How to get a list of loaded ejabberd modules?

Question

I'm writing an ejabberd module and need to perform different cleanup actions on stop in the two following cases:

• The same module is running on other cluster nodes at the current moment.
• This is the last still running instance of my module.

I consider the following solution:

is_there_running_instances() ->
    {Results, _} = rpc:multicall(nodes(), ?MODULE, ejabberd_loaded_modules, []),
    lists:member(?MODULE, lists:append(Results)).

ejabberd_loaded_modules() -> ???.

But don't know how to get the list of loaded modules. How can I do it? Or is my problem has a better solution?

Answer 1

code:all_loaded/0 returns a list of tuple of the type {ModuleName,ModuleAbsolutePath} where ModuleName is an atom and ModuleAbsolutePath a string. You can filter this list with the path information, and unzip it to get only the module it contains. I test it with the eunit library after loading all modules:

26> Filter = fun(Path,Lib) -> string:str(Path,Lib) > 0 end.                         
#Fun<erl_eval.12.80484245>
27> [Mod || {Mod,Path} <- code:all_loaded() , is_list(Path), Filter(Path,"eunit")].
[eunit,eunit_proc,eunit_test,eunit_data,eunit_surefire,
 eunit_serial,eunit_tests,eunit_autoexport,eunit_tty,
 eunit_server,eunit_striptests,eunit_lib,eunit_listener]

Answer 2

try if

gen_mod:loaded_modules(Host)

is what you need

Answer 3

First of all get all loaded modules list with code:all_loaded/0 and than filter result with "mod_" preffix.

ejabberd_loaded_modules() -> 
    AllLoaded = code:all_loaded(),
    Filter = fun({Module, _}) ->
        case re:run(atom_to_list(Module), "mod_") of
            {match,[{0,4}]} -> true;
            _ -> false
        end
    end,
    lists:filter(Filter, AllLoaded).

Also you can perform behaviour check. It should be gen_mod.

is_gen_mod(Module) ->
    BehavioursList = 
    case lists:getkey(1, behaviour, Module:module_info(attributes)) of
        {behaviour, L} -> L;
        false -> []
    end,
    lists:member(gen_mod, BehavioursList).

In this case ejabberd_loaded_modules/0 function will be:

ejabberd_loaded_modules() ->
    ...
    ModPreffixed = lists:filter(Filter, AllLoaded),
    lists:filter(fun is_gen_mod/1, ModPreffixed).