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LimeSurvey Community Edition Version 6.15.5+250724 
Private Server running Ubuntu 11.4.0
Survey theme:  Bootstrap Vanilla, customized

We run a survey every month for our organization, about 250-300 respondents.  Every month I get a small number ( 4-8 ) people complain because they get an error message AFTER they click Submit.  It is a one page survey.  The error message is *usually* a 400: Bad Request message, but not always.  I have customized the "layout_errors.twig" to inform the user that the survey is open only between 1st and 10th of the month.  But, they are getting the message even when the survey is OPEN during the correct window.  Again, some are getting a 400: Bad Request error, sometimes no error number is reported.

It's impossible for me to duplicate it.  The errors are coming from Mac/Safari and Windows/Chrome.  

Only about 1% of the respondents report an error.  If they retry the survey page, it almost always works the 2nd time, but the user has to re-enter their data, which they are not happy about.  I have my php session timer set to 2 hours, and the respondents will get the error even after just 5-8 minutes entering their answers.

I have tried to figure out what error(s) the server side (apache or LimeSurvey) is seeing, but I can't figure out what to look for or where to look.

any suggestions?
thanks,
Rick

Error 400 indicates some kind of server issue. I don't think it has to do with the session or anything like that (you can never exclude it, but I think chances are little).

I think you will have to try to get any logs from the server to see what happened.

Do you send admin notification emails in your survey?

In general, we do not recommend one page surveys, for this very reason. If something goes wrong, everything is lost. Of course, this is not a big deal with very short surveys, but if there are more than 2-3 questions, I always recommend to separate them, either by using question per question or group by group. These are usually the standard anyway.

Is this a closed (using tokens) or an open survey?

Thank you for taking the time. Ive looked all over for the server logs, including the Apache 2 logs and can't find any information that helps. We used to have the survey on several pages and had too many complaints.

Open survey

holch wrote:

Do you send admin notification emails in your survey?

What about the sending of admin notifications?
When there are problems with sending the email (Email server doesn't respond, etc.), Limesurvey likes to throw errors.

Sorry, I missed that question.

Yes, we send out admin notifications. The basic admin email goes to me directly with just the name of the person who completed the survey (entered by the user in the survey). The admin email goes to the individual with their responses; the user enters their own email address with validation of the domain name = @ourdomain.org. When there is no error, the emails are sent out correctly. I have scoured the mail logs in /var/log (mail.err, maillog, maillog.processed, syslog) and I don't see any error messages related to this failure. I am stumped.

Thanks again for your assistance, on your own free time. I do appreciate it.

there is a good chance that this error is caused by the email server. When sending the the admin notification fails, generally Limesurvey throws an error.

When there is no error, the emails are sent out correctly.

I assume this means that when the error occurs no email is sent? That doesn't necessarily mean that this is caused through a failure of sending the email, but there is a good chance that this is related. E.g. the email server is momentarily down or the connection between the LS server and the email server is not working.

What is the email method chosen? SMTP?

One other thing: Are there any responses saved in the database for those cases where the error occurs?

Thanks again, @holch, for taking the time to help me on this. I know you are a volunteer and your time is valuable. Thank you.

email method is SMTP via gmail. smtp.gmail.com:587. Almost all (99% or more) emails are sent and received successfully. I understand there could be a glitch for a very short window, but we have people completing the survey frequently throughout the day. Since the basic admin notification comes to my email box I can see when people submit their surveys. There were successful submissions and emails within a few minutes on either side of the failures. I don't see any errors or failures in the mail logs. I know the email server could be the cause, but I can't think of any way to determine that.

I have enabled DEBUG=1 within the LS system, but, if I understand it correctly, those errors are displayed in the browser and not logged anywhere. Is that correct? Is there a way to log these errors to a server file?

With the 2 most recent failures where I was actively working with the user, I got their public IP address and looked in the DB.
One of the failures was a "400: Bad Request" error and there was no entry in the DB around that time. The other failure had no http error (such as 400, 401, 404) but the layout_error.twig was activated and displayed. For that failure there is an incomplete survey response in the DB for his IP address.

How we get here: our organization sends out a reminder email every month on the 1st day. (the survey is active only from 1st to the 10th of the month). The email is sent via an email service that attaches a tracking code to the survey URL. Such as: survey.ourorgdomain.org / index.php / 123456? lang=en & ct=YTo1OntzOjY6InNvdXJjZSI........

99% of the people click on the link in the email and the entire process works successfully. A small handful clikc on the link and they get to the first (and only) page of the survey, but then get a failure when they click on "Submit"

With the two failures that I know of this week, I asked each of them to use the direct link and not the tracking link in the email. In both cases it worked correctly, but that could be that the small window of email failure was resolved, too. I'm stumped.

Is there more information in some log area somewhere that I don't know about and should be looking at? I've looked at the apache2 logs, and seeing nothing there either.

thanks again for your help.
Rick

Sorry that I can't be of more help. I think users like Denis might be more knowledgeable about these issues related to server issues and debug mode.

thanks so much for your time to look into it.