[PATCH 2/2] xcpdb: support cindex upgrades and resharding

[Eric Wong <e@80x24.org>]

xcpdb is necessary for upgrading Xapian backends (e.g. glass to
honey), thus codesearch indices (cindex) must be supported.
Resharding is also useful if CPU count is altered on system
upgrades or downgrades.

cindex Xapian sharding is completely different than anything
else we do, so the resharding operation must be a special case
based on existing cindex sharding rules.
---
 lib/PublicInbox/Xapcmd.pm | 130 +++++++++++++++++++++++++++++---------
 script/public-inbox-xcpdb |  20 +++---
 t/cindex.t                |   5 ++
 3 files changed, 117 insertions(+), 38 deletions(-)

diff --git a/lib/PublicInbox/Xapcmd.pm b/lib/PublicInbox/Xapcmd.pm
index 1547ce53..ff5c0eab 100644
--- a/lib/PublicInbox/Xapcmd.pm
+++ b/lib/PublicInbox/Xapcmd.pm
@@ -6,6 +6,7 @@ use PublicInbox::Spawn qw(which popen_rd);
 use PublicInbox::Syscall;
 use PublicInbox::Admin qw(setup_signals);
 use PublicInbox::Over;
+use PublicInbox::Search qw(xap_terms);
 use PublicInbox::SearchIdx;
 use File::Temp 0.19 (); # ->newdir
 use File::Path qw(remove_tree);
@@ -76,14 +77,14 @@ sub commit_changes ($$$$) {
 	if (!$opt->{-coarse_lock}) {
 		$opt->{-skip_lock} = 1;
 		$im //= $ibx if $ibx->can('eidx_sync') || $ibx->can('cidx_run');
-		if ($im->can('count_shards')) { # v2w or eidx
+		if ($im->can('count_shards')) { # v2w, eidx, cidx
 			my $pr = $opt->{-progress};
 			my $n = $im->count_shards;
 			if (defined $reshard && $n != $reshard) {
 				die
 "BUG: counted $n shards after resharding to $reshard";
 			}
-			my $prev = $im->{shards};
+			my $prev = $im->{shards} // $ibx->{nshard};
 			if ($pr && $prev != $n) {
 				$pr->("shard count changed: $prev => $n\n");
 				$im->{shards} = $n;
@@ -93,9 +94,7 @@ sub commit_changes ($$$$) {
 		local %ENV = (%ENV, %$env) if $env;
 		if ($ibx->can('eidx_sync')) {
 			$ibx->eidx_sync($opt);
-		} elsif ($ibx->can('cidx_run')) {
-			$ibx->cidx_run($opt);
-		} else {
+		} elsif (!$ibx->can('cidx_run')) {
 			PublicInbox::Admin::index_inbox($ibx, $im, $opt);
 		}
 	}
@@ -150,8 +149,9 @@ sub kill_pids {
 }
 
 sub process_queue {
-	my ($queue, $cb, $opt) = @_;
+	my ($queue, $task, $opt) = @_;
 	my $max = $opt->{jobs} // scalar(@$queue);
+	my $cb = \&$task;
 	if ($max <= 1) {
 		while (defined(my $args = shift @$queue)) {
 			$cb->($args, $opt);
@@ -263,7 +263,6 @@ sub check_compact () { runnable_or_die($XAPIAN_COMPACT) }
 
 sub run {
 	my ($ibx, $task, $opt) = @_; # task = 'cpdb' or 'compact'
-	my $cb = \&$task;
 	PublicInbox::Admin::progress_prepare($opt ||= {});
 	my $dir;
 	for my $fld (qw(inboxdir topdir cidx_dir)) {
@@ -298,7 +297,11 @@ sub run {
 	}
 
 	$ibx->cleanup if $ibx->can('cleanup');
-	process_queue($queue, $cb, $opt);
+	if ($task eq 'cpdb' && $opt->{reshard} && $ibx->can('cidx_run')) {
+		cidx_reshard($ibx, $queue, $opt);
+	} else {
+		process_queue($queue, $task, $opt);
+	}
 	($im // $ibx)->lock_acquire if !$opt->{-coarse_lock};
 	commit_changes($ibx, $im, $tmp, $opt);
 }
@@ -411,17 +414,95 @@ sub cpdb_loop ($$$;$$) {
 	} while (cpdb_retryable($src, $pfx));
 }
 
