limit_req_zone and limit_req in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a rate limit zone named 'mylimit' with 10 requests per second.

Nginx

limit_req_zone $binary_remote_addr zone=mylimit:10m rate=[1]r/s;

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

A5

B50

C10

D20

Attempts:

3 left

💡 Hint

Common Mistakes

Using a rate value too low or too high for the example.

Forgetting to add 'r/s' after the number.

The rate parameter sets the allowed requests per second. Here, 10r/s means 10 requests per second.

2fill in blank

medium

Complete the code to apply the 'mylimit' zone to limit requests in the server block.

Nginx

limit_req zone=[1] burst=5 nodelay;

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

Amylimit

Bfastlimit

Cdefault

Dzone1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a zone name that was not defined.

Leaving the zone name empty.

The zone name must match the name defined in limit_req_zone. Here, it is 'mylimit'.

3fill in blank

hard

Fix the error in the limit_req_zone directive to correctly set the zone size to 20 megabytes.

Nginx

limit_req_zone $binary_remote_addr zone=mylimit:[1] rate=10r/s;

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

A20m

B20k

C20g

D20

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the unit, which causes a syntax error.

Using incorrect units like 'k' or 'g' unintentionally.

The zone size must be specified with a unit. 'm' means megabytes, so '20m' is correct for 20 megabytes.

4fill in blank

hard

Fill both blanks to create a limit_req_zone using the client IP and apply a burst of 10 in the limit_req directive.

Nginx

limit_req_zone [1] zone=iplimit:10m rate=5r/s;
limit_req zone=iplimit burst=[2];

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

A$binary_remote_addr

B10

C5

D$remote_addr

Attempts:

3 left

💡 Hint

Common Mistakes

Using $remote_addr instead of $binary_remote_addr for the zone key.

Setting burst to a wrong number.

The variable $binary_remote_addr is used for client IP in binary form for efficiency. The burst value controls how many requests can exceed the rate temporarily.

5fill in blank

hard

Fill all three blanks to define a limit_req_zone with 15r/s rate, apply it with a burst of 7, and enable nodelay.

Nginx

limit_req_zone [1] zone=fastlimit:15m rate=[2]r/s;
limit_req zone=fastlimit burst=[3] nodelay;

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

A$binary_remote_addr

B15

C7

D$remote_addr

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up $remote_addr and $binary_remote_addr.

Using wrong numbers for rate or burst.

The zone key is $binary_remote_addr. The rate is 15 requests per second. The burst is set to 7 to allow some bursts without delay. The nodelay option sends excess requests immediately as errors.

Practice

1. What is the main purpose of the limit_req_zone directive in nginx?

easy

A. To log requests that exceed the limit

B. To apply the rate limit rules to a specific location

C. To define the key and rate limit parameters for request limiting

D. To restart nginx when limits are reached

Solution

1. Step 1: Understand the role of limit_req_zone

   This directive sets the shared memory zone and key used to track requests for limiting.

2. Step 2: Differentiate from limit_req

   limit_req applies the rules, but limit_req_zone defines them.

3. Final Answer:

   To define the key and rate limit parameters for request limiting -> Option C

4. Quick Check:

   limit_req_zone defines limits [OK]

Hint: Remember: zone defines limits, limit_req applies them [OK]

Common Mistakes:

• Confusing limit_req_zone with limit_req
• Thinking it applies limits directly
• Assuming it logs requests

2. Which of the following is the correct syntax to define a rate limit zone named mylimit with 10MB memory and 5 requests per second per IP?

easy

A. limit_req_zone $binary_remote_addr zone=mylimit:10m rate=5r/s;

B. limit_req_zone zone=mylimit:10m $binary_remote_addr rate=5r/s;

C. limit_req_zone $remote_addr zone=mylimit:5m rate=10r/s;

D. limit_req_zone $binary_remote_addr zone=mylimit:10m rate=5r/m;

Solution

1. Step 1: Check the correct order of parameters

   The syntax is limit_req_zone key zone=name:size rate=rate; so key first, then zone with name and size, then rate.

2. Step 2: Validate values

   $binary_remote_addr is preferred key, zone name is mylimit, size is 10m, rate is 5r/s (requests per second).

