Cluster Basis & type of Clusters.
Two or more computers that work together to perform a task is called a cluster.
Example:
Storage Cluster Provides a consistent file system image across servers in a cluster, which allows servers to simultaneously read and write to a single shared file system.
Type of clusters:
Load Balancing cluster to dispatch network service requests to multiple cluster nodes.
Storage cluster to provide consistent file system storage image.
High Performance cluster to perform concurrent calculations for applications.
High Availability or Fail-over clusters provides continuous availability of services.
Example:
Red Hat Cluster is an integrated set of software components. RHCS consists of the following major, components.
Cluster infrastructure - which Provides fundamental functions for nodes to work together as a cluster.
High-availability Service Management — Provides failover of services from one cluster node to another in case a node becomes inoperative.
Cluster administration tools — Configuration and management tools for setting up, configuring, and managing a Red Hat cluster.
Linux Virtual Server (LVS) — Routing software that provides IP-Load-balancing.
Other optional package (and not part of Red Hat Cluster Suite) are as follows:
GFS (Global File System) and GFS2 (Global File System2) allows multiple nodes to share storage at a block level as if the storage were connected locally to each cluster node.
Cluster Logical Volume Manager (CLVM) — Provides volume management of cluster storage.
The munin.conf configuration file.
Open the file /etc/munin/munin.conf so that you can change a couple important settings.
# Drop somejuser@fnord.comm and anotheruser@blibb.comm an email everytime
# something changes (OK -> WARNING, CRITICAL -> OK, etc)
#contact.someuser.command mail -s “Munin notification” somejuser@fnord.comm
#contact.anotheruser.command mail -s “Munin notification” anotheruser@blibb.comm
You can use the example above in the munin.conf as a template to add your own email notifications.
The “host tree” section of munin.conf describes the organization of any monitored nodes on munin’s overview page. Setting up one node on the same server leave the default address of 127.0.0.1 alone. You might want to change the host tree name to something more descriptive.
# a simple host tree
[localhost]
address 127.0.0.1
use_node_name yes
Open the /etc/munin/munin-node.conf file and look for an entry with “host”.
Now to restrict the node to listen to localhost only, you should change the host entry to:
# Which address to bind to;
host 127.0.0.1
start the munin-node service
sudo /etc/init.d/munin-node start
To make sure the munin-node service starts on reboot.
sudo /sbin/chkconfig munin-node on
munin - network-wide graphing framework (grapher/gatherer)
A monitoring tool like munin lets you watch your server resource use over time. The graphs will highlight issues before they cause downtime or bandwidth quota overages.
Munin is a networked resource monitoring tool that can help analyze resource trends and “what just happened to kill our performance?” problems. It is designed to be very plug and play. A default installation provides a lot of graphs with almost no work.
To download and install the munin master package and munin node package to your master server, run the following command:
# yum install munin munin-node
Creating a Rewrite for Ruby on Rails Application in cPanel
Ruby on Rails uses its own server, users visiting your Ruby on Rails application will need to be redirected to the appropriate port.
Because Ruby on Rails uses its own server, users visiting your website (and subsequently your Ruby on Rails application) will need to be redirected to the appropriate port.
Ruby does not respond on the standard HTTP port number, 80. Thus, visitors would need to specify the port number with the domain — for example, example.com:12001.
To configure a rewrite for Ruby on Rails Application in cPanel
1. Log into cPanel.
2. Navigate to the Software/Services section of your cPanel interface.
3. Click the Ruby on Rails icon. This step will open the Ruby on Rails management interface.
4. Click the Create Rewrite button corresponding to the appropriate application in the Create A Rewrite table.
