Please help us help you and fill where relevant:
Your LimeSurvey version: 6.1.8+230717
Own server or LimeSurvey hosting: Own server
Survey theme/template: Custom extended from bootswatch
==================
Hello Folks,

Recently upgraded to this newer version. We have a pretty long survey that has around 135 questions. After submitting a survey, it hangs for several seconds and then I get a '504 Gateway Time-out' error. I can see that the survey responses are being saved in the database. I have debug log turned on to display as well to write at the application level. But I am not getting any detailed error log. Could someone please provide some guidance on how to debug this issue? BTW, I ran the Survey Logic File and got the 'No syntax errors detected in this survey.' message. Thanks in advance!

Debug setting examples:

---

        'log' => array(
            'routes' => array(
                'fileError' => array(
                    'class' => 'CFileLogRoute',
                    'levels' => 'warning, error',
                    'except' => 'exception.CHttpException.404',
                ),
            ),
        ),

---

debug=>1,
'debugsql'=>1,
 

After spending hours and hours troubleshooting the issue, I found that there is an issue with sending out admin notification emails on submission of the survey. As a result the submission of the survey failed as well. Once I turned off the admin notification the survey submission worked. Not sure if this is a bug with LimeSurvey or not.

Setting this as resolved.

A fail in sending the admin notification should not cause an error message like this, in my opinion.

Limesurvey had some issues with this before but I am not sure if this has ever been fixed and came back or if this has never been fixed.

In my opinion, Limesurvey should not show any error to the respondents, just because the admin notification failed.

I would say this is worth a bug report: bugs.limesurvey.org (same credentials as the forum).

holch wrote:

A fail in sending the admin notification should not cause an error message like this, in my opinion.
 

The notification system has no queue, to separate submission and notification. If there is an issue when sending an email (e.g. the sending mailserver is responding very slow), you will end up with unpredictible behaviour during the submit process of an survey. I never use notification to prevent loss of submissions.
It would be nice to allow to switch the process. Accept submission and then try to send a notification. The risk here is that you get no notification for a submission done.

Remark: I haven't inspect the php code around admin notification in LS5/LS6. Perhaps there was an inprovement.

@Jello: I know. However, I stlll think there should be a way to avoid error messages to the respondents the way it is presented, just because the admin notification wasn't sent.

I think Limesurvey should either not show any error message to the respondent if the admin notification couldn't be sent, or it should tell them that their survey data has been stored, but there was an error with the admin notification (but I don't think that this information is relevant for survey takes, so I would rather leave it out).

There must be a better way to seperate those two processes (submit survey data and send admin notification). Priority should always be on survey data, I think. Not receiving a admin notification is bad, but storing survey data is more important (and avoiding to confuse respondents as well).