fix NXDOMAIN error in Docker Compose environments

Add fallback to /etc/hosts lookup when DNS resolution fails in
hackney_happy.erl. This fixes issue #764 where hostnames resolved
via /etc/hosts (common in Docker Compose) would fail with NXDOMAIN
when using inet_res:getbyname alone.

The hybrid approach tries DNS first (faster), then falls back to
inet:gethostbyname which checks /etc/hosts when DNS fails.

Author: benoitc

src/hackney_happy.erl

@@ -124,14 +124,34 @@ getaddrs(Name) ->
   {IP6Addrs, IP4Addrs}.
 
 getbyname(Hostname, Type) ->
+  %% First try DNS resolution using inet_res:getbyname
   case (catch inet_res:getbyname(Hostname, Type)) of
-    {'ok', #hostent{h_addr_list=AddrList}} -> lists:usort(AddrList);
-    {error, _Reason} -> [];
+    {'ok', #hostent{h_addr_list=AddrList}} -> 
+      lists:usort(AddrList);
+    {error, _Reason} -> 
+      %% DNS failed, try fallback to /etc/hosts using inet:gethostbyname
+      %% This fixes NXDOMAIN errors in Docker Compose environments where
+      %% hostnames are resolved via /etc/hosts entries
+      fallback_hosts_lookup(Hostname, Type);
     Else ->
-      %% ERLANG 22 has an issue when g matching somee DNS server messages
+      %% ERLANG 22 has an issue when g matching some DNS server messages
       ?report_debug("DNS error", [{hostname, Hostname}
                                  ,{type, Type}
                                  ,{error, Else}]),
+      %% Try fallback on unexpected errors too
+      fallback_hosts_lookup(Hostname, Type)
+  end.
+
+%% Fallback to check /etc/hosts when DNS resolution fails
+fallback_hosts_lookup(Hostname, Type) ->
+  InetType = case Type of
+    a -> inet;
+    aaaa -> inet6
+  end,
+  case (catch inet:gethostbyname(Hostname, InetType)) of
+    {'ok', #hostent{h_addr_list=AddrList}} -> 
+      lists:usort(AddrList);
+    _ -> 
       []
   end.