backporting logging changes of PR owncloud#27144

cron.php

@@ -118,11 +118,9 @@
 				break;
 			}
 
-			$logger->debug('Run ' . get_class($job) . ' job with ID ' . $job->getId(), ['app' => 'cron']);
 			$job->execute($jobList, $logger);
 			// clean up after unclean jobs
 			\OC_Util::tearDownFS();
-			$logger->debug('Finished ' . get_class($job) . ' job with ID ' . $job->getId(), ['app' => 'cron']);
 
 			$jobList->setLastJob($job);
 			$executedJobs[$job->getId()] = true;

lib/private/BackgroundJob/Job.php

@@ -49,7 +49,20 @@ abstract class Job implements IJob {
 	public function execute($jobList, ILogger $logger = null) {
 		$jobList->setLastRun($this);
 		try {
+			//storing job start time
+			$jobStartTime = time();
+
+			\OCP\Util::writeLog('cron', 'Started background job of class : ' . get_class($this) . ' with arguments : ' . print_r($this->argument, true), \OCP\Util::DEBUG
+			);
+
 			$this->run($this->argument);
+
+			//storing job end time
+			$jobEndTime = time();
+			$timeTaken = $jobEndTime - $jobStartTime;
+
+			\OCP\Util::writeLog('cron', "Finished background job, the job took : $timeTaken seconds, " . "this job is an instance of class : " . get_class($this) . ' with arguments : ' . print_r($this->argument, true), \OCP\Util::DEBUG
+			);
 		} catch (\Exception $e) {
 			if ($logger) {
 				$logger->logException($e, [