Scenario
If you are attempting to leverage Top-Down Service Mapping (using patterns) on a Service which runs through an F5 Load Balancer, you might see the following error:
This will cause Service Mapping to stop, and a warning icon will be displayed.
Resolving the Issue
F5s use a concept called iRules to direct traffic through the Load Balancer/Pools/Services. These are customisable (as they're scripted). While you don't need to understand the inner workings of an F5, a useful introduction is published here if you're curious:
The challenge that we have as Discovery/Service Mapping admins is that iRules require additional credentials. That is effectively the crux of the error message - the Pattern (likely the F5 Load Balancer - SSH one) is missing the connection detail it needs to continue. This happens because iRules - if configured - aren't accessible from SNMP.
How I have had success resolving this myself is by configuring SSH credentials for the F5s, which have access - as specified in the docs [section 'prerequisites'] - to various commands:
*note - this is not the exhaustive list, check the docs linked above.
What this allows you to do, then, is to have Service Mapping use the failover from SNMP - a requirement where iRules are configured - to capture the required detail and jump through the Load Balancer Pools/Services to the next node in the map.
Alternative Approaches
Ymmv, as I have not attempted at the time of writing - but instead of SSH, a REST based pattern can be used to Discover the F5s. That approach is documented at the same place as the above link for SSH credentials.
Result
Once you have configured credentials allowing the SSH pattern to see the iRules and retrieve the outgoing connections, Service Mapping will continue through to the components - in this instance, the web server:
I hope this helps - and if you have experience using the REST approach, please share comments or guidance below!
