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wpcom_file_get_contents()
/*
* Fetch a remote URL and cache the result for a certain period of time
* See http://lobby.vip.wordpress.com/best-practices/fetching-remote-data/ for more details
*
* This function originally used file_get_contents(), hence the function name.
* While it no longer does, it still operates the same as the basic PHP function.
*
* We strongly recommend not using a $timeout value of more than 3 seconds as this
* function makes blocking requests (stops page generation and waits for the response).
*/
function wpcom_vip_file_get_contents( $url, $timeout = 3, $cache_time = 900, $extra_args = array() ) {
global $blog_id;
$extra_args_defaults = array(
'obey_cache_control_header' => true, // Uses the "cache-control" "max-age" value if greater than $cache_time
'http_api_args' => array(), // See http://codex.wordpress.org/Function_API/wp_remote_get
);
$extra_args = wp_parse_args( $extra_args, $extra_args_defaults );
$cache_key = md5( serialize( array_merge( $extra_args, array( 'url' => $url ) ) ) );
$backup_key = $cache_key . '_backup';
$disable_get_key = $cache_key . '_disable';
$cache_group = 'wpcom_vip_file_get_contents';
// Temporary legacy keys to prevent mass cache misses during our key switch
$old_cache_key = md5( $url );
$old_backup_key = 'backup:' . $old_cache_key;
$old_disable_get_key = 'disable:' . $old_cache_key;
// Let's see if we have an existing cache already
// Empty strings are okay, false means no cache
if ( false !== $cache = wp_cache_get( $cache_key, $cache_group) )
return $cache;
// Legacy
if ( false !== $cache = wp_cache_get( $old_cache_key, $cache_group) )
return $cache;
// The timeout can be 1 to 10 seconds, we strongly recommend no more than 3 seconds
$timeout = min( 10, max( 1, (int) $timeout ) );
if ( $timeout > 3 )
_doing_it_wrong( __FUNCTION__, 'Using a timeout value of over 3 seconds is strongly discouraged because users have to wait for the remote request to finish before the rest of their page loads.', null );
$server_up = true;
$response = false;
$content = false;
// Check to see if previous attempts have failed
if ( false !== wp_cache_get( $disable_get_key, $cache_group ) ) {
$server_up = false;
}
// Legacy
elseif ( false !== wp_cache_get( $old_disable_get_key, $cache_group ) ) {
$server_up = false;
}
// Otherwise make the remote request
else {
$http_api_args = (array) $extra_args['http_api_args'];
$http_api_args['timeout'] = $timeout;
$response = wp_remote_get( $url, $http_api_args );
}
// Was the request successful?
if ( $server_up && ! is_wp_error( $response ) && 200 == wp_remote_retrieve_response_code( $response ) ) {
$content = wp_remote_retrieve_body( $response );
$cache_header = wp_remote_retrieve_header( $response, 'cache-control' );
if ( is_array( $cache_header ) )
$cache_header = array_shift( $cache_header );
// Obey the cache time header unless an arg is passed saying not to
if ( $extra_args['obey_cache_control_header'] && $cache_header ) {
$cache_header = trim( $cache_header );
// When multiple cache-control directives are returned, they are comma separated
foreach ( explode( ',', $cache_header ) as $cache_control ) {
// In this scenario, only look for the max-age directive
if( 'max-age' == substr( trim( $cache_control ), 0, 7 ) )
list( $cache_header_type, $cache_header_time ) = explode( '=', trim( $cache_control ) );
}
// If the max-age directive was found and had a value set that is greater than our cache time
if ( isset( $cache_header_type ) && isset( $cache_header_time ) && $cache_header_time > $cache_time )
$cache_time = (int) $cache_header_time; // Casting to an int will strip "must-revalidate", etc.
}
// The cache time shouldn't be less than a minute
// Please try and keep this as high as possible though
// It'll make your site faster if you do
$cache_time = (int) $cache_time;
if ( $cache_time < 60 )
$cache_time = 60;
// Cache the result
wp_cache_set( $cache_key, $content, $cache_group, $cache_time );
// Additionally cache the result with no expiry as a backup content source
wp_cache_set( $backup_key, $content, $cache_group );
// So we can hook in other places and do stuff
do_action( 'wpcom_vip_remote_request_success', $url, $response );
}
// Okay, it wasn't successful. Perhaps we have a backup result from earlier.
elseif ( $content = wp_cache_get( $backup_key, $cache_group ) ) {
// If a remote request failed, log why it did
if ( $response && ! is_wp_error( $response ) ) {
error_log( "wpcom_vip_file_get_contents: Blog ID {$blog_id}: Failure for $url and the result was: " . maybe_serialize( $response['headers'] ) . ' ' . maybe_serialize( $response['response'] ) );
} elseif ( $response ) { // is WP_Error object
error_log( "wpcom_vip_file_get_contents: Blog ID {$blog_id}: Failure for $url and the result was: " . maybe_serialize( $response ) );
}
}
// Legacy
elseif ( $content = wp_cache_get( $old_backup_key, $cache_group ) ) {
// If a remote request failed, log why it did
if ( $response && ! is_wp_error( $response ) ) {
error_log( "wpcom_vip_file_get_contents: Blog ID {$blog_id}: Failure for $url and the result was: " . maybe_serialize( $response['headers'] ) . ' ' . maybe_serialize( $response['response'] ) );
} elseif ( $response ) { // is WP_Error object
error_log( "wpcom_vip_file_get_contents: Blog ID {$blog_id}: Failure for $url and the result was: " . maybe_serialize( $response ) );
}
}
// We were unable to fetch any content, so don't try again for another 60 seconds
elseif ( $response ) {
wp_cache_set( $disable_get_key, 1, $cache_group, 60 );
// If a remote request failed, log why it did
if ( $response && ! is_wp_error( $response ) ) {
error_log( "wpcom_vip_file_get_contents: Blog ID {$blog_id}: Failure for $url and the result was: " . maybe_serialize( $response['headers'] ) . ' ' . maybe_serialize( $response['response'] ) );
} elseif ( $response ) { // is WP_Error object
error_log( "wpcom_vip_file_get_contents: Blog ID {$blog_id}: Failure for $url and the result was: " . maybe_serialize( $response ) );
}
// So we can hook in other places and do stuff
do_action( 'wpcom_vip_remote_request_error', $url, $response );
}
return $content;
}
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