Troubleshooting search error 422

When you use the advanced search feature in HTML files exported from Dr.Explain, you may encounter error messages with code 422 instead of search results.

A 422 error means the web server is forwarding requests to the backend, but the path is incorrect. This is usually a web server configuration issue.

Common causes

Missing path capture in nginx: add /$1$is_args$args to the proxy_pass directive.
Missing path capture in Apache: add /$1 to the RewriteRule.
Typo in the location pattern: make sure it says /drexsearch/ not /drxsearch/.

Step 1: Test the backend in browser

Open your documentation in a web browser.
Click on any topic in the menu.
In the browser's address bar, change the URL by removing the filename at the end and adding /drexsearch/ping, for example:

Change from: http://your-server.com/docs/some-file.htm

Change to: http://your-server.com/docs/drexsearch/ping
Press Enter.

What you should see: a message saying "If you see this text, Dr.Explain Search Backend is working..."

If you see this message: the backend is working, but your web server is not configured to forward search requests correctly. Go to Step 3.

If you see this error (or similar):

{"error":"URL \"/drexsearch/ping\" is invalid..."}

This means your web server is adding an extra prefix (/drexsearch in example above) when forwarding to the backend. Go to Step 3.

If you get a different error: the backend might not be running. Go to Step 2 to check if the backend is running.

Step 2: Test the backend directly

If you have access to the server, connect to it (e.g. via SSH) and open a terminal, then try this command:

curl http://127.0.0.1:8082/ping

What you should see: a message saying "If you see this text, Dr.Explain Search Backend is working..."

If you see this message: the backend is working, but your web server is not configured to forward requests correctly. Go to Step 3.

If you get an error: the backend might not be running. Go to Troubleshooting search error 502 to check if the backend service is running.

Step 3: Fix web server configuration

This step requires access to your server's configuration files.

For nginx servers:

Your configuration should look like this:

location ~ /drexsearch/(.*)$ {

proxy_pass http://127.0.0.1:8082/$1$is_args$args;

}

Common mistake: missing the /$1$is_args$args part:

location ~ /drexsearch/(.*)$ {

proxy_pass http://127.0.0.1:8082;

}

For Apache servers:

Your configuration should look like this:

RewriteEngine On

RewriteRule ^(?:.*/)?drexsearch/(.*)$ http://127.0.0.1:8082/$1 [P,L]

Common mistake: missing the /$1 part:

RewriteRule ^(?:.*/)?drexsearch/(.*)$ http://127.0.0.1:8082 [P,L]

If you find a mistake: correct the configuration and restart your web server. Then test again.

Step 4: Check error logs

This step requires access to your server's log files.

For nginx:

sudo tail -f /var/log/nginx/error.log

For Apache:

sudo tail -f /var/log/apache2/error.log

Look for: "upstream sent unexpected response code 422".