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[PATCH 18/24] gitweb/lib - Configure running 'generating_info' when generating data

From
Jakub Narebski <jnareb@gmail.com>
Date
Dec 6, 2010, 23:11 UTC
Message-ID
<1291677069-6559-19-git-send-email-jnareb@gmail.com>
In-Reply-To
<1291677069-6559-1-git-send-email-jnareb@gmail.com>

Add a new 'generating_info_is_safe' cache option; if true, then process generating data (one that acquired exclusive writer's lock) would run 'generating_info' if there is no stale data and background cache generation is enabled.

If function generating (or printing) exits, which leads to cache entry not being generated (for gitweb this means that there are pages which are not cached, i.e. error pages), and 'generating_info' also exits, this could result in bad behavior. Therefore this new option is false by default.

Updates t9503 test appropriately.
Signed-off-by: Jakub Narebski <jnareb@gmail.com>
---
This patch was not present in previous version of this series.

This is one solution to the problem mentioned in commit message; another is to use initial delay in "Generating..." page, as it is done in next patch, and as it was done in previous version of this series.

 gitweb/lib/GitwebCache/FileCacheWithLocking.pm |   17 ++++++++++++++---
 t/t9503/test_cache_interface.pl                |    1 +
 2 files changed, 15 insertions(+), 3 deletions(-)
diff --git a/gitweb/lib/GitwebCache/FileCacheWithLocking.pm b/gitweb/lib/GitwebCache/FileCacheWithLocking.pm
index 694c318..0823c55 100644
--- a/gitweb/lib/GitwebCache/FileCacheWithLocking.pm
+++ b/gitweb/lib/GitwebCache/FileCacheWithLocking.pm
@@ -80,26 +80,35 @@ use POSIX qw(setsid);
 #    instead), for other process (or bacground process).  It is passed
 #    $cache instance, $key, and opened $lock_fh filehandle to lockfile.
 #    Unset by default (which means no activity indicator).
+#  * 'generating_info_is_safe' (boolean)
+#    If true, run 'generating_info' subroutine also in the project that
+#    is generating data.  This has effect only when 'background_cache'
+#    is true (both 'background_cache' and 'generating_info_is_safe' must
+#    be true for project generating data to run 'generating_info').
+#    Defaults to false for safety.
 sub new {
 	my $class = shift;
 	my %opts = ref $_[0] ? %{ $_[0] } : @_;
 
 	my $self = $class->SUPER::new(\%opts);
 
-	my ($max_lifetime, $background_cache, $generating_info);
+	my ($max_lifetime, $background_cache, $generating_info, $gen_info_is_safe);
 	if (%opts) {
 		$max_lifetime =
 			$opts{'max_lifetime'} ||
 			$opts{'max_cache_lifetime'};
 		$background_cache = $opts{'background_cache'};
 		$generating_info  = $opts{'generating_info'};
+		$gen_info_is_safe = $opts{'generating_info_is_safe'};
 	}
 	$max_lifetime = -1 unless defined($max_lifetime);
 	$background_cache = 1 unless defined($background_cache);
+	$gen_info_is_safe = 0 unless defined($gen_info_is_safe);
 
 	$self->set_max_lifetime($max_lifetime);
 	$self->set_background_cache($background_cache);
 	$self->set_generating_info($generating_info);
+	$self->set_generating_info_is_safe($gen_info_is_safe);
 
 	return $self;
 }
@@ -110,7 +119,8 @@ sub new {
 # http://perldesignpatterns.com/perldesignpatterns.html#AccessorPattern
 
