Programming Erlang读书笔记9: 并行程序里的错误

最新推荐文章于 2022-05-14 18:54:47 发布

最新推荐文章于 2022-05-14 18:54:47 发布 · 163 阅读

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本文介绍了Erlang中进程间的连接方式及错误处理机制，包括使用BIFlink连接节点、设置进程标志trap_exit来捕获进程退出信号的方法，并提供了三种处理进程崩溃的常见模式。

使用BIF link将两个节点连接起来，如果其中一个节点B退出，则另一个节点A会收到{'EXIT', B, Why}的信号

可以创建一个on_exit(Pid, Fun)方法来捕获某个Pid进程的死掉:
[code]
on_exit(Pid, Fun) ->
spawn(fun() ->
process_flag(trap_exit, true),
link(Pid),
receive
{'EXIT', Pid, Why} ->
Fun(Why)
end
end).
[/code]

Erlang可以远程捕获和处理错误(跨机器)

调用BIF process_flag(trap_exit, true)来将一个正常的进程转换为一个可以trap exits的系统进程

[code]
trap_exit Exit Signal Action
true kill Die: Broadcast the exit signal killed to the link set.
true X Add {'EXIT', Pid, X} to the mailbox.
false normal Continue: Do-nothing signal vanishes.
false kill Die: Broadcast the exit signal killed to the link set.
false X Die: Broadcast the exit signal X to the link set.
[/code]

Idiom1: I Don't Care If a Process I Created Crashes
[code]
Pid = spawn(fun() -> ... end)
[/code]

Idiom2: I Want to Die If a Process I Created Crashes
[code]
Pid = spawn_link(fun() -> ... end)
[/code]

Idiom3: I Want to Handle Errors If a Process I Create Crashes
[code]
...
process_flag(trap_exit, true),
Pid = spawn_link(fun() -> ... end),
...
loop(...).

loop(State) ->
receive
{'EXIT', SomePid, Reason} ->
%% do something with the error
loop(State1);
...
end
[/code]

Error Handling Primitives
[code]
@spec spawn_link(Fun) -> Pid

@spec process_flag(trap_exit, true)

@spec link(Pid) -> true

@spec unlink(Pid) -> true

@spec exit(Why) -> none()

@spec exit(Pid, Why) -> true

@spec erlang:monitor(process, Item) -> MonitorRef
[/code]