limit_req_zone and limit_req in Nginx - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of limit_req_zone in nginx?

limit_req_zone defines a shared memory zone to store request states for limiting request rates from clients. It sets the key to identify clients and the rate limit.

beginner

How does limit_req work in nginx configuration?

limit_req applies the rate limiting defined by limit_req_zone to a specific location or server block, controlling how many requests per second a client can make.

intermediate

What does the burst parameter do in limit_req?

The burst parameter allows a client to exceed the rate limit temporarily by queuing extra requests. This helps smooth traffic spikes without immediate rejection.

beginner

Explain the role of the zone parameter in limit_req.

The zone parameter in limit_req specifies which shared memory zone (defined by limit_req_zone) to use for rate limiting.

intermediate

What happens if a client exceeds the rate limit set by limit_req without a burst?

Requests exceeding the limit are rejected with HTTP status 503 (Service Unavailable) immediately if no burst is configured.

What does limit_req_zone $binary_remote_addr zone=mylimit:10m rate=5r/s; do?

A Limits each client IP to 5 requests per second using a 10MB shared memory zone

B Limits total server requests to 5 per second

C Blocks clients after 5 requests total

D Allows unlimited requests but logs them

This command sets a limit of 5 requests per second per client IP, storing state in a 10MB shared memory zone named 'mylimit'.

Which directive applies the rate limit defined by limit_req_zone?

A limit_req

B limit_conn

C limit_rate

D limit_zone

limit_req applies the rate limiting rules defined by limit_req_zone to requests.

What is the effect of setting burst=10 in limit_req?

A Increases rate limit by 10 requests per second

B Blocks 10 requests immediately

C Allows 10 extra requests to queue temporarily beyond the rate limit

D Disables rate limiting

burst=10 lets clients send 10 extra requests that are queued and processed smoothly.

If no burst is set, what happens when a client exceeds the rate limit?

A Requests are logged but allowed

B Requests are rejected with HTTP 503

C Requests are delayed but accepted

D Requests are queued indefinitely

Without burst, exceeding the limit causes immediate rejection with HTTP 503.

What key is commonly used in limit_req_zone to identify clients?

A $server_name

B $request_uri

C $host

D $binary_remote_addr

$binary_remote_addr is the binary form of the client IP address, commonly used as the key.

Describe how to configure nginx to limit each client IP to 10 requests per second with a burst of 5.

Think about defining the shared zone first, then applying it with burst.

Explain what happens internally when a client sends requests faster than the configured rate limit in nginx using limit_req.

Consider how nginx tracks and controls request flow per client.