aggregate: Write timestamp next aggregation can happen to .ikiwiki/aggregatetime, to allow for more sophisticated cron jobs.

IkiWiki/Plugin/aggregate.pm

@@ -298,7 +298,7 @@ sub loadstate () {
 	return if $state_loaded;
 	$state_loaded=1;
 	if (-e "$config{wikistatedir}/aggregate") {
-		open(IN, "$config{wikistatedir}/aggregate") ||
+		open(IN, "<", "$config{wikistatedir}/aggregate") ||
 			die "$config{wikistatedir}/aggregate: $!";
 		while (<IN>) {
 			$_=IkiWiki::possibly_foolish_untaint($_);
@@ -335,7 +335,7 @@ sub savestate () {
 	garbage_collect();
 	my $newfile="$config{wikistatedir}/aggregate.new";
 	my $cleanup = sub { unlink($newfile) };
-	open (OUT, ">$newfile") || error("open $newfile: $!", $cleanup);
+	open (OUT, ">", $newfile) || error("open $newfile: $!", $cleanup);
 	foreach my $data (values %feeds, values %guids) {
 		my @line;
 		foreach my $field (keys %$data) {
@@ -356,6 +356,20 @@ sub savestate () {
 	close OUT || error("save $newfile: $!", $cleanup);
 	rename($newfile, "$config{wikistatedir}/aggregate") ||
 		error("rename $newfile: $!", $cleanup);
+
+	my $timestamp=undef;
+	foreach my $feed (keys %feeds) {
+		my $t=$feeds{$feed}->{lastupdate}+$feeds{$feed}->{updateinterval};
+		if (! defined $timestamp || $timestamp > $t) {
+			$timestamp=$t;
+		}
+	}
+	$newfile=~s/\.new$/time/;
+	open (OUT, ">", $newfile) || error("open $newfile: $!", $cleanup);
+	if (defined $timestamp) {
+		print OUT $timestamp."\n";
+	}
+	close OUT || error("save $newfile: $!", $cleanup);
 }
 
 sub garbage_collect () {

debian/changelog

@@ -3,6 +3,8 @@ ikiwiki (3.20100705) UNRELEASED; urgency=low
   * img: Add a margin around images displayed by this directive.
   * comments: Added commentmoderation directive for easy linking to the
     comment moderation queue.
+  * aggregate: Write timestamp next aggregation can happen to
+    .ikiwiki/aggregatetime, to allow for more sophisticated cron jobs.
 
  -- Joey Hess <joeyh@debian.org>  Mon, 05 Jul 2010 13:59:42 -0400
 

doc/plugins/aggregate.mdwn

@@ -5,9 +5,13 @@ This plugin allows content from other feeds to be aggregated into the
 wiki. To specify feeds to aggregate, use the
 [[ikiwiki/directive/aggregate]] [[ikiwiki/directive]].
 
-The [[meta]] and [[tag]] plugins are also recommended. Either the
+## requirements
-[[htmltidy]] or [[htmlbalance]] plugin is suggested, since feeds can easily
+
-contain html problems, some of which these plugins can fix.
+The [[meta]] and [[tag]] plugins are also recommended to be used with this
+one. Either the [[htmltidy]] or [[htmlbalance]] plugin is suggested, since
+feeds can easily contain html problems, some of which these plugins can fix.
+
+## triggering aggregation
 
 You will need to run ikiwiki periodically from a cron job, passing it the
 --aggregate parameter, to make it check for new posts. Here's an example
@@ -15,6 +19,11 @@ crontab entry:
 
 	*/15 * * * * ikiwiki --setup my.wiki --aggregate --refresh
 
+The plugin updates a file `.ikiwiki/aggregatetime` with the unix time stamp
+when the next aggregation run could occur. (The file may be empty, if no
+aggregation is required.) This can be integrated into more complex cron
+jobs or systems to trigger aggregation only when needed.
+
 Alternatively, you can allow `ikiwiki.cgi` to trigger the aggregation. You
 should only need this if for some reason you cannot use cron, and instead
 want to use a service such as [WebCron](http://webcron.org). To enable