933
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. Additionally to run locally with webpack hot reloading and other conveniences, use

npm run dev

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.

API

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.

init(options)

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: 'statsd.example.com'
})

app.use(async function(ctx, next) {
  sdc.increment('http.request')
  await next()
})
.init()
.listen(7000)

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

Licence

MIT License, please see LICENSE for details.