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<blockquote style="margin: 10px 0 0; margin-top: 0; border-left: 1px solid #cccccc; color: #707070; margin-left: 19px; padding: 10px 20px">
<p style="margin: 10px 0 0; margin-top: 0">Session implementing CTC is a bit messy, IMO. Creating a separate object on session open would increase the number of objects allocated while CTC does not have to be used (especially if 2LC is off). </p>
</blockquote> <p style="margin: 10px 0 0">Having the Session implement CTC is not "clean", I definitely agree with that. The point of that suggestion was to handle your second point.. to minimize instantiations/allocations of some separate "no txn" CTC delegate. Personally I think that the performance gain here is going to be more important than the "messiness".</p>
<blockquote style="margin: 10px 0 0; border-left: 1px solid #cccccc; color: #707070; margin-left: 19px; padding: 10px 20px">
<p style="margin: 10px 0 0; margin-top: 0">The timestamp should be acquired before the data is loaded from DB (this may be later used for putFromLoad) - is there a good place to initialize it? If not, session open would be preferred.</p>
</blockquote> <p style="margin: 10px 0 0">Right. The "Session is a CacheTransactionContext" option is maybe a bit hard to visualize, so perhaps some code would help:</p>
<div class="code panel" style="border-width: 1px;; border: 1px solid #cccccc; background: #f5f5f5; font-size: 12px; line-height: 1.333; font-family: monospace; border: 1px solid #cccccc; -moz-border-radius: 3px; border-radius: 3px; margin: 9px 0">
<div class="codeContent panelContent" style="padding: 9px 12px">
<pre class="code-java" style="margin: 10px 0 0; margin-top: 0; max-height: 30em; overflow: auto; white-space: pre-wrap; word-wrap: normal">
/**
* ...
*
* @apiNote Note that Session <span class="code-keyword" style="color: #000091">implements</span> CacheTransactionContext <span class="code-keyword" style="color: #000091">for</span> cases where either
* L2C is not enabled or when L2C is enabled but we are not joined to a txn context. In <span class="code-keyword" style="color: #000091">this</span>
* <span class="code-keyword" style="color: #000091">case</span>, the Session itself will act as the CacheTransactionContext <span class="code-keyword" style="color: #000091">for</span> calls to the cache. This
* is done to minimize instantiations of a separate CacheTransactionContext delegate <span class="code-keyword" style="color: #000091">for</span> these
* cases which would get expensive resource-wise.
*/
<span class="code-keyword" style="color: #000091">class </span>SessionImpl ... <span class="code-keyword" style="color: #000091">implements</span> ..., CacheTransactionContext {
...
<span class="code-keyword" style="color: #000091">private</span> CacheTransactionContext explicitCurrentCacheTransactionContext;
<span class="code-keyword" style="color: #000091">private</span> <span class="code-object" style="color: #910091">long</span> nonTransactedStartTimestamp;
<span class="code-keyword" style="color: #000091">public</span> SessionImpl(...) {
...
resetNonTransactedStartTimestamp();
}
<span class="code-keyword" style="color: #000091">private</span> void resetNonTransactedStartTimestamp() {
<span class="code-keyword" style="color: #000091">this</span>.nonTransactedStartTimestamp = sessionFactory.getCacheEngine().getRegionFactory().nextTimestamp();
}
@Override
<span class="code-keyword" style="color: #000091">public</span> CacheTransactionContext getCurrentCacheTransactionContext() {
<span class="code-keyword" style="color: #000091">return</span> explicitCurrentCacheTransactionContext == <span class="code-keyword" style="color: #000091">null</span>
? <span class="code-keyword" style="color: #000091">this</span>
: explicitCurrentCacheTransactionContext;
}
/**
* ...
* @implNote <span class="code-keyword" style="color: #000091">this</span> method is called whenever we join a txn context. This will happen when either
* a JDBC-based transaction is started via the Hibernate Transaction API or we join a JTA-based
* transaction.
*/
@Override
<span class="code-keyword" style="color: #000091">public</span> void startTransactionBoundary() {
<span class="code-keyword" style="color: #000091">this</span>.cacheTransactionContext = factory.getCache().getRegionFactory().startingTransaction( <span class="code-keyword" style="color: #000091">this</span> );
}
@Override
<span class="code-keyword" style="color: #000091">public</span> void beforeTransactionCompletion() {
getCurrentCacheTransactionContext().transactionCompleting();
...
}
@Override
<span class="code-keyword" style="color: #000091">public</span> void afterTransactionCompletion(<span class="code-object" style="color: #910091">boolean</span> successful, <span class="code-object" style="color: #910091">boolean</span> delayed) {
...
getCurrentCacheTransactionContext().transactionCompleted(); <span class="code-comment" style="color: #808080">// anything to pass?
