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如何将网站转成小程序,网站开发技术有哪些,上海公司核名查询,东莞正规的企业网站设计多少钱在ejabberd 中，hooks 是很重要的一个模块，作为系统hook(钩子)，通过调用ejabberd_hooks:add函数，注册一系列方法在ets表hook中，为某些特定事件(event)钩挂相应的行为(action)，使在事件(event)发生时&#xf…

在ejabberd 中，hooks 是很重要的一个模块，作为系统hook(钩子)，通过调用ejabberd_hooks:add函数，注册一系列方法在ets表hook中，为某些特定事件(event)钩挂相应的行为(action)，使在事件(event)发生时，触发对应的所有行为(actions)

1 ejabberd_hooks启动
查看ejabberd_app.erl文件，启动过程语句

%%%启动一个supervisor，并启动和监控定义子进程Sup = ejabberd_sup:start_link()

ejabberd_sup:

start_link() ->supervisor:start_link({local, ?MODULE}, ?MODULE, []).

init([]) ->Hooks ={ejabberd_hooks,{ejabberd_hooks, start_link, []},permanent,brutal_kill,worker,[ejabberd_hooks]},...{ok, {{one_for_one, 10, 1},[Hooks,NodeGroups,SystemMonitor,Router,Router_multicast,S2S,Local,Captcha,S2SInSupervisor,S2SOutSupervisor,ServiceSupervisor,IQSupervisor,FrontendSocketSupervisor,Listener]}}.

启动详细参数可以参照supervisor行为规范
ejabberd_hooks:

start_link() ->gen_server:start_link({local, ejabberd_hooks}, ejabberd_hooks, [], []).

由上述代码可知ejabberd_hooks启动的是一个gen_sever进程，作为ejabberd_sup子进程存在

init([]) ->ets:new(hooks, [named_table]),{ok, #state{}}.

gen_server:start_link/4执行后，调用init/1函数新建ets表hooks，用于存储绑定事件行为，存储格式以disco_info为例：

{{disco_info,<<"localhost">>},[{50,mod_offline,get_info},{75,mod_caps,disco_info},{100,mod_disco,get_info}]}

2 add hooks
add hooks是需要绑定事件行为(event-action)的模块，通过调用ejabberd_hooks:add和ejabberd_hooks:add_dist函数绑定
add在ejabberd_hooks中定义如下

%%%以下针对不同情况是否包含主机模块等参数匹配不同处理，最终都会调用gen_server:call/2
%%%然后在handle_call回调模块中实现添加
%%% @doc See add/4.
add(Hook, Function, Seq) when is_function(Function) ->add(Hook, global, undefined, Function, Seq).-spec add(atom(), HostOrModule :: binary() | atom(), fun() | atom() , number()) -> ok.
add(Hook, Host, Function, Seq) when is_function(Function) ->add(Hook, Host, undefined, Function, Seq);%%% @doc Add a module and function to this hook.
%%% The integer sequence is used to sort the calls: low number is called before high number.
add(Hook, Module, Function, Seq) ->add(Hook, global, Module, Function, Seq).-spec add(atom(), binary() | global, atom(), atom() | fun(), number()) -> ok.add(Hook, Host, Module, Function, Seq) ->gen_server:call(ejabberd_hooks, {add, Hook, Host, Module, Function, Seq}).-spec add_dist(atom(), atom(), atom(), atom() | fun(), number()) -> ok.add_dist(Hook, Node, Module, Function, Seq) ->gen_server:call(ejabberd_hooks, {add, Hook, global, Node, Module, Function, Seq}).-spec add_dist(atom(), binary() | global, atom(), atom(), atom() | fun(), number()) -> ok.add_dist(Hook, Host, Node, Module, Function, Seq) ->gen_server:call(ejabberd_hooks, {add, Hook, Host, Node, Module, Function, Seq}).

%%%handle_call回调模块
handle_call({add, Hook, Host, Module, Function, Seq}, _From, State) ->HookFormat = {Seq, Module, Function},Reply = handle_add(Hook, Host, HookFormat),{reply, Reply, State};
handle_call({add, Hook, Host, Node, Module, Function, Seq}, _From, State) ->HookFormat = {Seq, Node, Module, Function},Reply = handle_add(Hook, Host, HookFormat),{reply, Reply, State};

%%% in-memory storage operation: Handle adding hook in ETS table
handle_add(Hook, Host, El) ->case ets:lookup(hooks, {Hook, Host}) of[{_, Ls}] ->case lists:member(El, Ls) oftrue ->ok;false ->NewLs = lists:merge(Ls, [El]),ets:insert(hooks, {{Hook, Host}, NewLs}),okend;[] ->NewLs = [El],ets:insert(hooks, {{Hook, Host}, NewLs}),okend.

