Weighted round-robin in Nginx - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set up a basic upstream block for load balancing.

Nginx

upstream backend {
    server 192.168.1.1[1];
}

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

A:80 weight=5

B;

Cweight=5

D:80

Attempts:

3 left

💡 Hint

Common Mistakes

Adding weight without a space or without the port number

Using only weight without specifying port or semicolon

The correct syntax to specify a server with default settings is just the IP and optional port, like 192.168.1.1:80. Adding :80 specifies the port.

2fill in blank

medium

Complete the code to assign a weight of 3 to the server in the upstream block.

Nginx

upstream backend {
    server 192.168.1.2:80 [1];
}

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

Aweight=3

Bweight:3

Cweight 3

Dweight=5

Attempts:

3 left

💡 Hint

Common Mistakes

Using space instead of equals sign

Using colon instead of equals sign

Wrong weight number

In nginx, weights are assigned using weight=number syntax with an equals sign and no spaces.

3fill in blank

hard

Fix the error in the upstream block to correctly assign weights to two servers.

Nginx

upstream backend {
    server 192.168.1.3:80 weight=2;
    server 192.168.1.4:80 [1];
}

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

Aweight 3

Bweight= 3

Cweight=3

Dweight:3

Attempts:

3 left

💡 Hint

Common Mistakes

Missing semicolon at end of server line

Using space or colon instead of equals sign

Each server line must end with a semicolon. Also, weight assignment uses weight=number with no spaces after equals.

4fill in blank

hard

Fill both blanks to create an upstream block with two servers having weights 4 and 6.

Nginx

upstream backend {
    server 192.168.1.5:80 [1];
    server 192.168.1.6:80 [2];
}

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

Aweight=4

Bweight=6

C;

Dweight=5

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong weight numbers

Missing semicolons

Using incorrect syntax for weight

Each server line must specify the weight with weight=number and end with a semicolon.

5fill in blank

hard

Fill all three blanks to configure an upstream with weighted round-robin load balancing.

Nginx

upstream backend {
    [1] 192.168.1.7:80 [2];
    [3] 192.168.1.8:80 weight=7;
}

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

Aserver

Bweight=5

Dweight=3

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the 'server' keyword

Incorrect weight syntax

Missing semicolons

Each server line starts with server. The first server has weight 5, the second weight 7. Weighted round-robin is the default when weights are specified.

Practice

1. What does the weight parameter control in nginx's weighted round-robin load balancing?

easy

A. The maximum number of connections a server can handle

B. The timeout duration for server responses

C. The order in which servers are listed in the config

D. The number of requests sent to a server relative to others

Solution

1. Step 1: Understand the role of weight in load balancing

   The weight defines how many requests a server receives compared to others.

2. Step 2: Relate weight to request distribution

   Higher weight means more requests go to that server, balancing load by capacity.

3. Final Answer:

   The number of requests sent to a server relative to others -> Option D

4. Quick Check:

   Weight controls request share [OK]

Hint: Weight sets request share per server [OK]

Common Mistakes:

• Confusing weight with timeout
• Thinking weight limits connections
• Assuming weight sets server order

2. Which of the following is the correct syntax to assign weights to servers in nginx for weighted round-robin?

easy

A. server backend1.example.com weight:3;

B. server backend1.example.com weight 3;

C. server backend1.example.com weight=3;

D. server backend1.example.com weight(3);

Solution

1. Step 1: Recall nginx upstream server syntax

   Weights are assigned using weight=number with an equal sign and semicolon.

2. Step 2: Check each option's syntax

   Only server backend1.example.com weight=3; uses the correct weight=3; format.

3. Final Answer:

   server backend1.example.com weight=3; -> Option C

4. Quick Check:

   Correct syntax uses equal sign and semicolon [OK]

Hint: Use weight=number; syntax for servers [OK]

Common Mistakes:

• Omitting equal sign
• Using colon instead of equal sign
• Using parentheses incorrectly

3. Given this nginx upstream block:

upstream backend {
  server backend1.example.com weight=3;
  server backend2.example.com weight=1;
}

If 8 requests arrive, how many requests will backend2 receive approximately?

medium

A. 2

B. 6

C. 4

D. 1

Solution

1. Step 1: Calculate total weight

   backend1 weight=3, backend2 weight=1, total = 4.

2. Step 2: Calculate requests for backend2

   Requests for backend2 = (1/4) * 8 = 2.

3. Final Answer:

   2 -> Option A

4. Quick Check:

   Requests proportional to weight [OK]

Hint: Requests split by weight ratio [OK]

Common Mistakes:

• Ignoring total weight sum
• Assigning equal requests despite weights
• Miscounting total requests

4. You configured nginx with weighted round-robin but all servers receive equal requests. What is the most likely cause?

medium

A. nginx does not support weighted round-robin

B. Weights were not specified correctly in the config

C. The servers have identical IP addresses

D. The upstream block is missing the weight directive

Solution

1. Step 1: Understand weighted round-robin requires correct weight syntax

   If weights are missing or incorrect, nginx defaults to equal distribution.

2. Step 2: Analyze the options

   Weights were not specified correctly in the config states weights not specified correctly, which explains equal requests.

3. Final Answer:

   Weights were not specified correctly in the config -> Option B

4. Quick Check:

   Incorrect weights cause equal load [OK]

Hint: Check weight syntax if load is equal [OK]

Common Mistakes:

• Assuming nginx lacks weighted support
• Confusing IP issues with load balancing
• Missing weight directive entirely

5. You have three servers with weights 5, 3, and 2. You want to add a fourth server but keep the total weight sum at 10. What weight should you assign to the new server to maintain the same total weight and keep the relative proportions of the first three servers?

hard

A. 0 (do not add the server)

B. 5

C. 2

D. 1

Solution

1. Step 1: Calculate current total weight

   Sum of existing weights = 5 + 3 + 2 = 10.

2. Step 2: Determine weight for new server

   To keep total sum at 10 when adding a fourth server, assign weight=0 to it.

3. Step 3: Verify proportions

   Weight=0 means no requests to the new server, so first three retain exact proportions (5:3:2 out of total 10).

4. Final Answer:

   0 (do not add the server) -> Option A

5. Quick Check:

   Weight=0 keeps total and proportions unchanged [OK]

Hint: Assign weight=0 to keep total sum and proportions [OK]

Common Mistakes:

• Assigning positive weight that increases total sum
• Forgetting to maintain exact total of 10
• Ignoring impact on relative proportions