+sub xapian_write_prep ($) {
+	my ($opt) = @_;
+	PublicInbox::SearchIdx::load_xapian_writable();
+	my $flag = eval($PublicInbox::Search::Xap.'::DB_CREATE()');
+	die if $@;
+	$flag |= $PublicInbox::SearchIdx::DB_NO_SYNC if !$opt->{fsync};
+	(\%PublicInbox::Search::X, $flag);
+}
+
+sub compact_tmp_shard ($) {
+	my ($wip) = @_;
+	my $new = $wip->dirname;
+	my ($dir) = ($new =~ m!(.*?/)[^/]+/*\z!);
+	same_fs_or_die($dir, $new);
+	my $ft = File::Temp->newdir("$new.compact-XXXX", DIR => $dir);
+	PublicInbox::Syscall::nodatacow_dir($ft->dirname);
+	$ft;
+}
+
+sub cidx_reshard { # not docid based
+	my ($cidx, $queue, $opt) = @_;
+	my ($X, $flag) = xapian_write_prep($opt);
+	my $src = $cidx->xdb;
+	delete($cidx->{xdb}) == $src or die "BUG: xdb != $src";
+	my $pfx = $opt->{-progress_pfx} = progress_pfx($cidx->xdir.'/0');
+	my $pr = $opt->{-progress};
+	my $pr_data = { pr => $pr, pfx => $pfx, nr => 0 } if $pr;
+	local @SIG{keys %SIG} = values %SIG;
+
+	# like copydatabase(1), be sure we don't overwrite anything in case
+	# of other bugs:
+	setup_signals() if $opt->{compact};
+	my @tmp;
+	my @dst = map {
+		my $wip = $_->[1];
+		my $tmp = $opt->{compact} ? compact_tmp_shard($wip) : $wip;
+		push @tmp, $tmp;
+		$X->{WritableDatabase}->new($tmp->dirname, $flag);
+	} @$queue;
+	my $l = $src->get_metadata('indexlevel');
+	$dst[0]->set_metadata('indexlevel', $l) if $l eq 'medium';
+	my $fmt;
+	if ($pr_data) {
+		my $tot = $src->get_doccount;
+		$fmt = "$pfx % ".length($tot)."u/$tot\n";
+		$pr->("$pfx copying $tot documents\n");
+	}
+	my $cur = $src->postlist_begin('');
+	my $end = $src->postlist_end('');
+	my $git_dir_hash = $cidx->can('git_dir_hash');
+	my ($n, $nr);
+	for (; $cur != $end; $cur++) {
+		my $doc = $src->get_document($cur->get_docid);
+		if (my @cmt = xap_terms('Q', $doc)) {
+			$n = hex(substr($cmt[0], 0, 8)) % scalar(@dst);
+			warn "W: multi-commit: @cmt" if scalar(@cmt) != 1;
+		} elsif (my @P = xap_terms('P', $doc)) {
+			$n = $git_dir_hash->($P[0]) % scalar(@dst);
+			warn "W: multi-path @P " if scalar(@P) != 1;
+		} else {
+			warn "W: skipped, no terms in ".$cur->get_docid;
+			next;
+		}
+		$dst[$n]->add_document($doc);
+		$pr->(sprintf($fmt, $nr)) if $pr_data && !(++$nr & 1023);
+	}
+	return if !$opt->{compact};
+	$src = undef;
+	@dst = (); # flushes and closes
+	my @q;
+	for my $tmp (@tmp) {
+		my $arg = shift @$queue // die 'BUG: $queue empty';
+		my $wip = $arg->[1] // die 'BUG: no $wip';
+		push @q, [ "$tmp", $wip ];
+	}
+	delete $opt->{-progress_pfx};
+	process_queue(\@q, 'compact', $opt);
+}
+
 # Like copydatabase(1), this is horribly slow; and it doesn't seem due
 # to the overhead of Perl.
 sub cpdb ($$) { # cb_spawn callback
 	my ($args, $opt) = @_;
-	my ($old, $newdir) = @$args;
-	my $new = $newdir->dirname;
+	my ($old, $wip) = @$args;
 	my ($src, $cur_shard);
 	my $reshard;
-	PublicInbox::SearchIdx::load_xapian_writable();
-	my $XapianDatabase = $PublicInbox::Search::X{Database};
+	my ($X, $flag) = xapian_write_prep($opt);
 	if (ref($old) eq 'ARRAY') {
+		my $new = $wip->dirname;
 		($cur_shard) = ($new =~ m!(?:xap|ei)[0-9]+/([0-9]+)\b!);
 		defined $cur_shard or
 			die "BUG: could not extract shard # from $new";
@@ -431,36 +512,27 @@ sub cpdb ($$) { # cb_spawn callback
 		# resharding, M:N copy means have full read access
 		foreach (@$old) {
 			if ($src) {
-				my $sub = $XapianDatabase->new($_);
+				my $sub = $X->{Database}->new($_);
 				$src->add_database($sub);
 			} else {
-				$src = $XapianDatabase->new($_);
+				$src = $X->{Database}->new($_);
 			}
 		}
 	} else {
-		$src = $XapianDatabase->new($old);
+		$src = $X->{Database}->new($old);
 	}
 
-	my ($tmp, $ft);
+	my $tmp = $wip;
 	local @SIG{keys %SIG} = values %SIG;
 	if ($opt->{compact}) {
-		my ($dir) = ($new =~ m!(.*?/)[^/]+/*\z!);
-		same_fs_or_die($dir, $new);
-		$ft = File::Temp->newdir("$new.compact-XXXX", DIR => $dir);
+		$tmp = compact_tmp_shard($wip);
 		setup_signals();
-		$tmp = $ft->dirname;
-		PublicInbox::Syscall::nodatacow_dir($tmp);
-	} else {
-		$tmp = $new;
 	}
 
