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Add support for stale-if-error Cache-Control directive #58

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Add support for stale-if-error Cache-Control directive #58

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20 changes: 18 additions & 2 deletions advanced-cache.php
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,8 @@ class batcache {
// This is the base configuration. You can edit these variables or move them into your wp-config.php file.
var $max_age = 300; // Expire batcache items aged this many seconds (zero to disable batcache)

var $stale_if_error = 0; // If not zero, will set stale-if-error extension for Cache-Control (e.g. for Squid)

var $remote = 0; // Zero disables sending buffers to remote datacenters (req/sec is never sent)

var $times = 2; // Only batcache a page after it is accessed this many times... (two or more)
Expand Down Expand Up @@ -107,6 +109,20 @@ function redirect_status( $status, $location ) {
return $status;
}

function get_cache_control_directives() {
$directives = array();
$max_age = $this->max_age;
if ( ! empty( $this->cache['time'] ) ) {
$max_age = max( 0, $max_age - time() + $this->cache['time'] );
}
$directives[] = sprintf( 'max-age=%d', $max_age );
$directives[] = 'must-revalidate';
if ( $this->stale_if_error > 0 ) {
$directives[] = sprintf( 'stale-if-error=%d', $this->stale_if_error );
}
return $directives;
}

function do_headers( $headers1, $headers2 = array() ) {
// Merge the arrays of headers into one
$headers = array();
Expand Down Expand Up @@ -228,7 +244,7 @@ function ob($output) {
if ( !isset($this->cache['headers']['Last-Modified']) )
header( 'Last-Modified: ' . gmdate( 'D, d M Y H:i:s', $this->cache['time'] ) . ' GMT', true );
if ( !isset($this->cache['headers']['Cache-Control']) )
header("Cache-Control: max-age=$this->max_age, must-revalidate", false);
header( 'Cache-Control: ' . join( ', ', $this->get_cache_control_directives() ), false );
}

$this->do_headers( $this->headers );
Expand Down Expand Up @@ -509,7 +525,7 @@ function add_debug_html_to_output( $debug_html ) {
// Use the batcache save time for Last-Modified so we can issue "304 Not Modified" but don't clobber a cached Last-Modified header.
if ( $batcache->cache_control && !isset($batcache->cache['headers']['Last-Modified'][0]) ) {
header( 'Last-Modified: ' . gmdate( 'D, d M Y H:i:s', $batcache->cache['time'] ) . ' GMT', true );
header('Cache-Control: max-age=' . ($batcache->cache['max_age'] - time() + $batcache->cache['time']) . ', must-revalidate', true);
header( 'Cache-Control: ' . join( ', ', $batcache->get_cache_control_directives() ), true );
}

// Add some debug info just before </head>
Expand Down