From: Steinar H. Gunderson <sgunderson@bigfoot.com>
Date: Sun, 16 Nov 2014 12:35:07 +0000 (+0100)
Subject: Add a separate script for counting viewers from Varnish logs.
X-Git-Url: https://git.sesse.net/?p=remoteglot;a=commitdiff_plain;h=d5d7dc50fe8f44711a2e4d52563ff40db029e819

Add a separate script for counting viewers from Varnish logs.
---

diff --git a/varnishcount.pl b/varnishcount.pl
new file mode 100755
index 0000000..82356d6
--- /dev/null
+++ b/varnishcount.pl
@@ -0,0 +1,61 @@
+#! /usr/bin/perl
+use Time::HiRes;
+use LWP::Simple;
+require 'config.pm';
+use strict;
+use warnings;
+no warnings qw(once);
+
+$SIG{ALRM} = sub { output(); };
+Time::HiRes::alarm(1.0, 1.0);
+
+open my $fh, "-|", "varnishncsa -F '%{%s}t %U %q tffb=%{Varnish:time_firstbyte}x' -q 'ReqURL ~ \"^/analysis.pl\"'"
+	or die "varnishncsa: $!";
+my %uniques = ();
+
+while (<$fh>) {
+	chomp;
+	m#(\d+) /analysis.pl \?ims=\d+&unique=(.*) tffb=(.*)# or next;
+	$uniques{$2} = {
+		last_seen => $1 + $3,
+		grace => undef,
+	};
+	my $now = time;
+	print "[$now] $1 $2 $3\n";
+}
+
+sub output {
+	my $mtime = (stat($remoteglotconf::json_output))[9] - 1;  # Compensate for subsecond issues.
+	my $now = time;
+
+	while (my ($unique, $hash) = each %uniques) {
+		my $last_seen = $hash->{'last_seen'};
+		if ($now - $last_seen <= 5) {
+			# We've seen this user in the last five seconds;
+			# it's okay.
+			next;
+		}
+		if ($last_seen >= $mtime) {
+			# This user has the latest version;
+			# they are probably just hanging.
+			next;
+		}
+		if (!defined($hash->{'grace'})) {
+			# They have five seconds after a new JSON has been
+			# provided to get get it, or they're out.
+			# We don't simply use $mtime, since we don't want to
+			# reset the grace timer just because a new JSON is
+			# published.
+			$hash->{'grace'} = $mtime;
+		}
+		if ($now - $hash->{'grace'} > 5) {
+			printf "Timing out %s (last_seen=%d, now=%d, mtime=%d, grace=%d)\n",
+				$unique, $last_seen, $now, $mtime, $hash->{'grace'};
+			delete $uniques{$unique};
+		}
+	}
+
+	my $num_viewers = scalar keys %uniques;	
+	printf "%d entries in hash, mtime=$mtime\n", scalar keys %uniques;
+	LWP::Simple::get('http://127.0.0.1:5000/override-num-viewers?num=' . $num_viewers);	
+}
diff --git a/www/serve-analysis.js b/www/serve-analysis.js
index 362b14b..19ab936 100644
--- a/www/serve-analysis.js
+++ b/www/serve-analysis.js
@@ -32,6 +32,10 @@ var last_seen_clients = {};
 // hanging indefinitely (which might have them return errors).
 var touch_timer = undefined;
 
+// If we are behind Varnish, we can't count the number of clients
+// ourselves, so some external log-tailing daemon needs to tell us.
+var viewer_count_override = undefined;
+
 var reread_file = function(event, filename) {
 	if (filename != path.basename(json_filename)) {
 		return;
@@ -84,6 +88,21 @@ var send_404 = function(response) {
 	response.write('Something went wrong. Sorry.');
 	response.end();
 }
+var handle_viewer_override = function(request, u, response) {
+	// Only accept requests from localhost.
+	var peer = request.socket.localAddress;
+	if ((peer != '127.0.0.1' && peer != '::1') || request.headers['x-forwarded-for']) {
+		console.log("Refusing viewer override from " + peer);
+		send_404(response);
+	} else {
+		viewer_count_override = (u.query)['num'];
+		response.writeHead(200, {
+			'Content-Type': 'text/plain',
+		});
+		response.write('OK.');
+		response.end();
+	}
+}
 var send_json = function(response, accept_gzip, num_viewers) {
 	var headers = {
 		'Content-Type': 'text/json',
@@ -110,6 +129,10 @@ var mark_recently_seen = function(unique) {
 	}
 }
 var count_viewers = function() {
+	if (viewer_count_override !== undefined) {
+		return viewer_count_override;
+	}
+
 	var now = (new Date).getTime();
 
 	// Go through and remove old viewers, and count them at the same time.
@@ -146,7 +169,10 @@ server.on('request', function(request, response) {
 	var unique = (u.query)['unique'];
 
 	console.log((new Date).getTime()*1e-3 + " " + request.url);
-
+	if (u.pathname === '/override-num-viewers') {
+		handle_viewer_override(request, u, response);
+		return;
+	}
 	if (u.pathname !== '/analysis.pl') {
 		// This is not the request you are looking for.
 		send_404(response);