What does nginx load balancing mean?

Load Balancing

nginx plays the role of a reverse proxy server. What rules does it use to distribute requests? What load balancing scheduling algorithm does it have?

The number of requests sent by the client and received by the nginx reverse proxy server mentioned here is what we call the load

The number of requests is distributed to different servers for processing according to certain rules, which is a balancing rule

So~the requests received by the server are distributed according to the rules The process is called load balancing.

In the actual project operation process, there are two types of load balancing: hardware load balancing and software load balancing. Hardware load balancing is also called hard load, such as F5 load balancing, which is relatively expensive. However, the stability and security of data are very well guaranteed. Only companies such as China Mobile and China Unicom will choose hard load operations; more companies will choose to use software load balancing due to cost reasons,Software load balancing is a message queue distribution mechanism implemented using existing technology combined with host hardware

The load balancing scheduling algorithm supported by Nginx is as follows: (Key points)

weight polling (default):

The received requests are assigned to different back-end servers one by one in order, even if a certain back-end server is used during use If it goes down, Nginx will automatically remove the server from the queue, and the request acceptance will not be affected in any way. In this way, a weight value (weight) can be set for different back-end servers to adjust the allocation rate of requests on different servers; the larger the weight data, the greater the probability of being allocated to the request; the weight value, It is mainly adjusted for different back-end server hardware configurations in actual working environments.

ip_hash:

Each request is matched according to the hash result of the initiating client's IP. Under this algorithm, a client with a fixed IP address will always access the same address. A back-end server, which also solves the problem of session sharing in a cluster deployment environment to a certain extent.

fair:

Intelligent adjustment of the scheduling algorithm, dynamic and balanced distribution based on the time from request processing to response of the back-end server, a server with short response time and high processing efficiency Servers with a high probability of being assigned requests and long response times and low processing efficiency are assigned fewer requests; a scheduling algorithm that combines the advantages of the first two. However, it should be noted that Nginx does not support the fair algorithm by default. If you want to use this scheduling algorithm, please install the upstream_fair module.

url_hash:

Requests are allocated according to the hash result of the accessed URL. The URL of each request will point to a fixed server on the backend, which can be used as a static in Nginx Improve cache efficiency in the case of servers. It should also be noted that Nginx does not support this scheduling algorithm by default. If you want to use it, you need to install the Nginx hash software package.

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