Added Systemd.log documentation to config.sample.php

Changed name of default system (not systemd) logger from ownCloud to Nextcloud, to be consistent
Fixed license per https://github.com/nextcloud/server/pull/9760#discussion_r195026784
Pulled upstream updates

Signed-off-by: Johannes Ernst <jernst@indiecomputing.com>

config/config.sample.php

@@ -710,18 +710,24 @@ $CONFIG = array(
  */
 
 /**
- * By default the Nextcloud logs are sent to the ``nextcloud.log`` file in the
- * default Nextcloud data directory.
- * If syslogging is desired, set this parameter to ``syslog``.
- * Setting this parameter to ``errorlog`` will use the PHP error_log function
- * for logging.
+ * This parameter determines where the Nextcloud logs are sent.
+ * ``file``: the logs are written to file ``nextcloud.log`` in the default
+ * Nextcloud data directory. The log file can be changed with parameter
+ * ``logfile``.
+ * ``syslog``: the logs are sent to the system log. This requires a syslog daemon
+ * to be active.
+ * ``errorlog``: the logs are sent to the PHP ``error_log`` function.
+ * ``systemd``: the logs are sent to the Systemd journal. This requires a system
+ * that runs Systemd and the Systemd journal. The PHP extension ``systemd``
+ * must be installed and active.
  *
  * Defaults to ``file``
  */
 'log_type' => 'file',
 
 /**
- * Log file path for the Nextcloud logging type.
+ * Name of the file to which the Nextcloud logs are written if parameter
+ * ``log_type`` is set to ``file``.
  *
  * Defaults to ``[datadirectory]/nextcloud.log``
  */
@@ -738,7 +744,9 @@ $CONFIG = array(
 /**
  * If you maintain different instances and aggregate the logs, you may want
  * to distinguish between them. ``syslog_tag`` can be set per instance
- * with a unique id. Only available if ``log_type`` is set to ``syslog``.
+ * with a unique id. Only available if ``log_type`` is set to ``syslog`` or
+ * ``systemd``.
+ *
  * The default value is ``Nextcloud``.
  */
 'syslog_tag' => 'Nextcloud',

lib/private/Log/Syslog.php

@@ -39,7 +39,7 @@ class Syslog implements IWriter {
 	];
 
 	public function __construct(IConfig $config) {
-		openlog($config->getSystemValue('syslog_tag', 'ownCloud'), LOG_PID | LOG_CONS, LOG_USER);
+		openlog($config->getSystemValue('syslog_tag', 'Nextcloud'), LOG_PID | LOG_CONS, LOG_USER);
 	}
 
 	public function __destruct() {

lib/private/Log/Systemdlog.php

@@ -4,7 +4,7 @@
  *
  * @author Johannes Ernst <jernst@indiecomputing.com>
  *
- * @license AGPL-3.0
+ * @license GNU AGPL version 3 or any later version
  *
  * This code is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License, version 3,
@@ -22,6 +22,7 @@
 
 namespace OC\Log;
 
+use OC\HintException;
 use OCP\ILogger;
 use OCP\IConfig;
 use OCP\Log\IWriter;
@@ -50,11 +51,20 @@ class Systemdlog implements IWriter {
 		ILogger::FATAL => 2,
 	];
 
+	protected $syslogId;
+
 	public function __construct(IConfig $config) {
+		if(!function_exists('sd_journal_send')) {
+			throw new HintException(
+				'PHP extension php-systemd is not available.',
+				'Please install and enable PHP extension systemd if you wish to log to the Systemd journal.');
+
+		}
+		$this->syslogId = $config->getSystemValue('syslog_tag', 'Nextcloud');
 	}
 
 	/**
-	 * write a message in the log
+	 * Write a message to the log.
 	 * @param string $app
 	 * @param string $message
 	 * @param int $level
@@ -62,7 +72,7 @@ class Systemdlog implements IWriter {
 	public function write(string $app, $message, int $level) {
 		$journal_level = $this->levels[$level];
 		sd_journal_send('PRIORITY='.$journal_level,
-				'SYSLOG_IDENTIFIER=nextcloud',
+				'SYSLOG_IDENTIFIER='.$this->syslogId,
 				'MESSAGE={'.$app.'} '.$message);
 	}
 }