Edgio
Edgio Console

Error Handling

This guide covers how to handle origin errors at the edge to display custom error pages or retry requests from a different origin.
The examples found in this guide can be found in the edgio-v7-error-handling-example repository.

The catch method

EdgeJS provides a catch method that you can use to responses that result in an error. There are two main ways to use this method:

Displaying a custom error page

In this example we catch all responses with a 5xx status code and serve a static error page with a 500 status code:
JavaScript
1import {Router} from '@edgio/core';
2

3export default new Router()
4  .get('/500', ({serveStatic}) => {
5    // Serve a static error page with a 500 status code
6    serveStatic('public/500.html', {
7      statusCode: 500,
8    });
9  })
10  .catch(/^5.*/, {
11    // Match all responses with a 5xx status code and redirect internally to /500
12    response: {
13      set_status_code: 302, // redirect
14    },
15    headers: {
16      set_response_headers: {
17        location: '%{scheme}://%{host}/500', // Set the path to /500
18      },
19    },
20    // This makes the redirect invisible to the client. They will just see the 500.html page.
21    // You can leave this out to send the redirect all the way back to the client.
22    url: {
23      follow_redirects: true,
24    },
25  });

Retrying the request from a different origin

In this example, we have a legacy origin that we want to use as a fallback if the primary origin returns a 5xx status code. Assuming you have an origin called “legacy” configured in your edgio.config.js file, you can use the set_origin option to retry the request from the legacy origin:
JavaScript
1import {Router} from '@edgio/core';
2

3export default new Router()
4  .get('/legacy/:path*', {
5    origin: {
6      // This will retry the request from the legacy origin if the primary origin returns a 5xx status code
7      set_origin: 'legacy',
8    },
9    url_rewrite: [
10      // strip the "/legacy" prefix from the path
11      {source: '/legacy/(.*)', syntax: 'regexp', destination: '/$1'},
12    ],
13  })
14  .match(
15    // Redirect all 5xx responses to the same path with "/legacy" prepended (unless we already have a "/legacy" in the path)
16    {path: {not: /^\/legacy\/.*/}, response: {status_code: /5.*/}},
17    {
18      response: {
19        set_status_code: 302,
20      },
21      url: {
22        // This makes the redirect invisible to the client. They will just see the 500.html page.
23        follow_redirects: true,
24      },
25      headers: {
26        set_response_headers: {
27          // Redirect to the same URL with "/legacy" prepended
28          location:
29            '%{scheme}://%{host}/legacy%{path}%{is_args}%{query_string}',
30        },
31      },
32    }
33  );
Note that here we use match({ response: { status_code: /5.*/}}). This is equivalent to catch(/5.*/) but allows us to add an additional criteria to exclude paths starting with “/legacy” from being retried.