Burst and nodelay options in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the burst limit in the rate limiting configuration.

Nginx

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

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

A10

B5

C20

D50

Attempts:

3 left

💡 Hint

Common Mistakes

Using a very high burst value can cause server overload.

Omitting the burst option disables bursting.

The burst option sets how many requests can exceed the rate limit temporarily. Here, 5 means up to 5 extra requests can burst.

2fill in blank

medium

Complete the code to enable the nodelay option in the limit_req directive.

Nginx

limit_req zone=mylimit burst=5 [1];

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

Anodelay

Bimmediate

Cfast

Ddelay

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'delay' instead of 'nodelay' causes requests to be delayed.

Misspelling the option name.

The nodelay option makes requests exceeding the rate limit and burst limit processed immediately without delay.

3fill in blank

hard

Fix the error in the limit_req directive to correctly apply burst and nodelay options.

Nginx

limit_req zone=mylimit burst=[1] nodelay;

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

Aten

B10

C5

Dfive

Attempts:

3 left

💡 Hint

Common Mistakes

Writing numbers as words causes syntax errors.

Using values not supported by nginx.

The burst value must be a number, not a word. '5' is correct, 'five' or 'ten' are invalid.

4fill in blank

hard

Fill both blanks to configure a limit_req with burst and nodelay options correctly.

Nginx

limit_req zone=mylimit burst=[1] [2];

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

A10

Bnodelay

Cdelay

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping burst and nodelay positions.

Using 'delay' instead of 'nodelay'.

Use 5 for burst and nodelay to process excess requests immediately.

5fill in blank

hard

Fill all three blanks to create a limit_req_zone and limit_req with burst and nodelay options.

Nginx

limit_req_zone $binary_remote_addr zone=mylimit:10m rate=[1];
limit_req zone=mylimit burst=[2] [3];

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

A1r/s

Bnodelay

C5

D10r/s

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect rate format.

Omitting nodelay when bursts should be immediate.

The rate is set to 1r/s, burst to 5, and nodelay enables immediate processing of bursts.

Practice

1. What does the burst option do in nginx rate limiting?

easy

A. Processes all requests without any limit

B. Immediately rejects extra requests beyond the limit

C. Allows extra requests to wait in a queue before being processed

D. Delays all requests by a fixed time

Solution

1. Step 1: Understand the purpose of burst

   The burst option in nginx allows extra requests that exceed the rate limit to be queued temporarily instead of being rejected immediately.

2. Step 2: Compare with other options

   Unlike rejecting or delaying all requests, burst specifically queues extra requests to handle traffic spikes smoothly.

3. Final Answer:

   Allows extra requests to wait in a queue before being processed -> Option C

4. Quick Check:

   Burst = queue extra requests [OK]

Hint: Burst queues extra requests to handle spikes smoothly [OK]

Common Mistakes:

• Thinking burst rejects extra requests immediately
• Confusing burst with fixed delay
• Assuming burst processes all requests without limit

2. Which is the correct syntax to enable burst with 10 requests and nodelay in nginx?

easy

A. limit_req_zone $binary_remote_addr zone=mylimit:10m rate=1r/s; limit_req zone=mylimit burst=10 nodelay;

B. limit_req_zone $binary_remote_addr zone=mylimit:10m rate=1r/s; limit_req zone=mylimit burst=10 delay;

C. limit_req_zone $binary_remote_addr zone=mylimit:10m rate=1r/s; limit_req zone=mylimit burst=10;

D. limit_req_zone $binary_remote_addr zone=mylimit:10m rate=1r/s; limit_req zone=mylimit nodelay burst=10;

Solution

1. Step 1: Identify correct order and keywords

   The correct syntax places burst=10 followed by nodelay without extra keywords like delay.

2. Step 2: Validate syntax correctness

   limit_req_zone $binary_remote_addr zone=mylimit:10m rate=1r/s; limit_req zone=mylimit burst=10 nodelay; correctly uses limit_req_zone and limit_req directives with proper parameters and order.

