[erlang-bugs] Freeze in re:run

[Éric Pailleau]

Hi,

Your regexp is compiled at each call.
Your should compile it in your shell and set it in your code by a define.
It is probably not your problem, but it should increase perfs...
Regards

Le 22 mai 2015 00:42, Miroslav Urbanek <mu@REDACTED> a écrit :
>
> Hi, 
>
> I'm using Erlang 17.5 and I'm experiencing freezes in re:run that take 
> tens of seconds. I've isolated the problematic part into the following 
> code: 
>
> ---- 
> #!/usr/bin/env escript 
>
> log(Term) -> 
>     {_ , {Hour, Minute, Second}} = calendar:now_to_universal_time(os:timestamp()), 
>     io:format("~2..0w:~2..0w:~2..0w ~p~n", [Hour, Minute, Second, Term]). 
>
> test(Filename) -> 
>     {ok, IoDevice} = file:open(Filename, [binary, read]), 
>     {ok, Data} = file:read(IoDevice, 1048576), 
>     Regexp = "(?i)(?m)(?s)(?U)(?<=\n)--(?|.*^content-disposition:(?:(?!\n\\S).)*filename=\"[^\"]*\\.([^\".]*)\".*|.*^content-type:(?:(?!\n\\S).)*name=\"[^\"]*\\.([^\".]*)\").*\n\n", 
>     re:run(Data, Regexp, [report_errors]). 
>
> main([Filename]) -> 
>     spawn_link(fun Fun() -> 
>                        log(heartbeat), 
>                        timer:sleep(1000), 
>                        Fun() 
>                end), 
>     log(test(Filename)). 
> ---- 
>
> Processing the complex regexp above takes about 50 seconds for my test 
> data. Sometimes, the whole Erlang VM freezes for several seconds. The 
> output then looks like this: 
>
> ---- 
> $ ./test.erl test.eml 
> 18:27:48 heartbeat 
> 18:27:49 heartbeat 
> 18:27:50 heartbeat 
> 18:27:51 heartbeat 
> 18:27:52 heartbeat 
> 18:27:53 heartbeat 
> 18:27:54 heartbeat 
> 18:27:55 heartbeat 
> 18:27:56 heartbeat 
> 18:27:57 heartbeat 
> 18:27:58 heartbeat 
> 18:27:59 heartbeat 
> 18:28:00 heartbeat 
> 18:28:01 heartbeat 
> 18:28:02 heartbeat 
> 18:28:03 heartbeat 
> 18:28:04 heartbeat 
> 18:28:05 heartbeat 
> 18:28:06 heartbeat 
> 18:28:07 heartbeat 
> 18:28:08 heartbeat 
> 18:28:36 heartbeat 
> 18:28:36 nomatch 
> ---- 
>
> The VM froze between 18:28:08 and 18:28:36. The manual page re(3) 
> states that "re:run always give control back to the scheduler of 
> Erlang processes at intervals that ensures the real time properties of 
> the Erlang system". I believe this is a bug, because re:run clearly 
> didn't give control back to the scheduler during the interval above. 
>
> Why does it happen? Is there any option to limit the number of time VM 
> spends in re:run? 
>
> The program and the data file can be downloaded here: 
>
> http://miroslavurbanek.com/re.tgz 
>
> Thanks, 
> Miro 
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