 # creates get_depth() and set_depth($depth) etc. methods
-foreach my $i (qw(max_lifetime background_cache generating_info)) {
+foreach my $i (qw(max_lifetime background_cache
+                  generating_info generating_info_is_safe)) {
 	my $field = $i;
 	no strict 'refs';
 	*{"get_$field"} = sub {
@@ -214,7 +224,8 @@ sub _set_maybe_background {
 		# to regenerate/refresh the cache (generate data),
 		# or if main process would show progress indicator
 		$pid = fork()
-			if (@stale_result || $self->{'generating_info'});
+			if (@stale_result ||
+			    ($self->{'generating_info'} && $self->{'generating_info_is_safe'}));
 	}
 
 	if ($pid) {
diff --git a/t/t9503/test_cache_interface.pl b/t/t9503/test_cache_interface.pl
index 81f0b76..480cfbc 100755
--- a/t/t9503/test_cache_interface.pl
+++ b/t/t9503/test_cache_interface.pl
@@ -333,6 +333,7 @@ subtest 'serving stale data when (re)generating' => sub {
 
 	# with background generation
 	$cache->set_background_cache(1);
+	$cache->set_generating_info_is_safe(1);
 
 	$cache->set($key, $stale_value);
 	$cache->set_expires_in(0);    # set value is now expired
-- 
1.7.3
Previous: Jakub NarebskiNext: Jakub Narebski
Message 19 of 25 in “[PATCHv6/RFC 00/24] gitweb: Simple file based output caching”
  1. Jakub NarebskiDec 6, 2010
  2. 01/24 t/test-lib.sh: Export also GIT_BUILD_DIR in test_externalJakub Narebski, Dec 6, 2010
  3. 02/24 gitweb: Prepare for splitting gitwebJakub Narebski, Dec 6, 2010
  4. 03/24 gitweb/lib - Very simple file based cacheJakub Narebski, Dec 6, 2010
  5. 04/24 gitweb/lib - Stat-based cache expirationJakub Narebski, Dec 6, 2010
  6. 05/24 gitweb/lib - Regenerate entry if the cache file has size of 0Jakub Narebski, Dec 6, 2010
  7. 06/24 gitweb/lib - Simple output capture by redirecting STDOUTJakub Narebski, Dec 6, 2010
  8. 07/24 gitweb/lib - Cache captured output (using get/set)Jakub Narebski, Dec 6, 2010
  9. 08/24 gitweb: Add optional output cachingJakub Narebski, Dec 6, 2010
  10. 09/24 gitweb/lib - Adaptive cache expiration timeJakub Narebski, Dec 6, 2010
  11. 10/24 gitweb/lib - Use CHI compatibile (compute method) caching interfaceJakub Narebski, Dec 6, 2010
  12. 11/24 gitweb/lib - capture output directly to cache entry fileJakub Narebski, Dec 6, 2010
  13. 12/24 gitweb/lib - Use locking to avoid 'cache miss stampede' problemJakub Narebski, Dec 6, 2010
  14. 13/24 gitweb/lib - No need for File::Temp when lockingJakub Narebski, Dec 6, 2010
  15. 14/24 gitweb/lib - Serve stale data when waiting for filling cacheJakub Narebski, Dec 6, 2010
  16. 15/24 gitweb/lib - Regenerate (refresh) cache in backgroundJakub Narebski, Dec 6, 2010
  17. 16/24 gitweb: Introduce %actions_info, gathering information about actionsJakub Narebski, Dec 6, 2010
  18. 17/24 gitweb: Show appropriate "Generating..." page when regenerating cacheJakub Narebski, Dec 6, 2010
  19. 18/24 gitweb/lib - Configure running 'generating_info' when generating dataJakub Narebski, Dec 6, 2010
  20. 19/24 gitweb: Add startup delay to activity indicator for cacheJakub Narebski, Dec 6, 2010
  21. 20/24 gitweb/lib - Add support for setting error handler in cacheJakub Narebski, Dec 6, 2010
  22. 21/24 gitweb: Wrap die_error to use as error handler for caching engineJakub Narebski, Dec 6, 2010
  23. 22/24 gitweb: Support legacy options used by kernel.org caching engineJakub Narebski, Dec 6, 2010
  24. 23/24 gitweb/lib - Add clear() and size() methods to caching interfaceJakub Narebski, Dec 6, 2010
  25. 24/24 gitweb: Add beginnings of cache administration page (proof of concept)Jakub Narebski, Dec 6, 2010

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