User guide

ExtremeWarePx1 1.2 Command Reference Guide 201
6 Health-Check Commands
This chapter describes commands for conÞguring health checks.
Types of Health Checks
The application switch supports the following types of health checks:
¥ ICMP PingÑUses ICMP Òecho requestÓ to ensures that the host is reachable. In general, this does
not provide any information about application health, but provides the simplest check.
¥ TCP Open ÑOpens a connection to a speciÞed TCP/IP port. Optionally, the application switch can
compare the response sent upon open to a preconÞgured string to further ensure that the application
responded correctly.
¥ HTTPÑ Sends an actual HTTP request to the server, typically a GET request. Optionally, the
application switch can compare the returned page to a preconÞgured string to further ensure that the
application responded correctly.
You conÞgure the type of health check for each server group. The same type of health check is
performed on all servers in a given server group. The server itself always performs ping health checks.
If you conÞgure TCP-open or HTTP checks, those checks will be performed as well.
If health checks are enabled, and you do not speciÞcally conÞgured the type of health check for a
particular server group, that group uses ping health checks by default.
Health Check Properties
The application switch maintains values for four properties that control the health-check procedure:
Property Meaning
Global
Default Value
interval Time interval between successful configured health checks 30 seconds
retry-interval Time interval between rechecks after a failed health check 10 seconds
fail-after Number of consecutive failed health checks after which a server is removed
from service
2
restore-after Number of consecutive successful health checks after which a server is
returned to service
2