如果gen_server在监控树中不需要stop函数,gen_server会由其supervisor根据shutdown策略自动终止掉.如果要在进程终止之前执行清理,shutdown策略必须设定一个timeout值而不是brutal_kill并且gen_server要在init设置trap_exit.当被supervisor命令shutdown的时候,gen_server会调用terminnate(shutdown,State),特别注意: 被supervisor终止掉,终止的原因是Reason=shutdown,这个我们之前也
init(Args) ->
...,
process_flag(trap_exit, true),
...,
{ok, State}.
...
terminate(shutdown, State) ->
..code forcleaning up here..
ok.
如果gen_server不是supervisor的一部分,stop方法就很有用了:
...
export([stop/0]).
...
stop() ->
gen_server:cast(ch3, stop).
...
handle_cast(stop, State) ->
{stop, normal, State};
handle_cast({free, Ch}, State) ->
....
...
terminate(normal, State) ->
ok.
通过调用terminate方法,gen_server可以优雅的关闭掉了. 如果结束的消息不是normal,shutdowngen_server就会被认为是异常终止并通过error_logger:format/2产生错误报告.
Note: if any reason other than normal, shutdown or {shutdown, Term} is used whenterminate/2 is called, the OTP framework will see this as a failure and start logging a bunch of stuff here and there for you.