# Do sweepers work across app servers?

**URL:** <https://www.ruby-forum.com/t/do-sweepers-work-across-app-servers/141561>\
**Category:** Rails\
**Created:** [June 27, 2008, 2:29am UTC](https://www.ruby-forum.com/t/do-sweepers-work-across-app-servers/141561 "2008-06-27T02:29:19Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![nolman](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/e274bd/32.png) [@nolman](https://www.ruby-forum.com/u/nolman)\
**Post date:** [June 27, 2008, 2:29am UTC](https://www.ruby-forum.com/t/do-sweepers-work-across-app-servers/141561/1 "2008-06-27T02:29:19Z")

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If I had a dozen App servers and one DB would my all my app servers be  
notified via sweepers when a given representation was updated? If not  
what cache expiring mechanisms are there that can be used across multi  
app servers?

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<div class="post-metadata">

**Author:** ![nolman](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/e274bd/32.png) [@nolman](https://www.ruby-forum.com/u/nolman)\
**Post date:** [June 27, 2008, 6:30am UTC](https://www.ruby-forum.com/t/do-sweepers-work-across-app-servers/141561/2 "2008-06-27T06:30:02Z")

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> If I had a dozen App servers and one DB would my all my app servers be  
> notified via sweepers when a given representation was updated? If not  
> what cache expiring mechanisms are there that can be used across multi  
> app servers?

No. I’m assuming you mean you are caching a page to disk on several  
separate servers and then something on that page changes and you  
expire it, will all servers expire it. No.

You could use a central memcache store, but that won’t be as fast as  
page caching. Or you can have each app server use a central disk  
(SAN, etc.). Or you can write something that tells each server to  
expire a page. Perhaps by overriding expire\_page().

-philip