[GitHub] [trafficserver] shinrich commented on a change in pull request #7276: Remove the last remnants of the enable_url_expandomatic

[GitBox <gi...@apache.org>]

shinrich commented on a change in pull request #7276:
URL: https://github.com/apache/trafficserver/pull/7276#discussion_r512659302



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File path: proxy/http/HttpTransact.cc
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@@ -1856,12 +1852,9 @@ HttpTransact::ReDNSRoundRobin(State *s)
 void
 HttpTransact::OSDNSLookup(State *s)
 {
-  static const int max_dns_lookups = 3;
-
   ink_assert(s->dns_info.looking_up == ORIGIN_SERVER);
 
-  TxnDebug("http_trans", "[HttpTransact::OSDNSLookup] This was attempt %d", s->dns_info.attempts);

Review comment:
       I removed DNS_ATTEMPTS_EXHAUSTED because the current try_to_expand_host_name() never returns that.  It only returns EXPANSION_NOT_ALLOWED in the non-parent selection case or RETRY_EXPANDED_NAME in the parent selection case.  So got rid of the extra cases and inlined the contents of try_to_expand host name.
   
   With the most of the expandomatic logic gone, only the parent select case exercises this path, and it will only exercise it once to check the IP address of the parent machine rather than the parent path directly (here is where my knowledge of why the parent select logic flips over to OSDNSLookup becomes shakey).
   
   The underlying DNS lookup logic in iocore/DNS will still do multiple DNS requests. 
   
   The origin server looking up logic will pass through OSDNSLookup multiple times for a transaction if the connection for an IP address fails . Then OSDNSLookup will be triggered again and either the same address is selected again or if it failed too many times, the logic will move onto the next address (assuming DNS returns multiple addresses for the name)




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