[GitHub] janl commented on a change in pull request #1778: Cache query servers in ets table

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

janl commented on a change in pull request #1778: Cache query servers in ets table
URL: https://github.com/apache/couchdb/pull/1778#discussion_r237489954
 
 

 ##########
 File path: src/couch/src/couch_proc_manager.erl
 ##########
 @@ -372,23 +382,36 @@ new_proc(Client) ->
     end,
     exit(Resp).
 
-get_env_for_spec(Spec, Target) ->
-    % loop over os:getenv(), match SPEC_TARGET
-    lists:filtermap(fun(VarName) ->
-        SpecStr = Spec ++ Target,
-        case string:tokens(VarName, "=") of
-            [SpecStr, Cmd] -> {true, Cmd};
-            _Else -> false
+split_string_if_longer(String, Pos) ->
+    case length(String) > Pos of
+        true -> lists:split(Pos, String);
+        false -> false
+    end.
+
+split_by_char(String, Char) ->
+    %% 17.5 doesn't have string:split
+    %% the function doesn't handle errors
+    %% it is designed to be used only in specific context
+    Pos = string:chr(String, Char),
+    {Key, [_Eq | Value]} = lists:split(Pos - 1, String),
+    {Key, Value}.
+
+get_servers_from_env(Spec) ->
+    SpecLen = length(Spec),
+    % loop over os:getenv(), match SPEC_
+    lists:filtermap(fun(EnvStr) ->
+        case split_string_if_longer(EnvStr, SpecLen) of
+            {Spec, Rest} ->
+                {true, split_by_char(Rest, $=)};
+            _ ->
+                false
         end
     end, os:getenv()).
 
 get_query_server(LangStr) ->
-    % look for COUCH_QUERY_SERVER_LANGSTR in env
-    % if exists, return value, else undefined
-    UpperLangString = string:to_upper(LangStr),
-    case get_env_for_spec("COUCHDB_QUERY_SERVER_", UpperLangString) of
-        [] -> undefined;
-        [Command] -> Command
+    case ets:lookup(?SERVERS, string:to_upper(LangStr)) of
 
 Review comment:
   doubtful it’s a performance issue, but we could do `to_lower()` when populating the ets table so we can avoid `to_upper()` here on each call. not blocking a merge, just leaving this here.

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