Conditional redirects with if in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the result of this nginx config snippet?

Given this nginx server block snippet, what will happen when a user visits http://example.com/oldpage?

Nginx

server {
    listen 80;
    server_name example.com;

    location / {
        if ($request_uri = "/oldpage") {
            return 301 /newpage;
        }
        root /var/www/html;
    }
}

A The server returns a 500 Internal Server Error

B The user sees the content of /oldpage from the root directory

C The server returns a 404 Not Found error

D The user is redirected permanently to http://example.com/newpage

💡 Hint

Think about what the 'if' directive does with the 'return 301' inside the location block.

The if condition checks if the requested URI is exactly /oldpage. If true, it sends a permanent redirect (301) to /newpage. Otherwise, it serves files from the root directory.

❓ Troubleshoot

intermediate

Why does this nginx config cause a redirect loop?

Consider this nginx config snippet:

location / {
    if ($request_uri ~* "/oldpage") {
        return 301 /oldpage;
    }
}

Why does this cause a redirect loop when visiting /oldpage?

A Because the location block is missing a root directive

B Because the return directive is missing a status code

C Because the redirect points to the same URI, causing infinite redirects

D Because the regex in the if condition is invalid syntax

💡 Hint

Check what the redirect target is compared to the requested URI.

The config redirects /oldpage to /oldpage again, causing the browser to keep requesting the same URL and nginx to keep redirecting it, creating a loop.

❓ Configuration

advanced

Which config correctly redirects only POST requests to /submit to /process?

You want to redirect only POST requests to /submit to /process permanently. Which nginx config snippet achieves this?

A

if ($request_method = POST) {
    if ($request_uri = "/submit") {
        return 301 /process;
    }
}

B

location = /submit {
    if ($request_method = POST) {
        return 301 /process;
    }
}

C

if ($request_method = POST) {
    return 301 /process;
}

D

location /submit {
    if ($request_method = POST) {
        return 301 /process;
    }
}

💡 Hint

Use a location block that matches exactly /submit and then check the method inside.

Option B uses an exact match location for /submit and inside it checks if the method is POST, then redirects. This ensures only POST requests to /submit are redirected.

🧠 Conceptual

advanced

What is a limitation of using 'if' for redirects in nginx?

Which statement best describes a limitation of using the if directive inside nginx location blocks for conditional redirects?

A The 'if' directive can cause unexpected behavior and is not recommended for complex logic

B The 'if' directive cannot access variables like $request_uri

C The 'if' directive always causes nginx to reload the configuration

D The 'if' directive only works with GET requests

💡 Hint

Think about nginx official recommendations regarding 'if' usage.

nginx documentation warns that 'if' inside location blocks can cause unexpected results and should be used carefully, especially for complex logic. It's better to use other directives or map blocks when possible.

🔀 Workflow

expert

Order the steps to safely implement a conditional redirect in nginx

Put these steps in the correct order to safely add a conditional redirect using 'if' in nginx configuration.

A 4,2,1,3

B 2,4,1,3

C 1,4,2,3

D 4,1,2,3

💡 Hint

Always backup before making changes, then test syntax before reload.

First backup current configs to avoid loss. Then add the new 'if' redirect. Test syntax to catch errors. Finally reload nginx to apply changes.