xapcmd: xcpdb supports compaction

To minimize the delay on active inboxes, it's actually ideal to
run xapian-compact at the end of the per-partition cpdb process;
since the new DB isn't accessible yet and so we don't have to
deal with lock contention with -mda or -watch processes.  The
downside is temporary file overhead (3x instead of 2x) required.

2 files changed, 38 insertions, 4 deletions

diff --git a/lib/PublicInbox/Xapcmd.pm b/lib/PublicInbox/Xapcmd.pm
index ca74ea0c..d2de8743 100644
--- a/lib/PublicInbox/Xapcmd.pm
+++ b/lib/PublicInbox/Xapcmd.pm
@@ -8,6 +8,10 @@ use PublicInbox::Over;
 use File::Temp qw(tempdir);
 use File::Path qw(remove_tree);
 
+# support testing with dev versions of Xapian which installs
+# commands with a version number suffix (e.g. "xapian-compact-1.5")
+our $XAPIAN_COMPACT = $ENV{XAPIAN_COMPACT} || 'xapian-compact';
+
 sub commit_changes ($$$) {
         my ($im, $old, $new) = @_;
         my @st = stat($old) or die "failed to stat($old): $!\n";
@@ -38,17 +42,23 @@ sub xspawn {
         }
 }
 
+sub runnable_or_die ($) {
+        my ($exe) = @_;
+        which($exe) or die "$exe not found in PATH\n";
+}
+
 sub run {
         my ($ibx, $cmd, $env, $opt) = @_;
         $opt ||= {};
         my $dir = $ibx->{mainrepo} or die "no mainrepo in inbox\n";
         my $exe = $cmd->[0];
         my $pfx = $exe;
+        runnable_or_die($XAPIAN_COMPACT) if $opt->{compact};
         if (ref($exe) eq 'CODE') {
                 $pfx = 'CODE';
                 require Search::Xapian::WritableDatabase;
         } else {
-                which($exe) or die "$exe not found in PATH\n";
+                runnable_or_die($exe);
         }
         $ibx->umask_prepare;
         my $old = $ibx->search->xdir(1);
@@ -107,11 +117,12 @@ sub cpdb {
         my ($args, $env, $opt) = @_;
         my ($old, $new) = @$args;
         my $src = Search::Xapian::Database->new($old);
+        my $tmp = $opt->{compact} ? "$new.compact" : $new;
 
         # like copydatabase(1), be sure we don't overwrite anything in case
         # of other bugs:
         my $creat = Search::Xapian::DB_CREATE();
-        my $dst = Search::Xapian::WritableDatabase->new($new, $creat);
+        my $dst = Search::Xapian::WritableDatabase->new($tmp, $creat);
         my ($it, $end);
 
         do {
@@ -140,6 +151,25 @@ sub cpdb {
                         # (and public-inbox does not use those features)
                 };
         } while (cpdb_retryable($src, $@));
+
+        return unless $opt->{compact};
+
+        $src = $dst = undef; # flushes and closes
+
+        # this is probably the best place to do xapian-compact
+        # since $dst isn't readable by HTTP or NNTP clients, yet:
+        my $cmd = [ $XAPIAN_COMPACT, '--no-renumber', $tmp, $new ];
+        my $rdr = {};
+        foreach my $fd (0..2) {
+                defined(my $dst = $opt->{$fd}) or next;
+                $rdr->{$fd} = $dst;
+        }
+        my $pid = spawn($cmd, $env, $rdr);
+        my $r = waitpid($pid, 0);
+        if ($? || $r != $pid) {
+                die join(' ', @$cmd)." failed: $? (pid=$pid, reaped=$r)\n";
+        }
+        remove_tree($tmp) or die "failed to remove $tmp: $!\n";
 }
 
 1;
diff --git a/script/public-inbox-xcpdb b/script/public-inbox-xcpdb
index d494991d..78d37da2 100755
--- a/script/public-inbox-xcpdb
+++ b/script/public-inbox-xcpdb
@@ -2,17 +2,21 @@
 # Copyright (C) 2019 all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 # xcpdb: Xapian copy database, a wrapper around Xapian's copydatabase(1)
+use Getopt::Long qw(:config gnu_getopt no_ignore_case auto_abbrev);
 use PublicInbox::InboxWritable;
 use PublicInbox::Xapcmd;
 use PublicInbox::Admin;
 PublicInbox::Admin::require_or_die('-search');
 my $usage = "Usage: public-inbox-xcpdb INBOX_DIR\n";
+my $opt = {};
+GetOptions($opt, qw(compact)) or die "bad command-line args\n$usage";
 my @ibxs = PublicInbox::Admin::resolve_inboxes(\@ARGV) or die $usage;
+
 my $cmd = [ \&PublicInbox::Xapcmd::cpdb ];
 open my $null, '>', '/dev/null' or die "failed to open /dev/null: $!\n";
-my $rdr = { 1 => fileno($null) };
+$opt->{1} = fileno($null);
 foreach (@ibxs) {
         my $ibx = PublicInbox::InboxWritable->new($_);
         # we rely on --no-renumber to keep docids synched to NNTP
-        PublicInbox::Xapcmd::run($ibx, $cmd, undef, $rdr);
+        PublicInbox::Xapcmd::run($ibx, $cmd, undef, $opt);
 }