3 delete hooks
delete hooks处理逻辑和add hooks是同样的，这里不做详细说明，可自行查看ejabberd_hooks源码
4 run hooks
在发生某个event 的时候，run相对应的hook，从而执行该hook对应的**所有**actions
1 run(Hook, Host, Args) 根据hook名字依次调用，不管每次的调用结果
2 run_fold(Hook, Host, Val, Args) 根据hook名字依次调用，每次的调用结果下次继续使用
run和run_fold在ejabberd_hooks中定义如下：

-spec run(atom(), list()) -> ok.%%% @doc Run the calls of this hook in order, don't care about function results.
%%% If a call returns stop, no more calls are performed.
run(Hook, Args) ->run(Hook, global, Args).-spec run(atom(), binary() | global, list()) -> ok.run(Hook, Host, Args) ->%%%查询ets表hooks信息，然后执行run1/3case ets:lookup(hooks, {Hook, Host}) of[{_, Ls}] ->run1(Ls, Hook, Args);[] ->okend.-spec run_fold(atom(), any(), list()) -> any().%%% @doc Run the calls of this hook in order.
%%% The arguments passed to the function are: [Val | Args].
%%% The result of a call is used as Val for the next call.
%%% If a call returns 'stop', no more calls are performed and 'stopped' is returned.
%%% If a call returns {stop, NewVal}, no more calls are performed and NewVal is returned.
run_fold(Hook, Val, Args) ->run_fold(Hook, global, Val, Args).-spec run_fold(atom(), binary() | global, any(), list()) -> any().run_fold(Hook, Host, Val, Args) ->%%%查询ets表hooks，然后执行run_fold1/4case ets:lookup(hooks, {Hook, Host}) of[{_, Ls}] ->run_fold1(Ls, Hook, Val, Args);[] ->Valend.

-spec run1([local_hook()|distributed_hook()], atom(), list()) -> ok.run1([], _Hook, _Args) ->ok;
%%% Run distributed hook on target node.
%%% It is not attempted again in case of failure. Next hook will be executed
run1([{_Seq, Node, Module, Function} | Ls], Hook, Args) ->%%% MR: Should we have a safe rpc, like we have a safe apply or is bad_rpc enough ?%%%远程节点执行M:F:Acase ejabberd_cluster:call(Node, Module, Function, Args) oftimeout ->?ERROR_MSG("Timeout on RPC to ~p~nrunning hook: ~p",[Node, {Hook, Args}]),run1(Ls, Hook, Args);{badrpc, Reason} ->?ERROR_MSG("Bad RPC error to ~p: ~p~nrunning hook: ~p",[Node, Reason, {Hook, Args}]),run1(Ls, Hook, Args);stop ->?INFO_MSG("~nThe process ~p in node ~p ran a hook in node ~p.~n""Stop.", [self(), node(), Node]), % debug codeok;Res ->?INFO_MSG("~nThe process ~p in node ~p ran a hook in node ~p.~n""The response is:~n~s", [self(), node(), Node, Res]), % debug coderun1(Ls, Hook, Args)end;
run1([{_Seq, Module, Function} | Ls], Hook, Args) ->%%%本地执行M:F:ARes = safe_apply(Module, Function, Args),case Res of{'EXIT', Reason} ->?ERROR_MSG("~p~nrunning hook: ~p", [Reason, {Hook, Args}]),run1(Ls, Hook, Args);stop ->ok;_ ->run1(Ls, Hook, Args)end.run_fold1([], _Hook, Val, _Args) ->Val;
run_fold1([{_Seq, Node, Module, Function} | Ls], Hook, Val, Args) ->case ejabberd_cluster:call(Node, Module, Function, [Val | Args]) of{badrpc, Reason} ->?ERROR_MSG("Bad RPC error to ~p: ~p~nrunning hook: ~p",[Node, Reason, {Hook, Args}]),run_fold1(Ls, Hook, Val, Args);timeout ->?ERROR_MSG("Timeout on RPC to ~p~nrunning hook: ~p",[Node, {Hook, Args}]),run_fold1(Ls, Hook, Val, Args);stop ->stopped;{stop, NewVal} ->?INFO_MSG("~nThe process ~p in node ~p ran a hook in node ~p.~n""Stop, and the NewVal is:~n~p", [self(), node(), Node, NewVal]), % debug codeNewVal;NewVal ->?INFO_MSG("~nThe process ~p in node ~p ran a hook in node ~p.~n""The NewVal is:~n~p", [self(), node(), Node, NewVal]), % debug coderun_fold1(Ls, Hook, NewVal, Args)end;
run_fold1([{_Seq, Module, Function} | Ls], Hook, Val, Args) ->Res = safe_apply(Module, Function, [Val | Args]),case Res of{'EXIT', Reason} ->?ERROR_MSG("~p~nrunning hook: ~p", [Reason, {Hook, Args}]),run_fold1(Ls, Hook, Val, Args);stop ->stopped;{stop, NewVal} ->NewVal;NewVal ->run_fold1(Ls, Hook, NewVal, Args)end.