erlang - 用户断开连接时的 ejabberd 在线状态

Question

我将 ejabberd 设置为移动应用程序之间的 xmpp 服务器，即。自定义 iPhone 和 Android 应用程序。

但我似乎遇到了 ejabberd 处理在线状态的方式的限制。

设想:

用户 A 正在通过他们的手机向用户 B 发送消息。

用户 B 失去所有连接，因此客户端无法与服务器断开连接。

ejabberd 仍将用户 B 列为在线。

由于 ejabberd 假定用户 B 仍然在线，因此来自用户 A 的任何消息都会传递到死连接。

因此，用户 B 不会收到消息，也不会将其保存为离线消息，因为 ejabberd 假定用户在线。

消息丢失。

直到 ejabberd 意识到连接已过时，它才会将其视为在线用户。

再加上数据连接的变化(wifi 到 3G 到 4G 到……)，你会发现这种情况经常发生。

mod_ping:

我尝试以 10 秒的间隔实现 mod_ping。
https://www.process-one.net/docs/ejabberd/guide_en.html#modping
但正如文档所述，ping 将在断开用户连接之前等待 32 秒的响应。
这意味着将有一个 42 秒的窗口，用户可能会丢失他们的消息。

理想解决方案:

即使可以减少 ping 等待时间，它仍然不是一个完美的解决方案。
有没有办法让 ejabberd 在丢弃消息之前等待来自客户端的 200 响应？如果没有响应，则离线保存。
是否可以编写一个钩子(Hook)来解决这个问题？
还是我在某个地方错过了一个简单的设置？

仅供引用:我没有使用 BOSH。

Answer 1

这是我写的解决我的问题的mod。

为了使其工作，您需要在客户端激活收据，并且客户端应该能够处理重复的消息。

首先，我创建了一个名为 confirm_delivery 的表。我将每条“聊天”消息都保存到该表中。我设置了一个 10 秒的计时器，如果我收到确认回复，我会删除表条目。

如果我没有收到确认回复，我会手动将消息保存到 offline_msg 表并尝试重新发送(这可能超出顶部，但由您决定)，然后将其从我们的 confirm_delivery 表中删除

我已经删除了所有我认为不必要的代码，所以我希望它仍然可以编译。

希望这对其他 ejabberd 开发人员有帮助!

https://github.com/johanvorster/ejabberd_confirm_delivery.git

%% name of module must match file name
-module(mod_confirm_delivery).

-author("Johan Vorster").

%% Every ejabberd module implements the gen_mod behavior
%% The gen_mod behavior requires two functions: start/2 and stop/1
-behaviour(gen_mod).

%% public methods for this module
-export([start/2, stop/1, send_packet/3, receive_packet/4, get_session/5, set_offline_message/5]).

%% included for writing to ejabberd log file
-include("ejabberd.hrl").

-record(session, {sid, usr, us, priority, info}).
-record(offline_msg, {us, timestamp, expire, from, to, packet}).

-record(confirm_delivery, {messageid, timerref}).

start(_Host, _Opt) -> 

        ?INFO_MSG("mod_confirm_delivery loading", []),
        mnesia:create_table(confirm_delivery, 
            [{attributes, record_info(fields, confirm_delivery)}]),
        mnesia:clear_table(confirm_delivery),
        ?INFO_MSG("created timer ref table", []),

        ?INFO_MSG("start user_send_packet hook", []),
        ejabberd_hooks:add(user_send_packet, _Host, ?MODULE, send_packet, 50),   
        ?INFO_MSG("start user_receive_packet hook", []),
        ejabberd_hooks:add(user_receive_packet, _Host, ?MODULE, receive_packet, 50).   

stop(_Host) -> 
        ?INFO_MSG("stopping mod_confirm_delivery", []),
        ejabberd_hooks:delete(user_send_packet, _Host, ?MODULE, send_packet, 50),
        ejabberd_hooks:delete(user_receive_packet, _Host, ?MODULE, receive_packet, 50). 

