Detailed explanation of Nginx upstream configuration to repair website failures

Nginx upstream configuration details to repair website failures

Introduction:
Nginx is a high-performance HTTP and reverse proxy server. Its powerful functions and flexible configuration make it an ideal choice for many websites and Ideal for service. During the operation of the website, failures and load peaks will inevitably occur. In order to ensure the availability and stability of the website, we need to master the skills of Nginx upstream configuration. This article will introduce in detail the principles and usage of Nginx upstream configuration, and demonstrate through code examples how to use upstream configuration to repair website failures.

1. Principle of Nginx upstream configuration
Nginx’s upstream module allows us to define a group of backend servers and forward client requests to these backend servers according to certain policies. Through upstream configuration, functions such as load balancing and failover can be achieved. Nginx automatically selects a backend server based on the configured policy and forwards client requests to the selected server. When the backend server fails, Nginx supports automatically eliminating the failed server and redistributing requests to other normal servers.

2. How to use Nginx upstream configuration

1. Define upstream block
   In the Nginx configuration file, define an upstream block through the upstream keyword. Each upstream block can contain multiple backend servers and can set load balancing strategies and related parameters. The following is an example:

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

In the above configuration, we define an upstream block named "backend", which contains three backend servers.

2. Using the upstream block
   In the Nginx configuration file, the client request can be forwarded to the backend server defined by the upstream block through the proxy_pass directive. The following is an example configuration:

location / {
    proxy_pass http://backend;
}

In the above configuration, we forward client requests to the backend server defined in the upstream block named "backend".

3. How to use upstream configuration to repair website failures
In actual website operations, we often encounter back-end server failures. In order to maintain the availability of the website, we need to detect and resolve failures in a timely manner and ensure that the failed server does not affect the overall service quality. By properly configuring the upstream block, we can easily implement failover and repair.

1. Detecting the availability of the backend server
   Nginx supports multiple methods to detect the availability of the backend server, including HTTP, TCP and UDP. In the upstream block, we can enable the health check feature by setting the health_check keyword. The following is a sample configuration:

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

    health_check;
}

In the above configuration, we enable the health check function by setting the health_check keyword. Nginx will periodically send requests to the backend server and determine the server's availability based on the returned status code.

2. Remove the faulty server
   When the server fails, we can remove the faulty server manually or automatically. The following is an example configuration:

upstream backend {
    server backend1.example.com;
    server backend2.example.com down;
    server backend3.example.com;

    health_check;
}

In the above configuration, we added the down keyword after the failed server configuration. When Nginx detects a server failure, it will automatically remove the server marked down from the selection range of the upstream block.

3. Set the maximum number of failures
   In order to avoid misjudgments and frequent failovers, we can limit the maximum number of failures of the failed server by setting the max_fails keyword. The following is an example configuration:

upstream backend {
    server backend1.example.com max_fails=3 fail_timeout=30s;
    server backend2.example.com down;
    server backend3.example.com max_fails=3 fail_timeout=30s;

    health_check;
}

In the above configuration, we use the max_fails keyword to set the maximum number of failures for the faulty server to 3 times. When the number of failures of a certain server reaches the limit, Nginx will remove it from the selection range and no longer try to connect within the set timeout period.

Conclusion:
By properly configuring Nginx's upstream block, we can achieve functions such as load balancing and failover, and improve the availability and stability of the website. During the operation of the website, we should promptly discover and repair back-end server failures, and ensure server availability through upstream's health check and fault elimination functions. I hope this article will help you understand the principles and usage of Nginx upstream configuration, and provide help and guidance when repairing website failures.

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