extmsg: prevent cross-inbox matches from hogging event loop

With many inboxes, checking multiple SQLite repos will be slow
and time-consuming, so ensure we can schedule it fairly between
multiple inboxes.

diff --git a/lib/PublicInbox/ExtMsg.pm b/lib/PublicInbox/ExtMsg.pm
index 929737f1b9d1961f4c63f556c313494df0db90fb..ce1a47bb84fd70da06e617dd0d1ee34a2e409b99 100644 (file)
--- a/lib/PublicInbox/ExtMsg.pm
+++ b/lib/PublicInbox/ExtMsg.pm
@@ -74,69 +74,106 @@ sub search_partial ($$) {
 }
 
 sub ext_msg_i {
-       my ($other, $cur, $mid, $ibxs, $found) = @_;
+       my ($other, $ctx) = @_;
 
-       return if $other->{name} eq $cur->{name} || !$other->base_url;
+       return if $other->{name} eq $ctx->{-inbox}->{name} || !$other->base_url;
 
        my $mm = $other->mm or return;
 
        # try to find the URL with Msgmap to avoid forking
-       my $num = $mm->num_for($mid);
+       my $num = $mm->num_for($ctx->{mid});
        if (defined $num) {
-               push @$found, $other;
+               push @{$ctx->{found}}, $other;
        } else {
                # no point in trying the fork fallback if we
                # know Xapian is up-to-date but missing the
                # message in the current repo
-               push @$ibxs, $other;
+               push @{$ctx->{again}}, $other;
+       }
+}
+
+sub ext_msg_step {
+       my ($pi_cfg, $section, $ctx) = @_;
+       if (defined($section)) {
+               return if $section !~ m!\Apublicinbox\.([^/]+)\z!;
+               my $ibx = $pi_cfg->lookup_name($1) or return;
+               ext_msg_i($ibx, $ctx);
+       } else { # undef == "EOF"
+               finalize_exact($ctx);
        }
 }
 
 sub ext_msg {
        my ($ctx) = @_;
-       my $cur = $ctx->{-inbox};
-       my $mid = $ctx->{mid};
+       sub {
+               $ctx->{-wcb} = $_[0]; # HTTP server write callback
+
+               if ($ctx->{env}->{'pi-httpd.async'}) {
+                       require PublicInbox::ConfigIter;
+                       my $iter = PublicInbox::ConfigIter->new(
+                                               $ctx->{www}->{pi_config},
+                                               \&ext_msg_step, $ctx);
+                       $iter->event_step;
+               } else {
+                       $ctx->{www}->{pi_config}->each_inbox(\&ext_msg_i, $ctx);
+                       finalize_exact($ctx);
+               }
+       };
+}
 
-       eval { require PublicInbox::Msgmap };
-       my $ibxs = [];
-       my $found = [];
+# called via PublicInbox::DS->EventLoop
+sub event_step {
+       my ($ctx, $sync) = @_;
+       # can't find a partial match in current inbox, try the others:
+       my $ibx = shift @{$ctx->{again}} or goto \&finalize_partial;
+       my $mids = search_partial($ibx, $ctx->{mid}) or
+                       return ($sync ? undef : PublicInbox::DS::requeue($ctx));
+       $ctx->{n_partial} += scalar(@$mids);
+       push @{$ctx->{partial}}, [ $ibx, $mids ];
+       $ctx->{n_partial} >= PARTIAL_MAX ? goto(\&finalize_partial)
+                       : ($sync ? undef : PublicInbox::DS::requeue($ctx));
+}
 
-       $ctx->{www}->{pi_config}->each_inbox(\&ext_msg_i,
-                                               $cur, $mid, $ibxs, $found);
+sub finalize_exact {
+       my ($ctx) = @_;
 
-       return exact($ctx, $found, $mid) if @$found;
+       return $ctx->{-wcb}->(exact($ctx)) if $ctx->{found};
 
        # fall back to partial MID matching
-       my @partial;
-       my $n_partial = 0;
+       my $mid = $ctx->{mid};
+       my $cur = $ctx->{-inbox};
        my $mids = search_partial($cur, $mid);
        if ($mids) {
-               $n_partial = scalar(@$mids);
-               push @partial, [ $cur, $mids ];
-       }
-
-       # can't find a partial match in current inbox, try the others:
-       if (!$n_partial && length($mid) >= $MIN_PARTIAL_LEN) {
-               foreach my $ibx (@$ibxs) {
-                       $mids = search_partial($ibx, $mid) or next;
-                       $n_partial += scalar(@$mids);
-                       push @partial, [ $ibx, $mids];
-                       last if $n_partial >= PARTIAL_MAX;
+               $ctx->{n_partial} = scalar(@$mids);
+               push @{$ctx->{partial}}, [ $cur, $mids ];
+       } elsif ($ctx->{again} && length($mid) >= $MIN_PARTIAL_LEN) {
+               bless $ctx, __PACKAGE__;
+               if ($ctx->{env}->{'pi-httpd.async'}) {
+                       $ctx->event_step;
+                       return;
                }
+
+               # synchronous fall-through
+               $ctx->event_step while @{$ctx->{again}};
        }
+       goto \&finalize_partial;
+}
 
+sub finalize_partial {
+       my ($ctx) = @_;
+       my $mid = $ctx->{mid};
        my $code = 404;
        my $href = mid_href($mid);
        my $html = ascii_html($mid);
        my $title = "<$html> not found";
        my $s = "<pre>Message-ID &lt;$html&gt;\nnot found\n";
-       if ($n_partial) {
+       if (my $n_partial = $ctx->{n_partial}) {
                $code = 300;
                my $es = $n_partial == 1 ? '' : 'es';
                $n_partial .= '+' if ($n_partial == PARTIAL_MAX);
                $s .= "\n$n_partial partial match$es found:\n\n";
-               my $cur_name = $cur->{name};
-               foreach my $pair (@partial) {
+               my $cur_name = $ctx->{-inbox}->{name};
+               foreach my $pair (@{$ctx->{partial}}) {
                        my ($ibx, $res) = @$pair;
                        my $env = $ctx->{env} if $ibx->{name} eq $cur_name;
                        my $u = $ibx->base_url($env) or next;
@@ -155,7 +192,7 @@ sub ext_msg {
        $ctx->{-html_tip} = $s .= '</pre>';
        $ctx->{-title_html} = $title;
        $ctx->{-upfx} = '../';
-       html_oneshot($ctx, $code);
+       $ctx->{-wcb}->(html_oneshot($ctx, $code));
 }
 
 sub ext_urls {
@@ -177,7 +214,9 @@ sub ext_urls {
 }
 
 sub exact {
-       my ($ctx, $found, $mid) = @_;
+       my ($ctx) = @_;
+       my $mid = $ctx->{mid};
+       my $found = $ctx->{found};
        my $href = mid_href($mid);
        my $html = ascii_html($mid);
        my $title = "&lt;$html&gt; found in ";