Conditional logging in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to disable logging for requests with status 404.

Nginx

map $status $loggable {
    404 [1];
    default 1;
}

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

A1

Bdisable

C0

Doff

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'off' or 'disable' instead of 0 disables logging incorrectly.

Setting 404 to 1 will enable logging instead of disabling it.

Setting the value to 0 disables logging for status 404.

2fill in blank

medium

Complete the code to use the variable $loggable to control access log.

Nginx

access_log /var/log/nginx/access.log combined if=[1];

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

A$loggable

B$request_method

C$status

D$remote_addr

Attempts:

3 left

💡 Hint

Common Mistakes

Using $status directly in the 'if' condition does not work as expected.

Using unrelated variables like $request_method or $remote_addr.

The 'if' parameter uses the $loggable variable to conditionally enable logging.

3fill in blank

hard

Fix the error in the map block to correctly disable logging for 500 errors.

Nginx

map $status $loggable {
    500 [1];
    default 1;
}

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

Aoff

Bfalse

Cdisable

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'off' or 'disable' causes configuration errors.

Using 'false' is not recognized by nginx in map.

Only 0 disables logging correctly in the map block; 'off', 'disable', or 'false' are invalid.

4fill in blank

hard

Fill both blanks to log only POST requests with status 200.

Nginx

map "$request_method:$status" $loggable {
    "[1]:[2]" 1;
    default 0;
}

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

APOST

BGET

C200

D404

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'GET' instead of 'POST' will log wrong requests.

Using '404' instead of '200' will log wrong status.

The map matches 'POST:200' to enable logging only for POST requests with status 200.

5fill in blank

hard

Fill all three blanks to log requests from 192.168.1.1 with status 403 or 404.

Nginx

map "$remote_addr:$status" $loggable {
    "[1]:[2]" 1;
    "[1]:[3]" 1;
    default 0;
}

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

A192.168.1.1

B403

C404

D200

Attempts:

3 left

💡 Hint

Common Mistakes

Using different IPs for the two entries.

Using status 200 instead of 403 or 404.

The map enables logging for IP 192.168.1.1 with status 403 or 404 only.

Practice

1. What is the main purpose of conditional logging in nginx?

easy

A. To log only specific requests based on conditions

B. To disable all logging permanently

C. To log every request without any filter

D. To log errors only, ignoring access logs

Solution

1. Step 1: Understand logging basics in nginx

   Logging records requests to help monitor and debug web traffic.

2. Step 2: Identify the role of conditional logging

   Conditional logging allows filtering which requests get logged based on rules.

3. Final Answer:

   To log only specific requests based on conditions -> Option A

4. Quick Check:

   Conditional logging = selective logging [OK]

Hint: Conditional logging means logging only some requests [OK]

Common Mistakes:

• Thinking conditional logging disables all logs
• Confusing conditional logging with error-only logging
• Assuming it logs every request without filtering

2. Which of the following is the correct syntax to enable conditional logging in nginx using the access_log directive?

easy

A. access_log /var/log/nginx/access.log on_condition=$if;

B. access_log /var/log/nginx/access.log if=$condition;

C. access_log /var/log/nginx/access.log condition=$if;

D. access_log if=$condition /var/log/nginx/access.log;

Solution

1. Step 1: Recall the correct order of parameters in access_log

   The syntax is: access_log <path> [format] [if=condition];

2. Step 2: Identify the correct use of the if= option

   The condition must be specified as if=$variable after the log path.

3. Final Answer:

   access_log /var/log/nginx/access.log if=$condition; -> Option B

4. Quick Check:

   access_log path if=condition [OK]

Hint: Remember: if= comes after log file path in access_log [OK]

Common Mistakes:

• Placing if= before the log file path
• Using wrong parameter names like condition= or on_condition=
• Omitting the $ sign before the variable

3. Given the following nginx configuration snippet, what will be the effect on logging?

map $request_uri $loggable {
    default 1;
    "/health" 0;
}

access_log /var/log/nginx/access.log combined if=$loggable;

medium

A. Only requests to /health will be logged

B. No requests will be logged

C. All requests except to /health will be logged

D. All requests will be logged regardless of URI

Solution

1. Step 1: Understand the map directive

   The map sets $loggable to 0 for "/health" and 1 for all others.

2. Step 2: Analyze the access_log condition

   Logging happens only if $loggable is true (1), so requests to "/health" (0) are skipped.

3. Final Answer:

   All requests except to /health will be logged -> Option C

4. Quick Check:

   map 0 disables logging for /health [OK]

Hint: map 0 disables logging; 1 enables it [OK]

Common Mistakes:

• Assuming /health requests are logged
• Thinking map disables all logging
• Confusing default and specific URI values

4. Identify the error in this nginx configuration for conditional logging:

map $status $loggable {
    200 1;
    default 0;
}

access_log /var/log/nginx/access.log combined if=loggable;

medium

A. access_log path is invalid

B. map directive syntax is incorrect

C. Cannot use $status variable in map

D. Missing $ before loggable in access_log condition

Solution

1. Step 1: Check variable usage in access_log

   Variables must be prefixed with $ in conditions, so if=loggable is wrong.

2. Step 2: Confirm correct syntax

   Correct syntax is if=$loggable to reference the variable properly.

3. Final Answer:

   Missing $ before loggable in access_log condition -> Option D

4. Quick Check:

   Variables need $ prefix in if= [OK]

Hint: Always prefix variables with $ in if= conditions [OK]

Common Mistakes:

• Omitting $ before variable in if= condition
• Miswriting map syntax
• Assuming $status cannot be used in map

5. You want to log all requests except those with user agent containing "Googlebot". Which configuration correctly implements this conditional logging?

hard

A. map $http_user_agent $loggable {
default 1;
~Googlebot 0;
}
access_log /var/log/nginx/access.log combined if=$loggable;

B. map $http_user_agent $loggable {
default 0;
~Googlebot 1;
}
access_log /var/log/nginx/access.log combined if=$loggable;

C. map $http_user_agent $loggable {
default 1;
Googlebot 0;
}
access_log /var/log/nginx/access.log combined if=$loggable;

D. map $http_user_agent $loggable {
default 1;
~Googlebot 1;
}
access_log /var/log/nginx/access.log combined if=$loggable;

Solution

1. Step 1: Use map with regex to detect "Googlebot" in user agent

   The ~ prefix allows regex matching; setting 0 disables logging for matching agents.

2. Step 2: Set default to 1 to log all other requests

   Default 1 means log unless user agent matches Googlebot.

3. Step 3: Use if=$loggable in access_log to apply condition

   This ensures only requests with $loggable=1 are logged.

4. Final Answer:

   map $http_user_agent $loggable { default 1; ~Googlebot 0; } access_log /var/log/nginx/access.log combined if=$loggable; -> Option A

5. Quick Check:

   Regex ~Googlebot disables logging for bots [OK]

Hint: Use ~ for regex in map to match user agents [OK]

Common Mistakes:

• Using exact string without ~ for regex
• Reversing default values causing wrong logging
• Not prefixing variable with $ in if= condition