将大数据写入管道时进程挂起 [英] process hangs when writing large data to pipe

问题描述

我的 Perl 程序遇到挂起进程的问题，我想我已经将其隔离到每当我将大量数据写入管道时.

I have a problem with hung processes with my Perl program, and I think I have isolated it to whenever I write significant amounts of data to a pipe.

以下是我认为与我的程序相关的所有代码.程序挂起时，挂在ResponseConstructor.pm中的一行:print { $self->{writer} } $data;.

Below is all of the code that I think is relevant from my program. When the program hangs, it hangs on the line in ResponseConstructor.pm: print { $self->{writer} } $data;.

我已经用不同的数据大小进行了测试，它似乎没有以确切的大小挂起.不过，随着大小的增加，它可能变得更有可能:大约 32KB 的大小有时有效，有时则无效.每次我尝试 110KB 字符串时，它都失败了.

I've tested with different data sizes, and it doesn't appear to hang at an exact size. It may become more likely with size, though: sizes around 32KB sometimes work, sometimes don't. Every time I've tried a 110KB string it has failed.

我相信我也排除了数据的内容作为原因，因为相同的数据有时会导致挂起，有时不会.

I believe I've also ruled out the contents of the data as a cause, because the same data sometimes causes a hang, and othertimes doesn't.

这可能是我第一次在程序中使用管道，所以我不确定接下来要尝试什么.有什么想法吗?

This is probably the first time I have used pipes in a program before, so I'm not sure what to try next. Any ideas?

use POSIX ":sys_wait_h";
STDOUT->autoflush(1);

pipe(my $pipe_reader, my $pipe_writer);
$pipe_writer->autoflush(1);
my $pid = fork;
if ($pid) {
    #I am the parent
    close $pipe_writer;
    while (waitpid(-1, WNOHANG) <= 0){
        #do some stuff while waiting for child to send data on pipe
    }
    #process the data it got
    open(my $fh, '>', "myoutfile.txt");
    while ( my $line = <$pipe_reader>){
        print $fh $line;
    }
    close $pipe_reader;
    close $fh;
else {
    #I am the child
    die "cannot fork: $!" unless defined $pid;
    close $pipe_reader;
    my $response = ResponseConstructor->new($pipe_writer);

    if ([a condition where we want to return small data]){
        $response->respond('small data');
        exit;
    }
    elsif ([a condition where we want to return big data]){
        $response->respond('imagine this is a really big string');
    }
}

ResponseConstructor.pm:

ResponseConstructor.pm:

package ResponseConstructor;

use strict;
use warnings;

sub new {
    my $class = shift;
    my $writer = shift;

    my $self = {
        writer => $writer
    };
    bless($self, $class);
    return($self);
}

#Writes the response then closes the writer (pipe)
sub respond {
    my $self = shift;
    my $data = shift;
    print { $self->{writer} } $data;
    close $self->{writer};
}


1;

推荐答案

您可能不应该在管道返回数据时忽略它:您可以在管道上使用 select(而不是waitpid) 以查看在等待循环期间是否有任何数据要读取，但是如果您真的想要更大的管道缓冲区以便可以一次读取所有数据，则可以使用 socketpair 而不是管道，然后您可以使用 setsockopt 使缓冲区尽可能大.

You probably shouldn't be ignoring your pipe while it is returning data: you can use a select on the pipe (instead of waitpid) to see if there's any data to read during your waiting loop, but if you really want a larger pipe buffer so you can read it all at once, you can use a socketpair instead of a pipe and then you can use setsockopt to make the buffer as large as you need it.

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