1. Load balancing: configuring real columns

  implementation effect: enter the address in the browser address bar http://192.168.xxx.xxx/www/a.html , load balancing effect, average to ports 8081 and 8082
preparation:
  1. Prepare two tomcat servers, one 8081 and one 8082

[root@localhost ~]# docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                    NAMES
802047bd7530        nginx               "/docker-entrypoin..."   17 hours ago        Up 27 minutes       0.0.0.0:80->80/tcp       mynginx
afb277b2006e        mytomcat            "catalina.sh run"        21 hours ago        Up 16 minutes       0.0.0.0:8081->8080/tcp   mytomcat1
ba962911646b        mytomcat            "catalina.sh run"        21 hours ago        Up 11 minutes       0.0.0.0:8082->8080/tcp   mytomcat2

  2. Create folders and test pages
   since you will find it from the ROOT file under webapps, you can create it in the ROOT directory
Access path: http://192.168.3.3:8081/www/a.html

[root@localhost ~]# docker exec -it afb277b2006e bash
root@ba962911646b:/usr/local/tomcat# cd webapps/ROOT/www/
root@ba962911646b:/usr/local/tomcat/webapps/ROOT/www# ls
a.html

  8081 port display interface

  access path: http://192.168.3.3:8082/www/a.html

[root@localhost ~]# docker exec -it ba962911646b bash
root@ba962911646b:/usr/local/tomcat# cd webapps/ROOT/www/
root@ba962911646b:/usr/local/tomcat/webapps/ROOT/www# ls
a.html

  8082 port display interface

  3. Configure in nginx
  3.1 the document is in root@802047bd7530 : / # CD nginx under etc / nginx / conf

user  nginx;
worker_processes  1;

error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;


events {
    worker_connections  1024;
}


http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    access_log  /var/log/nginx/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    keepalive_timeout  65;

    #gzip  on;
    #Add myserver for load balancing
    upstream myserver {
        server  192.168.3.3:8081;
        server  192.168.3.3:8082;
    }


    include /etc/nginx/conf.d/*.conf;
}

   3.2 the document is in root@802047bd7530:/# cd etc/nginx/conf.d/ conf

server {
    listen       80;
    listen  [::]:80;
    #Change localhost to ip address
    server_name  192.168.3.3;

    #charset koi8-r;
    #access_log  /var/log/nginx/host.access.log  main;

    location / {
        root   /usr/share/nginx/html;
    #    proxy_pass  http://192.168.3.3:8080;
    #Load the configured myserver to achieve load balancing
        proxy_pass  http://myserver;
        index  index.html index.htm;
    }
    
   # location ~ /yee/ {
   #      proxy_pass  http://192.168.3.3:8081;    
   # }    
    
   # location ~ /yew/ {
   #      proxy_pass  http://192.168.3.3:8082;
   # }


    #error_page  404              /404.html;

    # redirect server error pages to the static page /50x.html
    #
    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
        root   /usr/share/nginx/html;
    }

    # proxy the PHP scripts to Apache listening on 127.0.0.1:80
    #
    #location ~ \.php$ {
    #    proxy_pass   http://127.0.0.1;
    #}

    # pass the PHP scripts to FastCGI server listening on 127.0.0.1:9000
    #
    #location ~ \.php$ {
    #    root           html;
    #    fastcgi_pass   127.0.0.1:9000;
    #    fastcgi_index  index.php;
    #    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name;
    #    include        fastcgi_params;
    #}

    # deny access to .htaccess files, if Apache's document root
    # concurs with nginx's one
    #
    #location ~ /\.ht {
    #    deny  all;
    #}
}

  nginx. The listening port defaults to 80. Access test: http://192.168.3.3/www/a.html

2. Equilibrium strategy

2.1 round robin (default)
  each request is allocated to different application servers one by one in chronological order. If the application server goes down, it can be automatically eliminated.

2.2 weight
  specify the polling probability by configuring the weight. The weight is directly proportional to the access ratio, which is used in the case of uneven performance of the application server. Default: weight=1

2.3 ip_ Hash algorithm
  each request is allocated according to the hash result of the access ip. In this way, each visitor accesses an application server regularly, which can solve the problem of session sharing

2.4 least_conn minimum connection
  forward the request to the back-end server with fewer connections. Polling algorithm is to forward requests to each back end evenly to make their load roughly the same; However, some requests take a long time, resulting in a high load on the back end. In this case, least_conn this way can achieve better load balancing effect

upstream dynamic_zuoyu {
  least_conn;  #Forward the request to the back-end server with fewer connections
  server localhost:8080  weight=2; #tomcat 7.0
  server localhost:8001; #tomcat 8.0
  server localhost:8082 backup; #tomcat 8.5
  server localhost:8083  max_fails=3 fail_timeout=20s; #tomcat 9.0
}

2.5 Fair (third party)
  requests are allocated according to the response time of the back-end server, and those with short response time are allocated first

2.6 url_hash (third party)
   allocate the request according to the hash result of the access url, so that each url is directed to the same back-end server, which is more effective when the back-end server is cache

fail_timeout	max_ Use with failures
max_fails	Set in fail_ The maximum number of failures within the time set by the timeout parameter. If all requests to the server fail within this time, the server is considered to be down
fail_time	The length of time that the server will be considered down. The default is 10s
backup	Mark the server as an alternate server. When the primary server stops, requests are sent to it
down	Mark the server down permanently