Dima, LOCAL cache adds very little value to the product. It doesn't support cross-cache transactions, consumes a lot of memory, much slower than any widely-used concurrent hash map. Let's go the same way as Java - mark LOCAL cache as "deprecated for removal", and then remove it in 3.0.
On Wed, Jul 25, 2018 at 12:10 PM Dmitrii Ryabov <somefire...@gmail.com> wrote: > +1 to make LOCAL as filtered PARTITIONED cache. I think it would be much > easier and faster than fixing all bugs. > > 2018-07-25 11:51 GMT+03:00 Dmitriy Setrakyan <dsetrak...@apache.org>: > > > I would stay away from deprecating such huge pieces as a whole LOCAL > cache. > > In retrospect, we should probably not even have LOCAL caches, but now I > am > > certain that it is used by many users. > > > > I would do one of the following, whichever one is easier: > > > > - Fix the issues found with LOCAL caches, including persistence > support > > - Implement LOCAL caches as PARTITIONED caches over the local node. In > > this case, we would have to hide any distribution-related config from > > users, like affinity function, for example. > > > > D. > > > > On Wed, Jul 25, 2018 at 9:05 AM, Valentin Kulichenko < > > valentin.kuliche...@gmail.com> wrote: > > > > > It sounds like the main drawback of LOCAL cache is that it's > implemented > > > separately and therefore has to be maintained separately. If that's the > > > only issue, why not keep LOCAL cache mode on public API, but implement > it > > > as a PARTITIONED cache with a node filter forcefully set? That's > similar > > to > > > what we do with REPLICATED caches which are actually PARTITIONED with > > > infinite number of backups. > > > > > > This way we fix the issues described by Stan and don't have to > deprecate > > > anything. > > > > > > -Val > > > > > > On Wed, Jul 25, 2018 at 12:53 AM Stanislav Lukyanov < > > > stanlukya...@gmail.com> > > > wrote: > > > > > > > Hi Igniters, > > > > > > > > I’d like to start a discussion about the deprecation of the LOCAL > > caches. > > > > > > > > LOCAL caches are an edge-case functionality > > > > I haven’t done any formal analysis, but from my experience LOCAL > caches > > > > are needed very rarely, if ever. > > > > I think most usages of LOCAL caches I’ve seen were misuses: the users > > > > actually needed a simple HashMap, or an actual PARTITIONED cache. > > > > > > > > LOCAL caches are easy to implement on top of PARTITIONED > > > > If one requires a LOCAL cache (which is itself questionable, as > > discussed > > > > above) it is quite easy to implement one on top of PARTITIONED cache. > > > > A node filter of form `node -> node.id().equals(localNodeId)` is > > enough > > > > to make the cache to be stored on the node that created it. > > > > Locality of access to the cache (i.e. making it unavailable from > other > > > > nodes) can be achieved on the application level. > > > > > > > > LOCAL caches are hard to maintain > > > > A quick look at the open issues mentioning “local cache” suggests > that > > > > this is a corner case for implementation of many Ignite features: > > > > > > > > https://issues.apache.org/jira/issues/?jql=text%20~%20% > > > 22local%20cache%22%20and%20%20project%20%3D%20IGNITE% > > > 20and%20status%20%3D%20open > > > > In particular, a recent SO question brought up the fact that LOCAL > > caches > > > > don’t support native persistence: > > > > > > > > https://stackoverflow.com/questions/51511892/how-to- > > > configure-persistent-storage-for-apache-ignite-cache > > > > Having to ask ourselves “how does it play with LOCAL caches” every > time > > > we > > > > write any code in Ignite seems way to much for the benefits we gain > > from > > > it. > > > > > > > > Proposal > > > > Let’s deprecate LOCAL caches in 2.x and remove them in 3.0. > > > > As a part of deprecation let’s do the following: > > > > - Put @Deprecated on the CacheMode.LOCAL > > > > - Print a warning every time a LOCAL cache is created > > > > - Remove all mentions of LOCAL caches from readme.io, if any, except > > for > > > > the page about cache modes > > > > - On the page about cache modes explain that LOCAL is deprecated and > > can > > > > be replaced with a PARTITIONED cache with a node filter > > > > > > > > Thanks, > > > > Stan > > > > > > > > > >
