ASM_REQUEST_DONE and HTTP/1.1 POST request with Expect: header

I ran into this same problem just recently. You can get around the error by setting the uri as a variable in HTTP_REQUEST and use that

when HTTP_REQUEST {
  set uri [string tolower [HTTP::uri]]
}

when ASM_REQUEST_DONE {
    if { $uri matches_regex {^/[a-z0-9\-]+$} } {
     log local0. "found short start URL $uri, unblocking"
     ASM::unblock
}

HOWEVER! I then came across a new error. I no longer got the context errors, but instead starting getting the following for every unblock attempt.

warning tmm[12751]" 01480001:4: No Held transaction to sink.

The Event Logs would even show as unblocked, but the traffic would make it through to the OWS. The only way I was able to get around this issue was to strip out the Expect header in my HTTP_REQUEST

when HTTP_REQUEST {
  if {(HTTP::method eq "POST") && ([HTTP::header exists "Expect"])} {
    HTTP::header remove "Expect"
  }
}

This adds an ~3 second delay but was finally able to unblock the traffic with ASM::unblock. Looking around it seems like Expect: 100-continues causes a bunch of issues across the board with F5 modules. This was on 11.6 HF1, not sure if it exists in 11.5.X.

-Drew