Guys, I just want to make sure we are all on the same page. The main use case for LOCAL caches is to have a local hash map querable with SQL and automatically persisted to a 3rd party DB.
I want to discourage people from saying "nobody needs some feature". None of the people in this discussion are users of any features - we are all developers of the features. Instead of guessing whether to deprecate something or not, I would actually see if it is even worth a discussion. How much effort is required to fix the bug found in the LOCAL cache? D. On Thu, Jul 26, 2018 at 12:19 PM, Dmitry Pavlov <dpavlov....@gmail.com> wrote: > Hi Alexey, > > There is nothing to be sorry about :) Сommunity appreciates an alternative > vision, this allows us to make as informed decisions as it possible. > > Thank you for finding this fact, it is very interesting. > > I'm not sure all these examples were prepared by experienced Ignite users. > So idea of deprecation may have one more argument. Deprecation will help us > to inform users about LOCAL cache: Probably local cache is not what they > need. > > Sincerely, > Dmitriy Pavlov > > чт, 26 июл. 2018 г. в 16:57, Alexey Zinoviev <zaleslaw....@gmail.com>: > > > Sorry, guys, I'll put my 1 cent > > > > I'd like this idea "Implement LOCAL caches as PARTITIONED caches over > the > > local node." > > It make sense for examples/testing in pseudo-distributed mode and so far. > > > > But I think that the deprecation based on user-list mentions is a wrong > > way. Please look here > > https://github.com/search?q=%22CacheMode.LOCAL%22+%26+ignite&type=Code > > There a lot of hello world examples with LOCAL mode. > > > > And of course, we can ask about that on user-list, not here, to vote for > > the deprecation like this. > > > > 2018-07-26 11:23 GMT+03:00 Vladimir Ozerov <voze...@gridgain.com>: > > > > > I meant LOCAL + non-LOCAL transactions of course. > > > > > > On Wed, Jul 25, 2018 at 10:42 PM Dmitriy Setrakyan < > > dsetrak...@apache.org> > > > wrote: > > > > > > > Vladimir, > > > > > > > > Are you suggesting that a user cannot span more than one local cache > > in a > > > > cross cache LOCAL transactions. This is extremely surprising to me, > as > > it > > > > would require almost no effort to support it. As far as mixing the > > local > > > > caches with distributed caches, then I agree, cross-cache > transactions > > do > > > > not make sense. > > > > > > > > I am not sure why deprecating local caches has become a pressing > > issue. I > > > > can see that there are a few bugs, but why not just fix them and move > > on? > > > > Can someone explain why supporting LOCAL caches is such a burden? > > > > > > > > Having said that, I am not completely opposed to deprecating LOCAL > > > caches. > > > > I just want to know why. > > > > > > > > D. > > > > > > > > On Wed, Jul 25, 2018 at 10:55 AM, Vladimir Ozerov < > > voze...@gridgain.com> > > > > wrote: > > > > > > > > > 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 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