 	# like copydatabase(1), be sure we don't overwrite anything in case
 	# of other bugs:
-	my $flag = eval($PublicInbox::Search::Xap.'::DB_CREATE()');
-	die if $@;
-	my $XapianWritableDatabase = $PublicInbox::Search::X{WritableDatabase};
-	$flag |= $PublicInbox::SearchIdx::DB_NO_SYNC if !$opt->{fsync};
-	my $dst = $XapianWritableDatabase->new($tmp, $flag);
+	my $new = $wip->dirname;
+	my $dst = $X->{WritableDatabase}->new($tmp->dirname, $flag);
 	my $pr = $opt->{-progress};
 	my $pfx = $opt->{-progress_pfx} = progress_pfx($new);
 	my $pr_data = { pr => $pr, pfx => $pfx, nr => 0 } if $pr;
@@ -502,7 +574,7 @@ sub cpdb ($$) { # cb_spawn callback
 		# individually.
 		$src = undef;
 		foreach (@$old) {
-			my $old = $XapianDatabase->new($_);
+			my $old = $X->{Database}->new($_);
 			cpdb_loop($old, $dst, $pr_data, $cur_shard, $reshard);
 		}
 	} else {
diff --git a/script/public-inbox-xcpdb b/script/public-inbox-xcpdb
index 24fc5a25..fac54559 100755
--- a/script/public-inbox-xcpdb
+++ b/script/public-inbox-xcpdb
@@ -1,11 +1,10 @@
 #!perl -w
-# Copyright (C) 2019-2021 all contributors <meta@public-inbox.org>
+# Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
-use strict;
-use v5.10.1;
+use v5.12;
 use Getopt::Long qw(:config gnu_getopt no_ignore_case auto_abbrev);
 my $help = <<EOF; # the following should fit w/o scrolling in 80x24 term:
-usage: public-inbox-xcpdb [options] <INBOX_DIR|EXTINDEX_DIR>
+usage: public-inbox-xcpdb [options] <INBOX_DIR|EXTINDEX_DIR|CINDEX_DIR>
 
   upgrade or reshard Xapian DB(s) used by public-inbox
 
@@ -26,7 +25,8 @@ index options (see public-inbox-index(1) man page for full description):
 
 See public-inbox-xcpdb(1) man page for full documentation.
 EOF
-my $opt = { quiet => -1, compact => 0, fsync => 1, -eidx_ok => 1 };
+my $opt = { quiet => -1, compact => 0, fsync => 1,
+	-eidx_ok => 1, -cidx_ok => 1 };
 GetOptions($opt, qw(
 	fsync|sync! compact|c reshard|R=i
 	max_size|max-size=s batch_size|batch-size=s
@@ -42,8 +42,9 @@ PublicInbox::Admin::do_chdir(delete $opt->{C});
 
 require PublicInbox::Config;
 my $cfg = PublicInbox::Config->new;
-my ($ibxs, $eidxs) = PublicInbox::Admin::resolve_inboxes(\@ARGV, $opt, $cfg);
-unless ($ibxs) { print STDERR $help; exit 1 }
+my ($ibxs, $eidxs, $cidxs) =
+	PublicInbox::Admin::resolve_inboxes(\@ARGV, $opt, $cfg);
+unless (@$ibxs || @$eidxs || @$cidxs) { print STDERR $help; exit 1 }
 my $idx_env = PublicInbox::Admin::index_prepare($opt, $cfg);
 
 # we only set XAPIAN_FLUSH_THRESHOLD for index, since cpdb doesn't
@@ -63,6 +64,7 @@ for my $ibx (@$ibxs) {
 	PublicInbox::Xapcmd::run($ibx, 'cpdb', $opt);
 }
 
-for my $eidx (@$eidxs) {
-	PublicInbox::Xapcmd::run($eidx, 'cpdb', $opt);
+for my $ibxish (@$eidxs, @$cidxs) {
+	my $restore = $ibxish->can('prep_umask') ? $ibxish->prep_umask : undef;
+	PublicInbox::Xapcmd::run($ibxish, 'cpdb', $opt);
 }
diff --git a/t/cindex.t b/t/cindex.t
index b0d6f204..473287aa 100644
--- a/t/cindex.t
+++ b/t/cindex.t
@@ -185,4 +185,9 @@ ok(run_script([qw(-cindex --dangerous -q -d), "$tmp/ext", $zp]),
 	is($st[2] & 0777, 0604, 'created lock respects odd permissions');
 }
 
+ok(run_script([qw(-xcpdb), "$tmp/ext"]), 'xcpdb upgrade');
+ok(run_script([qw(-xcpdb -R4), "$tmp/ext"]), 'xcpdb reshard');
+ok(run_script([qw(-xcpdb -R2 --compact), "$tmp/ext"]), 'xcpdb reshard+compact');
+ok(run_script([qw(-xcpdb --compact), "$tmp/ext"]), 'xcpdb compact');
+
 done_testing;