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Net-HTTP 6.06 intermittent death in Net::HTTP::Methods sub my_readline() (solved) [rt.cpan.org #86448]

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
25/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Stale
Tech stack
perl
Domain
networking

Research direction

Review Net/HTTP/Methods.pm, focusing on the my_readline() entry point and the reported failure at line 265. Compare the supplied patch with the SSL_WANT_READ and SSL_WANT_WRITE behavior described in the issue. Done means intermittent HTTPS reads no longer die when IO::Socket::SSL requests another read or write first.

Written by the indexing model from the issue text.

Description

Migrated from rt.cpan.org#86448 (status was 'new')

Requestors:

From [email protected] on 2013-06-26 15:46:52:

Description:

Net::HTTP::Methods from Net-HTTP 6.06 dies intermittently with:

Status read failed: No such file or directory at …/perl/vendor/lib/Net/HTTP/Methods.pm line 265.


Cause:

IO::Socket::SSL object can reject the read request with an error of either "SSL wants a read first" or "SSL wants a write first."  This is apparently some overhead of SSL where it wants a read/write before allowing you to read/write in some cases.  It's described somewhat (but not much) better under errstr() in the latest IO::Socket::SSL perldoc.


Reproducing:

I'm not sure how hard this is to reproduce since triggers are unknown.  I'm accessing cloud based SOAP via SOAP::WSDL over https from a busy server and it occurs maybe one out of a dozen times.  It seems to correlate with SSL taking an extra bit of time to setup the connection when something in the chain is busier or has a little latency.  Thus far, I've only seen SSL_WANT_READ, and it clears immediately on the next redo READ, but there seems to be no harm in preparing for SSL_WANT_WRITE in the patch as well.


Patch:

--- broken/Net/HTTP/Methods.pm    2013-03-10 23:35:42.000000000 -0500
+++ fixed/Net/HTTP/Methods.pm 2013-06-26 10:12:37.205639200 -0500
@@ -243,40 +243,41 @@
 sub my_readline {
     my $self = shift;
     my $what = shift;
     for (${*$self}{'http_buf'}) {
        my $max_line_length = ${*$self}{'http_max_line_length'};
        my $pos;
        while (1) {
            # find line ending
            $pos = index($_, "\012");
            last if $pos >= 0;
            die "$what line too long (limit is $max_line_length)"
                if $max_line_length && length($_) > $max_line_length;

            # need to read more data to find a line ending
           READ:
             {
                 die "read timeout" unless $self->can_read;
                 my $n = $self->sysread($_, 1024, length);
                 unless (defined $n) {
                     redo READ if $!{EINTR} || $!{EAGAIN};
+                    redo READ if ( $self->isa('IO::Socket::SSL') && $self->errstr() =~ /^SSL wants a (?:read|write) first$/ );
                     # if we have already accumulated some data let's at least
                     # return that as a line
                     die "$what read failed: $!" unless length;
                 }
                 unless ($n) {
                     return undef unless length;
                     return substr($_, 0, length, "");
                 }
             }
        }
        die "$what line too long ($pos; limit is $max_line_length)"
            if $max_line_length && $pos > $max_line_length;

        my $line = substr($_, 0, $pos+1, "");
        $line =~ s/(\015?\012)\z// || die "Assert";
        return wantarray ? ($line, $1) : $line;
     }
 }


Thanks for your time and your code.

--

Raymond Ferguson

Integrated Applications Engineer  | CDW
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