# Maddening error: "marshal data too short" **URL:** \ **Category:** Rails\ **Created:** [August 7, 2009, 9:25am UTC](https://www.ruby-forum.com/t/maddening-error-marshal-data-too-short/173359 "2009-08-07T09:25:05Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Kyle\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/ecd19e/32.png) [@Kyle\_F](https://www.ruby-forum.com/u/Kyle_F)\ **Post date:** [August 7, 2009, 9:25am UTC](https://www.ruby-forum.com/t/maddening-error-marshal-data-too-short/173359/1 "2009-08-07T09:25:05Z")
I’m occasionally getting an odd Rails error that says “marshal data too short”. Our entire web app seems to be working fine – we can post forms, save models, redirect, login, etc, without any problems. Then out of nowhere a request will result in the 500 error “marshal data too short”. Subsequent requests to _any_ page then result in the same error – even pages that were previously working. The only way to (temporarily) make the problem go away is to `rake db:sessions:clear` – but I need to determine what the root cause is. Some forum posts led me to believe the `data` column in the Rails sessions table was too short. I have it as ‘text’, which should support roughly 65,000 characters. The data in my actual session is only 305 characters, so I doubt this is the problem. It’s basically impossible for me to replicate the problem exactly, as I have no idea what’s triggering it. If anyone could shed some light on how I could investigate further, I’d be ever so thankful 🙂 Kyle. ---
**Author:** ![Kyle\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/ecd19e/32.png) [@Kyle\_F](https://www.ruby-forum.com/u/Kyle_F)\ **Post date:** [August 7, 2009, 9:28am UTC](https://www.ruby-forum.com/t/maddening-error-marshal-data-too-short/173359/2 "2009-08-07T09:28:01Z")
On Aug 7, 12:07 am, Kyle F. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Some forum posts led me to believe the `data` column in the Rails > sessions table was too short. I have it as ‘text’, which should > support roughly 65,000 characters. The data in my actual session is > only 305 characters, so I doubt this is the problem. I wouldn’t use a text column (use a blob column instead). If you use a text column then the database is expecting the content to be actual text. If it’s expecting utf8 and you give it invalid utf8 data it may well truncate your data at the first occurrence of illegal data. Fred ---
**Author:** ![Kyle\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/ecd19e/32.png) [@Kyle\_F](https://www.ruby-forum.com/u/Kyle_F)\ **Post date:** [August 7, 2009, 5:03pm UTC](https://www.ruby-forum.com/t/maddening-error-marshal-data-too-short/173359/3 "2009-08-07T17:03:25Z")
> I wouldn’t use a text column (use a blob column instead). AFAIK, we just used the default table and column types that Rails creates for sessions. Why in the world wouldn’t it use a more robust column type in the first place? ---
**Author:** ![Kyle\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/ecd19e/32.png) [@Kyle\_F](https://www.ruby-forum.com/u/Kyle_F)\ **Post date:** [August 7, 2009, 5:08pm UTC](https://www.ruby-forum.com/t/maddening-error-marshal-data-too-short/173359/4 "2009-08-07T17:08:04Z")
Kyle F. wrote: > > I wouldn’t use a text column (use a blob column instead). > > AFAIK, we just used the default table and column types that Rails > creates for sessions. Why in the world wouldn’t it use a more robust > column type in the first place? Kyle, How much stuff are you storing in user sessions? ilan ---
**Author:** ![Kyle\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/ecd19e/32.png) [@Kyle\_F](https://www.ruby-forum.com/u/Kyle_F)\ **Post date:** [August 7, 2009, 5:43pm UTC](https://www.ruby-forum.com/t/maddening-error-marshal-data-too-short/173359/5 "2009-08-07T17:43:49Z")
On Aug 7, 4:02 pm, Kyle F. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > I wouldn’t use a text column (use a blob column instead). > > AFAIK, we just used the default table and column types that Rails > creates for sessions. Why in the world wouldn’t it use a more robust > column type in the first place? What session store are you using? if it’s the default activerecord store then it’s base64 encoding everything and so you can ignore my comment. If I were you I’d instrument the session store code to log when it updates the sessions table and when it loads from it: if you can spot how the data changes when this error occurs that may be a valuable clue into why it changes. Fred ---
**Author:** ![Kyle\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/ecd19e/32.png) [@Kyle\_F](https://www.ruby-forum.com/u/Kyle_F)\ **Post date:** [August 7, 2009, 5:46pm UTC](https://www.ruby-forum.com/t/maddening-error-marshal-data-too-short/173359/6 "2009-08-07T17:46:45Z")
> How much stuff are you storing in user sessions? We’re storing basic authentication info and then a little object that holds some data to pre-populate a form. I wouldn’t think that’s too much data to be storing in a session… The last time I encountered this error I ran `SELECT LENGTH(data) FROM sessions;` and it returned “305”, which from what I understand is the number of bytes – well below the max length of TEXT columns. I’m going to try using a BLOB, and we’ll see if the error occurs again. However, I have a feeling the problem isn’t too much data in the session, so feel free to post any other suggestions 🙂 ---
**Author:** ![Kyle\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/ecd19e/32.png) [@Kyle\_F](https://www.ruby-forum.com/u/Kyle_F)\ **Post date:** [August 7, 2009, 5:48pm UTC](https://www.ruby-forum.com/t/maddening-error-marshal-data-too-short/173359/7 "2009-08-07T17:48:30Z")
Fred: we’re using activerecord. Perhaps I’ll try adding some code to log what’s happening behind the scenes.