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Leading edge features
Configures a dedicated HAProxy load balancer. The ServerTemplate contains scripts and inputs that allow it to connect to application servers private/public IP address. The ServerTemplate is one of the core ServerTemplates in a typical a three-tier website architecture.
Note: For a complete list of the ServerTemplate's features and support, view the detailed description under its Info tab.
HAProxy (High Availability Proxy) is a software load balancer. It is generally used to direct client web traffic to an array of application servers. The recipes associated with the ServerTemplate installs the HAProxy version 1.5. The following are the scripts in the Boot Sequence and Operational section:
Although the ServerTemplate is commonly used to launch a set of load balancer servers that round-robin incoming web requests for a single application across an array of dedicated applications servers, it can also be configured to load balance across multiple applications using multiple vhosts. For example, if you have two different applications (e.g. free and pay versions) where both applications connect to the same database, you could create a single deployment where the same load balancer servers send traffic to the appropriate application tier.
Example: 1 Load Balancing Pool
Example: 2 Load Balancing Pools
If you want a user's session to be maintained, set the 'Use Session Stickiness' input to 'True' to configure the load balancers to send a user's subsequent requests to the same application server. However, it's important to remember that session stickiness will only work if an end user's browser allows and stores the session cookie from the load balancer. Set to 'False' to disable session stickiness and configure the load balancers to distribute incoming requests in a round-robin fashion across all serviceable application servers.
By default, the load balancers will distribute incoming requests to the application servers in its load balancing pool in a round-robin fashion. (e.g. 1,2,3,1,2,3,1...) However, the ServerTemplate also has built-in supports for a few other configurations. Use the 'Load Balancing Algorithm' input to select the load balancing logic that's best suited for your application.
To learn more, see the HAProxy Configuration Manual.
HAProxy includes a built-in health-checking feature that allows it to monitor registered application servers to determine if they are running and accepting connections (up). To enable this feature, each application server must have an identically named health check page that will return an HTTP 200 OK status back to the HAProxy server each time a load balancer issues an HTTP GET request. The health-check page helps distinguish your application servers from other servers running outside of your deployment.
Go to the HAProxy Status page to verify that all of the application servers are properly connected to the load balancer servers. The default location of the status page is defined by the 'Statistics URI' input. By default, it's set to the value ‘/haproxy-status’. (e.g. http://www.example.com/haproxy-status) You may optionally set the Statistics Page Username and Statistics Page Password inputs in order to require a user name and password to log in and view the page.
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