[infinispan-dev] PutForExternalRead performance in 5.1

[Mircea Markus]

On 15 Dec 2011, at 10:28, Galder Zamarreño wrote:

> Hi,
> 
> Re: https://issues.jboss.org/browse/ISPN-1615, https://issues.jboss.org/browse/ISPN-1617 and http://lists.jboss.org/pipermail/infinispan-dev/2011-November/009577.html
> 
> I think in Infinispan 5.1, the fact that caches are either transaction or not transactional are affecting the functionality and performance of operations such as putForExternalRead().
> 
> The point of PFER is to make data available to other nodes and transactions which has just been read from the database, without blocking, ignoring failures…etc.
> 
> This operation makes most sense when autoCommit is false and there's an external transaction going on, i.e. Hibernate 2LC. As shown in ISPN-1617, this does not work (Note: currently I have 2LC set to autoCommit=true to make this work but it's not performant as indicated by Slorg1).
> 
> So, to make this work, we can do three things:
> 
> 1. As Mircea suggested, we could start a new transaction for PFER after suspending the on-going one. Apart from this being wasteful (suspend and start a new tx) it's pointless because pFER is FORCE_ASYNCHRONOUS operation, so we're ignoring any failures in other nodes to apply the data.
+1
> 
> 2. Another option is to avoid suspending the transaction. Ever since https://issues.jboss.org/browse/ISPN-1556 was implemented, a failure within a transaction when FAIL_SILENT is on won't rollback the tx. Not suspending the tx has the advantage of not being wasteful from a tx management perspective. The problem though is that PFER won't be applied until the external tx has been commited, so it delays this operation.
The semantics also changes in the case the tx is rolled back, as the effect of PFER call would not be visible (now PFER does not depend on the way the transaction completes). I don't think this is a bad thing though.
> On top of this, I have the feeling that if the cache is configured with SYNC, this PFER might be become 2PC (mircea, can you clarify?)
yes, would result in 2pc.
> 
> 3. The third and final option is to basically allow PFER to act as non-transactional even if the cache is transactional so that the transaction can be suspended and PFER can do its job as quick as possible (like it did in 5.0 and before). We know PFER is an special operation with particular options, can't we make room for this non-transactional op? This seems to me the best middle ground between a PFER that does its job and it's performant. I've implemented this in https://github.com/galderz/infinispan/commit/d10fee9b2800d75269505953044006a27ba1b44f and both the newly created test and PutForExternalReadTest pass at least (the rest of testsuite needs checking). Mircea, WDYT?
+1, this sounds the most sensible and clean. I'll also take a look at your impl.

Thank you for looking into this,
Mircea