This guide shows you how to debug applications running locally behind Layer0.

To debug a Layer0 application in Visual Studio Code:

  • open .vscode/launch.json
  • Click "Add Configuration..." and select "Node.js: Launch Program"

Edit the resulting configuration to look like this:

  "name": "Debug Layer0 App",
  "type": "node",
  "request": "launch",
  "cwd": "${workspaceFolder}",
  "autoAttachChildProcesses": true,
  "program": "${workspaceFolder}/node_modules/@layer0/cli",
  "args": ["run"]

The above assumes that the workspace folder is your app's root directory. If that is not the case, adjust program and cwd accordingly. The program config should always point to @layer0/cli. The cwd config should point to the root directory of your app.

Note that this configuration will allow you to set breakpoints in both your Layer0 router as well as your application code (for example in Next.js, Nuxt.js, Angular, etc...).

Layer0 provides two types of logs to you debug issues with your application:

By viewing the server logs in the Layer0 Developer Console, you can see all of the messages logged by your application using console.log, console.warn, etc... By enabling Deep Request Inspection in your environment, you can also see the headers and body of every request and response served by your application via the Layer0 serverless cloud. You can also see each upstream API request made by your application.

You can also use the server logs to debug routing issues going to custom backends by temporarily moving the proxying from the edge to serverless:

  .get('/p/:productId', ({ cache }) => {
    proxy('origin', {
      // The presence of transformRequest and transformResponse ensure that proxying is done in serverless, not at the edge.
      transformRequest: (req) => {
        console.log('Request ID', req.headers['x-request-id'])
        // Log request properties that you want to troubleshoot.
      transformResponse: (res, req) => {
        console.log('Response for request ID', req.headers['x-request-id'], 'status code', res.statusCode)
        // Log response properties that you want to troubleshoot.

Once you have this deployed, you can observe the output in your server logs.

Note that whenever possible, we strongly recommend to always proxy the traffic from the edge, as that is more performant and avoids serverless surcharges. The solution above should only be used as a temporary measure while debugging issues.

Access logs contain information about all requests, even those that never reach your application code (e.g. cache hits, static assets, requests routed to custom backends, edge redirects, and so on).

Layer0 automatically produces a source map for your router file so that all runtime errors that occur during routing will have a stacktrace that references the original source file. If your application build produces source maps for the server bundle, these will also be used when reporting errors. Layer0 provides a convenient way to enable source maps when using Next and Nuxt:

Set layer0SourceMaps: true in your next.config.js:

// next.config.js

const { withLayer0, withServiceWorker } = require('@layer0/next/config')

module.exports = withLayer0(
    // Output sourcemaps so that stacktraces have original source filenames and line numbers when tailing
    // the logs in the Layer0 developer console.
    layer0SourceMaps: true,

Set layer0SourceMaps: true in the config for @layer0/nuxt/module in buildModules in nuxt.config.js:

// nuxt.config.js

module.exports = {
  // ...
  buildModules: [['@layer0/nuxt/module', { layer0SourceMaps: true }]],
  // ...

Note: The reason that application level source maps are not enabled by default is that they can be quite large and cause the serverless bundle to be larger than the 50MB limit.