[ic] Out of memory problems with Downloadable products.

[interchange-users@icdevgroup.org (Paul Jordan)]

> Quoting Nathan Pitts (npitts@cybernet.com):
> > Hello.
> >   I have recently put Interchange online as the ecommerce application
> > for my company. We are offering our software products for download,
> > available as CD-ROM ISO images.
> >   Each time that a customer attempts to download a product, the
> > webserver runs out of  memory.
> >   I have figured out what the problem is, but not how to fix it.
> >   It appears that in /usr/lib/interchange/bin/interchange, a
> download is
> > handled by a subroutine called do_deliver. This do_deliver sub
> is a call
> > to /usr/lib/interchange/lib/Vend/Util.pm->readfile and then a call
> > to /usr/lib/interchange/lib/Vend/Server.pm->respond.
> >   The problem is that Util::readfile performs a "slurp" on the file to
> > be delivered, meaning it tries to read the entire file into memory
> > before delivering it. With a 650 MB ISO image, this is not a viable
> > solution, especially considering that more than one user may be
> > downloading at 1 time.
> >   Has anyone out there used Interchange to serve large downloads? Is it
> > possible?
>
> You have to have interchange symlink in the ISO and hand it off to
> HTTP or FTP. There have been multiple examples of this on this list over
> the years.
>
> --
> Mike Heins


Mike wrote one for us Nathan. Here is the usertag:

UserTag enable-download Order resource
UserTag enable-download addAttr
UserTag enable-download Routine <<EOR
 sub {
 my ($resource, $opt) = @_;
 my $docroot = $opt->{document_root} || $::Variable->{DOCROOT};
 my $dl_dir  = $opt->{base_dir} || 'tmp_download';
 my $server  = $opt->{server}   || $::Variable->{SERVER_NAME};
 ## Routine comes from Vend::Util
 ## We will use session ID, but this would make totally random
 #my $random = random_string();

 my $random = $Vend::Session->{id};

 require File::Path;

 my $dir = "$docroot/$dl_dir/$random";

 if(-d $dir) {

 # Must have been made previously

 }

 elsif ( File::Path::mkpath($dir)
 ) {
 ## Need to ensure readable for HTTP download
 chmod 0755, $dir;
 }
 else {
 logError("Unable to make user download directory %s", $dir);
 return undef;
 }
 # Routine comes from Vend::Util
 unless ( file_name_is_absolute($resource) ) {
 $resource = "$Vend::Cfg->{VendRoot}/$resource";
 }

 # Get the base file name
 my $filebase = $resource;
 $filebase =~ s,.*/,,;
 ## Now do the symlink
 symlink $resource, "$dir/$filebase"
 or do {
 logError("Unable to symlink %s to %s", $resource, $dir);
 return undef;
 };
 ## Return the URL of the now-symlinked resource
 return "http://$server/$dl_dir/$random/$filebase";;
 }

EOR


This should be accompanied by a cron job which runs every half hour
or so:

	## Wherever that temporary base is
	BASEDIR=/var/www/html/tmp_download
	find $BASEDIR -type l -mmin +60 -exec rm '{}' ';'
	find $BASEDIR -type d -depth -mindepth 1 -empty -exec rmdir '{}' ';'


You can call the download script with:
[enable-download resource="/path/to/download/dir/[item-code].zip"]

-------------
You may have to edit up that xxx/xxx/xx/[item-code].zip to fit your needs.
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This was all written by Mike Heins, in like 4 seconds :)


Paul