Manual Chapter :
About gating criteria in subroutines
Applies To:
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BIG-IP APM
- 15.1.10, 15.1.9, 15.1.8, 15.1.7, 15.1.6, 15.1.5, 15.1.4, 15.1.3, 15.1.2, 15.1.1, 15.1.0
About gating criteria in subroutines
You can use gating criteria in the subroutine properties to allow the same
subroutine to control multiple subsessions. A distinct subsession is created for each distinct
gating criteria value. In the Gating Criteria field in the subroutine properties, you can select
a perflow variable (such as
perflow.client.ip.address
), or you can specify
a Tcl expression (such as expr {[mcget
{session.logon.last.username}]}
).The gating criteria value is the value that results from evaluating the specified gating
criteria expression, which is the value stored in the selected perflow variable, or the value
computed from a iRule/Tcl expression. If you leave the Gating Criteria field blank, the
subroutine runs once and applies the same ending to all requests for resources for the duration
of the subsession.
APM uses the value in this field to determine whether to run the subroutine. If a subsession
already exists for the particular resource (such as a URL or an application) or the group of
resources (such as those represented by a URL category or an application family), APM does not
run the subroutine again for the current request, but uses the same subsession, applying the
result that was obtained when the subroutine ran.
If APM does not find a matching subsession, APM validates the gating criteria before running
the subroutine. If the field contains a perflow variable, APM looks up its value. If the perflow
variable does not contain a value, APM returns an error. (The per-request policy must be
configured to provide a value for the perflow variable before you're trying to use it.) If the
perflow variable contains a valid value or if the gating criteria is blank, APM runs the
subroutine.
Here are some examples of gating criteria that you can use in a subroutine:
- perflow.client.ip.address– You can use this variable as gating criteria for requests to double check whether the user's IP address has changed since the subsession started. So if, for example, the user moves from a wired to a wireless network connection, you can ask again for user credentials.
- expr { [ mcget {session.adStepUpAuth.gatingCounterPath} ] }– To use this variable as gating criteria, another part of the policy needs to populate the session variablesession.adStepUpAuth.gatingCounterPath
