JSON error responses in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the content type to JSON in the error response.

Nginx

error_page 404 /404.json;
location = /404.json {
    default_type [1];
    return 404 '{"error": "Not Found"}';
}

Drag options to blanks, or click blank then click option'

Aapplication/json

Btext/html

Ctext/plain

Dapplication/xml

Attempts:

3 left

💡 Hint

Common Mistakes

Using text/html instead of application/json causes browsers to treat the response as a webpage.

Forgetting to set the content type leads to incorrect response handling.

The default_type directive sets the MIME type. For JSON responses, use application/json.

2fill in blank

medium

Complete the code to return a 500 error with a JSON message.

Nginx

location /500.json {
    default_type application/json;
    return [1] '{"error": "Internal Server Error"}';
}

Drag options to blanks, or click blank then click option'

A400

B200

C404

D500

Attempts:

3 left

💡 Hint

Common Mistakes

Using 200 means success, not an error.

Using 404 is for not found errors, not server errors.

The return directive sends the HTTP status code. For server errors, use 500.

3fill in blank

hard

Fix the error in the JSON error response to properly escape quotes.

Nginx

location /403.json {
    default_type application/json;
    return 403 '{"error": [1]Forbidden[2]';
}

Drag options to blanks, or click blank then click option'

A\"

B'

C"

D\'

Attempts:

3 left

💡 Hint

Common Mistakes

Using unescaped double quotes breaks JSON syntax.

Using single quotes inside single quotes causes errors.

Inside single quotes, double quotes must be escaped with a backslash to form valid JSON.

4fill in blank

hard

Fill both blanks to create a JSON error response with a custom message and status code.

Nginx

location /custom_error.json {
    default_type [1];
    return [2] '{"error": "Custom Error"}';
}

Drag options to blanks, or click blank then click option'

Aapplication/json

Btext/plain

C404

D500

Attempts:

3 left

💡 Hint

Common Mistakes

Using text/plain causes browsers to treat the response as plain text.

Using 500 instead of 404 changes the error meaning.

Set default_type to application/json and return status code 404 for not found errors.

5fill in blank

hard

Fill all three blanks to define a JSON error response with a dynamic error message and status code.

Nginx

location /error.json {
    default_type [1];
    set $err_msg '[2]';
    return [3] '{"error": "$err_msg"}';
}

Drag options to blanks, or click blank then click option'

Aapplication/json

BForbidden

C403

DInternal Server Error

Attempts:

3 left

💡 Hint

Common Mistakes

Using plain text content type breaks JSON formatting.

Mixing error messages and status codes incorrectly.

Set content type to application/json, error message to 'Forbidden', and status code to 403.

Practice

1. What is the main benefit of sending JSON error responses in nginx?

easy

A. They automatically fix server errors without manual intervention.

B. They make error information easy for applications to read and process.

C. They reduce the size of error messages to save bandwidth.

D. They prevent users from seeing any error messages.

Solution

1. Step 1: Understand JSON error response purpose

   JSON error responses format error details in a way apps can easily parse and handle.

2. Step 2: Compare options

   Only They make error information easy for applications to read and process. correctly states the benefit of JSON error responses; others are incorrect or unrelated.

3. Final Answer:

   They make error information easy for applications to read and process. -> Option B

4. Quick Check:

   JSON error responses = easy app reading [OK]

Hint: JSON errors help apps read errors clearly [OK]

Common Mistakes:

• Thinking JSON errors fix server issues automatically
• Believing JSON errors hide all error messages
• Assuming JSON errors reduce bandwidth significantly

2. Which nginx directive is used to specify a custom error page that returns JSON?

easy

A. error_page

B. listen

C. proxy_pass

D. server_name

Solution

1. Step 1: Identify directive for custom error pages

   The error_page directive tells nginx which page to serve on specific errors.

2. Step 2: Eliminate unrelated directives

   proxy_pass forwards requests, listen sets ports, server_name sets domain names; none define error pages.

3. Final Answer:

   error_page -> Option A

4. Quick Check:

   Custom error page directive = error_page [OK]

Hint: Use error_page to set custom error responses [OK]

Common Mistakes:

• Confusing proxy_pass with error_page
• Using listen or server_name for error handling
• Forgetting to set content type for JSON

3. Given this nginx config snippet, what is the JSON response body for a 404 error?

error_page 404 /404.json;
location = /404.json {
  internal;
  default_type application/json;
  return 404 '{"error":"Not Found"}';
}

medium

A. 404 Not Found

B. Not Found

C. {"error":"Not Found"}

D. Error 404

Solution

1. Step 1: Analyze the error_page and location block

   The 404 error triggers /404.json, which is internal and returns JSON with content type application/json.

2. Step 2: Check the return statement

   The return sends status 404 with JSON string '{"error":"Not Found"}' as the body.

3. Final Answer:

   {"error":"Not Found"} -> Option C

4. Quick Check:

   Return JSON string = {"error":"Not Found"} [OK]

Hint: Look at return content for JSON body [OK]

Common Mistakes:

• Assuming default HTML error page is returned
• Ignoring internal directive effect
• Confusing status code text with response body

4. You configured nginx to return JSON errors but clients receive HTML error pages instead. What is the likely mistake?

medium

A. The server_name directive is not set.

B. The error_page directive is missing or incorrect.

C. The return directive uses invalid JSON syntax.

D. The internal directive is missing in the error location block.

Solution

1. Step 1: Understand internal directive role

   The internal directive prevents direct client access to error pages, ensuring nginx uses them only for error responses.

2. Step 2: Identify why HTML is returned

   If internal is missing, clients can access the error page URL directly, causing nginx to serve default HTML instead of JSON error.

3. Final Answer:

   The internal directive is missing in the error location block. -> Option D

4. Quick Check:

   Missing internal = HTML errors shown [OK]

Hint: Always mark error locations internal for JSON errors [OK]

Common Mistakes:

• Forgetting internal causes direct access to error pages
• Blaming server_name for error response format
• Assuming JSON syntax error causes HTML output

5. How would you configure nginx to return a JSON error response with status 500 and body {"error":"Server Error"} using an internal location?

hard

A. error_page 500 /500.json;
location = /500.json {
internal;
default_type application/json;
return 500 '{"error":"Server Error"}';
}

B. error_page 500 /500.html;
location = /500.html {
internal;
default_type text/html;
return 500 'Server Error';
}

C. location /500.json {
return 500 '{"error":"Server Error"}';
}

D. error_page 500 /500.json;
location /500.json {
default_type application/json;
return 500 '{"error":"Server Error"}';
}

Solution

1. Step 1: Use error_page to map 500 to JSON location

   The directive error_page 500 /500.json; tells nginx to use /500.json for 500 errors.

2. Step 2: Define internal location with JSON content type and return JSON body

   The location must be internal to prevent direct access, set default_type application/json;, and return the JSON string with status 500.

3. Step 3: Verify options

   error_page 500 /500.json; location = /500.json { internal; default_type application/json; return 500 '{"error":"Server Error"}'; } matches all requirements. error_page 500 /500.html; location = /500.html { internal; default_type text/html; return 500 '

   Server Error

   '; } uses HTML. The others lack the internal directive or miss the error_page directive.

4. Final Answer:

   error_page 500 /500.json; location = /500.json { internal; default_type application/json; return 500 '{"error":"Server Error"}'; } -> Option A

5. Quick Check:

   Use error_page + internal + JSON return [OK]

Hint: Map error_page, mark internal, set JSON content, return JSON [OK]

Common Mistakes:

• Omitting internal directive
• Using wrong content type
• Not escaping JSON properly
• Not mapping error_page to location