Healthchecks
The Healthchecks page holds the library of health checks available to the appliance. How the library is used depends on the type of service:
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For Layer 4 Services, the library is the only way a health check is configured. The Health check field on the backend Health step selects a named check from this page - there are no inline check settings. See Backend Configuration - Health.
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For Layer 7 Services, the health check is configured inline on the backend Health step. The library is used only by the External Script check type, where a script is selected in the External check script field.
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For GSLB Services, the library is used when the Healthcheck mode is set to External Script or External Dynamic Weight, where a script is selected in the Healthcheck script field (see GSLB Healthcheck Scripts).
The appliance ships with a comprehensive set of built-in scripts covering many common applications and protocols. Custom scripts can also be added to support bespoke health checks.
To view the configured health checks:
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Using the WebUI, navigate to Manage services > Healthchecks.
The list shows the following information for each health check:
Column Description Name
The name of the health check script.
Description
A short description of the script’s purpose.
Services
The service type(s) the script applies to - Layer-7, Layer-4 and/or GSLB.
Created by
The origin of the script - Built-in for the scripts supplied with the appliance, or User for scripts that have been added on this appliance.
Usage
Whether the script is currently referenced by a service. A script that is not assigned to any service shows
Not in use.
| Use the Search box above the list to filter the health checks by name or description. |
Adding a health check
To add a custom health check script:
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Using the WebUI, navigate to Manage services > Healthchecks and click Add healthcheck.
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Configure the health check:
Field Description Name
A name for the health check script. Keep it short and descriptive - the name is how the script is identified in the service wizards. Spaces, hyphens and underscores are accepted.
Description
An optional, meaningful description of the script’s purpose.
Services
The service type(s) the script is intended for, selected using the Layer-4, Layer-7 and GSLB checkboxes. Each checkbox is independent - tick Layer-4 to offer the script to Layer 4 services, Layer-7 to offer it to Layer 7 services (as an External Script check), and GSLB to offer it to GSLB services. At least one service must be selected.
Script content
The contents of the script, typed or pasted into the editor. The editor numbers the lines but does not colour the syntax, so it is usually easier to write and test the script elsewhere and paste it in. The exit status of the script determines whether the Real Server is considered up or down. This field is required.
Parameters
An optional set of named values that are presented to the operator when the script is selected in a service wizard, so that one script can be reused with different settings. See below.
Name, Services and Script content are all required; Description and Parameters are optional. -
Click Submit.
Parameters
A health check script can declare parameters so that the values it needs - a port number, a URL path, a hostname - are supplied when the script is selected, rather than being hard-coded into the script itself. Click Add parameter to add a parameter, and Remove alongside a parameter to delete it. Each parameter has the following settings:
| Setting | Description |
|---|---|
Name |
The parameter name, used to reference the value from within the script. This field is required. |
Label |
The caption shown against the field when the operator is prompted for the value. This field is required. |
Type |
The kind of value expected, which determines how the entered value is validated. The options are Text (the default), Integer, Port, Path and Hostname. |
Required |
When enabled, a value must be supplied before the service can be submitted. |
Default |
The value pre-filled for the operator. |
Once added, the script appears in the Healthchecks list with Created by set to User and becomes available for selection in the relevant service wizards.
Viewing, duplicating, editing & deleting health checks
The actions available from a health check’s three-dots menu depend on how the script was created.
Built-in scripts (those supplied with the appliance) cannot be modified or deleted. The menu offers:
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View - display the script content (read-only).
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Duplicate - create an editable copy of the script to use as the starting point for a custom check. The copy is pre-populated with the original’s description, services and script content. Specify a new Name (following the naming rules above), adjust the settings and content as required, then click Submit. The new script is added as a User script.
User scripts (those added on this appliance) can be modified and removed. The menu offers:
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Edit - modify the script’s name, description, services and content.
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Delete - permanently remove the script. A confirmation dialog is displayed; click Confirm to delete.