Item10257: Caching broken in Solaris 10

Priority:	CurrentState:	AppliesTo:	Component:	WaitingFor:
Normal	New	Engine	PageCaching

I just tried out the PageCaching feature for the first time, and found it was broken on my Solaris 10 server:

| 2011-01-14T08:39:21Z warning | can't lock cache db: Bad file number at /data/www/wiki/lib/Foswiki/Cache/DB_File.pm line 167.
 at /usr/local/lib/perl5/5.8.8/CGI/Carp.pm line 356
        CGI::Carp::realdie('can\'t lock cache db: Bad file number at /data/www/wiki/lib/F...') called at /usr/local/lib/perl5/5.8.8/CGI/Carp.pm line 437
        CGI::Carp::die('can\'t lock cache db: Bad file number') called at /data/www/wiki/lib/Foswiki/Cache/DB_File.pm line 167
        Foswiki::Cache::DB_File::_tie('Foswiki::Cache::DB_File=HASH(0xaf59b8)', 'ro') called at /data/www/wiki/lib/Foswiki/Cache/DB_File.pm line 40
        Foswiki::Cache::DB_File::init('Foswiki::Cache::DB_File=HASH(0xaf59b8)', 'Foswiki=HASH(0x9a8b18)') called at /data/www/wiki/lib/Foswiki/Cache.pm line 31
        Foswiki::Cache::new('Foswiki::Cache::DB_File', 'Foswiki=HASH(0x9a8b18)') called at /data/www/wiki/lib/Foswiki/Cache/DB_File.pm line 29
        Foswiki::Cache::DB_File::new('Foswiki::Cache::DB_File', 'Foswiki=HASH(0x9a8b18)') called at /data/www/wiki/lib/Foswiki/PageCache.pm line 62
        Foswiki::PageCache::new('Foswiki::PageCache', 'Foswiki=HASH(0x9a8b18)') called at /data/www/wiki/lib/Foswiki.pm line 1665
        Foswiki::new('Foswiki', 'undef', 'Foswiki::Request=HASH(0x98fd3c)', 'HASH(0x97f178)') called at /data/www/wiki/lib/Foswiki/UI.pm line 309
        Foswiki::UI::__ANON__() called at /usr/local/lib/perl5/site_perl/5.8.8/Error.pm line 415
        eval {...} called at /usr/local/lib/perl5/site_perl/5.8.8/Error.pm line 407
        Error::subs::try('CODE(0x98f994)', 'HASH(0x9a88c0)') called at /data/www/wiki/lib/Foswiki/UI.pm line 435
        Foswiki::UI::_execute('Foswiki::Request=HASH(0x98fd3c)', 'CODE(0x98fa0c)', 'view', 1) called at /data/www/wiki/lib/Foswiki/UI.pm line 277
        Foswiki::UI::handleRequest('Foswiki::Request=HASH(0x98fd3c)') called at /data/www/wiki/lib/Foswiki/Engine/CGI.pm line 37
        Foswiki::Engine::CGI::run('Foswiki::Engine::CGI=HASH(0x6846b8)') called at /data/www/wiki/bin/view line 24
        ModPerl::ROOT::ModPerl::Registry::data_www_wiki_bin_view::handler('Apache2::RequestRec=SCALAR(0x418c4c)') called at /usr/local/lib/perl5/site_perl/5.8.8/sun4-solaris/ModPerl/RegistryCooker.pm line 204
        eval {...} called at /usr/local/lib/perl5/site_perl/5.8.8/sun4-solaris/ModPerl/RegistryCooker.pm line 204
        ModPerl::RegistryCooker::run('ModPerl::Registry=HASH(0x4748a8)') called at /usr/local/lib/perl5/site_perl/5.8.8/sun4-solaris/ModPerl/RegistryCooker.pm line 170
        ModPerl::RegistryCooker::default_handler('ModPerl::Registry=HASH(0x4748a8)') called at /usr/local/lib/perl5/site_perl/5.8.8/sun4-solaris/ModPerl/Registry.pm line 31
        ModPerl::Registry::handler('ModPerl::Registry', 'Apache2::RequestRec=SCALAR(0x418c4c)') called at /data/www/wiki/lib/Foswiki/PageCache.pm line 0
        eval {...} called at /data/www/wiki/lib/Foswiki/PageCache.pm line 0.
 |

Looking into this further, it appears to be due to Foswiki::Cache::DB_File::_tie opening the lock file for writing and then requesting a shared lock. The error raised fits with the documented behaviour:

EBADF The fildes argument is not a valid open file descriptor; or the cmd argument is F_SETLK, F_SETLK64, F_SETLKW, or F_SETLKW64, the type of lock, l_type, is a shared lock (F_RDLCK), and fildes is not a valid file descriptor open for reading; or the type of lock l_type is an exclusive lock (F_WRLCK) and fildes is not a valid file descriptor open for writing.

I was able to fix this in my local codebase with the following, but not sure if this has ramifications to any intended functionality (everything appears to be working for me..):

--- DB_File.pm.orig     2010-11-10 11:29:12.000000000 +1100
+++ DB_File.pm  2011-01-14 19:27:36.409280000 +1100
@@ -154,15 +154,17 @@

     # aquire a file lock
     my $lockfile = "$this->{filename}.lock";
-    open( $this->{lock}, ">$lockfile" )
-      or die "can't create lockfile $lockfile";

     if ( $mode eq 'rw' ) {
+        open( $this->{lock}, ">$lockfile" )
+          or die "can't create lockfile $lockfile";
         $mode = O_CREAT | O_RDWR;
         flock( $this->{lock}, LOCK_EX )
           or die "can't lock cache db: $!";
     }
     elsif ( $mode eq 'ro' ) {
+        open( $this->{lock}, "<$lockfile" )
+          or die "can't create lockfile $lockfile";
         $mode = O_CREAT | O_RDONLY;
         flock( $this->{lock}, LOCK_SH )
           or die "can't lock cache db: $!";

-- MatthewFlint - 14 Jan 2011