iRule to test tcp availability

I still tend to believe the pool option is your best approach, and you can certainly automate the management and creation of these pools with some pretty simple TMSH scripts.

 

 

That said, and this is a little on the wacky side, but you might also be able to do something like this:

 

1. Maintain a data group of all of the applications by port number (essentially a list of ports - assuming all of the servers will serve every application).

 

 

2. Create an internally-accessible "service" virtual server that maintains a table. It would also have an iRule that both populates/creates the table and that accepts simple HTTP requests to update the table entries. The table consist of one subtable per application (port) and each subtable defines the status of each IP per that port.

 

Ex. subtable "9500":

 

IP1: down

 

IP2: down

 

IP3: up

 

IP4: down

 

IP5: down

 

IP6: down

 

 

3. A monitor script attached to the service VIP that cycles through the data group (or subtables) and updates the status of each value (up or down) in the subtables - via a simple HTTP call to the VIP.

 

 

4. You application virtual servers would then check for the one "up" value in a given subtable before forwarding to the node.

 

 

It's absolutely imperative that the service VIP not be accessible to users. Also, depending on the frequency of the VIP's monitor and how many applications it has to cycle through, it may not respond as quickly as having a monitor attached to individual pools.