# Ajax Request Caching by Timestamp?

**URL:** <https://www.ruby-forum.com/t/ajax-request-caching-by-timestamp/134357>\
**Category:** Rails\
**Created:** [April 10, 2008, 3:03am UTC](https://www.ruby-forum.com/t/ajax-request-caching-by-timestamp/134357 "2008-04-10T03:03:31Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![b0rdslide](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/a9a28c/32.png) [@b0rdslide](https://www.ruby-forum.com/u/b0rdslide)\
**Post date:** [April 10, 2008, 3:03am UTC](https://www.ruby-forum.com/t/ajax-request-caching-by-timestamp/134357/1 "2008-04-10T03:03:31Z")

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Hi everyone, first post here in the forum. I’m usually in #rubyonrails  
on freenode.

I’ve been thinking about the various types of caching, and I was  
wondering if its possible to have the server selectively send back data,  
instead sending nothing ‘0’ if user has the newest data.

My example is a presence monitor, and it seems like the logic is:

- Rails caches the ‘current user’ list fragment with a timestamp.
- User requests a view that contains a periodic\_updater to the current  
user list (and the updater passes the timestamp in its requests back to  
server)
- the server compares it to the current timestamp on that fragment. if  
its identical. send back a 0/nochange notice. otherwise send back the  
newer data with its timestamp.
- now further xhr requests from client contain the updated timestamp.

I’d like to know if anyones already attempted or thought of this before.

Thanks!  
-zer0

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<div class="post-metadata">

**Author:** ![b0rdslide](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/a9a28c/32.png) [@b0rdslide](https://www.ruby-forum.com/u/b0rdslide)\
**Post date:** [April 10, 2008, 4:26am UTC](https://www.ruby-forum.com/t/ajax-request-caching-by-timestamp/134357/2 "2008-04-10T04:26:46Z")

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Yes, or id.

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<div class="post-metadata">

**Author:** ![b0rdslide](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/a9a28c/32.png) [@b0rdslide](https://www.ruby-forum.com/u/b0rdslide)\
**Post date:** [April 10, 2008, 3:26pm UTC](https://www.ruby-forum.com/t/ajax-request-caching-by-timestamp/134357/3 "2008-04-10T15:26:23Z")

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Julian L. wrote:

> Yes, or id.

Not quite sure I understand your response.

After I posted I took a look over the cache api again. And one can use  
regex to delete multiple fragments.

So for what I’m trying todo, it would be something like:

- user requests index that has current\_users partial, do a regex find  
for “current\_users.\*” (there should be only one)
- the time stamp of that fragment is added to the params of a periodic  
updater.
- each time the ajax request comes in, just do a straight find by name  
on the fragment. (ie current\_users200804100923)
- the fragment is found, send back nothing/0/nochange, (unless its been  
expired by someone logging in or logging out), in which case a new one  
is made, and time stamped.
- rinse, repeat as needed =)

I’m really just thinking out loud and curious if anyone has tried  
anything like this. I welcome your input.