shinrich opened a new pull request #7276:
URL: https://github.com/apache/trafficserver/pull/7276


   Ran into this while working through the outbound connection logic.  The 
comments and logic around try_to_expand_host_name seemed odd, and I didn't see 
any relevant configuration.  I found some old 4.1.x documentation stashed on 
the internet which pointed me to proxy.config.http.enable_url_expandomatic, and 
from there got to @reveller's PR #918 which removed the configuration for this 
feature.  Cool name, but confusing feature.
   
   This PR removes the last confusing implementation remnants of this feature.  
I may have gone a bit too far in the parent selection case (the only case that 
did anything in the try_to_expand_host_name method), so I would appreciate some 
eyes on from parent selection experts like @rob05c, @ezelkow1  and @randall.
   
   From within HttpTransact::OSDNSLookup, I inlined the remaining logic of 
try_to_expand_host_name, which is to always fail if is not a parent lookup.  
Then I remembered that there is a parallel parent version of this method, 
HttpTransact::PPDNSLookup, so I removed the retry logic entirely.  There was a 
static max_dns_lookups = 3 within the OSDNSLookup method, and the dns_info has 
an attempts member.  I removed both of those on the assumption that the parent 
selection does not go through OSDNSLookup, so it will not trigger the logic to 
do a DNS lookup on the hostname instead of the parent name.  If this 
functionality is indeed used, I will add it back.
   
   In terms of DNS retries, that is handled at the DNS level and controlled by 
the config proxy.config.dns.retries.
   
   If we are not changing the name and re-issuing the DNS request, we can also 
get rid of the logic that returns a redirect if the name change lookup 
succeeded.
   


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