API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) · 课时

负载均衡算法

探索 Nginx 的不同负载均衡算法，例如轮询、最少连接和 IP 哈希，并了解各自的适用场景。

第 1 / 4 课12 个步骤

负载均衡算法 是 CoddyKit 上的免费 API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) 课时。这是第 1 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Why Algorithms Matter

Load balancing isn't just about distributing traffic; it's about doing it smartly. Different approaches, or algorithms, help Nginx decide which backend server should handle an incoming request.

Choosing the right algorithm can significantly impact your application's performance, reliability, and user experience.

Beyond Simple Distribution

Imagine you have multiple servers doing the same job. How do you pick one for a new request? A simple random choice might work, but it doesn't consider server load or specific client needs.

Performance: Prevent individual servers from being overloaded.
Reliability: Distribute requests even if some servers are slower.
Consistency: Ensure certain clients always hit the same server if needed.

Round Robin: Simple & Fair

Round Robin is the simplest and default load balancing algorithm in Nginx. It works by sending requests to backend servers in a sequential, rotating order.

Think of it like dealing cards in a game: Server 1 gets the first request, Server 2 gets the second, and so on. Once the last server receives a request, the cycle starts again with Server 1.

Pros: Easy to configure, ensures even distribution over time.
Cons: Doesn't account for server processing power or current load.

Nginx Round Robin Config

Here's how to configure Nginx for basic Round Robin load balancing. Nginx uses this method by default if no other algorithm is specified within the upstream block.

This example defines two backend servers, and Nginx will distribute requests to them equally.

http {
  upstream my_backend_app {
    server 192.168.1.100;
    server 192.168.1.101;
  }

  server {
    listen 80;
    location / {
      proxy_pass http://my_backend_app;
    }
  }
}

Weighted Round Robin: Prioritize Servers

Sometimes, your backend servers aren't equal. You might have one powerful server and another less powerful, or a new server being tested.

Weighted Round Robin allows you to assign a 'weight' to each server. Servers with higher weights receive more requests than those with lower weights, making the distribution proportional to their capacity.

Nginx Weighted Round Robin

To implement Weighted Round Robin, simply add the weight parameter to each server line in your upstream block. A higher weight means more requests.

In this example, 192.168.1.100 will receive twice as many requests as 192.168.1.101.

http {
  upstream my_weighted_app {
    server 192.168.1.100 weight=2;
    server 192.168.1.101 weight=1;
  }

  server {
    listen 80;
    location / {
      proxy_pass http://my_weighted_app;
    }
  }
}

Least Connections: Smart Load

Least Connections is a dynamic algorithm. Instead of just rotating, Nginx checks which backend server currently has the fewest active connections and sends the new request there.

This is ideal when requests vary in processing time. It helps prevent a single server from becoming a bottleneck while others are idle, leading to better overall resource utilization.

Pros: Excellent for uneven loads, improves response times.
Cons: Requires Nginx to track active connections, slightly more overhead.

Nginx Least Connections

To enable the Least Connections algorithm, add the least_conn directive to your upstream block. Nginx will then intelligently route requests based on active connections.

This ensures that new requests go to the server that is currently least busy.

http {
  upstream my_least_conn_app {
    least_conn;
    server 192.168.1.100;
    server 192.168.1.101;
  }

  server {
    listen 80;
    location / {
      proxy_pass http://my_least_conn_app;
    }
  }
}

IP Hash: Client Consistency

Sometimes, a client needs to consistently connect to the same backend server, often due to session data stored locally on that server. This is known as a "sticky session".

The IP Hash algorithm solves this by using the client's IP address to determine which server to send the request to. The same IP address will always be routed to the same server.

Pros: Ensures session persistence without complex server-side session management.
Cons: Can lead to uneven distribution if many clients share the same IP (e.g., behind a NAT).

Nginx IP Hash Config

To use IP Hash, simply add the ip_hash directive within your upstream block. Nginx will then use the client's IP address to consistently route them.

This is crucial for applications that rely on session-specific data being maintained on a particular backend instance.

http {
  upstream my_ip_hash_app {
    ip_hash;
    server 192.168.1.100;
    server 192.168.1.101;
  }

  server {
    listen 80;
    location / {
      proxy_pass http://my_ip_hash_app;
    }
  }
}

Algorithm Choice

You are setting up an Nginx reverse proxy for a web application. You have three backend servers, but one is significantly more powerful than the other two. Additionally, users often perform multi-step transactions that require session data to be maintained on the same server.

Which combination of Nginx load balancing features would best suit this scenario?

在交互式课程中回答

Algorithms Recap

We've explored key Nginx load balancing algorithms today:

Round Robin: Simple, default, sequential distribution.
Weighted Round Robin: Distributes requests based on server capacity (weights).
Least Connections: Routes to the server with the fewest active connections, great for uneven processing times.
IP Hash: Ensures a client consistently connects to the same backend server (sticky sessions).

Choosing the right algorithm helps you optimize performance and user experience for your specific application needs!

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「负载均衡算法」这节课中我会学到什么？

探索 Nginx 的不同负载均衡算法，例如轮询、最少连接和 IP 哈希，并了解各自的适用场景。你通过在浏览器中直接运行的动手代码来练习 API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway)，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 API Gateway & Reverse Proxy (Nginx + Spring Cloud Gateway) 需要有经验吗？

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大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

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