Thanks Yakov! It could be used as a possible solution for multi-cache transactions, which persistent stores implementation sharing the same data source/session.
Igor Rudyak On Mon, Aug 1, 2016 at 1:32 AM, Yakov Zhdanov <yzhda...@apache.org> wrote: > Igor, you factory should return the same instance for all caches started > locally. This way Ignite should call sessionEnd() once. Can you please > check? > > --Yakov > > 2016-07-30 4:40 GMT+03:00 Igor Rudyak <irud...@gmail.com>: > > > Hi guys, > > > > Playing with Ignite multi-cache transactions(transactions involving > > multiple caches) we run into the lack of proper/easy mechanism to support > > such transactions on persistent store side (while implementing particular > > *CacheStore*). > > > > The problem is there is no easy way for *CacheStore *implementation to > get > > information about caches involved in the transaction. > > > > Here are more details: > > > > When committing multi-cache transaction, Ignite produces multiple > > *sessionEnd(...)* calls (in *CacheStore *implementation) - one for each > > cache. Thus to support multi-cache transaction in persistent store, we > need > > to accumulate all the changes made to multiple caches (by > > *write/writeAll/delete/deleteAll* operations) and apply them as one > > transaction/batch to a persistent store in the final(last) *sessionEnd > > *call. > > To do this we need to know exact number of caches participating in the > > transaction. Having this number we can skip all *sessionEnd *calls except > > the last - which we will use to commit/persist all the changes we > > previously accumulated. > > > > As for now, the only way to get the number of caches participating in a > > transaction is to register *CacheStoreSessionListener *and count number > of > > caches in its "*onSessionStart*" method. Such approach doesn't look very > > elegant cause we always need to keep in mind that specifying " > > *cacheStoreFactory*" in cache configuration is not enough. In addition to > > this we also need to specify appropriate " > > *cacheStoreSessionListenerFactories*" property - otherwise it will not > work > > for multi-cache transactions. > > > > Here is an example chunk from cache configuration: > > > > * <property name="cacheStoreFactory">* > > * <bean > > > > > class="org.apache.ignite.cache.store.cassandra.CassandraCacheStoreFactory">* > > * <property name="dataSourceBean" value="cassandraDataSource"/>* > > * <property name="persistenceSettingsBean" > > value="cache1_persistence_settings"/>* > > * </bean>* > > * </property>* > > * <property name="cacheStoreSessionListenerFactories">* > > * <list>* > > * <bean class="org.apache.ignite.tests.MyCacheStoreSessionListener"/>* > > * </list>* > > * </property>* > > > > We see that, instead of specifying only one property > "*cacheStoreFactory*" > > for a cache we should always specify two properties in case we need > > multi-cache transactions support in persistent store. Conceptually it > > doesn't look good, cause users thinking about *CacheStore *implementation > > like something self-contained - once it specified in cache configuration > > everything should be smooth. But in case of multi-cache transactions > > support we always need to remember about registering some strange > > "listener". > > > > In Ignite we already have such concept as " > > *org.apache.ignite.transactions.Transaction*" which defines our > > transaction. It looks logical if it will also provide information about > > transaction boundaries (caches involved into transaction). Such approach > > can simplify persistent store implementation for multi-cache > transactions. > > > > Any thoughts? > > > > > > Igor Rudyak > > >
