On Wed, Sep 10, 2008 at 10:57 AM, Louis Ryan <[EMAIL PROTECTED]> wrote:
> A little reading would indicate the MD5 is about 40% faster to compute than > SHA1 so I would suggest we use it. It would also make sense to stuff the > MD5 > of the cached content into an HTTP header on the cached version of the > original content so we can avoid re-computing it. Since HTTP response is immutable, we can do this at construction time in pretty much the same way that it's done for GadgetSpec (i.e. adding a getChecksum method). > > > On Tue, Sep 9, 2008 at 6:28 PM, Louis Ryan <[EMAIL PROTECTED]> wrote: > > > 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 > >> > > > >> > > >> > > > >> > >> > > > > > >> > > > > >> > > > >> > > >> > > > > >
