Subject: Re: TAP test started using meson, can get a tcp port already used by another test.

From: Andres Freund <[email-masked]>
Date: Fri, 21 Feb 2025 10:50:14 -0500

Hi,

On 2025-02-21 15:58:45 +0700, Zharkov Roman wrote:
> We running TAP tests which operates with a lot of instances. And some of
> these tests randomly fail due "address already in use". It turned out that
> the meson does not set environment variable MESON_BUILD_ROOT when running
> the test() function [0].

I don't think meson ever set MESON_BUILD_ROOT during tests, so afaict the
portlock logic just just never worked with meson?

> As a result each test uses its own "portlock" directory [1]. The small TAP
> test 001_portlock_env_test.pl shows the test environment variables. As we
> can see MESON_BUILD_ROOT is really undefined.

I'm rather baffled this hasn't caused more problems...

I have recently seen a CI failure that looked like it likely was caused by
this. It was in a back branch, and I thought that was the explanation, due to
the portlock logic not yet existing. But the portlock logic is old enough, so
it likely was this.

But I would have expected many more errors.

> Can we explicitly set the MESON_BUILD_ROOT environment variable when running
> a test? With included patch for the src/tools/testwrap file, each instance
> gets an unique TCP port.

I don't like that, feels like a "namespace violation" to set a MESON_*
variable, why not set the top_builddir or a dedicated variable?

And I don't think it should be done in testwrap, but to test_env in the
top-level meson.build.

Something like the attached?

Greetings,

Andres Freund
diff --git c/meson.build i/meson.build
index cdf55957629..bed36153c7b 100644
--- c/meson.build
+++ i/meson.build
@@ -3414,6 +3414,8 @@ test_initdb_template = meson.build_root() / 'tmp_install' / 'initdb-template'
 test_env.set('PG_REGRESS', pg_regress.full_path())
 test_env.set('REGRESS_SHLIB', regress_module.full_path())
 test_env.set('INITDB_TEMPLATE', test_initdb_template)
+# for Cluster.pm's portlock logic
+test_env.set('top_builddir', meson.build_root())
 
 # Add the temporary installation to the library search path on platforms where
 # that works (everything but windows, basically). On windows everything
diff --git c/src/test/perl/PostgreSQL/Test/Cluster.pm i/src/test/perl/PostgreSQL/Test/Cluster.pm
index f31af70edb6..01ddaec4502 100644
--- c/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ i/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -169,8 +169,7 @@ INIT
 	# Otherwise, try to use a directory at the top of the build tree
 	# or as a last resort use the tmp_check directory
 	my $build_dir =
-		 $ENV{MESON_BUILD_ROOT}
-	  || $ENV{top_builddir}
+		 $ENV{top_builddir}
 	  || $PostgreSQL::Test::Utils::tmp_check;
 	$portdir ||= "$build_dir/portlock";
 	$portdir =~ s!\\!/!g;