Brocade Virtual ADX Server Load Balancing Guide (Supporting ADX v03.1.00) - Manual (Page 227)

Brocade Virtual ADX Server Load Balancing Guide 211
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Health check with content match
4
In this example, the port http content-match m4 command binds matching list m4 to real server
rs1. HTTP response messages coming from real server rs1 are examined using the selection
criteria in matching list m4.
The port http url command sets the method used for HTTP keepalive requests and the URL of the
page to be retrieved. This command is used in HTTP content verification health checks because the
default method and URL page for HTTP keepalive requests used in HTTP health checks, “HEAD
/1.0”, does not return an HTML file that the Brocade Virtual ADX can search and verify. You can
instead specify the GET method, which does return an HTML file that can be examined using the
matching list.
Content match for non-HTTP ports
Configuring scripted health checks
You can configure scripted health checks (also known as content checking), which are content
verification health checks for ports that do not use one of the well-known port numbers recognized
by the Brocade Virtual ADX. Previous releases supported content verification health checks on port
80 only.
In a scripted health check, the Brocade Virtual ADX opens a connection to a port on a real server by
sending a SYN packet. The Brocade Virtual ADX completes the three-way handshake and then
waits for the server to send a packet containing ASCII strings in response. It then searches for the
configured ASCII string in the received packet. The port on the real server is then marked ACTIVE or
FAILED, based on configuration settings in the matching list. For example, a matching list can be
configured to mark a port ACTIVE or FAILED if the string is found, or mark the port ACTIVE or FAILED
if the string is not found.
If no response is received within the configured interval (the default is five seconds), the Brocade
Virtual ADX sends an RST and retries the health check. After the configured number of retries (the
default is two retries), if the server still does not respond, the Brocade Virtual ADX marks the server
port FAILED.
A scripted health check can also be part of a health-check policy. In this case, the scripted health
check checks the health of a configured port in the policy. The health-check policy can be
evaluated to true or false depending on the response from the server.
Follow the steps given below to configure a scripted health check.
1. Configuring a port profile
2. Configuring a matching list
3. Binding the matching list to the real server
Configuring a port profile
Port profiles enable you to globally configure the attributes for individual TCP/UDP ports. A scripted
health check will not work on a TCP port that does not have a profile, because the Brocade Virtual
ADX assumes any port without a profile is a UDP port, and will perform UDP health checking on the
port. To use a scripted health check on a TCP port, you must create a port profile and explicitly
identify the port as a TCP port.