Bug 1073264 - allow attachment download to be offloaded to the webserver using…

Bugzilla/Attachment.pm

@@ -308,7 +308,8 @@ sub is_viewable {
 
 =item C<data>
 
-the content of the attachment
+Returns the content of the attachment.
+As a side-effect, sets $self->is_on_filesystem.
 
 =back
 
@@ -325,10 +326,16 @@ sub data {
                                                      undef,
                                                      $self->id);
 
+    # Setting the property here is cheap, as opposed to making an extra
+    # query later, and hitting the filesystem to see if the file is
+    # still there.
+    $self->{is_on_filesystem} = 0;
     # If there's no attachment data in the database, the attachment is stored
     # in a local file, so retrieve it from there.
     if (length($self->{data}) == 0) {
         if (open(AH, $self->_get_local_filename())) {
+            # file is actually on disk.
+            $self->{is_on_filesystem} = 1;
             local $/;
             binmode AH;
             $self->{data} = <AH>;
@@ -341,9 +348,36 @@ sub data {
 
 =over
 
+=item C<is_on_filesystem>
+
+Returns true if the attachment is stored on disk (via maxlocalattachment
+parameter), as opposed to in the database.
+
+=back
+
+=cut
+
+# When the attachment is on the filesystem, you can let the backend
+# (nginx, apache, lighttpd) serve it for you if it supports the X-Sendfile
+# feature. This means that the attachment CGI script may have a reduced
+# footprint. e.g. bug 906010 and bug 1073241.
+
+sub is_on_filesystem {
+    my $self = shift;
+    return $self->{is_on_filesystem} if exists $self->{is_on_filesystem};
+    # In order to serve an attachment, you also send the datasize in the
+    # content-length header. Making additional queries which are exactly
+    # the same as found in the datasize code path is just wasteful.
+    my $datasize = $self->datasize;
+    return $self->{is_on_filesystem};
+}
+
+=over
+
 =item C<datasize>
 
-the length (in bytes) of the attachment content
+Returns the length (in bytes) of the attachment content.
+As a side-effect, sets $self->is_on_filesystem.
 
 =back
 
@@ -370,11 +404,17 @@ sub datasize {
                                         WHERE id = ?",
                                        undef, $self->id) || 0;
 
+    # Setting the property here is cheap, as opposed to making an extra
+    # query later, and hitting the filesystem to see if the file is
+    # still there.
+    $self->{is_on_filesystem} = 0;
     # If there's no attachment data in the database, either the attachment
     # is stored in a local file, and so retrieve its size from the file,
     # or the attachment has been deleted.
     unless ($self->{datasize}) {
         if (open(AH, $self->_get_local_filename())) {
+            # file is actually on disk.
+            $self->{is_on_filesystem} = 1;
             binmode AH;
             $self->{datasize} = (stat(AH))[7];
             close(AH);

Bugzilla/Config/Attachment.pm

@@ -38,6 +38,14 @@ sub get_param_list {
   },
 
   {
+  name => 'xsendfile_header',
+  type => 's',
+  choices => ['off', 'X-Sendfile', 'X-Accel-Redirect', 'X-LIGHTTPD-send-file'],
+  default => 'off',
+  checker => \&check_multi
+  },
+
+  {
    name => 'maxattachmentsize',
    type => 't',
    default => '1000',

attachment.cgi

@@ -26,6 +26,7 @@ use Bugzilla::Attachment::PatchReader;
 use Bugzilla::Token;
 
 use Encode qw(encode find_encoding);
+use Cwd qw(realpath);
 
 # For most scripts we don't make $cgi and $template global variables. But
 # when preparing Bugzilla for mod_perl, this script used these
@@ -361,9 +362,24 @@ sub view {
             }
         }
     }
+    my $sendfile_header = {};
+    my $sendfile_param = Bugzilla->params->{'xsendfile_header'};
+    if ($attachment->is_on_filesystem && $sendfile_param ne 'off') {
+        # attachment is on filesystem and Admin turned on feature.
+        # This means we can let webserver handle the request and stream the file
+        # for us. This is called the X-Sendfile feature. see bug 1073264.
+        my $attachment_path = realpath($attachment->_get_local_filename());
+        $sendfile_header->{$sendfile_param} = $attachment_path;
+    }
     print $cgi->header(-type=>"$contenttype; name=\"$filename\"",
                        -content_disposition=> "$disposition; filename=\"$filename\"",
-                       -content_length => $attachment->datasize);
+                       -content_length => $attachment->datasize,
+                       %$sendfile_header);
+    if ($attachment->is_on_filesystem && $sendfile_param ne 'off') {
+        # in case of X-Sendfile, we do not print the data.
+        # that is handled directly by the webserver.
+        return;
+    }
     disable_utf8();
     print $attachment->data;
 }

template/en/default/admin/params/attachment.html.tmpl

@@ -58,5 +58,31 @@
   maxlocalattachment => "The maximum size (in megabytes) of attachments to be stored " _
                         "locally on the web server. If set to a value lower than the " _
                         "<a href=\"#maxattachmentsize\"><var>maxattachmentsize</var> parameter</a>, " _
-                        "attachments will never be kept on the local filesystem." }
+                        "attachments will never be kept on the local filesystem. " _
+                        "If you want to store all attachments on disk rather than in the " _
+                        "database, then set <a href=\"#maxattachmentsize\">" _
+                        "<var>maxattachmentsize</var> parameter</a> to 0. ",
+
+
+  xsendfile_header =>
+    "By default, attachments are served by the CGI script. " _
+    "If you enable filesystem file storage for large files using the " _
+    "<a href=\"#maxlocalattachment\"><var>maxlocalattachment</var> parameter</a> " _
+    "then you can have those files served directly by the webserver, which " _
+    "avoids copying them entirely into memory, and this may result in a " _
+    "performance improvement. To do this, configure your webserver appropriately " _
+    "and then set the correct header, as follows:" _
+    "<ul>" _
+    "<li>Apache: <code>X-Sendfile</code> header; see " _
+    "<code><a href=\"https://tn123.org/mod_xsendfile/\">mod_xsendfile</a></code> module</li>" _
+    "<li>nginx: <code>X-Accel-Redirect</code> header; see "_
+    "<a href=\"http://wiki.nginx.org/X-accel\">webserver documentation</a> for additional configuration</li>" _
+    "<li>lighttpd: <code>X-LIGHTTPD-send-file</code> header; see " _
+    "<a href=\"http://redmine.lighttpd.net/projects/1/wiki/X-LIGHTTPD-send-file\">webserver documentation</a> for additional configuration</li>" _
+    "</ul><br>" _
+    "Please note that attachments stored in the database cannot be offloaded " _
+    "to apache/nginx/lighttpd and are always handled by the CGI script."
+
+  }
+
 %]