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From Pradeep Badiger <PradeepBadi...@fico.com>
Subject RE: Evicted entry appears in Write-behind cache
Date Fri, 14 Oct 2016 15:55:09 GMT
I have some log statements in the load() which gets called when there is no entry in the cache
or write behind buffer. What I learnt is that there is a write behind buffer that holds on
to the entries (even the evicted ones) and whenever there is a get() for an entry, ignite
looks at both the cache and the write behind buffer and loads it. If it doesn’t find it
in any of the two, it then uses the read through mechanism to load the entry from the store.

Thanks,
Pradeep V.B.

From: Vladislav Pyatkov [mailto:vpyatkov@gridgain.com]
Sent: Friday, October 14, 2016 4:25 AM
To: user@ignite.apache.org
Subject: Re: Evicted entry appears in Write-behind cache

Hi Paradeep,

Why are you think, what the entry could not be read through your persistence storage:

.setReadThrough(stateQoS.isReadThroughEnabled())

When cache can not get data from in memory, it will try to get data from storage, which configured
as "ReadThrough".

On Thu, Oct 13, 2016 at 6:41 PM, Pradeep Badiger <PradeepBadiger@fico.com<mailto:PradeepBadiger@fico.com>>
wrote:
Hi Vladislav,

Please see the below cache configuration.

                                             LruEvictionPolicy evictionPolicy = new LruEvictionPolicy<>(getIntProperty(envConfig,
CACHE_SIZE, 10000));
                                             cacheConfiguration
                                                            .setEvictionPolicy(evictionPolicy)
                                                            .setWriteBehindFlushSize(getIntProperty(envConfig,
CACHE_WB_FLUSH_SIZE, 0))
                                                            .setWriteBehindBatchSize(getIntProperty(envConfig,
CACHE_WB_BATCH_SIZE, 200))
                                                            .setWriteBehindEnabled(stateQoS.isWriteBehindEnabled())
                                                            .setWriteBehindFlushFrequency(getIntProperty(envConfig,
CACHE_WB_FLUSH_FREQ_MS, 5000))
                                                            .setWriteBehindFlushThreadCount(getIntProperty(envConfig,
CACHE_WB_FLUSH_THREADS, 10))
                                                            .setCacheStoreFactory(new StateCacheStoreFactory<K,
V>(cacheName,
                                                                                         
storageManager))
                                                            .setName(cacheName)
                                                            .setReadThrough(stateQoS.isReadThroughEnabled())
                                                            .setWriteThrough(stateQoS.isWriteThroughEnabled());

Thanks,
Pradeep V.B.

From: Vladislav Pyatkov [mailto:vldpyatkov@gmail.com<mailto:vldpyatkov@gmail.com>]
Sent: Wednesday, October 12, 2016 2:59 AM

To: user@ignite.apache.org<mailto:user@ignite.apache.org>
Subject: Re: Evicted entry appears in Write-behind cache

Hi Pradeep,

Could you please provide cache configuration?

On Tue, Oct 11, 2016 at 6:57 PM, Denis Magda <dmagda@gridgain.com<mailto:dmagda@gridgain.com>>
wrote:
Looks like that my initial understanding was wrong. There is a related discussion
http://apache-ignite-users.70518.x6.nabble.com/Cache-read-through-with-expiry-policy-td2521.html

—
Denis

On Oct 11, 2016, at 8:55 AM, Pradeep Badiger <PradeepBadiger@fico.com<mailto:PradeepBadiger@fico.com>>
wrote:

Hi Denis,

I did the get() on the evicted entry from the cache, it still returned me the value without
calling the load() on the store. As you said, the entry would be cached in the write behind
store even for the evicted entry. Is that true?

Thanks,
Pradeep V.B.
From: Denis Magda [mailto:dmagda@gridgain.com]
Sent: Monday, October 10, 2016 9:13 PM
To: user@ignite.apache.org<mailto:user@ignite.apache.org>
Subject: Re: Evicted entry appears in Write-behind cache

Hi,

How do you see that the evicted entries are still in the cache? If you check this by calling
cache get like operations then entries can be loaded back from the write-behind store or from
your underlying store.

—
Denis

On Oct 8, 2016, at 1:00 PM, Pradeep Badiger <PradeepBadiger@fico.com<mailto:PradeepBadiger@fico.com>>
wrote:

Hi,

I am trying to evaluate Apache Ignite and trying to explore eviction policy and write behind
features. I am seeing that whenever a cache is configured with eviction policy and write behind
feature, the write behind cache always have all the changed entries including the ones that
are evicted, before the write cache is flushed. But soon after it is flushed, the store loads
again from DB. Is this the expected behavior? Is there a documentation on how the write behind
cache works?

Thanks,
Pradeep V.B.
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--
Vladislav Pyatkov
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