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From: Igor Rudyak <irudyak@gmail.com>
Date: Wed, 10 Aug 2016 13:22:00 -0700
Message-ID: <CAMpMOYFFWe4HtSdZT2qe=_cff4zGiGDy8kYMX5=hySoF1QfCMQ@mail.gmail.com>
Subject: Re: Multi-cache transactions & persistent store
To: dev@ignite.apache.org
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archived-at: Wed, 10 Aug 2016 20:22:24 -0000

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By the way Yakov. How should we handle multi-cache transactions for
"write-behind" caches? For different caches (participated in transaction)
we can receive several separate sessionEnd calls.

Igor

On Mon, Aug 1, 2016 at 1:32 AM, Yakov Zhdanov <yzhdanov@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 <irudyak@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
> >
>

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