HAproxy – KeepAlived important notes.

  • Multicast must be enabled for fail over to work. Otherwise, If the haproxy service stops but the keepalived service is still running, the VirtualIP will still be pingable however any requests made to that IP will not be forwarded via HAproxy simply because HAproxy is no longer running. The keepalived will switch to the standby server only when the keepalived service it self stops from ServerA. Then ServerB will automatically take over.  In other words, failure of HAproxy does not mean Keepalive will automatically switch to the standby server.
  • If for whatever reason you wish to run a HA service with out SSL then your HAproxy config files should listen to the virtual IP address.
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Centos 7 – Part 1 – NGINX – Apache – Load Balancing High Availability

These instructions show how to setup a web Load Balancer by using two NGINX servers as the Load Balancers and two Apache servers.

2 – Centos 7  servers running NGINX will be used as Load Balancers.

2 – Cent0s 7 serves running Apache will be used to serve web pages via virtual hosts.

The NGINX servers will:
– Determine the appropriate destination service based on the method chosen; in this case it will be Round Robin, which is the default option.
– Will use KeepAlive in order to create a virtual IP address. The IP address will based on the already NICs of the Load Balancers.

The Apache servers will:
– Act as your normal every day web servers with virtual hosts.
– Will log the IP of the actual client.

nginx-HA

Setting up the Apache web Servers.

  • Create the directories where the content of you virtual hosts will be placed.
mkdir /etc/httpd/vhosts.d
mkdir -p /sites/wordpress/
chown -R apache:apache /sites/wordpress/
chmod 755 /sites/wordpress/

 

  • Instruct Apache to look into the directory you created for your virtual hosts.
vim /etc/httpd/conf.d/vhosts.conf
IncludeOptional vhosts.d/*.conf

 

  • Create the config file for the corresponding web site.
vim /etc/httpd/vhosts.d/wordpress.sfentona.lol.conf
ServerAdmin webmaster@dummy-host.example.com
DocumentRoot /sites/wordpress/
ServerName wordpress.sfentona.lol
ServerAlias www.wordpress.sfentona.lol

Directory "/sites/wordpress";
DirectoryIndex index.html index.php
Options FollowSymLinks
AllowOverride All
Require all granted

 

  • Set up log x-fowarded-for in order to get the the IP of the actual client who visited the site and not the IP of the load balancer in your logs.
vi /etc/httpd/conf/httpd.conf
LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %b" common
LogFormat "%{X-Forwarded-For}i %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" forwarded

 

Configure NGINX as a load balancer (view lines 34-38)

vi /etc/nginx/nginx.conf
# For more information on configuration, see:
#   * Official English Documentation: http://nginx.org/en/docs/
#   * Official Russian Documentation: http://nginx.org/ru/docs/

user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log;
pid /run/nginx.pid;

events {
    worker_connections 1024;
}

http {
    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;
    tcp_nodelay         on;
    keepalive_timeout   65;
    types_hash_max_size 2048;

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

    # Load modular configuration files from the /etc/nginx/conf.d directory.
    # See http://nginx.org/en/docs/ngx_core_module.html#include
    # for more information.
    include /etc/nginx/conf.d/*.conf;
    proxy_set_header        X-Real-IP $remote_addr;
    proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
    upstream wordpress {
    server 10.0.0.42:80;
    server 10.0.0.43:80;
}


        server {
        listen       80;
        server_name  www.wordpress.sfentona.lol;

        # Load configuration files for the default server block.
        include /etc/nginx/default.d/*.conf;

        location / {
                proxy_pass http://wordpress;
        }

        error_page 404 /404.html;
            location = /40x.html {
        }

        error_page 500 502 503 504 /50x.html;
            location = /50x.html {
        }
    }
}

Allow NGINX to bind to a non-local shared ip

vi /etc/sysctl.conf
net.ipv4.ip_nonlocal_bind=1
sysctl -p

Set up your firewall in order for Multicast and VRRP to work correctly.

iptables -I INPUT -d 224.0.0.0/8 -j ACCEPT
iptables -I INPUT -p vrrp -j ACCEPT

 

Configure Keep Alive.

vi/etc/keepalived/keepalived.conf

This is for the Master Load Banacer LB1

 notification_email {
     sysadmin@mydomain.com
     support@mydomain.com
   }
   notification_email_from lb1@mydomain.com
   smtp_server localhost
   smtp_connect_timeout 30
}

vrrp_instance VI_1 {
    state MASTER
    interface ens192
    virtual_router_id 51
    priority 101
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        10.0.0.44
    }
}

This is for the Master Load Banacer LB2. Priority on the slave is a lower number.

global_defs {
   notification_email {
     sysadmin@mydomain.com
     support@mydomain.com
   }
   notification_email_from lb2@mydomain.com
   smtp_server localhost
   smtp_connect_timeout 30
}

vrrp_instance VI_1 {
    state MASTER
    interface ens192
    virtual_router_id 51
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        10.0.0.44
    }
}
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