Centos+nginx configure load balancing from scratch

Understanding of nginx load balancing

nginx is a lightweight, high-performance webserver. It can mainly do the following two things:

• As an http server (same effect as apache)
• Act as a reverse proxy server to achieve load balancing

Now nginx can be seen everywhere, and you often see the words nginx displayed on webpages after downtime. This also shows that nginx is accepted by more and more users due to its high performance, simple use and configuration, and open source. used.

The first one acts as an http server and combines with the php-fpm process to process incoming requests. nginx itself does not parse PHP. It just acts as a server to accept requests from the client. If it is a PHP request, Then it is handed over to the php process for processing, and the result after the php processing is completed is sent to the client. This is very simple. After installing nginx+php-fpm, configure the respective configuration files and start it. The operating principle can be seen in the following explanation:

Nginx does not support direct calling or parsing of external programs. All external programs (including PHP) must be called through the FastCGI interface. The FastCGI interface is a socket under Linux (this socket can be a file socket or an ip socket). In order to call a CGI program, a FastCGI wrapper is also needed (a wrapper can be understood as a program used to start another program). This wrapper is bound to a fixed socket, such as a port or file socket. When Nginx sends a CGI request to this socket, the wrapper receives the request through the FastCGI interface, and then spawns a new thread. This thread calls the interpreter or external program to process the script and read the return data; then, the wrapper The returned data is passed to Nginx along the fixed socket through the FastCGI interface; finally, Nginx sends the returned data to the client. This is the entire operation process of Nginx+FastCGI, as shown in the figure below.

The above paragraph explains the operating mechanism of nginx+fastcgi. The request will be matched in the nginx configuration file and processed accordingly, such as returning the error file directly (there is a little difference between this and the above, I guess nginx can perform analysis similar to the above picture on static files such as HTML), and use the PHP process to process PHP requests (there can be multiple PHP processes here).

The second is to use reverse proxy load balancing. This is actually very simple. To put it simply, you define a group of servers, match the requests, and transfer the requests to any one of the servers for processing to reduce the load on each server. To reduce the pressure, first take a look at the definition of reverse proxy online:

The Reverse Proxy method refers to using a proxy server to accept connection requests on the Internet, then forward the request to the server on the internal network, and return the results obtained from the server to the client requesting a connection on the Internet , at this time the proxy server appears as a reverse proxy server to the outside world.

Reverse proxy is the opposite of forward proxy (or proxy). You must have heard of proxy. In order to access resource B more conveniently, resource B is indirectly accessed through resource A. The characteristic is that the user knows what he will eventually access. What is the website, but reverse proxy users do not know what processing is done behind the proxy server. The real processing server of the service in the reverse proxy is placed on the intranet, and the external network can only access the reverse proxy server, which greatly Improved security.

Install software

nginx installation is very simple

1. The environment required to install nginx, pcre (for rewrite), zlib (for compression), ssl, you can also download, compile and install this yourself

yum -y install zlib;

yum –y install pcre;

yum –y install openssl;

2. Download and install nginx-*.tar.gz.

tar –zxvf nginx-1.2.8.tar.gz –C ./;

cd nginx-1.2.8;

./congigure --prefix=/usr/local/nginx;

make && make install;

3. Configuration

When configuring here, you only need to modify the content between http{}. The first place to modify is to set up the server group and add

between http nodes.

upstream myServer{
                                                                                                                                                                                                                                            #Here                                            

Upstream in nginx supports the following methods: polling (by default, all servers are accessed one by one in chronological order. If a server is down, it will be automatically eliminated), weight (the location probability of the server is proportional to the weight, this It can be configured when the server configuration is uneven), ip_hash (hash calculation is performed on each requested IP, and the corresponding server is allocated according to certain rules), fair (requests are allocated according to the response time (rt) of each server) , rt knows priority allocation), url_hash (distributes requests according to the hash value of the accessed URL), I use the default rotation method here.

