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GEO Layer7 HTTP Health Checks

This article relates to LoadMaster firmware version 7.2.53.

In LoadMaster firmware version 7.2.53, support was added to perform Layer7 (L7) HTTP and HTTPS health checks on back-end servers within GEO "sites" that are not handled from the LoadMaster for application delivery. In other words, site health determination can be enhanced directly from GEO by checking the health of back-end servers that are not being health-checked by LoadMaster (or another Application Delivery Controller (ADC)).

HTTP/1.1 is supported (HTTP/1.0 is not supported).

To configure this, perform the following steps in the LoadMaster User Interface (UI):

1. Go to Global Balancing > Manage FQDNs.

2. Click Modify on the relevant FQDN (or add a new one).

3. If needed, enter a New IP Address, select the relevant Cluster and click Add Address.

4. Select HTTP or HTTPS as the Checker.

The available options that appear when HTTP or HTTPS is selected as the Checker are as follows:

  • Address: Set the address and port to use to health check the IP address. The default port is 80 when HTTP is selected and 443 when HTTPS is selected.

  • URL: By default, the health checker tries to access the URL forward slash (/) to determine if the machine is available. You can specify a different URL here.

    • The URL must begin with a forward slash (/).

    • The URL cannot contain http: or https:.

    • The URL can be a maximum of 127 characters.

    • If the URL is left blank, a forward slash (/) is sent by default.

  • Status Codes: A space-separated list of HTTP and HTTPS status codes that should be treated as successful when received from the server.

    • Codes must be between 300-599.

    • There is a maximum of 32 codes.

    • There is a limit of 127 characters.

  • Host: A hostname can be supplied in the request to the server. If this is not set, the server address is sent as the host.

    • There is a limit of 127 characters.

    • Allowed characters: alphanumerics and -._:

  • Method: When accessing the health check URL, the system can use either the GET or the POST method. If POST is selected, another field appears to set the POST data. Up to 2047 characters of POST data can be passed to the server.

The status of the health check displays in the Availability column.

It is not possible to override the GEO health checks on a per-FQDN basis (like you can with Virtual Services).

The Check Parameters in Rules & Checking > Check Parameters do not apply to GEO. Only the settings in Global Balancing > Miscellaneous Params apply to GEO.

For further details on GEO in general, refer to the GEO Feature Description.

RESTful Application Programming Interface (API) Details

To retrieve details about existing FQDNs, run the listfqdns API command, for example:

/access/listfqdns

To modify the checker address, run the changecheckeraddr command, for example:

/access/changecheckeraddr?fqdn=<FQDN>&ip=<IPAddress>&checkerip=<CheckerIPAddress>&port=<CheckerPort>

To modify the other HTTP and HTTPS health check parameters, run the modmap command, for example:

/access/modmap?fqdn=<FQDN>&ip=<IPAddress>&checker=http&checkerurl=<URL>

The modmap command accepts the following optional parameters relating to HTTP and HTTPS health checks:

Name

Type

Default

Range

Additional Information

checker S icmp

none
icmp
tcp
clust
http

https

Specify the type of checking to be done on this IP address (http or https in this case).
checkerurlS/Maximum of 127 characters By default, the health checker tries to access the URL forward slash (/) to determine if the machine is available. You can specify a different URL using the checkerurl parameter.
The URL must begin with a forward slash (/).
The URL cannot contain http: or https:.
The URL can be a maximum of 127 characters.
checkercodesS 300-599 A space-separated list of HTTP status codes that should be treated as successful when received from the server.
There is a maximum of 32 codes.
There is a limit of 127 characters.
checkerhostS   A hostname can be supplied in the request to the server. If this is not set, the server address is sent as the host.
There is a limit of 127 characters.
Allowed characters: alphanumerics and -._:
checkerhttpmethodSget

1 - GET

2 - POST

When accessing the health check URL, the system can use either the GET or the POST method. If POST is selected, the checkerpostdata parameter is also valid.
checkerpostdataS  Up to 2047 characters of POST data can be passed to the server. This parameter is only relevant if the checkerhttpmethod parameter is set to 2 (POST).

The maximum length of an API call is 1024 characters. If you want to make a larger call, use the POST method.

To delete a health check, set the checker parameter to none. For example:

/access/modmap?fqdn=<FQDN>&ip=<IPAddress>&checker=none


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