File 3301-Do-not-centralize-type-cname-lookups-throu... of Package erlang

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File 3301-Do-not-centralize-type-cname-lookups-through-inet_db.patch of Package erlang (Revision 1e94e72e3f4fed1ca9cd5c2fd777ed02)

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From b972eb723cb850983f27695930ac5dbc6093a2c7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Valim?= <jose.valim@dashbit.co>
Date: Wed, 21 Oct 2020 10:24:43 +0200
Subject: [PATCH] Do not centralize type/cname lookups through inet_db

Before this patch, inet_res:getbyname by name lookups
were centralized through the inet_db process, which
made it a bottleneck on concurrent machines that need
to establish many connections to several hosts quickly.

Given these lookups are concurrent, the update of
resolve.conf has been changed to use atomic operations
that replace the list of servers and list of names.

The inet_db API has also been cleaned up to no longer
expose operations that delete all searches/namespaces/etc.
Those functions seemed safe to remove as they are not
used anywhere within Erlang/OTP. The atomic replace
operations can be made public if desired in the future.
---
 lib/kernel/src/inet_db.erl | 54 ++++++++++++++++----------------------
 1 file changed, 23 insertions(+), 31 deletions(-)

diff --git a/lib/kernel/src/inet_db.erl b/lib/kernel/src/inet_db.erl
index 1dae042d1f..3d36b06527 100644
--- a/lib/kernel/src/inet_db.erl
+++ b/lib/kernel/src/inet_db.erl
@@ -35,10 +35,10 @@
 -export([start/0, start_link/0, stop/0, reset/0, clear_cache/0]).
 -export([add_rr/1,add_rr/5,del_rr/4]).
 -export([add_ns/1,add_ns/2, ins_ns/1, ins_ns/2,
-	 del_ns/2, del_ns/1, del_ns/0]).
--export([add_alt_ns/1,add_alt_ns/2, ins_alt_ns/1, ins_alt_ns/2, 
-	 del_alt_ns/2, del_alt_ns/1, del_alt_ns/0]).
--export([add_search/1,ins_search/1,del_search/1, del_search/0]).
+	 del_ns/2, del_ns/1]).
+-export([add_alt_ns/1,add_alt_ns/2, ins_alt_ns/1, ins_alt_ns/2,
+	 del_alt_ns/2, del_alt_ns/1]).
+-export([add_search/1,ins_search/1,del_search/1]).
 -export([set_lookup/1, set_recurse/1]).
 -export([set_socks_server/1, set_socks_port/1, add_socks_methods/1,
 	 del_socks_methods/1, del_socks_methods/0,
@@ -166,9 +166,6 @@ del_ns(IP) ->
 del_ns(IP, Port) ->
     call({listop, nameservers, del, {IP,Port}}).
 
-del_ns() -> 
-    call({listdel, nameservers}).
-
 %% ALTERNATIVE NAME SERVER
 %% add to the end of name server list
 add_alt_ns(IP) -> 
@@ -188,9 +185,6 @@ del_alt_ns(IP) ->
 del_alt_ns(IP, Port) ->
     call({listop, alt_nameservers, del, {IP,Port}}).
 
-del_alt_ns() -> 
-    call({listdel, alt_nameservers}).
-
 %% add this domain to the search list
 add_search(Domain) when is_list(Domain) -> 
     call({listop, search, add, Domain}).
@@ -201,9 +195,6 @@ ins_search(Domain) when is_list(Domain) ->
 del_search(Domain) ->
     call({listop, search, del, Domain}).
 
-del_search() ->
-    call({listdel, search}).
-
 %% set host name used by inet
 %% Should only be used by inet_config at startup!
 set_hostname(Name) ->
@@ -706,7 +697,7 @@ lookup_cname(Domain) ->
 %% Have to do all lookups (changes to the db) in the
 %% process in order to make it possible to refresh the cache.
 lookup_rr(Domain, Class, Type) ->
-    call({lookup_rr, Domain, Class, Type}).
+    match_rr({Domain, Class, Type}).
 
 %%
 %% hostent_by_domain (newly resolved version)
@@ -992,9 +983,6 @@ handle_call(Request, From, #state{db=Db}=State) ->
 	    ets:delete(Cache, cache_key(RR)),
 	    {reply, ok, State};
 
-	{lookup_rr, Domain, Class, Type} ->
-	    {reply, match_rr({Domain, Class, Type}), State};
-
 	{listop, Opt, Op, E} ->
 	    El = [E],
 	    case res_check_option(Opt, El) of
@@ -1012,9 +1000,14 @@ handle_call(Request, From, #state{db=Db}=State) ->
 		    {reply,error,State}
 	    end;
 
-	{listdel, Opt} ->
- 	    ets:insert(Db, {res_optname(Opt), []}),
- 	    {reply, ok, State};
+	{listreplace, Opt, Els} ->
+	    case res_check_option(Opt, Els) of
+		true ->
+		    ets:insert(Db, {res_optname(Opt), Els}),
+		    {reply,ok,State};
+		false ->
+		    {reply,error,State}
+	    end;
 
 	{set_hostname, Name} ->
 	    case inet_parse:visible_string(Name) of
@@ -1065,11 +1058,10 @@ handle_call(Request, From, #state{db=Db}=State) ->
 					(_, S) ->
 					    S
 				    end, [], Opts),
-			      [del_ns,
-			       clear_search,
-			       clear_cache,
-			       {search,Search}
-			       |[Opt || {nameserver,_}=Opt <- Opts]];
+			      NSs = [{NS,?NAMESERVER_PORT} || {nameserver,NS} <- Opts],
+			      [{replace_search,Search},
+			       {replace_ns,NSs},
+			       clear_cache];
 			  _ -> error
 		      end
 	      end,
@@ -1556,6 +1548,10 @@ rc_opt_req({lookup, Ls}) ->
     try {res_set, lookup, translate_lookup(Ls)}
     catch error:_ -> undefined
     end;
+rc_opt_req({replace_ns,Ns}) ->
+    {listreplace,nameservers,Ns};
+rc_opt_req({replace_search,Search}) ->
+    {listreplace,search,Search};
 rc_opt_req({Name,Arg}) ->
     case rc_reqname(Name) of
 	undefined ->
@@ -1565,14 +1561,10 @@ rc_opt_req({Name,Arg}) ->
 	    end;
 	Req -> {Req, Arg}
     end;
-rc_opt_req(del_ns) ->
-    {listdel,nameservers};
-rc_opt_req(del_alt_ns) ->
-    {listdel,alt_nameservers};
 rc_opt_req(clear_ns) ->
-    [{listdel,nameservers},{listdel,alt_nameservers}];
+    [{listreplace,nameservers,[]},{listreplace,alt_nameservers,[]}];
 rc_opt_req(clear_search) ->
-    {listdel,search};
+    {listreplace,search,[]};
 rc_opt_req(Opt) when is_atom(Opt) ->
     case is_reqname(Opt) of
 	true -> Opt;
-- 
2.26.2

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File 3301-Do-not-centralize-type-cname-lookups-through-inet_db.patch of Package erlang (Revision 1e94e72e3f4fed1ca9cd5c2fd777ed02)

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