From 21efb4dd7e6f276e2ee12c668696ae26c2e7a19c Mon Sep 17 00:00:00 2001
From: Daniel Nichter <daniel@percona.com>
Date: Sat, 2 Mar 2013 17:02:08 -0700
Subject: [PATCH] Truly fix t[/pt-fifo-split/pt-fifo-split.t.

---
 t/pt-fifo-split/pt-fifo-split.t | 95 +++++++++++++++++++++++----------
 1 file changed, 66 insertions(+), 29 deletions(-)

diff --git a/t/pt-fifo-split/pt-fifo-split.t b/t/pt-fifo-split/pt-fifo-split.t
index 2742714c..c7a6e39f 100644
--- a/t/pt-fifo-split/pt-fifo-split.t
+++ b/t/pt-fifo-split/pt-fifo-split.t
@@ -11,7 +11,8 @@ use warnings FATAL => 'all';
 use English qw(-no_match_vars);
 use Test::More;
 use File::Temp qw(tempfile);
-use IO::File;
+use Data::Dumper;
+use Time::HiRes qw(sleep);
 
 use PerconaTest;
 require "$trunk/bin/pt-fifo-split";
@@ -27,24 +28,60 @@ like($output, qr/Options and values/, 'It lives');
 my ($fh, $filename) = tempfile("pt-fifo-split-data.XXXXXXXXX", OPEN => 1, TMPDIR => 1, UNLINK => 1);
 $fh->autoflush(1);
 print { $fh } "$_\n" for 1..9;
+close $fh;
+
+# WARNING: This can "deadlock" if not done correctly.  First, for Perl open():
+# "When you open a fifo, the program will block until there's something on
+# the other end."  So pt-fifo-split needs to mkfifo and open() it first,
+# then we open it.  That's ok, but the problem is: after we read everything,
+# pt-fifo-split will close, rm, mkfifo, and open() it again.  That can take
+# a few microseconds longer than the test closing and trying to read the
+# fifo again.  In fact, the test can close, -p $fifo, and open() before
+# pt-fifo-split has done rm (unlink).  When this happens, the test holds
+# open the fifo it just read, then pt-fifo-split creates a new fifo and
+# open()s it and blocks because there's no program on the other end--
+# because the test is reading a phantom fifo.  Rather make the tool sleep
+# some arbitrary time before re-open()ing the fifo, we check for a new
+# file inode which ensures the fifo is new.
+sub read_fifo {
+   my ($n_reads) = @_;
+   my $last_inode = 0;
+   my @data;
+   for (1..$n_reads) {
+      PerconaTest::wait_until(sub {
+         my $inode;
+         (undef, $inode) = stat($fifo) if -p $fifo;
+         if ( $inode && $inode != $last_inode ) {
+            $last_inode = $inode;
+            return 1;
+         }
+         return;
+      });
+      open my $read_fifo_fh, '<', $fifo
+         or die "Cannot open $fifo: $OS_ERROR";
+      my $data = '';
+      while ( <$read_fifo_fh> ) {
+         $data .= $_;
+      }
+      close $read_fifo_fh;
+      push @data, $data;
+   }
+   return \@data;
+}
 
 local $SIG{CHLD} = 'IGNORE';
 my $pid = fork();
 die "Cannot fork: $OS_ERROR" unless defined $pid;
 if ( !$pid ) {
    exec { $cmd } $cmd, qw(--lines 2), $filename;
-   exit 1;
 }
 
-PerconaTest::wait_until(sub { -p $fifo });
-my @fifo;
-while (kill 0, $pid) {
-   push @fifo, slurp_file($fifo) if -e $fifo;
-}
+my $data = read_fifo(5);
+
 waitpid($pid, 0);
 
 is_deeply(
-   \@fifo,
+   $data,
    [
       "1\n2\n",
       "3\n4\n",
@@ -53,53 +90,53 @@ is_deeply(
       "9\n",
    ],
    "--lines=2 with 9 lines works as expected"
-);
+) or diag(Dumper($data));
 
 $pid = fork();
 die "Cannot fork: $OS_ERROR" unless defined $pid;
 if ( !$pid ) {
    exec { $cmd } $cmd, qw(--lines 15), $filename;
-   exit 1;
 }
-PerconaTest::wait_until(sub { -p $fifo });
 
-@fifo = ();
-while (kill 0, $pid) {
-   push @fifo, slurp_file($fifo) if -e $fifo;
-}
+$data = read_fifo(1);
+
 waitpid($pid, 0);
 
 is_deeply(
-   \@fifo,
-   [
-      "1\n2\n3\n4\n5\n6\n7\n8\n9\n",
-   ],
+   $data,
+   [ "1\n2\n3\n4\n5\n6\n7\n8\n9\n" ],
    "--lines=15 with 9 lines works as expected"
-);
-
-close $fh or die "Cannot close $filename: $OS_ERROR";
+) or diag(Dumper($data));
 
 system("($cmd --lines 10000 $trunk/bin/pt-fifo-split > /dev/null 2>&1 < /dev/null)&");
-PerconaTest::wait_until(sub { -p $fifo });
 
-my $contents  = slurp_file($fifo);
+$data = read_fifo(1);
+
 my $contents2 = load_file('bin/pt-fifo-split');
 
-is($contents, $contents2, 'I read the file');
+is_deeply(
+   $data,
+   [ $contents2 ],
+   'I read the file'
+);
 
 system("($cmd $trunk/t/pt-fifo-split/samples/file_with_lines --offset 2 > /dev/null 2>&1 < /dev/null)&");
-PerconaTest::wait_until(sub { -p $fifo });
 
-$contents = slurp_file($fifo);
+$data = read_fifo(1);
 
-is($contents, <<EOF
+is_deeply(
+   $data,
+   [
+<<EOF
      2	hi
      3	there
      4	b
      5	c
      6	d
 EOF
-, 'Offset works');
+   ],
+   'Offset works'
+);
 
 # #########################################################################
 # Issue 391: Add --pid option to all scripts