IP hash for session persistence in Nginx - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of using ip_hash in nginx?

The ip_hash directive in nginx ensures that requests from the same client IP address are always sent to the same backend server. This helps keep user sessions consistent.

intermediate

How does ip_hash differ from round-robin load balancing?

Round-robin sends requests to backend servers in order, cycling through them. ip_hash sends requests from the same IP to the same server, maintaining session persistence.

beginner

Show a simple nginx configuration snippet using ip_hash.

upstream backend { ip_hash; server backend1.example.com; server backend2.example.com; } server { location / { proxy_pass http://backend; } }

intermediate

What happens if a client IP changes when using ip_hash?

If the client IP changes, nginx may route the request to a different backend server, potentially breaking session persistence.

intermediate

Can ip_hash be used with SSL termination in nginx?

Yes, ip_hash works with SSL termination. The load balancer handles SSL and then uses ip_hash to route requests to backend servers.

What does the ip_hash directive do in nginx?

A Encrypts client IP addresses

B Distributes requests randomly to backend servers

C Blocks requests from unknown IPs

D Routes requests from the same IP to the same backend server

ip_hash ensures session persistence by routing requests from the same client IP to the same backend server.

Which load balancing method does ip_hash replace or complement?

A Round-robin

B Least connections

C Random

D Weighted

ip_hash is an alternative to round-robin, focusing on session persistence rather than equal distribution.

What is a limitation of using ip_hash for session persistence?

A It requires sticky cookies

B It only works with HTTP/2

C It depends on client IP, which can change

D It disables SSL

Client IP addresses can change, which may cause requests to be routed to different servers, breaking session persistence.

How do you enable ip_hash in an nginx upstream block?

A Add <code>ip_hash;</code> inside the upstream block

B Add <code>ip_hash on;</code> in the server block

C Set <code>proxy_pass ip_hash;</code>

D Use <code>sticky_ip;</code> directive

To enable ip_hash, add the line ip_hash; inside the upstream block.

If a user behind a proxy shares the same IP with others, what is a possible effect when using ip_hash?

A Users get distributed evenly

B All users share the same backend server

C Sessions are encrypted

D Requests are blocked

Since ip_hash uses client IP, users behind the same proxy IP will be routed to the same backend server.

Explain how ip_hash helps maintain session persistence in nginx load balancing.

Think about how nginx decides where to send requests from the same user.

Describe a scenario where using ip_hash might cause problems and why.

Consider what happens if the IP address is not stable or shared by many users.