</span> <span class="code-keyword" style="color: #000091">this</span>.explicitCurrentCacheTransactionContext = <span class="code-keyword" style="color: #000091">null</span>;
resetNonTransactedStartTimestamp();
}
<span class="code-comment" style="color: #808080">// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
</span> <span class="code-comment" style="color: #808080">// CacheTransactionContext implementation
</span>
@Override
<span class="code-keyword" style="color: #000091">public</span> <span class="code-object" style="color: #910091">long</span> getCurrentTransactionStartTimestamp() {
<span class="code-keyword" style="color: #000091">return</span> nonTransactedStartTimestamp;
}
@Override
<span class="code-keyword" style="color: #000091">public</span> void beforeCompletion() {
<span class="code-comment" style="color: #808080">// nothing to <span class="code-keyword" style="color: #000091; color: #808080">do</span> here
</span> }
@Override
<span class="code-keyword" style="color: #000091">public</span> void afterCompletion() {
<span class="code-comment" style="color: #808080">// nothing to <span class="code-keyword" style="color: #000091; color: #808080">do</span> here
</span> }
}
</pre>
</div>
</div> <p style="margin: 10px 0 0">Again, I agree this is "messy" - it is a matter of performance versus generating a new CacheTransactionContext instance for every call to "resetNonTransactedStartTimestamp".</p> <p style="margin: 10px 0 0">The other option I mentioned is to have that single CacheTransactionContext instance be in effect for the entire Session lifecycle, something like:</p>
<div class="code panel" style="border-width: 1px;; border: 1px solid #cccccc; background: #f5f5f5; font-size: 12px; line-height: 1.333; font-family: monospace; border: 1px solid #cccccc; -moz-border-radius: 3px; border-radius: 3px; margin: 9px 0">
<div class="codeContent panelContent" style="padding: 9px 12px">
<pre class="code-java" style="margin: 10px 0 0; margin-top: 0; max-height: 30em; overflow: auto; white-space: pre-wrap; word-wrap: normal">
<span class="code-keyword" style="color: #000091">class </span>SessionImpl ... {
<span class="code-keyword" style="color: #000091">private</span> CacheTransactionContext cacheTransactionContext;
<span class="code-keyword" style="color: #000091">public</span> SessionImpl(...) {
<span class="code-keyword" style="color: #000091">this</span>.cacheTransactionContext = factory.getCache().getRegionFactory().startingTransaction( <span class="code-keyword" style="color: #000091">this</span> );
}
@Override
<span class="code-keyword" style="color: #000091">public</span> CacheTransactionContext getCurrentCacheTransactionContext() {
<span class="code-keyword" style="color: #000091">return</span> cacheTransactionContext;
}
@Override
<span class="code-keyword" style="color: #000091">public</span> void startTransactionBoundary() {
<span class="code-comment" style="color: #808080">// potentially, <span class="code-keyword" style="color: #000091; color: #808080">if</span> deemed useful
</span> getCurrentCacheTransactionContext().transactionJoined();
}
@Override
<span class="code-keyword" style="color: #000091">public</span> void beforeTransactionCompletion() {
...
getCurrentCacheTransactionContext().transactionCompleting();
...
}
@Override
<span class="code-keyword" style="color: #000091">public</span> void afterTransactionCompletion(<span class="code-object" style="color: #910091">boolean</span> successful, <span class="code-object" style="color: #910091">boolean</span> delayed) {
...
getCurrentCacheTransactionContext().transactionCompleted(); <span class="code-comment" style="color: #808080">// anything to pass?
</span> ...
}
}
</pre>
</div>
</div> <p style="margin: 10px 0 0">here you can see that the CacheTransactionContext is given enough contextual callbacks to be aware of transaction boundaries.</p>
<blockquote style="margin: 10px 0 0; border-left: 1px solid #cccccc; color: #707070; margin-left: 19px; padding: 10px 20px">
<p style="margin: 10px 0 0; margin-top: 0">When the transaction is completed CTC does not change. The next non-transactional operation would use the same instance - do we want CTC tracking it's transaction state internally, or will we dispose the instance? (and get it to the same state as if Session was just open).</p>
</blockquote> <p style="margin: 10px 0 0">Exactly - see above </p>
<blockquote style="margin: 10px 0 0; border-left: 1px solid #cccccc; color: #707070; margin-left: 19px; padding: 10px 20px">
<p style="margin: 10px 0 0; margin-top: 0">Having rather a structured object is a good idea - as long as it does not increase allocation rates (but that shouldn't be the case, all instances should be created on startup).</p>
</blockquote> <p style="margin: 10px 0 0">As far as "real" caching calls, this is accurate. However, we'd also have to perform this when a user makes calls of the "caching engine" which happens:</p>
<ol>
<li>the various SessionFactory/EntityManagerFactory level cache eviction calls</li>
<li>caching statistics accessed</li>
</ol> <p style="margin: 10px 0 0">In these cases we could either generate the Name each time, or we could decide to maintain a map of "raw" region name to its Name reference. The latter is probably a premature optimization though at this point.</p> </td>
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