[infinispan-dev] Some flags are incompatible with implicit transactions

[Erik Salter]

I use the pattern:

tx.begin();
cache1.lock();
...
tx.commit();

There are other caches involved in the transaction, but cache1 doesn't
actually put any data.  It's just there so I don't have to acquire 8-13
explicit locks on the other caches.  Improved throughput in my application.

I also use this pattern:

tx.begin();
boolean result = cache.withFlags(FAIL_SILENT).lock(k); 
// Something interesting..
tx.commit();

...Same reason.  I have a pool of keys and if one fails, I go to the next
one.  Again, keeps me from needing to acquire a bunch of explicit locks.

Erik

-----Original Message-----
From: infinispan-dev-bounces at lists.jboss.org
[mailto:infinispan-dev-bounces at lists.jboss.org] On Behalf Of Galder
Zamarreño
Sent: Tuesday, December 13, 2011 8:49 AM
To: infinispan -Dev List
Subject: Re: [infinispan-dev] Some flags are incompatible with implicit
transactions


On Dec 13, 2011, at 2:39 PM, Sanne Grinovero wrote:

> Why would you avoid FORCE_WRITE_LOCK ?

Does the following make sense?

tx.begin()
cache.withFlags(FORCE_WRITE_LOCK).get(
)
tx.commit()

It doesn't in my view. You force a write lock to then to something within a
transaction with the knowledge that the key is locked.

> Will I still be able to use an
> explicit cache.lock() operation? Acquiring a pessimistic lock might be
> an important functionality in some use cases.

That's another interesting one, what's the point of doing:

tx.begin()
cache.lock()
tx.commit()

I don't see lock() being compatible with implicit tx.

> 
> About FAIL_SILENT.. I'm not sure about the use case, but I would
> expect it to just avoid logging errors and to swallow eventual
> exceptions ?

Javadoc:
    * <p>Swallows any exceptions, logging them instead at a low log level.
Will prevent a failing operation from
    * affecting any ongoing JTA transactions as well.</p>

I see not affecting the on going JTA transaction as the bigger motivator for
using it rather than just avoiding showing the errors. Do you have any
particular use case where the following makes sense?

tx.begin();
cache.withFlags(FAIL_SILENT).put(k, v);
tx.commit();

> 
> Sanne
> 
> On 13 December 2011 12:10, Galder Zamarreño <galder at jboss.org> wrote:
>> Hi all,
>> 
>> Re: https://issues.jboss.org/browse/ISPN-1556
>> Re: https://github.com/infinispan/infinispan/pull/719/files#r288994
>> 
>> The fix I suggest works well with explicit transactions, but if we leave
this as is, implicit txs might leak transactions. The reason is because if
we allow a put with FAIL_SILENT which fails with an implicit tx, then the tx
won't be committed nor removed from tx table.
>> 
>> But, does FAIL_SILENT make sense with implicit tx? Well, it doesn't. The
point of FAIL_SILENT is to avoid a failure rollbacking a tx and being noisy.
So, it implies that there's a bigger, external, transaction within which
this operation is called.
>> 
>> And it's not just FAIL_SILENT, there're other flags do not make sense
with implicit transactions, such as FORCE_WRITE_LOCK:
>> 
>>   /**
>>    * Forces a write lock, even if the invocation is a read operation.
Useful when reading an entry to later update it
>>    * within the same transaction, and is analogous in behavior and use
case to a <tt>select ... for update ... </tt>
>>    * SQL statement.
>>    */
>> 
>> So, I think my fix is right here, but what we really need is it's a way
to stop people from using certain flags with implicit transactions. Here's
my (quickly thought) list:
>> 
>> FORCE_WRITE_LOCK
>> FAIL_SILENTLY
>> PUT_FOR_EXTERNAL_READ
>> 
>> Any others?
>> 
>> Cheers,
>> --
>> Galder Zamarreño
>> Sr. Software Engineer
>> Infinispan, JBoss Cache
>> 
>> 
>> _______________________________________________
>> infinispan-dev mailing list
>> infinispan-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
> 
> _______________________________________________
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> infinispan-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/infinispan-dev

--
Galder Zamarreño
Sr. Software Engineer
Infinispan, JBoss Cache


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