send_packet(From, To, Packet) ->    
    ?INFO_MSG("send_packet FromJID ~p ToJID ~p Packet ~p~n",[From, To, Packet]),

    Type = xml:get_tag_attr_s("type", Packet),
    ?INFO_MSG("Message Type ~p~n",[Type]),

    Body = xml:get_path_s(Packet, [{elem, "body"}, cdata]), 
    ?INFO_MSG("Message Body ~p~n",[Body]),

    MessageId = xml:get_tag_attr_s("id", Packet),
    ?INFO_MSG("send_packet MessageId ~p~n",[MessageId]), 

    LUser = element(2, To),
    ?INFO_MSG("send_packet LUser ~p~n",[LUser]), 

    LServer = element(3, To), 
    ?INFO_MSG("send_packet LServer ~p~n",[LServer]), 

    Sessions = mnesia:dirty_index_read(session, {LUser, LServer}, #session.us),
    ?INFO_MSG("Session: ~p~n",[Sessions]),

    case Type =:= "chat" andalso Body =/= [] andalso Sessions =/= [] of
        true ->                

        {ok, Ref} = timer:apply_after(10000, mod_confirm_delivery, get_session, [LUser, LServer, From, To, Packet]),

        ?INFO_MSG("Saving To ~p Ref ~p~n",[MessageId, Ref]),

        F = fun() ->
            mnesia:write(#confirm_delivery{messageid=MessageId, timerref=Ref})
        end,

        mnesia:transaction(F);

    _ ->
        ok
    end.   

receive_packet(_JID, From, To, Packet) ->
    ?INFO_MSG("receive_packet JID: ~p From: ~p To: ~p Packet: ~p~n",[_JID, From, To, Packet]), 

    Received = xml:get_subtag(Packet, "received"), 
    ?INFO_MSG("receive_packet Received Tag ~p~n",[Received]),    

    if Received =/= false andalso Received =/= [] ->
        MessageId = xml:get_tag_attr_s("id", Received),
        ?INFO_MSG("receive_packet MessageId ~p~n",[MessageId]);       
    true ->
        MessageId = []
    end, 

    if MessageId =/= [] ->
        Record = mnesia:dirty_read(confirm_delivery, MessageId),
        ?INFO_MSG("receive_packet Record: ~p~n",[Record]);       
    true ->
        Record = []
    end, 

    if Record =/= [] ->
        [R] = Record,
        ?INFO_MSG("receive_packet Record Elements ~p~n",[R]), 

        Ref = element(3, R),

        ?INFO_MSG("receive_packet Cancel Timer ~p~n",[Ref]), 
        timer:cancel(Ref),

        mnesia:dirty_delete(confirm_delivery, MessageId),
        ?INFO_MSG("confirm_delivery clean up",[]);     
    true ->
        ok
    end.


get_session(User, Server, From, To, Packet) ->   
    ?INFO_MSG("get_session User: ~p Server: ~p From: ~p To ~p Packet ~p~n",[User, Server, From, To, Packet]),   

    ejabberd_router:route(From, To, Packet),
    ?INFO_MSG("Resend message",[]),

    set_offline_message(User, Server, From, To, Packet),
    ?INFO_MSG("Set offline message",[]),

    MessageId = xml:get_tag_attr_s("id", Packet), 
    ?INFO_MSG("get_session MessageId ~p~n",[MessageId]),    

    case MessageId =/= [] of
        true ->        

        mnesia:dirty_delete(confirm_delivery, MessageId),
        ?INFO_MSG("confirm_delivery clean up",[]);

     _ ->
        ok
    end.

set_offline_message(User, Server, From, To, Packet) ->
    ?INFO_MSG("set_offline_message User: ~p Server: ~p From: ~p To ~p Packet ~p~n",[User, Server, From, To, Packet]),    

    F = fun() ->
        mnesia:write(#offline_msg{us = {User, Server}, timestamp = now(), expire = "never", from = From, to = To, packet = Packet})
    end,

    mnesia:transaction(F).