Monitor GSLB services

When you bind a remote service to a GSLB virtual server, the GSLB sites exchange metric information, including network metric Information, which is the round-trip-time and persistence Information.

If a metric exchange connection is momentarily lost between any of the participating sites, the remote site is marked as DOWN and load balancing is performed on the remaining sites that are UP. When metric exchange for a site is DOWN, the remote services belonging to the site are marked DOWN as well.

The NetScaler appliance periodically evaluates the state of the remote GSLB services by using either MEP or monitors that are explicitly bound to the remote services. Binding explicit monitors to local services is not required, because the state of the local GSLB service is updated by default using the MEP. However, you can bind explicit monitors to a remote service. When monitors are explicitly bound, the state of the remote service is not controlled by the metric exchange.

By default, when you bind a monitor to a remote GSLB service, the NetScaler appliance uses the state of the service reported by the monitor. However, you can configure the NetScaler appliance to use monitors to evaluate services in the following situations:

  • Always use monitors (default setting).
  • Use monitors when MEP is DOWN.
  • Use monitors when remote services and MEP are DOWN.

The second and third of the above settings enable the appliance to stop monitoring when MEP is UP. For example, in a hierarchical GSLB setup, a GSLB site provides the MEP information about its child sites to its parent site. Such an intermediate site may evaluate the state of the child site as DOWN because of network issues, though the actual state of the site is UP. In this case, you can bind monitors to the services of the parent site and disable MEP to determine the actual state of the remote service. This option enables you to control the manner in which the states of the remote services are determined.

To use monitors, first create them, and then bind them to GSLB services.

Configure monitor trigger

You can configure a GSLB site to always use monitors (the default), use monitors when MEP is down, or use monitors when both the remote service and MEP are down. In the latter two cases, the NetScaler appliance stops monitoring when MEP returns to the UP state.

To configure monitor triggering by using the command line interface

At the command prompt, type:

set gslb site <siteName> –triggerMonitor (ALWAYS | MEPDOWN | MEPDOWN_SVCDOWN)

Example:

set gslb site Site-GSLB-North-America –triggerMonitor Always

To configure monitor triggering by using the configuration utility

  1. Navigate to Traffic Management > GSLBSites, and double-click the site.
  2. In the Trigger Monitors drop-down list, select an option for when to trigger monitoring.

Add or remove monitors

To add a monitor, you specify the type and the port. You cannot remove a monitor that is bound to a service. You must first unbind the monitor from the service.

To add a monitor by using the command line interface

At the command prompt, type the following commands to create a monitor and verify the configuration:

add lb monitor <monitorName> -type <monitorType> -destPort <portNumber>  

show lb monitor <monitorName>  

Example:

add lb monitor monitor-HTTP-1 -type HTTP -destPort 80
show lb monitor monitor-HTTP-1

To remove a monitor by using the command line interface

At the command prompt, type:

rm lb monitor <monitorName>

To add a monitor by using the configuration utility

Navigate to Traffic Management > Load Balancing > Monitors, and add or delete a monitor.

Bind monitors to a GSLB service

Once you create monitors, you must bind them to GSLB services. When binding monitors to the services, you can specify a weight for the monitor. After binding one or more weighted monitors, you can configure a monitor threshold for the service. This threshold takes the service down if the sum of the bound monitor weights falls below the threshold value.

Note: In the configuration utility, you can set both the weight and the monitoring threshold at the same time that you bind the monitor. When using the command line, you must issue a separate command to set the service’s monitoring threshold.

To bind the monitor to the GSLB service by using the command line interface

At the command prompt, type:

bind monitor <name> <serviceName> [ -state (Enabled | Disabled) ] -weight <positiveInteger>

Example:

bind monitor monitor-HTTP-1 service-GSLB-1 -state enabled -weight 2

To set the monitoring threshold for a GSLB service by using the command line interface

At the command prompt, type:

set gslb service <ServiceName> -monThreshold <PositiveInteger>

Example:

set gslb service service-GSLB-1 -monThreshold 9

To bind the monitor to the GSLB service by using the configuration utility

  1. Navigate to Traffic Management > GSLB > Services.
  2. Click the Monitor section and bind the monitor to the GSLB service.

To set the monitoring threshold for a GSLB service by using the configuration utility

  1. Navigate to Traffic Management > GSLB > Services.
  2. Click the Monitor Threshold section and enter a threshold value.

Monitor GSLB services