Configure a GSLB service group 编辑

Service group enables you to manage a group of services as easily as a single service. If you enable or disable any option for a service group, the option gets enabled or disabled for all the members of the service group. For example, you can apply this feature to options such as Compression, Health monitoring, and Graceful shutdown.

After creating a service group, you can do any of the following:

• Bind the service group to a virtual server.
• Add services to the service group.
• Bind monitors to the service groups.

Important

If the load balancing virtual server is either in a GSLB node itself or is in a child node (in parent-child deployment) and no monitors are bound to the GSLB service, then make sure the following:

The GLSB service group IP address, port number, and protocol match the virtual server that the service is representing. Else, the service state is marked as DOWN.

The Citrix ADC supports the following types of GSLB service groups.

• IP address based service groups
• Domain name based service groups
• Domain name based autoscale service groups

GSLB domain name based autoscale service groups

The Citrix ADC hybrid and multi-cloud global server load balancing (GSLB) solution enables customers to distribute application traffic across multiple data centers in hybrid clouds, multiple clouds, and on-premises. The Citrix ADC GSLB solution supports various load balancing solutions, such as the Citrix ADC load balancer, Elastic Load Balancing (ELB) for AWS, and other third-party load balancers. Also, the GSLB solution performs global load balancing even if the GSLB and load balancing layers are independently managed.

In cloud deployments, users are given a domain name as a reference when accessing the load balancing solution for management purposes. It is recommended that external entities do not use the IP addresses that these domain names resolve to. Also, the load balancing layers scale up or down based on the load, and the IP addresses are not guaranteed to be static. Therefore, it is recommended to use the domain name to refer to the load balancing endpoints instead of IP addresses. This requires the GSLB services to be referred using the domain name instead of IP addresses and it must consume all the IP addresses returned for the load balancing layer domain name and have a representation for the same in GSLB.

To use domain names instead of IP addresses when referring to the load balancing endpoints, you can use the domain name based service groups for GSLB.

Monitor GSLB domain name based service groups

The Citrix ADC appliance has two built-in monitors that monitor TCP-based applications; tcp-default and ping-default. The tcp-default monitor is bound to all TCP services and the ping-default monitor is bound to all non-TCP services. The built-in monitors are bound by default to the GSLB service groups. However, it is recommended to bind an application specific monitor to the GSLB service groups.

Recommendation for setting the trigger monitors option to MEPDOWN

The Trigger Monitors option can be used to indicate if the GSLB site must use the monitors always, or use monitors when metrics exchange protocol (MEP) is DOWN.

The Trigger Monitors option is set to ALWAYS by default.

When the Trigger Monitors option is set to ALWAYS, each GSLB node triggers the monitors independently. If each GSLB node triggers the monitors independently, then each GSLB node might operate on different set of GSLB services. This might result in discrepancies in the DNS responses for the DNS requests landing on these GSLB nodes. Also, if each GSLB node is monitoring independently, then the number of monitor probes reaching the load balancer entity increases. The persistence entries also become incompatible across the GSLB nodes.

Therefore, it is recommended that the Trigger Monitors option on the GSLB site entity is set to MEPDOWN. When the Trigger Monitors option is set to MEPDOWN, the load balancing domain resolution and monitoring ownership lies with the local GSLB node. When the Trigger Monitors option is set to MEPDOWN, the load balancing domain resolution and subsequent monitoring is done by the local GSLB node of a GSLB service group. The results are then propagated to all other nodes participating in GSLB by using the metrics exchange protocol (MEP).

Also, whenever the set of IP addresses associated with a load balancing domain are updated, it is notified through MEP.

Limitations of GSLB service groups

• For a load balancing domain, the IP address that is returned in the DNS response is generally the public IP address. The private IP address cannot be applied dynamically when the load balancing domain is resolved. Therefore, public IP port and private IP port for the GSLB domain name based autoscale service groups IP port bindings are the same. These parameters cannot be set explicitly for the domain name based autoscale service groups.
• Site persistence, DNS views, and clustering are not supported for GSLB service groups.

Configure and manage GSLB service groups by using the CLI

To add a GSLB service group:

add gslb serviceGroup <serviceGroupName>@ <serviceType> [-autoScale ( DISABLED | DNS )] -siteName <string>
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