How to mask URL

That's because the iRule is comparing the string "/join/events" and you passed in "/join/events/".

Something like this should work

when HTTP_REQUEST { 
  if { [HTTP::uri] equals "/join/events/" } { 
    HTTP::uri "/join" 
  } 
 }

But, that would ONLY match a url of "/join/events/". "/join/events", "/Join/Events/", etc would not match.

You could also use a "starts_with" to compare like this

when HTTP_REQUEST { 
  if { [HTTP::uri] starts_with "/join/events" } { 
    HTTP::uri "/join" 
  } 
 }

That would match "/join/events" and "/join/events/" but it would also match on "/join/eventsFOOBAR" or anything else after events in the URI.

If you want to have more options in your comparisons, I'd use a switch statement with the "string tolower" on the URI.

when HTTP_REQUEST {
  switch -glob [string tolower [HTTP::uri]] {
    "/join/events" -
    "/join/events/" {
      HTTP::uri "/join"
    }
  }
}

Lots of options, it really depends on your app logic how complex you want to go with the comparison.

-Joe