Point the request to myServer

location / {
            proxy_pass   http://myServer;
    }

The complete document (with comments removed) is as follows:

worker_processes  <span>1</span><span>;
events {
    worker_connections  </span><span>1024</span><span>;
}
http {
    include       mime.types;
    default_type  application</span>/octet-<span>stream;
    sendfile        on;
    keepalive_timeout  </span><span>65</span><span>;
    upstream myServer{
       server www.myapp1.com:</span><span>80</span><span>;
       server www.myapp2.com:</span><span>8080</span><span>;
    }
    server {
        listen       </span><span>80</span><span>;
        server_name  my22;
        location </span>/<span> {
            proxy_pass   http:</span><span>//</span><span>myServer;</span>
<span>        }
    }
}</span>

Set up reverse proxy backend as load balancing between two servers

You can see that there are two server addresses in the previous step, www.myapp1.com:80 and www.myapp2.com:8080. I installed the above nginx on the virtual machine. I installed these two servers on this server. In the win8 system of the computer, using apache's virtualhost, two domain names are set up. The codes under the two domain names are independent of each other, and the settings are also very simple:

1. Set up apache configuration file

I am using the xampp integrated environment. There are two places to modify. Add the listening port in httpd.conf

Listen 8080

That is to say, this place monitors two ports

Listen 80
Listen 8080

Check whether the following sentence is open. If not, open it. Open it as shown below

<span># Virtual hosts
Include conf</span>/extra/httpd-vhosts.conf

Add the following content in httpd-vhosts.conf,

<virtualhost>80><span>
    ServerName www.myapp1.com #对应的域名，负载均衡的服务器地址
    DocumentRoot E:\soft\xampp\htdocs\www.myapp1.com #代码文件夹
</span></virtualhost>
<virtualhost>8080><span>
    ServerName www.myapp2.com
    DocumentRoot E:\soft\xampp\htdocs\www.myapp2.com
</span></virtualhost>

Modify the windows hosts file and add the following content

<span>127.0</span>.<span>0.1</span><span>        www.myapp1.com
</span><span>127.0</span>.<span>0.1</span>        www.myapp2.com

Modify the /etc/hosts file of Linux and add the following content

<span>192.168</span>.<span>1.12</span><span>        www.myapp1.com #这里前面的地址对应我win8本机的ip地址
</span><span>192.168</span>.<span>1.12</span>        www.myapp2.com

I put a file index.php in www.myapp1.com:80 [E:softxampphtdocswww.myapp1.comindex.php]

　A file index.php is also placed in www.myapp2.com:8080 [E:softxampphtdocswww.myapp2.comindex.php]

　The content in the file is basically the same, except that I'm the myapp2 is different. One is myapp1 and the other is myapp2.

　If you can enter www.myapp1.com:80 and www.myapp2.com:8080 in the win8 browser to see different effects

　And when you see the following result under centos (beautified by yourself), it means that the configuration is successful

[root@bogon nginx]# curl www.myapp1.com:<span>80</span><span>
I</span><span>'</span><span>m the myapp1<br>【view】1</span>
[root@bogon nginx]# curl www.myapp2.com:<span>8080</span><span>
I</span><span>'</span><span>m the myapp2<br>【view】1</span>

<span>php
</span><span>session_save_path</span>("./"<span>);
</span><span>session_start</span><span>();
</span><span>header</span>("Content-type:text/html;charset=utf-8"<span>);
</span><span>if</span>(<span>isset</span>(<span>$_SESSION</span>['view'<span>])){
    </span><span>$_SESSION</span>['view'] = <span>$_SESSION</span>['view'] + 1<span>;
}</span><span>else</span><span>{
    </span><span>$_SESSION</span>['view'] = 1<span>;
}
</span><span>echo</span> "I'm the myapp2<br>"<span>;
</span><span>echo</span> "【view】{<span>$_SESSION</span>['view']}";

See the effect

After everything is ok, you can access it through the browser to see the effect

Forgot to mention, the address of nginx proxy server is http://192.168.1.113,

After entering http://192.168.1.113/index.php in the browser, keep refreshing, you will find that it will be in

I'm the myapp2、I'm the myapp1

　 When these two pages are exchanged back and forth, the view will be increased once without refreshing twice. This also proves the default rotation training method mentioned earlier, but there is another common problem here. When the user visits the website , without processing, the session will be saved on different servers (I use two different folders to simulate two servers here), and there may be multiple sets of session data. How to solve this problem? The next article will talk about it This question is actually very simple.

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The above has introduced centos+nginx to configure load balancing from scratch, including all aspects. I hope it will be helpful to friends who are interested in PHP tutorials.