¶ About Load Balancer
A load balancer is a highly available, fully-managed instance that distributes workload across multiple virtual servers. It ensures the scaling of your applications while maintaining continuous availability, even during heavy traffic. By balancing the traffic load, it enhances the performance and reliability of websites, applications, databases, and other services. The load balancer monitors the health of virtual servers and directs traffic only to those that are functioning properly. Additionally, it supports various algorithms for traffic distribution, such as round-robin, least connections, and IP hash, and enhances security by hiding the internal server structure from external users. This redundancy and distribution ensure consistent application performance and reliability in the cloud.
¶ Adding Load Balancer Rules
IaaS Cloud users or administrators can create load balancing rules to distribute traffic received at a public IP to one or more instances. To achieve this, a user creates a rule, specifies an algorithm, and assigns the rule to a set of instances. Follow these steps to set up load balancing:
1. Navigate to Network → Public IP addresses on the left navigation bar.
2. Select a specific IP address from the list view.
3. Choose Load balancing in the right management block:
4. Specify the following parameters:
- Name of the load balancing rule.
- Public & Private port that will allow traffic through.
- Comma-separated CIDR list to accept traffic only from specific IP addresses.
- Load balancing Algorithm & Protocol for the rule.
- Whether the load balancing rule should use AutoScale; for more information, refer to our AutoScale VM chapter.
5. Finally, click on the Add VMs button, select one or more instance from the list and click OK to apply the load balancing rule.
¶ Managing Load Balancer
¶ Changing Load Balancer Settings
To change and edit existing load balancer rules, follow these steps:
1. Navigate to Network → Public IP addresses on the left navigation bar.
2. Select a specific IP address from the list view.
3. Choose Load balancing in the right management block:
4. Select a load balancing rule from the list view and click on the Edit button:
5. Adjust the settings as desired and click OK to save the changes.
¶ Setting Up Sticky Session Polices
Sticky session policies ensure that a user's session data is consistently available across multiple requests in web-based applications, maintaining session state or stickiness. Any load balancer rule can have a stickiness policy, which includes a name, method, and parameters. The stickiness could be based on the following three methods:
- Lbcookie: This approach involves the load balancer generating a cookie and sends it to the client. Subsequently, the client forwards this cookie with each request. Utilizing the cookie data, the load balancer then determines the appropriate backend server to direct the request to.
- Appcookie: In this method, a cookie is generated by the application hosted on the backend servers and transmitted to the client. Upon receiving subsequent requests, the client includes this cookie. The load balancer leverages the cookie details to ascertain the suitable backend server for routing the request.
- SourceBased: With this method, the load balancer relies on the client's source IP address to decide the appropriate backend server for routing requests. By maintaining a mapping of client IP addresses to backend servers, the load balancer ensures that subsequent requests from the same client consistently reach the same backend server.
To set up a sticky session policy, follow these steps:
1. Navigate to Network → Public IP addresses on the left navigation bar.
2. Select a specific IP address from the list view.
3. Choose Load balancing in the right management block:
4. Select a load balancing rule from the list view and click on the Configure button:
5. Depending on the method selected from the above options, you'll need to configure the following settings:
¶ Lbcookie:
- Sticky name of the policy for the dashboard.
- Cookie name that will be sent to the client.
- Mode in which the load balancer should handle the cookie, choosing from the options: Insert, Rewrite, Prefix, and Indirect.
- Whether the cookie should be cached or not.
- With Indirect, if the cookie value should contain a reference to the actual value.
- Whether the cookie should be sent only with POST requests.
- Domain for which the cookie is valid.
¶ Appcookie:
- Sticky name of the policy for the dashboard.
- Cookie name that will be sent to the client.
- Mode in which the load balancer should handle the cookie, choosing from the options: query-string and path-parameter.
- Length of the cookie value (with default value 52).
- Duration for which the cookie should be held before expiring.
- Whether the load balancer should learn the cookie value from the first request.
- Prefix added to the cookie value.
¶ SourceBased
- Sticky name of the policy for the dashboard.
- Table size for the maximum number of entries that can be stored inside the stickiness table (default 200k).
- Maximum duration after which the mapping expires (default 30m).
6. Click on OK to save the sticky session policy.
¶ Deleting Load Balancer Rules
To delete existing load balancer rules, follow these steps:
1. Navigate to Network → Public IP addresses on the left navigation bar.
2. Select a specific IP address from the list view.
3. Choose Load balancing in the right management block:
4. Select a load balancing rule from the list view and click on the Delete button:
5. Click on Yes to confirm the process and delete the load balancer rule.