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Cache query servers in ets table #1778

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Merged
janl merged 1 commit into from
Nov 29, 2018
Merged

Cache query servers in ets table #1778

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80 changes: 46 additions & 34 deletions src/couch/src/couch_proc_manager.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,7 @@
-define(PROCS, couch_proc_manager_procs).
-define(WAITERS, couch_proc_manager_waiters).
-define(OPENING, couch_proc_manager_opening).
-define(SERVERS, couch_proc_manager_servers).
-define(RELISTEN_DELAY, 5000).

-record(state, {
Expand Down Expand Up @@ -104,6 +105,11 @@ init([]) ->
ets:new(?PROCS, TableOpts ++ [{keypos, #proc_int.pid}]),
ets:new(?WAITERS, TableOpts ++ [{keypos, #client.timestamp}]),
ets:new(?OPENING, [public, named_table, set]),
ets:new(?SERVERS, [public, named_table, set]),
ets:insert(?SERVERS, get_servers_from_env("COUCHDB_QUERY_SERVER_")),
ets:insert(?SERVERS, get_servers_from_env("COUCHDB_NATIVE_QUERY_SERVER_")),
ets:insert(?SERVERS, [{"QUERY", {mango_native_proc, start_link, []}}]),
maybe_configure_erlang_native_servers(),

{ok, #state{
config = get_proc_config(),
Expand Down Expand Up @@ -207,6 +213,7 @@ handle_cast(reload_config, State) ->
hard_limit = get_hard_limit(),
soft_limit = get_soft_limit()
},
maybe_configure_erlang_native_servers(),
{noreply, flush_waiters(NewState)};

handle_cast(_Msg, State) ->
Expand Down Expand Up @@ -267,6 +274,9 @@ handle_config_terminate(_Server, _Reason, _State) ->
gen_server:cast(?MODULE, reload_config),
erlang:send_after(?RELISTEN_DELAY, whereis(?MODULE), restart_config_listener).

handle_config_change("native_query_servers", _, _, _, _) ->
gen_server:cast(?MODULE, reload_config),
{ok, undefined};
handle_config_change("query_server_config", _, _, _, _) ->
gen_server:cast(?MODULE, reload_config),
{ok, undefined};
Expand Down Expand Up @@ -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

@janl janl Nov 29, 2018

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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.

@iilyak iilyak Nov 29, 2018

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in this case languages with mixed case will not work.

[{_, Command}] -> Command;
_ -> undefined
end.

native_query_server_enabled() ->
Expand All @@ -397,36 +420,25 @@ native_query_server_enabled() ->
NativeEnabled = config:get_boolean("native_query_servers", "enable_erlang_query_server", false),
NativeLegacyConfig = config:get("native_query_servers", "erlang", ""),
NativeLegacyEnabled = NativeLegacyConfig =:= "{couch_native_process, start_link, []}",

NativeEnabled orelse NativeLegacyEnabled.

get_native_query_server("query") -> % mango query server
"{mango_native_proc, start_link, []}";
get_native_query_server("erlang") -> % erlang query server
maybe_configure_erlang_native_servers() ->
case native_query_server_enabled() of
true -> "{couch_native_process, start_link, []}";
_Else -> undefined
end;
get_native_query_server(LangStr) ->
% same as above, but COUCH_NATIVE_QUERY_SERVER_LANGSTR
UpperLangString = string:uppercase(LangStr),
case get_env_for_spec("COUCHDB_NATIVE_QUERY_SERVER_", UpperLangString) of
[] -> undefined;
[Command] -> Command
true ->
ets:insert(?SERVERS, [
{"ERLANG", {couch_native_process, start_link, []}}]);
_Else ->
ok
end.

new_proc_int(From, Lang) when is_binary(Lang) ->
LangStr = binary_to_list(Lang),
case get_query_server(LangStr) of
undefined ->
case get_native_query_server(LangStr) of
undefined ->
gen_server:reply(From, {unknown_query_language, Lang});
SpecStr ->
{ok, {M,F,A}} = couch_util:parse_term(SpecStr),
{ok, Pid} = apply(M, F, A),
make_proc(Pid, Lang, M)
end;
gen_server:reply(From, {unknown_query_language, Lang});
{M, F, A} ->
{ok, Pid} = apply(M, F, A),
make_proc(Pid, Lang, M);
Command ->
{ok, Pid} = couch_os_process:start_link(Command),
make_proc(Pid, Lang, couch_os_process)
Expand Down