[RFC PATCHv4 17/17] gitweb: Add startup delay to activity indicator for cache

[Jakub Narebski <jnareb@gmail.com>]

This adds support for [optional] startup delay to git_generating_data_html()
subroutine, which is used to provide "Generating..." page as activity
indicator when waiting for page to be generated if caching.  If the data
(page contents) gets generated within $generating_options{'staryp_delay'}
seconds, the "Generating..." page won't get displayed.

This feature was created in response to complaint by Petr 'Pasky' Baudis'
about "Generating..." feature.

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
---
 gitweb/gitweb.perl |   20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)

diff --git a/gitweb/gitweb.perl b/gitweb/gitweb.perl
index 8d7540e..313114c 100755
--- a/gitweb/gitweb.perl
+++ b/gitweb/gitweb.perl
@@ -326,6 +326,9 @@ our %cache_options = (
 # (which means that $cache_options{'generating_info'} is set to coderef);
 # override them with $GITWEB_CONFIG as necessary.
 our %generating_options = (
+	# The delay before displaying "Generating..." page, in seconds.  It is
+	# intended for "Generating..." page to be shown only when really needed.
+	'startup_delay' => 1,
 	# The time between generating new piece of output to prevent from
 	# redirection before data is ready, i.e. time between printing each
 	# dot in activity indicator / progress info, in seconds.
@@ -3368,6 +3371,23 @@ sub git_generating_data_html {
 	#	return;
 	#}
 
+	# Initial delay
+	if ($generating_options{'startup_delay'} > 0) {
+		eval {
+			local $SIG{ALRM} = sub { die "alarm clock restart\n" }; # NB: \n required
+			alarm $generating_options{'startup_delay'};
+			flock($lock_fh, LOCK_SH); # blocking readers lock
+			alarm 0;
+		};
+		if ($@) {
+			# propagate unexpected errors
+			die $@ if $@ !~ /alarm clock restart/;
+		} else {
+			# we got response within 'startup_delay' timeout
+			return;
+		}
+	}
+
 	# Stop capturing response, just in case (we should be not generating response)
 	#
 	capture_stop(); # or gitweb could use 'print $STDOUT' in place of 'print STDOUT'
-- 
1.7.0.1