15.9. Load Balancer Rules

A CloudStack user or administrator may create load balancing rules that balance traffic received at a public IP to one or more VMs. A user creates a rule, specifies an algorithm, and assigns the rule to a set of VMs.

Nota

If you create load balancing rules while using a network service offering that includes an external load balancer device such as NetScaler, and later change the network service offering to one that uses the CloudStack virtual router, you must create a firewall rule on the virtual router for each of your existing load balancing rules so that they continue to function.

15.9.1. Adding a Load Balancer Rule

Log in to the CloudStack UI as an administrator or end user.
In the left navigation, choose Network.
Click the name of the network where you want to load balance the traffic.
Click View IP Addresses.
Click the IP address for which you want to create the rule, then click the Configuration tab.
In the Load Balancing node of the diagram, click View All.
In a Basic zone, you can also create a load balancing rule without acquiring or selecting an IP address. CloudStack internally assign an IP when you create the load balancing rule, which is listed in the IP Addresses page when the rule is created.
To do that, select the name of the network, then click Add Load Balancer tab. Continue with 7.
Fill in the following:
- Name: A name for the load balancer rule.
- Public Port: The port receiving incoming traffic to be balanced.
- Private Port: The port that the VMs will use to receive the traffic.
- Algorithm: Choose the load balancing algorithm you want CloudStack to use. CloudStack supports a variety of well-known algorithms. If you are not familiar with these choices, you will find plenty of information about them on the Internet.
- Stickiness: (Optional) Click Configure and choose the algorithm for the stickiness policy. See Sticky Session Policies for Load Balancer Rules.
- AutoScale: Click Configure and complete the AutoScale configuration as explained in Sezione 15.8.5, «Configuring AutoScale».
Click Add VMs, then select two or more VMs that will divide the load of incoming traffic, and click Apply.
The new load balancer rule appears in the list. You can repeat these steps to add more load balancer rules for this IP address.

15.9.2. Sticky Session Policies for Load Balancer Rules

Sticky sessions are used in Web-based applications to ensure continued availability of information across the multiple requests in a user's session. For example, if a shopper is filling a cart, you need to remember what has been purchased so far. The concept of "stickiness" is also referred to as persistence or maintaining state.

Any load balancer rule defined in CloudStack can have a stickiness policy. The policy consists of a name, stickiness method, and parameters. The parameters are name-value pairs or flags, which are defined by the load balancer vendor. The stickiness method could be load balancer-generated cookie, application-generated cookie, or source-based. In the source-based method, the source IP address is used to identify the user and locate the user’s stored data. In the other methods, cookies are used. The cookie generated by the load balancer or application is included in request and response URLs to create persistence. The cookie name can be specified by the administrator or automatically generated. A variety of options are provided to control the exact behavior of cookies, such as how they are generated and whether they are cached.

For the most up to date list of available stickiness methods, see the CloudStack UI or call listNetworks and check the SupportedStickinessMethods capability.