wikimedia/mediawiki-core

<?php
/**
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

namespace MediaWiki\Logger\Monolog;

use Monolog\Handler\SyslogUdpHandler;
use Monolog\Logger;

/**
 * Write logs to syslog with the channel appended to the application name.
 *
 * This use case for this handler is to emulate Wikimedia Foundation's
 * udp2log system by leveraging syslog (and e.g. Rsyslog/Kafka) and
 * allow an unstructured string to pass through mostly as-is, with the
 * exception of the channel name, which is encoded in transit as part
 * of the syslog "application name". It is intended that the syslog
 * consumer "wildcard" subscribes to all messages with the app prefix,
 * and then * strips it off at some point before writing the messages
 * to a log file named after the channel.
 *
 * Transition plan (2016):
 * - https://phabricator.wikimedia.org/T205856#4957430
 * - https://phabricator.wikimedia.org/T126989
 *
 * @unstable
 * @since 1.32
 * @ingroup Debug
 * @copyright © 2019 Wikimedia Foundation and contributors
 */
class MwlogHandler extends SyslogUdpHandler {

    /**
     * @var string
     */
    private $appprefix;

    /**
     * @var string
     */
    private $hostname;

    /**
     * @param string $appprefix Application prefix to use, channel will be appended.
     * @param string $host Syslog host
     * @param int $port Syslog port
     * @param int $facility Syslog message facility
     * @param int $level The minimum logging level at which this handler
     *   will be triggered
     * @param bool $bubble Whether the messages that are handled can bubble up
     *   the stack or not
     */
    public function __construct(
        $appprefix,
        $host,
        $port = 514,
        $facility = LOG_USER,
        $level = Logger::DEBUG,
        $bubble = true
    ) {
        parent::__construct( $host, $port, $facility, $level, $bubble );
        $this->appprefix = $appprefix;
        $this->hostname = php_uname( 'n' );
    }

    protected function syslogHeader( $severity, $app ) {
        $pri = $severity + $this->facility;

        // Goofy date format courtesy of RFC 3164 :(
        // RFC 3164 actually specifies that the day of month should be space
        // padded rather than unpadded but this seems to work with rsyslog and
        // Logstash.
        $timestamp = date( 'M j H:i:s' );

        return "<{$pri}>{$timestamp} {$this->hostname} {$app}: ";
    }

    private function splitMessageIntoLines( $message ): array {
        if ( is_array( $message ) ) {
            $message = implode( "\n", $message );
        }

        return preg_split( '/$\R?^/m', (string)$message, -1, PREG_SPLIT_NO_EMPTY );
    }

    protected function write( array $record ): void {
        $lines = $this->splitMessageIntoLines( $record['formatted'] );
        $header = $this->syslogHeader(
            $this->logLevels[$record['level']],
            $this->appprefix . $record['channel'] );

        foreach ( $lines as $line ) {
            $this->socket->write( $line, $header );
        }
    }
}