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Refactor start_backend_module out of gen_mod. #1172

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Jan 27, 2017
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Refactor start_backend_module out of gen_mod. #1172

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117 changes: 117 additions & 0 deletions apps/ejabberd/src/backend_module.erl
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Original file line number Diff line number Diff line change
@@ -0,0 +1,117 @@
%%%----------------------------------------------------------------------
%%% File : backend_module.erl
%%% Author : Alexey Shchepin <alexey@process-one.net>
%%%
%%%
%%% ejabberd, Copyright (C) 2002-2011 ProcessOne
%%% Copyright 2016 Erlang Solutions Ltd.
%%%
%%% This program is free software; you can redistribute it and/or
%%% modify it under the terms of the GNU General Public License as
%%% published by the Free Software Foundation; either version 2 of the
%%% License, or (at your option) any later version.
%%%
%%% This program is distributed in the hope that it will be useful,
%%% but WITHOUT ANY WARRANTY; without even the implied warranty of
%%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
%%% General Public License for more details.
%%%
%%% You should have received a copy of the GNU General Public License
%%% along with this program; if not, write to the Free Software
%%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
%%% 02111-1307 USA
%%%
%%%----------------------------------------------------------------------

-module(backend_module).
-author('alexey@process-one.net').
-author('konrad.zemek@gmail.com').

-export([create/2, create/3]).

%% Callback implemented by proxy modules.
-callback backend() -> module().

%% API

-spec create(For :: module(), Name :: atom()) ->
{ok, module()} | {error, already_loaded}.
create(For, Name) ->
create(For, Name, []).

-spec create(For :: module(), Name :: atom(), TrackedFuns :: [atom()]) ->
{ok, module()} | {error, already_loaded}.
create(Module, Backend, TrackedFuns) ->
ProxyModule = proxy_module(Module),
case catch ProxyModule:backend() of
Backend -> {error, already_loaded};
_ ->
{ProxyModuleStr, CodeString} = backend_code(Module, Backend, TrackedFuns),
{Mod, Code} = dynamic_compile:from_string(CodeString),
code:load_binary(Mod, ProxyModuleStr ++ ".erl", Code),
ensure_backend_metrics(Module, TrackedFuns),
{ok, ProxyModule}
end.

%% Internal functions

-spec proxy_module(Module :: module()) -> module().
proxy_module(Module) ->
list_to_atom(atom_to_list(Module) ++ "_backend").

-spec backend_code(module(), atom(), list()) -> {nonempty_string(), list()}.
backend_code(Module, Backend, TrackedFuns) when is_atom(Backend) ->
Callbacks = Module:behaviour_info(callbacks),
ModuleStr = atom_to_list(Module),
ProxyModuleName = ModuleStr ++ "_backend",
RealBackendModule = ModuleStr ++ "_" ++ atom_to_list(Backend),
BehaviourExports = [generate_export(F, A) || {F, A} <- Callbacks],

BehaviourImpl = [generate_fun(Module, RealBackendModule, F, A, TrackedFuns) ||
{F, A} <- Callbacks],
Code = lists:flatten(
["-module(", ProxyModuleName, ").\n",
"-behaviour(backend_module).\n"
"-export([backend/0]).\n",
BehaviourExports,


"-spec backend() -> atom().\n",
"backend() ->", RealBackendModule, ".\n",
BehaviourImpl
]),
{ProxyModuleName, Code}.

generate_export(F, A) ->
"-export([" ++ atom_to_list(F) ++ "/" ++ integer_to_list(A) ++ "]).\n".

generate_fun(BaseModule, RealBackendModule, F, A, TrackedFuns) ->
Args = string:join(["A" ++ integer_to_list(I) || I <- lists:seq(1, A)], ", "),
IsTracked = lists:member(F, TrackedFuns),
[fun_header(F, Args), " ->\n",
generate_fun_body(IsTracked, BaseModule, RealBackendModule, F, Args)].

fun_header(F, Args) ->
[atom_to_list(F), "(", Args, ")"].

