How can I disable caching in Satchmo

[Paul Walsh]

I want to disable caching in Satchmo, in production.

I can't find anything in the docs that explicitly declares how I can managing Satchmo's caching.

I'd love a pointer to the right place in the docs, if there is one, and also if anyone know hows I can disable caching.

[Mike Hostetler]

I'm surprised no one answered this. I'll take a shot . . 

You can't. Or you can, but then you can't sent credit card info to the payment processor. One of the decisions made in Satchmo was to use the cache to persist the credit card number from one screen to the next. I'm not going to express my opinion on that decision . . .

But why don't you want to use caching in production? That really doesn't make a lot of sense -- a properly configured caching system is worth the time in any Django app. I did have some problems with Memcache so I switched it to a database cache and that has helped a lot (YMMV with Memcache -- I actually would rather use that than the database cache).

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[Paul Walsh]

Thanks Mike,

Where did you find this information about the credit card info + cache? For the life of me, I can't find anything in the docs about this. 

I am not feeling the love for the Satchmo docs for a bunch of reasons right now.... but anyway, I digress.

It is not that I don't want to use caching in production. I have a problem where the cache doesn't seem to be invalidating in some cases, and I am therefore diving in to Satchmo's caching and just trying to understand what is going on (particularly, how it is different from Django's built in caching, or not). 

So, my first step was to work out how to turn caching off...

Also, is it possible to use Johnny Cache with Satchmo? Or, a Redis cache?

I am also wondering, concerned, why could you get a memached backend working with Satchmo? This is fairly trivial to setup with Django projects usually.

thanks.

Paul Walsh

0543551144

[Mike Hostetler]

I found the cache requirement in the code -- I was debugging why we were getting an occasional stopped transaction (transactions were saved as LINKED) and discovered that it how it worked. This was a problem with Memcache -- Memcache was working but once in a while I would have a cache miss on the credit card number, which is a bad thing. When I switched to the database cache, the problem with the LINKED transactions all but went away (now it happens when a user reloads a page when Satchmo is waiting for response to their external service request, al a AuthorizeNet or UPS).

Cache invalidation is always a tricky subject -- I kinda had the same problem. Did you try anything else but Memcache? I didn't look at any other caching except Database and Memcache (since they are well-documented and come standard with Django). I'm certain that someone has developed plugins for others.

For Satchmo:  you do have to setup the cache twice: once for Django using the 'CACHES' dictionary and another time with the 'old' way with CACHE_BACKEND,CACHE_MIDDLEWARE_SECONDS. and CACHE_MIDDLEWARE_KEY_PREFIX. That last one is how Satchmo uses the cache for cc numbers, etc.

--
Mike Hostetler
SquarePeg Systems
http://www.squarepegsystems.com

[Paul Walsh]

Thanks Mike, this is helping a great deal.

Seeing as caches like Memcached, Redis, are systems that by design can lose data, in preference for speed, using this for CC details is to me a very strange design decision, and I sure wish I knew about that via the documentation.

I don't mind using a DB cache (I am currently still using DB cache for SORL on this site too), so I will set up a db cache anyway. The site is on the production machine, but is not exposed to real trafic yet, so I am still actually using locmem for cache.

And again - the thing with the old style and new style cache declarations - is that in the docs? I'd love to know that I just missed it somehow... I am using latest django and Satchmo tip - do you know if this still applies?

Paul Walsh

0543551144

[Mike Hostetler]

I'm finally getting back to you. . . 

I had to hunt a bit but the items about caching configuration is here:

http://www.satchmoproject.com/docs/dev/settings.html

if you search for "CACHE_BACKEND" you will find see it.

CACHE_BACKEND is an old-style configuration. When I did that (with Memcache) I found that the pages, etc. weren't cached. I then looked at Django's Caching How-to docs and found that caching for Django 1.3 is not done like that anymore.

My $0.02 -- if you are still on tip, it probably still applies.

[Paul Walsh]

Great Mike, thanks for helping out, I appreciate it.

Paul Walsh

0543551144