What are the basic concepts and principles of Nginx

1. Basic concepts of Nginx

(engine x) is a high-performance HTTP and reverse proxy web server, and also provides IMAP/POP3/SMTP services. Its characteristics are that it occupies less memory and has strong concurrency capabilities. In fact, the concurrency capabilities of nginx perform better among web servers of the same type. Users of nginx websites in mainland China include: Baidu, JD.com, Sina, NetEase, Tencent, Taobao, etc.

Nginx is specially developed for performance optimization. Performance is the most important consideration of the server. The implementation pays great attention to efficiency and can withstand the test of high load. It is reported that it can support up to 50,000 concurrent connections.

Nginx can not only be used as a reverse proxy to achieve load balancing; it can also be used as a forward proxy for Internet access and other functions.

2. Reverse proxy

By setting up a proxy server, the client (browser) can use the proxy server to access the Internet. The proxy object is the client and does not know who the server is.

The client does not need any configuration to access it. It only needs to send the request to the reverse proxy server, and the reverse proxy server selects the target server and obtains the data. Returned to the client. The outside world can only access the reverse proxy server address, while the real server's IP address is hidden. The proxy object is the server and does not know who the client is.

3. Load balancing

The server will process multiple requests sent by the client. Some requests may require access to the database. Finally, the server will process Return the results to the client.

This architecture model is single and suitable for situations where there are few concurrent requests, but how to solve it when the amount of concurrency is large?

First of all, you may think of upgrading the server configuration, but the performance improvement of the hardware cannot meet the growing demand. At this time, you can think of server clusters, increase the number of servers, and then request a single server The situation is changed to distribute the request to multiple servers and distribute the load to multiple servers, which is what we are talking about

4. Separation of dynamic and static

In order to speed up website parsing, you can use different servers to parse dynamic pages and static pages respectively, thereby reducing the burden on the server and speeding up parsing.

##5. Principle

mater&worker

##master

After receiving the signal Assign tasks to workers for execution. There can be multiple workers.

6. How the worker works

After the client sends a request to the master, the mechanism for the worker to obtain the task is not direct allocation or polling, but A scramble mechanism that "grabs" the task before executing it, that is, selecting the target server tomcat, etc., and then returning the result.

worker_connection

Sending the request takes up two or four worker connections.

The maximum number of concurrent static accesses is:
• worker_connections *worker_processes/ 2 /2/2

If it is HTTP As a reverse proxy, the maximum number of concurrent connections should be
• worker_connections *worker_processes/ 4 /4/4

  .

Of course, the more workers the better, the most appropriate is when the number of workers is equal to the number of CPUs on the server.

Advantages:

##You can use

nginx –s reload
• Hot deployment, use nginx for hot deployment operations
  Each worker is an independent process. If one of the workers has a problem, the others will continue to compete and implement the request process without causing service interruption

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