Detailed explanation of two ways to implement session persistence in Nginx reverse proxy

1. ip_hash:

ip_hash uses a source address hash algorithm to always send requests from the same client to the same backend server unless the server is unavailable.

ip_hash syntax:

 upstream backend {
  ip_hash;
  server backend1.example.com;
  server backend2.example.com;
  server backend3.example.com down;
  server backend4.example.com;
}

ip_hash is simple and easy to use, but it has the following problems:

• When the backend server goes down, the session will be lost;
• Clients from the same LAN will be forwarded to the same backend server, which may cause load imbalance;
• It is not applicable to CDN networks, and it is not applicable to situations where there is a proxy in the front end.
  

2. sticky_cookie_insert:

Use sticky_cookie_insert to enable session affinity, which causes requests from the same client to be delivered to the same server for a group of servers. The difference from ip_hash is that it does not judge the client based on the IP, but based on the cookie. Therefore, the situation in which the client and the front-end proxy from the same LAN in the above ip_hash cause load imbalance can be avoided.

grammar:

 upstream backend {
  server backend1.example.com;
  server backend2.example.com;
  sticky_cookie_insert srv_id expires=1h domain=toxingwang.com path=/;
}

illustrate:

• expires: Set the time to keep the cookie in the browser
• domain: defines the domain of the cookie
• path: defines the path for the cookie

In addition, you can also use the backend server itself to keep the session synchronized through related mechanisms, which will be described in detail later!

The above is the full content of this article. I hope it will be helpful for everyone’s study. I also hope that everyone will support 123WORDPRESS.COM.