From db1aadf450a15cbd4041c5f9bf5a0b16f66c2ad5 Mon Sep 17 00:00:00 2001
From: Craig Ringer <craig@2ndquadrant.com>
Date: Wed, 12 Apr 2017 14:03:25 +0800
Subject: [PATCH] Add locking for initdb caching to allow parallel prove

---
 src/test/perl/PostgresNode.pm | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/src/test/perl/PostgresNode.pm b/src/test/perl/PostgresNode.pm
index eef9f66..0eacd41 100644
--- a/src/test/perl/PostgresNode.pm
+++ b/src/test/perl/PostgresNode.pm
@@ -94,6 +94,7 @@ use Socket;
 use Test::More;
 use TestLib ();
 use Scalar::Util qw(blessed);
+use Fcntl qw(:flock);
 
 our @EXPORT = qw(
   get_new_node
@@ -477,15 +478,27 @@ sub _initdb_cached
 	my $pgdata = $self->data_dir;
 
 	my $cachedir = TestLib::tmp_check_dir() . "/initdb_cache";
+	my $lockfile = TestLib::tmp_check_dir() . "/.initdb_cache.lock";
 
 	if (! -d $cachedir)
 	{
 		print(STDERR "initializing initdb cache\n");
-		# initdb into a tempdir, then rename the result so we don't risk
-		# leaving failed initdb results around
-		my $temp_dbdir = TestLib::tempdir("initdb_cache_");
-		$self->_initdb($temp_dbdir, %params);
-		rename($temp_dbdir, $cachedir);
+		open my $lockfh, ">", $lockfile
+			or die "cannot open $lockfile for writing: $1\n";
+		flock($lockfh, LOCK_EX)
+			or die "cannot flock($lockfile) in exclusive mode: $!\n";
+		# If running in parallel with other tests, someone else might've got
+		# the lock first and have swapped an initdb'd directory in already.
+		if (! -d $cachedir)
+		{
+			# initdb into a tempdir, then rename the result so we don't risk
+			# leaving failed initdb results around
+			my $temp_dbdir = TestLib::tempdir("initdb_cache_");
+			$self->_initdb($temp_dbdir, %params);
+			rename($temp_dbdir, $cachedir);
+		}
+		flock($lockfh, LOCK_UN)
+			or die "cannot unlock $lockfile: $!";
 	}
 
 	RecursiveCopy::copypath($cachedir, $pgdata);
-- 
2.5.5