用redis管理nitrogen中的session
nitrogen使用中session问题nitrogen中的session在集群情况下会找不到，经常会出现重新登录情况，试图修改成为mnesia管理session,在节点超过一定数量时mnesia同步机制会出现同步慢的问题，为此决定再次修改为redis来管理session。
修改为redis管理session
1 在nitrogen中调用wf:session/2设置session时调用了session_handler:set_value/2,回调behaviour (session_handler),wf_handler:call/3，这里实现了一个简单的session_handler，只要实现自己的session_handler行为，就可以了，在wf:context中会配置具体调用哪些handler,只要修改make_handler(session_handler, simple_session_handler), %simple_session_handler), 为自己的实现即可。
2 我实现的redis_session_handler
% Copyright (c) 2008-2010 Rusty Klophaus
% See MIT-LICENSE for licensing information.
% This is a "simple as possible" session handler. Unfortunately,
% due to time constraints, had to leave out some great code
% contributed by Dave Peticolas that fit Nitrogen sessions
% into a gen_server. My code below is far inferior.
% Someone please make it better! - Rusty
-module (redis_session_handler).
-include_lib ("wf.hrl").
-behaviour (session_handler).
-export ([
init/2,
finish/2,
get_value/4,
set_value/4,
clear_all/2
]).
-record (state, {unique}).
init(_Config, _State) ->
Cookie = wf:cookie(get_cookie_name()),
State = case wf:depickle(Cookie) of
undefined -> new_state();
Other -> Other
end,
{ok, State}.
finish(_Config, State) ->
% Drop the session cookie...
Timeout = wf:config_default(session_timeout, 20),
ok = wf:cookie(get_cookie_name(), wf:pickle(State), "/", Timeout),
{ok, []}.
get_value(Key, DefaultValue, _Config, State) ->
%Host = wf:config_default(erldis_host, "127.0.0.1"),
%Port = wf:config_default(erldis_port, 6379),
%{ok, Client} = erldis:connect(Host, Port),
%io:format("~p",[?LINE]),
%io:format("get_value, Key = ~p~n",),
Client = erldis_sup:client(),
Value = case erldis:hget(Client, State#state.unique, Key) of
nil ->
DefaultValue;
Any ->
binary_to_term(Any)
end,
%io:format("get_value, Key = ~p, Value = ~p~n",),
Timeout = wf:config_default(session_timeout, 20),
erldis:expire(Client, State#state.unique, Timeout*60),
{ok, Value, State}.
set_value(Key, Value, _Config, State) ->
%io:format("set_value, Key = ~p, Value = ~p~n",),
Client = erldis_sup:client(),
OldValue = case erldis:hget(Client, State#state.unique, Key) of
nil ->
undefined;
Any ->
binary_to_term(Any)
end,
%io:format("~p",[?LINE]),
%io:format("OldValue = ~n~p~n",),
erldis:hset(Client, State#state.unique, Key, term_to_binary(Value)),
Timeout = wf:config_default(session_timeout, 20),
erldis:expire(Client, State#state.unique, Timeout*60),
{ok, OldValue, State}.
clear_all(_Config, State) ->
Client = erldis_sup:client(),
case erldis:del(Client, State#state.unique) of
nil ->
undefined;
Any ->
%io:format("~p",[?LINE]),
%io:format("~n~p~n",),
Any
end,
{ok, State}.
%%% PRIVATE FUNCTIONS
get_cookie_name() ->
wf:config_default(cookie_name, "lxbssn").
new_state() ->
Unique = erlang:md5(term_to_binary({now(), erlang:make_ref()})),
#state { unique=Unique }.
3 在上面代码中我使用了erldis作为redis的erlang客户端，经测试未发现问题，很稳定。
4 问题： 以上代码实现中查阅过redis手册，想找到类似 setex直接设置过期时间的命令，但没有找到，用hash 实现是为了节省内存与方便管理，如有更好解决方案大家回复交流。
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