How to configure a highly available reverse proxy (such as Nginx) on Linux

How to configure a highly available reverse proxy (such as Nginx) on Linux

Abstract:
Reverse proxy is a technology commonly used in network architecture to improve the load balancing capabilities of services and fault tolerance. This article will introduce how to configure a highly available reverse proxy on a Linux system, taking Nginx as an example.

1. Installing Nginx
   First, we need to install Nginx on the Linux system. The installation can be completed with the following command:

   sudo apt-get update
   sudo apt-get install nginx

2. Configuring the reverse proxy
   Configuring the reverse proxy in Nginx is very simple. Edit the Nginx configuration file /etc/nginx/nginx.conf and add the following content in the http block:

   http {
    upstream backend {
        server backend1.example.com;
        server backend2.example.com;
        server backend3.example.com;
    }
   
    server {
        listen       80;
        server_name  example.com;
   
        location / {
            proxy_pass  http://backend;
        }
    }
   }

   In the above configuration, we defined a file named backend's upstream block, which lists the backend servers that require proxies. The server block specifies the listening port and domain name and forwards the request to backend.

3. Configuring load balancing strategy
   In the above configuration, the round-robin load balancing strategy is used by default. That is, each request is distributed to the backend server in sequence. If a more complex load balancing strategy is required, it can be configured as needed.
   The following are some common load balancing policy examples:

a. IP Hash

upstream backend {
    ip_hash;
    server backend1.example.com;
    server backend2.example.com;
    server backend3.example.com;
}

The IP Hash policy distributes the client's requests to a specific server based on its IP address. end server, so that all requests from the same client can be sent to the same server.

b. Least Connections

upstream backend {
    least_conn;
    server backend1.example.com;
    server backend2.example.com;
    server backend3.example.com;
}

The Least Connections policy will send requests to the server with the smallest number of current connections to achieve load balancing.

4. Reload Nginx configuration
   After completing the configuration, you need to reload the Nginx configuration file for the changes to take effect. The operation can be completed through the following command:

   sudo nginx -s reload

5. High availability configuration
   In order to achieve high availability, multiple Nginx nodes can be formed into a cluster and use tools such as Keepalived to achieve failover . The following is a simple example, assuming there are two nodes in the cluster:

   sudo apt-get install keepalived

   On each node, you need to edit the Keepalived configuration file, usually located at /etc/keepalived/keepalived.conf. The following is an example configuration:

   global_defs {
    router_id LB_NODE1
   }
   
   vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    priority 100
    
    virtual_ipaddress {
        192.168.1.100
    }
   }

   where state specifies the node's status (MASTER or BACKUP), virtual_router_id specifies the virtual router ID, virtual_ipaddress The virtual IP address is specified.

Finally, restart the Keepalived service to make the configuration take effect:

sudo service keepalived restart

Summary:
This article introduces the steps to configure a highly available reverse proxy on a Linux system , and related code examples. Through these configurations, the load balancing capability and fault tolerance of the service can be improved, thereby achieving higher availability and stability. At the same time, it also introduces how to use tools such as Keepalived to implement reverse proxy failover. I hope this content will be helpful to friends who want to build a highly available reverse proxy system.

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