-define(METRIC(Module, Op), [backends, Module, Op]).

generate_fun_body(false, _, RealBackendModule, F, Args) ->
[" ", RealBackendModule, ":", fun_header(F, Args), ".\n"];
generate_fun_body(true, BaseModule, RealBackendModule, F, Args) ->
FS = atom_to_list(F),
%% returned is the following
%% {Time, Result} = timer:tc(Backend, F, Args),
%% mongoose_metrics:update(global, ?METRIC(Backend, F), Time),
%% Result.
[" {Time, Result} = timer:tc(", RealBackendModule, ", ", FS, ", [", Args, "]), \n",
" mongoose_metrics:update(global, ",
io_lib:format("~p", [?METRIC(BaseModule, F)]),
", Time), \n",
" Result.\n"].

ensure_backend_metrics(Module, Ops) ->
EnsureFun = fun(Op) ->
mongoose_metrics:ensure_metric(global, ?METRIC(Module, Op), histogram)
end,
lists:foreach(EnsureFun, Ops).
62 changes: 1 addition & 61 deletions apps/ejabberd/src/gen_mod.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -62,7 +62,6 @@
loaded_modules/1,
loaded_modules_with_opts/1,
get_module_proc/2,
backend_code/3,
is_loaded/2,
get_deps/3]).

Expand Down Expand Up @@ -139,66 +138,7 @@ start_backend_module(Module, Opts) ->

start_backend_module(Module, Opts, TrackedFuncs) ->
Backend = gen_mod:get_opt(backend, Opts, mnesia),
{BackendModuleStr, CodeString} = backend_code(Module, Backend, TrackedFuncs),
{Mod, Code} = dynamic_compile:from_string(CodeString),
code:load_binary(Mod, BackendModuleStr ++ ".erl", Code),
ensure_backend_metrics(Module, TrackedFuncs).

-spec backend_code(module(), atom(), list()) -> {nonempty_string(), list()}.
backend_code(Module, Backend, TrackedFuncs) when is_atom(Backend) ->
Callbacks = Module:behaviour_info(callbacks),
ModuleStr = atom_to_list(Module),
BackendModuleName = ModuleStr ++ "_backend",
RealBackendModule = ModuleStr ++ "_" ++ atom_to_list(Backend),
BehaviourExports = [generate_export(F, A) || {F, A} <- Callbacks],

BehaviourImpl = [generate_fun(Module, RealBackendModule, F, A, TrackedFuncs) ||
{F, A} <- Callbacks],
Code = lists:flatten(
["-module(", BackendModuleName, ").\n",
"-export([backend/0]).\n",
BehaviourExports,


"-spec backend() -> atom().\n",
"backend() ->", RealBackendModule, ".\n",
BehaviourImpl
]),
{BackendModuleName, Code}.

generate_export(F, A) ->
"-export([" ++ atom_to_list(F) ++ "/" ++ integer_to_list(A) ++ "]).\n".

generate_fun(BaseModule, RealBackendModule, F, A, TrackedFuncs) ->
Args = string:join(["A" ++ integer_to_list(I) || I <- lists:seq(1, A)], ", "),
IsTracked = lists:member(F, TrackedFuncs),
[fun_header(F, Args), " ->\n",
generate_fun_body(IsTracked, BaseModule, RealBackendModule, F, Args)].

fun_header(F, Args) ->
[atom_to_list(F), "(", Args, ")"].

-define(METRIC(Module, Op), [backends, Module, Op]).

generate_fun_body(false, _, RealBackendModule, F, Args) ->
[" ", RealBackendModule, ":", fun_header(F, Args), ".\n"];
generate_fun_body(true, BaseModule, RealBackendModule, F, Args) ->
FS = atom_to_list(F),
%% returned is the following
%% {Time, Result} = timer:tc(Backend, F, Args),
%% mongoose_metrics:update(global, ?METRIC(Backend, F), Time),
%% Result.
[" {Time, Result} = timer:tc(", RealBackendModule, ", ", FS, ", [", Args, "]), \n",
" mongoose_metrics:update(global, ",
io_lib:format("~p", [?METRIC(BaseModule, F)]),
", Time), \n",
" Result.\n"].

ensure_backend_metrics(Module, Ops) ->
EnsureFun = fun(Op) ->
mongoose_metrics:ensure_metric(global, ?METRIC(Module, Op), histogram)
end,
lists:foreach(EnsureFun, Ops).
backend_module:create(Module, Backend, TrackedFuncs).

-spec is_app_running(_) -> boolean().
is_app_running(AppName) ->
Expand Down