Keepalive connections in Nginx - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the purpose of keepalive connections in nginx?

Choose the best explanation for why nginx uses keepalive connections.

A To close connections immediately after each request to save memory.

B To encrypt all connections automatically without extra configuration.

C To reuse TCP connections for multiple requests, reducing latency and CPU usage.

D To limit the number of simultaneous connections to a fixed number.

💡 Hint

Think about how reusing connections affects speed and resource use.

Keepalive connections allow nginx to reuse the same TCP connection for multiple HTTP requests, which reduces the overhead of opening new connections and improves performance.

❓ Configuration

intermediate

Identify the correct nginx directive to enable keepalive connections to an upstream server

Which configuration snippet correctly enables keepalive connections for upstream servers in nginx?

Nginx

upstream backend {
    server backend1.example.com;
    server backend2.example.com;
    # Which line enables keepalive?
}

A keepalive 32;

B keepalive_timeout 32;

C keepalive_disable off;

D keepalive_requests 32;

💡 Hint

Look for the directive that sets the number of idle keepalive connections.

The keepalive directive inside an upstream block sets how many idle keepalive connections nginx keeps open to upstream servers.

💻 Command Output

advanced

What is the output of this nginx status command regarding keepalive connections?

Given the following snippet from nginx_status output, what does the Keep-Alive field represent?

Nginx

Active connections: 291 
server accepts handled requests
 166309 166309 310704 
Reading: 12 Writing: 14 Waiting: 265
Keep-Alive: 150

A The total number of keepalive connections closed since server start.

B The number of currently open keepalive connections waiting for requests.

C The maximum allowed keepalive connections configured in nginx.

D The number of keepalive connections rejected due to timeout.

💡 Hint

Focus on what 'Waiting' and 'Keep-Alive' mean in nginx status.

The 'Keep-Alive' field shows how many connections are currently kept open and idle, ready to accept new requests without reopening TCP connections.

❓ Troubleshoot

advanced

Why might nginx close keepalive connections prematurely?

After enabling keepalive connections, nginx closes them too soon. Which configuration is most likely causing this?

A keepalive_timeout 5s;

B keepalive 100;

C client_max_body_size 1m;

D proxy_buffering off;

💡 Hint

Consider which setting controls how long idle connections stay open.

The keepalive_timeout directive sets how long nginx keeps idle connections open. A low value like 5 seconds causes early closing.

🔀 Workflow

expert

Order the steps to enable and verify keepalive connections in nginx

Put these steps in the correct order to enable and confirm keepalive connections work in nginx.

A 1,2,4,3

B 4,1,2,3

C 2,1,4,3

D 1,4,2,3

💡 Hint

Think about configuration first, then client setup, then reload, then verification.

First configure nginx upstream with keepalive, then ensure clients send keepalive headers, reload nginx to apply changes, and finally verify with status.