AppExpert framework provides various bind points for logical evaluation of request and response traffic. These bind points are evaluated in system defined order which ensures the logical flow of application intelligence defined on NetScaler. Following shows the bind points and order of evaluation:
The evaluation goes on with the above order and in between these system defined bind points. In between this processing one can switch to a policylabel which is treated as a soft or user defined bind point. Once policies bound to soft bind point are evaluated, system will start following the system defined order for further evaluation.
Goto expression is used to control the flow of policy evaluation and it also acts as a logical tool to get to the appropriate policy without going through everything bound sequentially. When binding the policy, you assign it a priority level to specify when it is invoked relative to other policies in the bank. In addition to assigning a priority level, you can configure an arbitrary evaluation order for policies in a bank by specifying Goto expressions. A Goto expression indicates the next policy to be evaluated, typically within the same policy bank. Goto expressions can only proceed forward in a bank to avoid looping scenarios. Here is a view of Goto processing order:
Correct usage of Goto expression will always simplify the configuration and will result in correct behavior. It also enhances system performance by ensuring that correct set of required policies are evaluated.