part 1 is here…
ok, now we have a clustered mysql (or better mariaDB) database running, next step is to setup the blog itself…
- Web Server
to serve the blog, we have to install the webserver first – i decided to use the de-facto standard apache2. on ubunto it’s very easy to install
sudo apt-get install apache2 php php-mysql
done… of course you can now modify the configuration etc – but for my purpose the default is sufficient.
- Storage for the blog
since i want to distribute all uploaded files and the blog binaries itself to both servers, i need either a shared volume(i.e. nfs from my nas) or a cluster file system… since i’m a nerd and nfs is too easy, I was seeking for a cluster solution – and found Gluster
the installation is again easier than i thought it might be…
sudo apt-get install software-properties-common sudo add-apt-repository ppa:gluster/glusterfs-3.8 sudo apt-get update sudo apt-get install -y glusterfs-server glusterfs-client sudo service glusterfs-server start
of course you have to do the installation on both servers… afterwards, you only have to create the volumes to be clustered. Therefore I have created the mountpoint /data on dedicated disks (one per server) – since there are thousands of tutorials describing how to add and partition a new disk I won’t repeat it here.
# on both servers sudo mkdir -p /data/gluster/gvol0 # on one node only sudo gluster peer probe <SERVER2> sudo gluster pool list sudo gluster volume create gvol0 replica 2 <SERVER1>:/data/gluster/gvol0 <SERVER2>:/data/gluster/gvol0 sudo gluster volume start gvol0 sudo gluster volume info gvol0
the last command should tell you that everything is fine. Now we just have to mount the gluster volume:
# on both nodes sudo mkdir -p /var/www/blog sudo mount -t glusterfs localhost:/gvol0 /var/www/blog
as you can see, we are mounting a device with file type glusterfs – this means the gluster client is connecting to the gluster server instead of directly accessing the local disk. In this way it’s guaranteed that we get the current data, event if it’s not distributed to all servers.
To make it permanent you can add the mount command to the /etc/fstab file, but be aware: the mountpoint /data must alreade be mounted and the glusterfs deamon must be running… so I recommend to configure it in the new systemctl config files where you can configure dependencies or define the upstart order in /etc/rc.local file.
- install wordpress
first we have to add the directory known by apache
sudo chown www-data:www-data /var/www/blog echo "<VirtualHost *:80>" > /etc/apache2/sites-available/blog.conf echo "DocumentRoot /var/www/blog" >> /etc/apache2/sites-available/blog.conf echo "ServerName <YOUR PUBLIC FQDN>" >> /etc/apache2/sites-available/blog.conf echo "</VirtualHost>" >> /etc/apache2/sites-available/blog.conf a2ensite blog service apache2 reload wget wordpress.org/latest.zip unzip latest.zip -d /var/www/blog/ mv /var/www/blog/wordpress/* /var/www/blog/ rm -rf /var/www/blog/wordpress/
now you just have to open a browser on your client and navigate to the FQDN you just entered in your apache config… I assume that you already configured your firewall. If you don’t want to open the firewall yet, it’s also possible to modify your /etc/hosts (*nix) or %windir%/system32/drivers/etc/hosts (win) file and enter the FQDN and private ip adress of one of your servers. The rest of the setup process is easy and not worth describing it here.
- automatic failover
nearly finished – the blog itself is running and the content is distributed on two independent servers… now we only have to establish some kind of failover or load balancing mechanism to make sure it’s always on. since the goal is always on and i do not expect thousends of users a day, I just searched for an IP based HA solution – and found UCARP
just install the packages and add a few lines to the network configuration – done
sudo apt-get install ucarp
and now just add some ucarp specific settings to the network configuration file /etc/network/interfaces
#######################
# ucarp configuration
#######################
ucarp-vid 1 # vid : The ID of the virtual server [1-255]
ucarp-vip 10.0.0.201 # vip : The virtual address
ucarp-password secret # password : A password used to encrypt Carp communications
ucarp-advskew 1 # advskew : Advertisement skew [1-255]
ucarp-advbase 1 # advbase : Interval in seconds that advertisements will occur
ucarp-master yes # master : determine if this server is the master. Must be "no" on 2nd server!
iface ens32:ucarp inet static
address 10.0.0.201
netmask 255.255.255.0
that’s it, now just restart the network and configure your firewall to forward to the virtual ip…
sudo service networking restart
done… ok, there are some other tasks you might do, i.e. secure the blog with an ssl certificate. Maybe I’m going to make another blog post describing how to do it 😉
If you have any questions or suggestions, just leave a note…
Benjamin