API routing with location blocks in Nginx - Mini Project: Build & Apply

API routing with location blocks

📖 Scenario: You are setting up a simple web server using nginx. Your goal is to route different API requests to different backend services using location blocks.This is like sorting mail into different boxes based on the address on the envelope.

🎯 Goal: Build an nginx configuration that routes requests starting with /api/users to one backend and requests starting with /api/products to another backend.

📋 What You'll Learn

Create an nginx server block with a root path

Add a location block for /api/users routing to http://users_backend

Add a location block for /api/products routing to http://products_backend

Add a default location block for all other requests routing to http://default_backend

💡 Why This Matters

🌍 Real World

Routing API requests to different backend services is common in microservices and web applications.

💼 Career

Understanding nginx location blocks is essential for DevOps roles managing web servers and load balancing.

1

Create the basic server block

Create an nginx server block listening on port 80 with a root path /var/www/html. Use server {} and listen 80; inside it.

Nginx

server {
    # Your code here
}

Hint

Use server {} to start the block, then add listen 80; and root /var/www/html; inside.

2

Add location block for /api/users

Inside the existing server block, add a location block for /api/users that proxies requests to http://users_backend using proxy_pass.

Nginx

server {
    listen 80;
    root /var/www/html;

    # Your code here
}

Hint

Use location /api/users {} and inside it add proxy_pass http://users_backend;.

3

Add location block for /api/products

Inside the server block, add another location block for /api/products that proxies requests to http://products_backend using proxy_pass.

Nginx

server {
    listen 80;
    root /var/www/html;

    location /api/users {
        proxy_pass http://users_backend;
    }

    # Your code here
}

Hint

Add location /api/products {} with proxy_pass http://products_backend; inside.

4

Add default location block and print config

Add a default location block / inside the server block that proxies requests to http://default_backend. Then print the full nginx configuration file content.

Nginx

server {
    listen 80;
    root /var/www/html;

    location /api/users {
        proxy_pass http://users_backend;
    }

    location /api/products {
        proxy_pass http://products_backend;
    }

    # Your code here
}

# Print the nginx config below

Hint

Add location / { proxy_pass http://default_backend; } inside the server block.

Practice

1. What does a location block in an nginx configuration do?

easy

A. Sets the maximum file upload size

B. Defines server IP addresses

C. Specifies the server's operating system

D. Routes incoming requests based on URL paths

Solution

1. Step 1: Understand the purpose of location blocks

   Location blocks in nginx are used to match parts of the URL path to decide how to handle requests.

2. Step 2: Identify what location blocks control

   They control routing of requests to different handlers or backends based on the URL.

3. Final Answer:

   Routes incoming requests based on URL paths -> Option D

4. Quick Check:

   Location blocks = URL routing [OK]

Hint: Location blocks match URL paths to route requests [OK]

Common Mistakes:

• Confusing location blocks with server IP settings
• Thinking location blocks set server OS
• Assuming location blocks control upload size

2. Which of the following is the correct syntax to define a location block that matches exactly the path /api/v1/users?

easy

A. location = /api/v1/users { ... }

B. location /api/v1/users { ... }

C. location ~ /api/v1/users { ... }

D. location ^~ /api/v1/users { ... }

Solution

1. Step 1: Recall nginx location modifiers

   The = modifier means exact match of the URL path.

2. Step 2: Match the exact path syntax

   Using location = /api/v1/users matches only that exact path.

3. Final Answer:

   location = /api/v1/users { ... } -> Option A

4. Quick Check:

   Exact match uses = modifier [OK]

Hint: Use '=' for exact path match in location [OK]

Common Mistakes:

• Using no modifier for exact match
• Using regex (~) when exact match needed
• Using ^~ which is prefix but not exact

3. Given this nginx config snippet:

location /api/ {
  proxy_pass http://backend-service/;
}

What happens when a client requests /api/users?

medium

A. Request is forwarded to http://backend-service/users

B. Request is forwarded to http://backend-service/api/users

C. Request is served locally from /api/users directory

D. Request returns 404 Not Found

Solution

1. Step 1: Understand proxy_pass with trailing slash

   When proxy_pass URL ends with a slash, nginx replaces the matching part of the request URI.

2. Step 2: Apply to the request path

   The matching prefix /api/ is replaced by / from proxy_pass, so /api/users becomes /users at backend.

3. Final Answer:

   Request is forwarded to http://backend-service/users -> Option A

4. Quick Check:

   proxy_pass with trailing slash replaces prefix [OK]

Hint: Trailing slash in proxy_pass replaces matched prefix [OK]

Common Mistakes:

• Assuming proxy_pass appends full original URI
• Confusing local serving with proxying
• Ignoring trailing slash effect in proxy_pass

4. Identify the error in this nginx location block:

location /api {
  proxy_pass http://backend-service/;
}

medium

A. Missing trailing slash in location path causes wrong proxying

B. location path should end with a slash to match subpaths

C. proxy_pass URL must not have a trailing slash

D. No error; configuration is correct

Solution

1. Step 1: Check location path matching behavior

   Without a trailing slash, location /api matches only the exact path /api and not subpaths like /api/users.

2. Step 2: Correct usage for subpath matching

   To match /api and all subpaths, use location /api/ with trailing slash.

3. Final Answer:

   location path should end with a slash to match subpaths -> Option B

4. Quick Check:

   Trailing slash in location matches subpaths [OK]

Hint: Add trailing slash in location to match subpaths [OK]

Common Mistakes:

• Thinking proxy_pass trailing slash is wrong here
• Assuming location without slash matches subpaths
• Believing config is error-free without checking path

5. You want to route all requests starting with /api/v2/ to http://v2-backend/ but requests exactly to /api/v2/status should return a static JSON response locally. Which nginx config achieves this?

hard

A. location /api/v2/status { return 200 '{"status":"ok"}'; }
location ^~ /api/v2/ { proxy_pass http://v2-backend/; }

B. location /api/v2/status { proxy_pass http://v2-backend/status; }
location /api/v2/ { proxy_pass http://v2-backend/; }

C. location = /api/v2/status { return 200 '{"status":"ok"}'; }
location /api/v2/ { proxy_pass http://v2-backend/; }

D. location /api/v2/ { proxy_pass http://v2-backend/; }
location = /api/v2/status { proxy_pass http://v2-backend/status; }

Solution

1. Step 1: Use exact match for static response

   Use location = /api/v2/status to match exactly that path and return static JSON.

2. Step 2: Use prefix match for all other /api/v2/ requests

   Use location /api/v2/ to proxy all other requests to backend.

3. Final Answer:

   location = /api/v2/status { return 200 '{"status":"ok"}'; } location /api/v2/ { proxy_pass http://v2-backend/; } -> Option C

4. Quick Check:

   Exact match first, then prefix proxy [OK]

Hint: Exact match location before prefix for special cases [OK]

Common Mistakes:

• Placing prefix location before exact match causing override
• Using proxy_pass for static JSON response
• Not escaping JSON properly in return directive