remove hard Devel::Peek dependency and lazy load for daemons

It's only useful for a corner case in long-running daemons when
an admin decides to compact or vacuum a Xapian or SQLite DB.

As a result, other scripts should run slightly faster.  For
instance, this saves about 80ms (2.710s => 2.630s) in t/mda.t
on my remote workstation.

While we're at it, make sure EvCleanup is properly require'd
in Daemon.pm and HTTP.pm and document our use of Devel::Peek.

1 files changed, 32 insertions, 13 deletions

diff --git a/lib/PublicInbox/Inbox.pm b/lib/PublicInbox/Inbox.pm
index 76aeefbd..0b118b28 100644
--- a/lib/PublicInbox/Inbox.pm
+++ b/lib/PublicInbox/Inbox.pm
@@ -7,25 +7,30 @@ use strict;
 use warnings;
 use PublicInbox::Git;
 use PublicInbox::MID qw(mid2path);
-use Devel::Peek qw(SvREFCNT);
 use PublicInbox::MIME;
 
+# Long-running "git-cat-file --batch" processes won't notice
+# unlinked packs, so we need to restart those processes occasionally.
+# Xapian and SQLite file handles are mostly stable, but sometimes an
+# admin will attempt to replace them atomically after compact/vacuum
+# and we need to be prepared for that.
 my $cleanup_timer;
-eval {
-        $cleanup_timer = 'disabled';
-        require PublicInbox::EvCleanup;
-        $cleanup_timer = undef; # OK if we get here
-};
-my $cleanup_broken = $@;
-
+my $cleanup_avail = -1; # 0, or 1
+my $have_devel_peek;
 my $CLEANUP = {}; # string(inbox) -> inbox
 sub cleanup_task () {
         $cleanup_timer = undef;
         my $next = {};
         for my $ibx (values %$CLEANUP) {
                 my $again;
-                foreach my $f (qw(mm search)) {
-                        delete $ibx->{$f} if SvREFCNT($ibx->{$f}) == 1;
+                if ($have_devel_peek) {
+                        foreach my $f (qw(mm search)) {
+                                # we bump refcnt by assigning tmp, here:
+                                my $tmp = $ibx->{$f} or next;
+                                next if Devel::Peek::SvREFCNT($tmp) > 2;
+                                delete $ibx->{$f};
+                                # refcnt is zero when tmp is out-of-scope
+                        }
                 }
                 my $expire = time - 60;
                 if (my $git = $ibx->{git}) {
@@ -36,16 +41,30 @@ sub cleanup_task () {
                                 $again = 1 if $git->cleanup($expire);
                         }
                 }
-                $again ||= !!($ibx->{mm} || $ibx->{search});
+                if ($have_devel_peek) {
+                        $again ||= !!($ibx->{mm} || $ibx->{search});
+                }
                 $next->{"$ibx"} = $ibx if $again;
         }
         $CLEANUP = $next;
 }
 
+sub cleanup_possible () {
+        # no need to require EvCleanup, here, if it were enabled another
+        # module would've require'd it, already
+        eval { PublicInbox::EvCleanup::enabled() } or return 0;
+
+        eval {
+                require Devel::Peek; # needs separate package in Fedora
+                $have_devel_peek = 1;
+        };
+        1;
+}
+
 sub _cleanup_later ($) {
         my ($self) = @_;
-        return if $cleanup_broken;
-        return unless PublicInbox::EvCleanup::enabled();
+        $cleanup_avail = cleanup_possible() if $cleanup_avail < 0;
+        return if $cleanup_avail != 1;
         $cleanup_timer ||= PublicInbox::EvCleanup::later(*cleanup_task);
         $CLEANUP->{"$self"} = $self;
 }