Local Development with ngrok
Develop cloud services locally by continuously forwarding real data from a Data Connector using ngrok.
This guide looks at how ngrok can be used to create a local development environment for Data Connectors applications. In summary, the Data Connector is configured to forward events to an URL generated by ngrok, a free proxy that points all incoming traffic to a specified port on localhost where we can receive the events and quickly develop and debug our application,
- Local Development It is assumed that you are familiar with the bare minimums of local development, like using a shell.
ngrok is a free proxy service that enables forwarding HTTPS traffic from a publicly accessible URL to a port on localhost.
In your shell of choice, run the
ngrok command with the http argument, followed by the port to which you want to forward incoming traffic.ngrok http 3000
Once the proxy has started, all traffic directed to the randomly generated HTTPS URL will be directed to the specified port on your localhost.
ngrok by @inconshreveable (Ctrl+C to quit)
Session Status online
Session Expires 1 hour, 59 minutes
Version 2.3.35
Region United States (us)
Web Interface http://127.0.0.1:4040
Forwarding http://5a880278718b.ngrok.io -> http://localhost:3000
Forwarding https://5a880278718b.ngrok.io -> http://localhost:3000
Connections ttl opn rt1 rt5 p50 p90
0 0 0.00 0.00 0.00 0.00
If you're using the free version of ngrok, your session will expire after two hours. To restart, rerun the command. Note that this changes the URL.
All modifications to the generated URL path is reflected on the localhost. This can be useful to know as some local development frameworks, such as the one used by Azure Functions, utilizes pathing.
- Original
https://5a880278718b.ngrok.io -> http://localhost:3000 - Added path
https://5a880278718b.ngrok.io/some/path -> http://localhost:3000/some/path
To continuously forward events to localhost, create a new Data Connector or use an existing one, setting the following configurations.
- Endpoint URL The generated HTTPS URL of the form
https://5a880278718b.ngrok.ioas provided by ngrok. Note that the HTTP URL will not be accepted by the Data Connector.
When forwarding Data Connector events to localhost using ngrok, if no response is given to the request, an
502 Bad Gateway error will the thrown.The following snippets implement a simple local server app that receives the Data Connector request, prints the content, and responds with a success message.
Python 3.10 - Flask
Node.js 16 - Express
Install the necessary dependencies.
pip install flask==2.1.3
Copy the following snippet to a local file
app.py.app.py
from flask import Flask, request # pip install flask==2.1.3
app = Flask(__name__)
@app.route('/', methods=['POST'])
def print_request_contents():
print(f'\nHeaders\n-------\n{request.headers}')
print(f'Body\n----\n{request.get_json()}')
return 'Success'
Start the local server by running
flask run --port 3000 in your shell.Install the necessary dependencies.
npm install [email protected] [email protected]
Copy the following snippet to a local file
index.js.index.js
const express = require("express") // npm install [email protected]
const bodyParser = require("body-parser") // npm install [email protected]
const app = express()
app.use(bodyParser.urlencoded({ extended: false }))
app.use(bodyParser.json())
app.post("/", (req, res) => {
console.dir(req.body, { depth: null })
res.send("Success")
})
app.listen(3000)
Start the local server by running
node index.js in your shell.Our sensors emit events every periodic heartbeat or when touched. When developing an application locally, being able to emit events at will can be quite useful. Our Sensor Emulator lets you create an emulated device for which events can be sent using a click of a button in DT Studio or the REST API.
Last modified 7mo ago