3. Final Answer:

   limit_req_zone $binary_remote_addr zone=mylimit:10m rate=1r/s; limit_req zone=mylimit burst=10 nodelay; -> Option A

4. Quick Check:

   Syntax with burst=10 and nodelay = limit_req_zone $binary_remote_addr zone=mylimit:10m rate=1r/s; limit_req zone=mylimit burst=10 nodelay; [OK]

Hint: Use burst=number before nodelay in limit_req [OK]

Common Mistakes:

• Using 'delay' instead of 'nodelay'
• Placing nodelay before burst
• Omitting limit_req_zone directive

3. Given this nginx config snippet:

limit_req_zone $binary_remote_addr zone=one:10m rate=1r/s;
limit_req zone=one burst=3 nodelay;

What happens if 5 requests arrive instantly from the same IP?

medium

A. All 5 requests are processed immediately

B. First 4 requests processed immediately, 5th rejected

C. First request processed immediately, next 4 delayed

D. Only 1 request processed, others rejected

Solution

1. Step 1: Understand rate and burst limits

   The rate is 1 request per second, burst allows 3 extra requests queued, and nodelay means queued requests run immediately.

2. Step 2: Analyze 5 instant requests

   The first request is within rate limit, next 3 fit in burst queue and run immediately due to nodelay, the 5th exceeds burst and is rejected.

3. Final Answer:

   First 4 requests processed immediately, 5th rejected -> Option B

4. Quick Check:

   Burst=3 + nodelay means 4 immediate, 5th rejected [OK]

Hint: Burst + nodelay = burst requests processed immediately [OK]

Common Mistakes:

• Assuming all 5 requests pass immediately
• Thinking requests after burst are delayed, not rejected
• Ignoring nodelay effect

4. You configured burst=5 but your nginx still rejects extra requests immediately. What is the likely cause?

medium

A. You forgot to add the nodelay option

B. The limit_req_zone directive is missing

C. The burst value must be less than 5

D. You need to restart nginx twice

Solution

1. Step 1: Check burst behavior without nodelay

   Without nodelay, burst requests are delayed, not processed immediately, but if delay is too long, clients may see rejections.

2. Step 2: Identify missing nodelay effect

   If extra requests are rejected immediately despite burst, likely nodelay is missing, causing strict rate enforcement.

3. Final Answer:

   You forgot to add the nodelay option -> Option A

4. Quick Check:

   Missing nodelay causes immediate rejection despite burst [OK]

Hint: Add nodelay to process burst requests immediately [OK]

Common Mistakes:

• Assuming burst alone allows immediate processing
• Thinking burst must be less than 5
• Believing multiple restarts fix config issues

5. You want to handle sudden spikes of up to 20 extra requests per second without delay, but reject any beyond that. Which nginx config snippet achieves this?

hard

A. limit_req_zone $binary_remote_addr zone=spike:10m rate=20r/s;
limit_req zone=spike burst=5 nodelay;

B. limit_req_zone $binary_remote_addr zone=spike:10m rate=25r/s;
limit_req zone=spike burst=0;

C. limit_req_zone $binary_remote_addr zone=spike:10m rate=5r/s;
limit_req zone=spike burst=0 nodelay;

D. limit_req_zone $binary_remote_addr zone=spike:10m rate=5r/s;
limit_req zone=spike burst=20 nodelay;

Solution

1. Step 1: Set base rate and burst for spikes

   The base rate is 5 requests per second, and burst=20 allows 20 extra requests queued.

2. Step 2: Use nodelay to process burst immediately

   Adding nodelay ensures the burst requests are processed right away without delay.

3. Step 3: Confirm rejection beyond burst

   Requests beyond burst=20 will be rejected, matching the requirement.

4. Final Answer:

   limit_req_zone $binary_remote_addr zone=spike:10m rate=5r/s; limit_req zone=spike burst=20 nodelay; -> Option D

5. Quick Check:

   Rate=5r/s + burst=20 + nodelay = limit_req_zone $binary_remote_addr zone=spike:10m rate=5r/s; limit_req zone=spike burst=20 nodelay; [OK]

Hint: Set burst high with nodelay to handle spikes immediately [OK]

Common Mistakes:

• Setting burst too low for spikes
• Omitting nodelay causing delays
• Setting rate too high ignoring burst