I would be a very wary of relying on VM implementation specifics like XXXRweriter.class.hashCode(). You certainly don't want the same class generating different coes on different instances in a cluster where the cache is shared. Also dont use serialVersionUID as that is only intended for serialization compatability. Reading the class as an InputStream from the ClassLoader and then computing a hash might work but seems more trouble than its worth.
In general I think a a manually maintained version no. might actually be your best bet. On Tue, Sep 9, 2008 at 5:29 PM, John Hjelmstad <[EMAIL PROTECTED]> wrote: > Back to this sub-thread... > Adding a getVersion() parameter seems error prone and a little burdensome. > In theory the version needs to change when any modification in potential > output for a given input is made, ie. not just optimization. That's not > always the easiest thing to analyze and get right. Meanwhile, invalidating > a > bunch of cache keys (by registering a new rewriter impl) isn't especially > costly: if the cache is useful at all, it will be hit often, ie. refreshed > quickly. > > --John > > On Tue, Sep 9, 2008 at 1:50 PM, Louis Ryan <[EMAIL PROTECTED]> wrote: > > > The versioning should be more explicit than that I think. Maybe add a > > getVersion function to the rewriter interface so they can manage their > own > > changes > > > > On Tue, Sep 9, 2008 at 12:39 PM, John Hjelmstad <[EMAIL PROTECTED]> > wrote: > > > > > Interesting suggestion. I can include the rewriter class names and > their > > > class hash codes or some other such versioning construct. > > > > > > On Tue, Sep 9, 2008 at 12:32 PM, Ben Laurie <[EMAIL PROTECTED]> wrote: > > > > > > > On Tue, Sep 9, 2008 at 8:17 PM, John Hjelmstad <[EMAIL PROTECTED]> > > wrote: > > > > > Excellent, agreed. CLs forthcoming. > > > > > > > > Can you include the version numbers of the rewriters in the cache > key? > > > > > > > > > > > > > > On Tue, Sep 9, 2008 at 12:14 PM, Kevin Brown <[EMAIL PROTECTED]> > > wrote: > > > > > > > > > >> #2 is the only really viable option. If we have to put caching > logic > > > in > > > > 10 > > > > >> different places we'll screw it up 9 different times :). > > > > >> > > > > >> On Tue, Sep 9, 2008 at 12:11 PM, John Hjelmstad <[EMAIL PROTECTED] > > > > > > wrote: > > > > >> > > > > >> > As discussed on a few threads and tracked in JIRA issue ( > > > > >> > http://issues.apache.org/jira/browse/SHINDIG-579), we need to > > move > > > > >> > rewriting > > > > >> > logic out of AbstractHttpCache. Yet we should maintain rewritten > > > > content > > > > >> > caching capability. The question is where to put it. > > > > >> > I see two options, at a high level: > > > > >> > 1. In code that calls > > > > >> ContentRewriterRegistry.rewrite(HttpResponse|Gadget). > > > > >> > Eg. MakeRequestHandler, ProxyHandler, ViewContentFetcher, > > > > GadgetServer, > > > > >> and > > > > >> > the near-future Renderer and Preloader. This allows > finer-grained > > > > control > > > > >> > over caching behavior in context, at the cost of distributing > > > caching > > > > >> logic > > > > >> > in various places. > > > > >> > 2. In ContentRewriterRegistry.rewrite(HttpResponse|Gadget) > itself, > > > if > > > > so > > > > >> > chosen. Caching logic can be consolidated in > > > > >> > CachingContentRewriterRegistry, > > > > >> > for instance (which will no longer subclass > > > > CachingWebRetrievalFactory), > > > > >> > and > > > > >> > be considered an optimization to rewriting. > > > > >> > > > > > >> > I'm inclined to go #2. Rewriters themselves can be augmented > with > > > > caching > > > > >> > hints if necessary, and be assumed deterministic for a given > cache > > > key > > > > in > > > > >> > the meantime. Consolidating rewriting logic makes it easier to > > share > > > > the > > > > >> > cache itself. > > > > >> > > > > > >> > Still, I might be missing situations in which additional context > > > > inherent > > > > >> > to > > > > >> > the calling context is needed to make a caching decision. > > > > >> > > > > > >> > --John > > > > >> > > > > > >> > > > > > > > > > > > > > > >
