Erlang：主管（3），添加一个子进程 [英] Erlang: supervisor(3), adding a child process
问题描述
在哪里可以找到关于如何向现有主管添加动态子进程的示例（ simple_one_for_one 重新启动策略）？
Where can I find example on how to add dynamic child processes to an existing supervisor (simple_one_for_one restart strategy) ?
推荐答案
我做了一些研究，下面是我的内容。
I did some research, and below is what I have.
是一个主管的示例回调模块：
First, this is a sample callback module of a supervisor:
-module(root_sup).
-behaviour(supervisor).
-export([start_link/0]).
-export([init/1]).
start_link() ->
{ok, Pid} = supervisor:start_link({local, ?MODULE},
?MODULE, []),
{ok, Pid}.
init(_Args) ->
RestartStrategy = {simple_one_for_one, 10, 60},
ChildSpec = {ch1, {ch1, start_link, []},
permanent, brutal_kill, worker, [ch1]},
Children = [ChildSpec],
{ok, {RestartStrategy, Children}}.
这是一个孩子的回调模块，将动态添加到supronvision树中： p>
And this is a callback module of a child which will be added to the suprervision tree dynamically:
-module(ch1).
-behaviour(gen_server).
% Callback functions which should be exported
-export([init/1]).
-export([handle_cast/2]).
% user-defined interface functions
-export([start_link/0]).
start_link() ->
gen_server:start_link(?MODULE, [], []).
init(_Args) ->
io:format("ch1 has started (~w)~n", [self()]),
% If the initialization is successful, the function
% should return {ok,State}, {ok,State,Timeout} ..
{ok, ch1State}.
handle_cast(calc, State) ->
io:format("result 2+2=4~n"),
{noreply, State};
handle_cast(calcbad, State) ->
io:format("result 1/0~n"),
1 / 0,
{noreply, State}.
这是我们通常启动主管的方式：
This is how we usually start the supervisor:
1> ch_sup:start_link().
{ok,<0.33.0>}
现在开始我们的第一个子进程：
Now let's start our first child process:
2> {ok, Child1Pid} = supervisor:start_child(ch_sup, []).
ch1 has started (<0.35.0>)
{ok,<0.35.0>}
您可以动态地启动子进程;让我们开始另一个孩子：
You can dynamically start child processes; let's start another child:
3> {ok, Child2Pid} = supervisor:start_child(ch_sup, []).
ch1 has started (<0.37.0>)
{ok,<0.37.0>}
您可能会看到我们的流程已经开始了（注意最后两个）：
You may see that our processes did start (note the last two):
4> erlang:processes().
[<0.0.0>,<0.2.0>,<0.4.0>,<0.5.0>,<0.7.0>,<0.8.0>,<0.9.0>,
<0.10.0>,<0.11.0>,<0.12.0>,<0.13.0>,<0.14.0>,<0.15.0>,
<0.16.0>,<0.17.0>,<0.18.0>,<0.19.0>,<0.20.0>,<0.21.0>,
<0.22.0>,<0.23.0>,<0.24.0>,<0.25.0>,<0.26.0>,<0.27.0>,
<0.31.0>,<0.33.0>,<0.35.0>,<0.37.0>]
现在让我们的第一个孩子进程做一些事情：
Now let's make our first child process do something:
5> gen_server:cast(Child1Pid, calc).
result 2+2=4
ok
到目前为止，这么好。现在我们让我们的第一个孩子评估一些坏的代码：
So far, so good. Now we'll make our first child to evaluate some bad code:
6> gen_server:cast(Child1Pid, calcbad).
result 1/0
ok
7>
=ERROR REPORT==== 10-Feb-2011::01:32:15 ===
** Generic server <0.35.0> terminating
** Last message in was {'$gen_cast',calcbad}
** When Server state == ch1State
** Reason for termination ==
** {'function not exported',
[{ch1,terminate,
[{badarith,
[{ch1,handle_cast,2},
{gen_server,handle_msg,5},
{proc_lib,init_p_do_apply,3}]},
ch1State]},
{gen_server,terminate,6},
{proc_lib,init_p_do_apply,3}]}
ch1 has started (<0.42.0>)
7>
在报告中，您可能会看到除以零导致异常，并且进程终止。但是主管会照顾它，并立即启动另一个子进程（请注意最后一行）。
In the report, you may see that the division by zero caused an exception and the process was terminated. But the supervisor takes care of it and immediately starts another child process (note the last line).
我们可以检查以确保我们以前启动的其他子进程是仍然存在（注意< 0.37.0> ）：
We can check to make sure that the other child process we started previously is still alive (note <0.37.0>):
7> erlang:processes().
[<0.0.0>,<0.2.0>,<0.4.0>,<0.5.0>,<0.7.0>,<0.8.0>,<0.9.0>,
<0.10.0>,<0.11.0>,<0.12.0>,<0.13.0>,<0.14.0>,<0.15.0>,
<0.16.0>,<0.17.0>,<0.18.0>,<0.19.0>,<0.20.0>,<0.21.0>,
<0.22.0>,<0.23.0>,<0.24.0>,<0.25.0>,<0.26.0>,<0.27.0>,
<0.31.0>,<0.33.0>,<0.37.0>,<0.42.0>]
8>
我们甚至可以为我们做点事情：
We can even make it do something for us:
8> gen_server:cast(Child2Pid, calc).
result 2+2=4
9>
以下是Erlang手册页面想要阅读：
The following are the Erlang manual pages you'll want to read:
- Supervisor Behaviour
- supervisor(3)
- gen_server(3)
这篇关于Erlang：主管（3），添加一个子进程的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
