Last updated 2nd June 2022
Effectively debugging web apps takes effort, especially when an HTTP request goes through multiple layers before reaching your web app. Follow the steps below to debug a specific app.
You can choose to debug in an environment deployed to Web PaaS or with your app running locally but connected to deployed services. In either case, make sure to debug in a non-production environment.
1. Create a new environment
Start by creating a new environment completely isolated from production but with the same data for debugging:
webpaas branch debug-branch
2. Get access
Access your app container via [SSH](../../development-ssh/): ```bash webpaas ssh
To access deployed apps and services, open tunnels to everything your app has relationships with: ```bash webpaas tunnel:open In the same terminal, set the relevant environment variables: ```bash export PLATFORM_RELATIONSHIPS="$(webpaas tunnel:info --encode)" export PORT=8888
3. Run your app in inspect mode
Stop the current process and restart it in inspect mode: ```bash sv stop app node --inspect <START_FILE>
In the same terminal as the previous step, run the following command: ```bash node --inspect <START_FILE>
<START_FILE> with the file defined for your app's
You should get an output similar to this:
Debugger listening on ws://127.0.0.1:9229/10701e5d-d627-4180-a967-d47a924c93c0 For help, see: https://nodejs.org/en/docs/inspector Listening on port 8888
4. (If debugging remotely) Forward the debugger port locally
In another terminal, create an SSH tunnel that forwards to the 9229 port:
ssh -N -L 9229:localhost:9229 $(webpaas ssh --pipe)
5. Connect the debugger
You can now connect the debugger as if you were debugging a local application. See examples with some common tools:
Go to `chrome://inspect`. Find your running app under the `Remote Target` list. Click **inspect** to start the debugger.
Use the `Node.js: Attach` debugger option. If you haven't created the option: 1. On the **Run and Debug** tab, click `create a launch.json file`. 2. Select `Node.js` as the environment. 3. In the `configurations` array, start IntelliSense (usually <kbd>ctrl</kbd>+<kbd>space</kbd>). 4. Select `Node.js: Attach`. 5. Make sure the port is the same as in [step 4 above](#4-if-debugging-remotely-forward-the-debugger-port-locally). Once you have the option: In the **Run and Debug** tab, select `Attach` from the menu and click **Start Debugging** (the green arrow). See more on [Node.js debugging in Visual Studio Code](https://code.visualstudio.com/docs/nodejs/nodejs-debugging).
Now when you load the site at your deployed URL (if debugging remote) or localhost (if debugging locally), the local debugger you've attached is called.
Directly in your source files.
pm2 process manager blocks other processes
If you're using the
pm2 process manager to start your app from a script,
you might find it daemonizes itself and blocks other processes (such as backups) by constantly respawning.
This may happen even if you use the
Instead of using a script, call
pm2 start directly in your
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