Fix RecursiveCopy.pm to cope with disappearing files.

When copying from an active database tree, it's possible for files to be
deleted after we see them in a readdir() scan but before we can open them.
(Once we've got a file open, we don't expect any further errors from it
getting unlinked, though.)  Tweak RecursiveCopy so it can cope with this
case, so as to avoid irreproducible test failures.

Back-patch to 9.6 where this code was added.  In v10 and HEAD, also
remove unused "use RecursiveCopy" in one recovery test script.

Michael Paquier and Tom Lane

Discussion: https://postgr.es/m/24621.1504924323@sss.pgh.pa.us

diff --git a/src/test/perl/RecursiveCopy.pm b/src/test/perl/RecursiveCopy.pm
index 3e9881328680fa2b08240e6325e5b7a826a7ecf8..8be9211c117d400e0214fd5684e33704e6114a1d 100644 (file)
--- a/src/test/perl/RecursiveCopy.pm
+++ b/src/test/perl/RecursiveCopy.pm
@@ -29,12 +29,17 @@ use File::Copy;
 =head2 copypath($from, $to, %params)
 
 Recursively copy all files and directories from $from to $to.
+Does not preserve file metadata (e.g., permissions).
 
 Only regular files and subdirectories are copied.  Trying to copy other types
 of directory entries raises an exception.
 
 Raises an exception if a file would be overwritten, the source directory can't
-be read, or any I/O operation fails. Always returns true.
+be read, or any I/O operation fails.  However, we silently ignore ENOENT on
+open, because when copying from a live database it's possible for a file/dir
+to be deleted after we see its directory entry but before we can open it.
+
+Always returns true.
 
 If the B<filterfn> parameter is given, it must be a subroutine reference.
 This subroutine will be called for each entry in the source directory with its
@@ -74,6 +79,9 @@ sub copypath
                $filterfn = sub { return 1; };
        }
 
+       # Complain if original path is bogus, because _copypath_recurse won't.
+       die "\"$base_src_dir\" does not exist" if !-e $base_src_dir;
+
        # Start recursive copy from current directory
        return _copypath_recurse($base_src_dir, $base_dest_dir, "", $filterfn);
 }
@@ -89,12 +97,8 @@ sub _copypath_recurse
        return 1 unless &$filterfn($curr_path);
 
        # Check for symlink -- needed only on source dir
-       die "Cannot operate on symlinks" if -l $srcpath;
-
-       # Can't handle symlinks or other weird things
-       die "Source path \"$srcpath\" is not a regular file or directory"
-         unless -f $srcpath
-                 or -d $srcpath;
+       # (note: this will fall through quietly if file is already gone)
+       die "Cannot operate on symlink \"$srcpath\"" if -l $srcpath;
 
        # Abort if destination path already exists.  Should we allow directories
        # to exist already?
@@ -104,25 +108,47 @@ sub _copypath_recurse
        # same name and we're done.
        if (-f $srcpath)
        {
-               copy($srcpath, $destpath)
+               my $fh;
+               unless (open($fh, '<', $srcpath))
+               {
+                       return 1 if ($!{ENOENT});
+                       die "open($srcpath) failed: $!";
+               }
+               copy($fh, $destpath)
                  or die "copy $srcpath -> $destpath failed: $!";
+               close $fh;
                return 1;
        }
 
-       # Otherwise this is directory: create it on dest and recurse onto it.
-       mkdir($destpath) or die "mkdir($destpath) failed: $!";
-
-       opendir(my $directory, $srcpath) or die "could not opendir($srcpath): $!";
-       while (my $entry = readdir($directory))
+       # If it's a directory, create it on dest and recurse into it.
+       if (-d $srcpath)
        {
-               next if ($entry eq '.' or $entry eq '..');
-               _copypath_recurse($base_src_dir, $base_dest_dir,
-                       $curr_path eq '' ? $entry : "$curr_path/$entry", $filterfn)
-                 or die "copypath $srcpath/$entry -> $destpath/$entry failed";
+               my $directory;
+               unless (opendir($directory, $srcpath))
+               {
+                       return 1 if ($!{ENOENT});
+                       die "opendir($srcpath) failed: $!";
+               }
+
+               mkdir($destpath) or die "mkdir($destpath) failed: $!";
+
+               while (my $entry = readdir($directory))
+               {
+                       next if ($entry eq '.' or $entry eq '..');
+                       _copypath_recurse($base_src_dir, $base_dest_dir,
+                               $curr_path eq '' ? $entry : "$curr_path/$entry", $filterfn)
+                         or die "copypath $srcpath/$entry -> $destpath/$entry failed";
+               }
+
+               closedir($directory);
+               return 1;
        }
-       closedir($directory);
 
-       return 1;
+       # If it disappeared from sight, that's OK.
+       return 1 if !-e $srcpath;
+
+       # Else it's some weird file type; complain.
+       die "Source path \"$srcpath\" is not a regular file or directory";
 }
 
 1;