From: Eric Wong (Contractor, The Linux Foundation) <e@80x24.org>
Date: Tue, 6 Mar 2018 07:28:56 +0000 (+0000)
Subject: v2writable: detect and use previous partition count
X-Git-Tag: v1.1.0-pre1~171
X-Git-Url: http://www.git.stargrave.org/?p=public-inbox.git;a=commitdiff_plain;h=cab22861f2a22482b74d20c05afbd6108a4590cb

v2writable: detect and use previous partition count

We need to detect the number of partitions the repository was
created with to ensure Xapian DBs can work across different
machines (or even CPU affinity changes) without leaving messages
unaffected by search.
---

diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index 3bcea37d..7728b91a 100644
--- a/lib/PublicInbox/V2Writable.pm
+++ b/lib/PublicInbox/V2Writable.pm
@@ -19,7 +19,9 @@ use PublicInbox::Inbox;
 my $PACKING_FACTOR = 0.4;
 
 # assume 2 cores if GNU nproc(1) is not available
-my $NPROC = int($ENV{NPROC} || `nproc 2>/dev/null` || 2);
+sub nproc () {
+	int($ENV{NPROC} || `nproc 2>/dev/null` || 2);
+}
 
 sub new {
 	my ($class, $v2ibx, $creat) = @_;
@@ -32,12 +34,28 @@ sub new {
 			die "$dir does not exist\n";
 		}
 	}
+
+	my $nparts = 0;
+	my $xpfx = "$dir/xap" . PublicInbox::Search::SCHEMA_VERSION;
+
+	# always load existing partitions in case core count changes:
+	if (-d $xpfx) {
+		foreach my $part (<$xpfx/*>) {
+			-d $part && $part =~ m!/\d+\z! or next;
+			eval {
+				Search::Xapian::Database->new($part)->close;
+				$nparts++;
+			};
+		}
+	}
+	$nparts = nproc() if ($nparts == 0);
+
 	my $self = {
 		-inbox => $v2ibx,
 		im => undef, #  PublicInbox::Import
 		xap_rw => undef, # PublicInbox::V2SearchIdx
 		xap_ro => undef,
-		partitions => $NPROC,
+		partitions => $nparts,
 		transact_bytes => 0,
 		# limit each repo to 1GB or so
 		rotate_bytes => int((1024 * 1024 * 1024) / $PACKING_FACTOR),
diff --git a/t/v2writable.t b/t/v2writable.t
index 2d35aca3..404c8651 100644
--- a/t/v2writable.t
+++ b/t/v2writable.t
@@ -30,7 +30,11 @@ my $mime = PublicInbox::MIME->create(
 	body => "hello world\n",
 );
 
-my $im = PublicInbox::V2Writable->new($ibx, 1);
+my $im = eval {
+	local $ENV{NPROC} = '1';
+	PublicInbox::V2Writable->new($ibx, 1);
+};
+is($im->{partitions}, 1, 'one partition when forced');
 ok($im->add($mime), 'ordinary message added');
 
 if ('ensure git configs are correct') {
@@ -182,5 +186,10 @@ EOF
 	}
 	is_deeply([sort keys %nn], [sort keys %uniq]);
 };
+{
+	local $ENV{NPROC} = 2;
+	$im = PublicInbox::V2Writable->new($ibx, 1);
+	is($im->{partitions}, 1, 'detected single partition from previous');
+}
 
 done_testing();