3. Final Answer:

   limit_req_zone $binary_remote_addr zone=mylimit:10m rate=5r/s; -> Option A

4. Quick Check:

   Correct syntax = limit_req_zone $binary_remote_addr zone=mylimit:10m rate=5r/s; [OK]

Hint: Syntax: key zone=name:size rate=numberr/s [OK]

Common Mistakes:

• Swapping zone and key order
• Using wrong memory size units
• Confusing rate units (r/s vs r/m)

3. Given this nginx config snippet:

limit_req_zone $binary_remote_addr zone=one:10m rate=1r/s;
server {
  location /api/ {
    limit_req zone=one burst=2;
  }
}

What happens if a client sends 4 requests instantly to /api/?

medium

A. All 4 requests are processed immediately

B. 1 request processed immediately, 2 delayed, 1 rejected

C. 1 request processed immediately, 3 rejected

D. All 4 requests rejected

Solution

1. Step 1: Understand rate and burst

   Rate is 1 request per second, burst=2 allows 2 extra requests to queue.

2. Step 2: Analyze 4 instant requests

   First request passes immediately, next 2 are delayed (burst), 4th exceeds burst and is rejected.

3. Final Answer:

   1 request processed immediately, 2 delayed, 1 rejected -> Option B

4. Quick Check:

   burst=2 allows 2 queued requests [OK]

Hint: burst allows extra queued requests before rejection [OK]

Common Mistakes:

• Assuming all requests pass immediately
• Ignoring burst parameter
• Thinking burst rejects requests

4. You configured:

limit_req_zone $binary_remote_addr zone=rlimit:10m rate=10r/s;
server {
  location / {
    limit_req zone=rlimit burst=5;
  }
}

But nginx logs show no rate limiting is applied. What is the likely error?

medium

A. Incorrect key used in limit_req_zone

B. The limit_req_zone directive must be inside server block

C. No nodelay option causing silent ignoring

D. Missing limit_req directive inside server block

Solution

1. Step 1: Check key correctness

   Using an incorrect key in limit_req_zone (e.g., $remote_addr instead of the preferred $binary_remote_addr) prevents proper rate limiting from being applied.

2. Step 2: Confirm directive placement

   limit_req_zone must be in http context, limit_req in server/location; placement here is correct.

3. Final Answer:

   Missing limit_req directive inside server block -> Option D

4. Quick Check:

   limit_req directive is required to apply limits [OK]

Hint: Check that limit_req directive is present inside server/location block [OK]

Common Mistakes:

• Placing limit_req_zone inside server block
• Assuming nodelay is required
• Not matching key with client IP

5. You want to limit requests to 10 per second per user IP but allow bursts of up to 20 requests without delay. Which configuration correctly achieves this?

hard

A. limit_req_zone $binary_remote_addr zone=fastlimit:10m rate=10r/s;
limit_req zone=fastlimit burst=20 nodelay;

B. limit_req_zone $remote_addr zone=fastlimit:10m rate=20r/s;
limit_req zone=fastlimit burst=10;

C. limit_req_zone $binary_remote_addr zone=fastlimit:10m rate=10r/s;
limit_req zone=fastlimit burst=20;

D. limit_req_zone $remote_addr zone=fastlimit:20m rate=10r/s;
limit_req zone=fastlimit burst=10 nodelay;

Solution

1. Step 1: Define correct rate and burst

   Rate is 10r/s, burst 20 means allow 20 extra requests queued without delay.

2. Step 2: Use nodelay to avoid delaying burst requests

   nodelay makes burst requests processed immediately, matching requirement.

3. Step 3: Validate key and zone size

   $binary_remote_addr is preferred key, 10m memory is sufficient.

4. Final Answer:

   limit_req_zone $binary_remote_addr zone=fastlimit:10m rate=10r/s; limit_req zone=fastlimit burst=20 nodelay; -> Option A

5. Quick Check:

   burst=20 with nodelay = immediate burst allowed [OK]

Hint: Use burst with nodelay for instant burst requests [OK]

Common Mistakes:

• Swapping burst and rate values
• Omitting nodelay causing delays
• Using wrong key variable