How nginx does load balancing

Load balancing:Load balancing is also a commonly used function of Nginx. When the number of visits per unit time of a server is larger, the pressure on the server will be greater, and when it exceeds its own capacity, The server will crash.

#In order to avoid server crashes and provide users with a better experience, we use load balancing to share server pressure. We can build many, many servers to form a server cluster. When a user accesses a website, he first accesses an intermediate server, then lets the intermediate server select a server with less pressure in the server cluster, and then introduces the access request to the server. (Recommended learning: nginx tutorial)

In this way, every time a user visits, it will ensure that the pressure of each server in the server cluster tends to be balanced, sharing the server pressure and avoiding server crash situation. Load balancing configuration generally requires configuring a reverse proxy at the same time, and jumping to load balancing through the reverse proxy.

nginx load balancing requires two or more application servers, and write relevant configurations in nginx.conf, mainly the use of proxy_pass, upstream

Common ones Load balancing method

1. Polling (default) - Each request is assigned to different back-end servers one by one in chronological order. If the back-end server goes down, it can be automatically eliminated.

2.weight - Specifies the polling probability, weight is proportional to the access ratio, and is used when the performance of the back-end server is uneven.

3. ip_hash - Each request is allocated according to the hash result of the accessed IP, so that each visitor accesses a back-end server.

4.backup——When all other non-backup machines are down or busy, request the backup machine. So this machine will have the least pressure.

5.down——Indicates that the previous server will not participate in the load temporarily

6.fair (third party) allocates requests according to the response time of the back-end server, and priority is given to those with short response times . Similar to weight allocation strategy

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