FQDN Health Check Options

The Checker options in the Configure FQDN screen defines the type of health checking that is performed. The options include:

• None: This implies that no health check is performed to check the health status of the machine (IP address) associated to the current FQDN.

• ICMP Ping: This tests the health status by pinging the IP address.

• TCP Connect: This will test the health by trying to connect to the IP address on a specified port.

• Cluster Checks: When this is selected, the health status check is performed using the method associated with the selected cluster.

  Note: If there are no clusters configured, the Cluster Checks value is grayed out.

• HTTP/HTTPS: 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.

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.

  Health check status codes can be set to override default functionality. Without any Status Codes set, the following HTTP status codes are considered to be Up:

  • 200-299: Success (for example 200 OK, 202 Accepted)
  • 301: Moved Permanently
  • 302: Found
  • 401: Unauthorized

  Additionally, 2xx status codes are subject to pattern matching the response data, if this is configured. Other codes are considered up without pattern matching, even if it is set.

  If custom health check codes are set:

  • Check codes may be set to a list of numbers, each from 300-599
  • Check codes may be up to 127 characters long, which means 32 valid codes
  • Any code in the list is considered to have a health check status of Up
  • Configured codes override the default set
    • 2xx codes are always considered up in all cases and are subject to pattern matching, if configured
    • Check codes may be official HTTP status codes, unofficial codes or custom-defined user codes – as long as they fall in the range of 300-599
      • For a list of official HTTP status codes, refer to: https://en.wikipedia.org/wiki/List_of_HTTP_status_codes
      • For a list of unofficial codes, refer to: https://en.wikipedia.org/wiki/List_of_HTTP_status_codes#Unofficial_codes
    • Microsoft sub-codes using decimals can be supported, but only by the top-level status code
      • For a list of Microsoft sub-codes using decimals, refer to: https://support.microsoft.com/en-us/kb/943891
      • Sub-codes may not be configured in the Status Codes field – please use the three digit code
      • Sub-codes are grouped by the top-level code

• 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 the GET, the POST, or the HEAD 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.

• Show/Hide Custom Headers: When you click the Show/Hide Custom Headers option, it displays the custom headers that are to be part of the health check request.

• Header: Add a custom header to be part of the health check request.

  • There is a limit of 255 characters for the total check headers string. The first text box allows you to specify a key for the custom header. The second text box allows you to specify a value for the custom header. The value has a maximum length of 128 characters.

  • Allowed characters for header keys: alphanumerics and _-

  • Allowed characters for header values: alphanumerics and _-.+=;()

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