git: unconditional expiry

A constant stream of traffic to either httpd/nntpd would mean
git-cat-file processes never expire.  Things can go bad after a
full repack, as a full repack will unlink old pack indices and
git-cat-file does not currently detect unlinked files.

We could do something complicated by recursively stat-ing
objects/pack of every git directory and alternate;
but that's probably not worth the trouble compared to
occasionally restarting the cat-file process.

So simplify the code and let httpd/nntpd expire them
periodically, since spawning a "git-cat-file --batch" process
isn't too expensive.  We already spawn for every request which
hits git-http-backend, cgit, and git-apply.

In the future, we may optionally support the Git::Raw module
to avoid IPC; but we must remain careful to not leave lingering
FDs open to unlinked files after repack.

3 files changed, 8 insertions, 20 deletions

diff --git a/lib/PublicInbox/Git.pm b/lib/PublicInbox/Git.pm
index a4daaa48..9a38d7c8 100644
--- a/lib/PublicInbox/Git.pm
+++ b/lib/PublicInbox/Git.pm
@@ -211,19 +211,9 @@ sub check {
 }
 
 sub _destroy {
-        my ($self, $in, $out, $pid, $expire) = @_;
-        my $rfh = $self->{$in} or return;
-        if (defined $expire) {
-                # at least FreeBSD 11.2 and Linux 4.20 update mtime of the
-                # read end of a pipe when the pipe is written to; dunno
-                # about other OSes.
-                my $mtime = (stat($rfh))[9];
-                return if $mtime > $expire;
-        }
+        my ($self, $in, $out, $pid) = @_;
         my $p = delete $self->{$pid} or return;
-        foreach my $f ($in, $out) {
-                delete $self->{$f};
-        }
+        delete @$self{($in, $out)};
         waitpid $p, 0;
 }
 
@@ -251,9 +241,9 @@ sub qx {
 
 # returns true if there are pending "git cat-file" processes
 sub cleanup {
-        my ($self, $expire) = @_;
-        _destroy($self, qw(in out pid), $expire);
-        _destroy($self, qw(in_c out_c pid_c), $expire);
+        my ($self) = @_;
+        _destroy($self, qw(in out pid));
+        _destroy($self, qw(in_c out_c pid_c));
         !!($self->{pid} || $self->{pid_c});
 }
 
diff --git a/lib/PublicInbox/Inbox.pm b/lib/PublicInbox/Inbox.pm
index 2771a241..b3178b98 100644
--- a/lib/PublicInbox/Inbox.pm
+++ b/lib/PublicInbox/Inbox.pm
@@ -32,13 +32,12 @@ sub cleanup_task () {
                                 # refcnt is zero when tmp is out-of-scope
                         }
                 }
-                my $expire = time - 60;
                 if (my $git = $ibx->{git}) {
-                        $again = $git->cleanup($expire);
+                        $again = $git->cleanup;
                 }
                 if (my $gits = $ibx->{-repo_objs}) {
                         foreach my $git (@$gits) {
-                                $again = 1 if $git->cleanup($expire);
+                                $again = 1 if $git->cleanup;
                         }
                 }
                 if ($have_devel_peek) {
diff --git a/t/git.t b/t/git.t
index 7edf82b4..913f6e5e 100644
--- a/t/git.t
+++ b/t/git.t
@@ -143,8 +143,7 @@ if ('alternates reloaded') {
         my $config = eval { local $/; <$fh> };
         is($$found, $config, 'alternates reloaded');
 
-        ok($gcf->cleanup(time - 30), 'cleanup did not expire');
-        ok(!$gcf->cleanup(time + 30), 'cleanup can expire');
+        ok(!$gcf->cleanup, 'cleanup can expire');
         ok(!$gcf->cleanup, 'cleanup idempotent');
 
         my $t = $gcf->modified;