[Koha-patches] [PATCH 3/3] Bug 11078 Address February QA concerns

[Doug Kingston]

1. Add code to check if flock is available and ignore locking if
its missing (from M. de Rooy)

2. Change default for adhoc invocations to abort if they cannot
obtain the lock.  Added option -wait-for-lock if the user prefers
to wait until the lock is free, and then continue processing.

3. added missing entry to t/db_dependent/zebra_config.pl

4. added a fallback locking directory of /tmp
---
 misc/migration_tools/rebuild_zebra.pl |   68 +++++++++++++++++++++++++++------
 t/db_dependent/zebra_config.pl        |    1 +
 2 files changed, 57 insertions(+), 12 deletions(-)

diff --git a/misc/migration_tools/rebuild_zebra.pl b/misc/migration_tools/rebuild_zebra.pl
index 6e713ff..e202316 100755
--- a/misc/migration_tools/rebuild_zebra.pl
+++ b/misc/migration_tools/rebuild_zebra.pl
@@ -44,6 +44,8 @@ my $where;
 my $offset;
 my $run_as_root;
 my $run_user = (getpwuid($<))[0];
+my $wait_for_lock = 0;
+my $use_flock;
 
 my $verbose_logging = 0;
 my $zebraidx_log_opt = " -v none,fatal,warn ";
@@ -65,11 +67,12 @@ my $result = GetOptions(
     'x'             => \$as_xml,
     'y'             => \$do_not_clear_zebraqueue,
     'z'             => \$process_zebraqueue,
-    'where:s'        => \$where,
-    'length:i'        => \$length,
+    'where:s'       => \$where,
+    'length:i'      => \$length,
     'offset:i'      => \$offset,
-    'v+'             => \$verbose_logging,
-    'run-as-root'    => \$run_as_root,
+    'v+'            => \$verbose_logging,
+    'run-as-root'   => \$run_as_root,
+    'wait-for-lock' => \$wait_for_lock,
 );
 
 if (not $result or $want_help) {
@@ -156,11 +159,16 @@ my ($biblioitemnumbertagfield,$biblioitemnumbertagsubfield) = &GetMarcFromKohaFi
 
 # Protect again simultaneous update of the zebra index by using a lock file.
 # Create our own lock directory if its missing.  This shouild be created
-# by koha-zebra-ctl.sh.
+# by koha-zebra-ctl.sh or at system installation.  If the desired directory
+# does not exist and cannot be created, we fall back on /tmp - which will
+# always work.
 
 my $lockdir = C4::Context->config("zebra_lockdir") // "/var/lock";
 $lockdir .= "/rebuild";
-mkpath($lockdir, 0, oct(755)) unless (-d $lockdir);
+unless (-d $lockdir) {
+    eval { mkpath($lockdir, 0, oct(755)) };
+    $lockdir = "/tmp" if ($@);
+}
 my $lockfile = $lockdir . "/rebuild..LCK";
 
 if ( $verbose_logging ) {
@@ -187,21 +195,31 @@ my $tester = XML::LibXML->new();
 # record being overwritten by a rebuild if the update is applied after the export
 # by the rebuild and before the rebuild finishes (more likely to effect large
 # catalogs).
+#
+# We have chosen to exit immediately by default if we cannot obtain the lock
+# to prevent the potential for a infinite backlog from cron invocations, but an
+# option (wait-for-lock) is provided to let the program wait for the lock.
+# See http://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=11078 for details.
 open my $LockFH, q{>}, $lockfile or die "$lockfile: $!";
 if ($daemon_mode) {
     while (1) {
         # For incremental updates, skip the update if the updates are locked
-        if (flock($LockFH, LOCK_EX|LOCK_NB)) {
+        if (_flock($LockFH, LOCK_EX|LOCK_NB)) {
             do_one_pass() if ( zebraqueue_not_empty() );
-            flock($LockFH, LOCK_UN);
+            _flock($LockFH, LOCK_UN);
         }
         sleep $daemon_sleep;
     }
 } else {
-    # all one-off invocations, wait for the lock to free
-    flock($LockFH, LOCK_EX);
-    do_one_pass();
-    flock($LockFH, LOCK_UN);
+    # all one-off invocations
+    my $lock_mode = ($wait_for_lock) ? LOCK_EX : LOCK_EX|LOCK_NB;
+    if (_flock($LockFH, $lock_mode)) {
+        do_one_pass();
+        _flock($LockFH, LOCK_UN);
+    } else {
+        # Can't die() here because we have files to dlean up.
+        print "Aborting rebuild.  Unable to flock $lockfile: $!\n";
+    }
 }
 
 
@@ -755,6 +773,26 @@ sub do_indexing {
 
 }
 
+sub _flock {
+# test if flock is present; if so, use it; if not, return true
+# op refers to the official flock operations incl LOCK_EX, LOCK_UN, etc.
+# combining LOCK_EX with LOCK_NB returns immediately
+    my ($fh, $op)= @_;
+    if( !defined($use_flock) ) {
+        #check if flock is present; if not, you will have a fatal error
+        my $i=eval { flock($fh, $op) };
+        #assuming that $fh and $op are fine(..), an undef i means no flock
+        $use_flock= defined($i)? 1: 0;
+        print "Warning: flock could not be used!\n" if $verbose_logging && !$use_flock;
+        return 1 if !$use_flock;
+        return $i;
+    }
+    else {
+        return 1 if !$use_flock;
+        return flock($fh, $op);
+    }
+}
+
 sub print_usage {
     print <<_USAGE_;
 $0: reindex MARC bibs and/or authorities in Zebra.
@@ -843,6 +881,12 @@ Parameters:
 
     --run-as-root           explicitily allow script to run as 'root' user
 
+    --wait-for-lock         when not running in daemon mode, the default
+                            behavior is to abort a rebuild if the rebuild
+                            lock is busy.  This option will cause the program
+                            to wait for the lock to free and then continue
+                            processing the rebuild request,
+
     --help or -h            show this message.
 _USAGE_
 }
diff --git a/t/db_dependent/zebra_config.pl b/t/db_dependent/zebra_config.pl
index 1395508..ceb9c0d 100755
--- a/t/db_dependent/zebra_config.pl
+++ b/t/db_dependent/zebra_config.pl
@@ -28,6 +28,7 @@ if ($indexing_mode eq 'dom') {
 make_path("$destination/var/lock/zebradb");
 make_path("$destination/var/lock/zebradb/biblios");
 make_path("$destination/var/lock/zebradb/authorities");
+make_path("$destination/var/lock/zebradb/rebuild");
 make_path("$destination/var/lib/zebradb");
 make_path("$destination/var/lib/zebradb/biblios");
 make_path("$destination/var/lib/zebradb/biblios/key");
-- 
1.7.9.5