[webkit-dev] setting a size limit for Application Cache

Michael Nordman michaeln at google.com
Wed May 6 12:09:29 PDT 2009

The chrome team had an interesting thread on this topic not long ago.
Unfortunately it wasn't on the public chromium-dev mailing list, so I
can't provide a link to it here :(

<summary (according to me at least:)>

The gist of it was that providing appcaching for general use w/o any
special privileges is a good thing, but not all usages of this feature
are qualitatively the same thing. In some cases it's purely about
performance enhancement or reduced network utilization (traditional
caching goals). In other cases it's about providing additional
guarantees around application availability. Its fair to evict data
cached for the former cases as needed, but not ok to evict data cached
for the latter cases.

There is no means for the system to distinguish between these two
cases. There is no API to indicate which use is which.

In the latter case (gauranteed app availability), there is more
involved than the appcache... there are also databases, localstorage
values to which the gaurantee extends to.

What's missing is a way for "applications" to declare themselves as
such and to establish privileges to keep data around forever. Given
that, the system could relate persistent resource with "applications",
and based on their privileges, evict or not when space becomes an

A handwavvy syntax for declaring an "application"... <html
application='someurl'>... the url uniquely identifies the app, the
resource loaded from that url contains a user friendly description and
set of desired privileges... all pages that refer to that application
url are considered part of that app... all resource created on behalf
of that app are tracked by the system as such.

Food for thought.

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