What is a reverse proxy server?

What is a reverse proxy server?

We often see the term "reverse proxy server". For example, we often see that nginx is a reverse proxy server and varnish is a reverse proxy server ...... Next, let's take a look at this concept.

Description

'Reverse proxy Server' has two concepts: one is 'proxy Server', and the other is 'reversely'

The 'proxy Server' is easy to understand. For example, if you need to access a website and do not want to or cannot access it directly, such as the reasons for the network and privacy, we connect to a proxy server, in this way, the user accessing this website is the proxy server, not ourselves.

'Reversely 'means that we didn't access the website through the proxy server, but the website has added a proxy in front of its own server. After we enter the URL to initiate a request, the request goes to the proxy server first, the proxy server then transfers the request to the website Server

Function

The reverse proxy server appears because it is very useful. As the website grows, it is necessary to use the reverse proxy server.

It has the following functions:

(1) Security Filtering

For security purposes, users are not allowed to directly access the Real Server. Any access request must first be sent to the reverse proxy server for authentication, filtering, and other security operations, requests that meet the conditions will be forwarded to the Real Server.

For example, in the simplest scenario, only the IP addresses in the IP whitelist can be accessed.

(2) content caching

When the traffic volume increases, the website server needs to process each request, which is under great pressure. According to the principle of local access, many of these requests must be repeated, the website server is tired of repetitive work.

In this case, the reverse proxy server is required to share part of the work. The Reverse Proxy Server caches some common content to itself, and users' requests are first sent to the reverse proxy server, he checks whether the user needs the content and returns the content directly to the user. Sometimes, the content is not sent to the website server for processing.

This is equivalent to having an assistant on the website server, which helped him deal with a lot of repetitive work and reduced the pressure.

(3) Server Load balancer

When the traffic is getting bigger and bigger, a website server can't afford it and needs to be added with N servers. So after the user requests come, what will happen to the server?

In this case, you need to add a reverse proxy server in front of the N servers as the Load balancer.

The user's request is sent to the server Load balancer first. He thinks about who the request should be handed over, and then forwards the request to the server Load balancer so that N servers can process the request in a balanced manner.

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