TMP SESS_files problem after FB links to survey

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8 months 4 weeks ago #147523 by Feorod
Feorod created the topic: TMP SESS_files problem after FB links to survey
Hi !

Surveys halted today when server space topped. Found out TMP files (SESS_...) 1Mb-sized have been piling up since last week when Facebook and LinkedIn links (bit.ly) were posted. Some of these SESS_ files have a clear "facebook.com" in the header.

So TMP folder doesn't seem to purge itself automatically since then.

1) Is this a known LS issue ? If so, is there a solution to get TMP to purge itself ?

2) If not, is it safe to delete manually some of the oldest SESS_ files to make disk space ?

Hope I expressed this clearly...

Thanx in advance,

Eric

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8 months 3 weeks ago #147526 by DenisChenu
DenisChenu replied the topic: TMP SESS_files problem after FB links to survey
Purge session directory is the job of server , not LimeSurvey

Assistance on LimeSurvey forum and LimeSurvey core development are on my free time.
I'm not a LimeSurvey GmbH member, professional service on demand (or search sondages pro).
An error happen ? Before make a new topic : remind the Debug mode .

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8 months 3 weeks ago #147533 by jelo
jelo replied the topic: TMP SESS_files problem after FB links to survey

DenisChenu wrote: Purge session directory is the job of server , not LimeSurvey

From the post of the threadstarter I cannot conclude that the purging of session isn't working.


LimeSurvey is abusive when it comes to session size.
I've never encountered a application which creates for every session files with 1MB and more.

The issues around Limesurvey and session are happening even when everything is working as intended.
The typical setups of webhosting are not expecting big session files like this.

Typical setup:
TMP-Directory is used as place to store PHP-Session files.
TMP-Directory is mounted as separate partition with a limited amount of storage space.
The session files have often the default lifetime of 1440 seconds.

When your survey is hit by many people in a small amount of time (e.g posting survey link of facebook, twitter etc), a session file of 1MB or more is created for every user visiting the survey. Even for everybody leaving the survey in the next seconds.

If the session storage space is filled up, the cleaning of the session files often is no longer working correctly. The php scripts no longer working in a stable way. You need to delete the oldest session files by hand. That sometimes means kicking out survey respondents.

To prevent these situation till Limesurvey comes up with a proper session handling you can do a few things.

1.) Reduce session lifetime via php.ini. Session files will be purged quicker, but you might loose surveys when respondents are doing the survey while they can be disturbed. E.g. if you conduct a B2B survey with sales people they might need to pause answering your survey and will come back in an hour. The session lifetime has to be related to your survey respondents.
I sometimes use session lifetimes of 24 hours. So reducing the session lifetime is often not an option.

2.) Increase session storage space. That can be done via changing the storage path for php session files away from the TMP directory. R.G. Create TMP_PHP without storage limits. Or increase the TMP partition to cope with a lot of 1MB session files from LimeSurvey.

3.) Distribute invitation links differently to prevent having to cope with a lot of visitors in a small amount of time.

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8 months 3 weeks ago #147543 by Feorod
Feorod replied the topic: TMP SESS_files problem after FB links to survey
Thank you so much for this extensive and comprehensive answer.
I should have sent a screen capture, sorry.

The server seems to have woken up during the night. Storage space went from 1045Mb to 175Mb...

I don't know what happened this week, but everything seems to be back in order.

Thanx again for being there :)

Eric

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8 months 3 weeks ago #147547 by jelo
jelo replied the topic: TMP SESS_files problem after FB links to survey

Feorod wrote: I don't know what happened this week, but everything seems to be back in order.

Looks like the "run" on your survey is over. The Facebook and Linkedn links are no longer clicked in a high rate.
That helps your webserver to clean up the session files.

That's an educated guess. It will depend on your hosting/server plan and if you get some kind of managed services.

If the free storage space changed from 1045Mb to 175Mb, you should be back to a higher amount of free storage space now.

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8 months 3 weeks ago #147549 by Feorod
Feorod replied the topic: TMP SESS_files problem after FB links to survey
Jelo,

Thank you very much for your knowledge. It's truly appreciated.

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