[infinispan-dev] Why DistTxInterceptor in use with Hot Rod ?

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[infinispan-dev] Why DistTxInterceptor in use with Hot Rod ?

Galder Zamarreno
Hi,

I'm looking at this failure http://goo.gl/NQw4h and I'm wondering why "org.infinispan.distribution.RehashInProgressException: Timed out waiting for the transaction lock" is thrown?

This is thrown DistTxInterceptor which is added by the InterceptorChainFactory:

      if (configuration.getCacheMode().isDistributed())
         interceptorChain.appendInterceptor(createInterceptor(DistTxInterceptor.class));
      else
         interceptorChain.appendInterceptor(createInterceptor(TxInterceptor.class));

However, this is a Hot Rod test and the cache is not configured with a transaction manager, so is DistTxInterceptor really needed?

In fact, why a TxInterceptor if no transaction manager is configured? (this kinda goes back to Mircea's email earlier today about a transactions enabled/disabled flag)

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


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Re: [infinispan-dev] Why DistTxInterceptor in use with Hot Rod ?

Mircea Markus

On 13 Sep 2011, at 17:22, Galder Zamarreño wrote:

> Hi,
>
> I'm looking at this failure http://goo.gl/NQw4h and I'm wondering why "org.infinispan.distribution.RehashInProgressException: Timed out waiting for the transaction lock" is thrown?
>
> This is thrown DistTxInterceptor which is added by the InterceptorChainFactory:
>
>      if (configuration.getCacheMode().isDistributed())
>         interceptorChain.appendInterceptor(createInterceptor(DistTxInterceptor.class));
>      else
>         interceptorChain.appendInterceptor(createInterceptor(TxInterceptor.class));
>
> However, this is a Hot Rod test and the cache is not configured with a transaction manager, so is DistTxInterceptor really needed?
>
> In fact, why a TxInterceptor if no transaction manager is configured? (this kinda goes back to Mircea's email earlier today about a transactions enabled/disabled flag)
All valid concerns, IMO.
5.1 will clarify this by not adding Tx interceptors for non tx caches.

>
> Cheers,
> --
> Galder Zamarreño
> Sr. Software Engineer
> Infinispan, JBoss Cache
>
>
> _______________________________________________
> infinispan-dev mailing list
> [hidden email]
> https://lists.jboss.org/mailman/listinfo/infinispan-dev


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Re: [infinispan-dev] Why DistTxInterceptor in use with Hot Rod ?

Galder Zamarreno

On Sep 13, 2011, at 6:38 PM, Mircea Markus wrote:

>
> On 13 Sep 2011, at 17:22, Galder Zamarreño wrote:
>
>> Hi,
>>
>> I'm looking at this failure http://goo.gl/NQw4h and I'm wondering why "org.infinispan.distribution.RehashInProgressException: Timed out waiting for the transaction lock" is thrown?
>>
>> This is thrown DistTxInterceptor which is added by the InterceptorChainFactory:
>>
>>     if (configuration.getCacheMode().isDistributed())
>>        interceptorChain.appendInterceptor(createInterceptor(DistTxInterceptor.class));
>>     else
>>        interceptorChain.appendInterceptor(createInterceptor(TxInterceptor.class));
>>
>> However, this is a Hot Rod test and the cache is not configured with a transaction manager, so is DistTxInterceptor really needed?
>>
>> In fact, why a TxInterceptor if no transaction manager is configured? (this kinda goes back to Mircea's email earlier today about a transactions enabled/disabled flag)
> All valid concerns, IMO.
> 5.1 will clarify this by not adding Tx interceptors for non tx caches.

Is this captured in some other JIRA? I'd like to reference the test and the JIRA from ISPN-1123 (stabilising testsuite jira)

>
>>
>> Cheers,
>> --
>> Galder Zamarreño
>> Sr. Software Engineer
>> Infinispan, JBoss Cache
>>
>>
>> _______________________________________________
>> infinispan-dev mailing list
>> [hidden email]
>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>
>
> _______________________________________________
> infinispan-dev mailing list
> [hidden email]
> https://lists.jboss.org/mailman/listinfo/infinispan-dev

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


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Re: [infinispan-dev] Why DistTxInterceptor in use with Hot Rod ?

Dan Berindei
Going back to your original question Galder, the exception is most
likely thrown because of this sequence of events:

0. Given a cluster {A, B}, a key k and a node C joining.
1. Put acquires the "transaction lock" on node A (blocking rehashing)
2. Put acquires lock for key k on node A
3. Rehashing starts on node B, blocking transactions
4. Put tries to acquire transaction lock on node B

Since it's impossible to finish rehashing while the put operation
keeps the transaction lock on node A, the best option was to kill the
put operation by throwing a RehashInProgressException.

I was thinking in the context of transactions when I wrote this code
(see https://github.com/danberindei/infinispan/commit/6ed94d3b2e184d4a48d4e781db8d404baf5915a3,
this scenario became just a footnote to the generic case with multiple
caches), but the scenario also occurs without transactions. Actually I
renamed it "state transfer lock" and I moved it to a separate
interceptor in my ISPN-1194 branch.

Maybe the locking changes in 5.1 will eliminate this scenario, but
otherwise we could improve the user experience by retrying the command
after the rehashing finishes.

Dan


On Tue, Sep 13, 2011 at 8:11 PM, Galder Zamarreño <[hidden email]> wrote:

>
> On Sep 13, 2011, at 6:38 PM, Mircea Markus wrote:
>
>>
>> On 13 Sep 2011, at 17:22, Galder Zamarreño wrote:
>>
>>> Hi,
>>>
>>> I'm looking at this failure http://goo.gl/NQw4h and I'm wondering why "org.infinispan.distribution.RehashInProgressException: Timed out waiting for the transaction lock" is thrown?
>>>
>>> This is thrown DistTxInterceptor which is added by the InterceptorChainFactory:
>>>
>>>     if (configuration.getCacheMode().isDistributed())
>>>        interceptorChain.appendInterceptor(createInterceptor(DistTxInterceptor.class));
>>>     else
>>>        interceptorChain.appendInterceptor(createInterceptor(TxInterceptor.class));
>>>
>>> However, this is a Hot Rod test and the cache is not configured with a transaction manager, so is DistTxInterceptor really needed?
>>>
>>> In fact, why a TxInterceptor if no transaction manager is configured? (this kinda goes back to Mircea's email earlier today about a transactions enabled/disabled flag)
>> All valid concerns, IMO.
>> 5.1 will clarify this by not adding Tx interceptors for non tx caches.
>
> Is this captured in some other JIRA? I'd like to reference the test and the JIRA from ISPN-1123 (stabilising testsuite jira)
>
>>
>>>
>>> Cheers,
>>> --
>>> Galder Zamarreño
>>> Sr. Software Engineer
>>> Infinispan, JBoss Cache
>>>
>>>
>>> _______________________________________________
>>> infinispan-dev mailing list
>>> [hidden email]
>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>>
>>
>> _______________________________________________
>> infinispan-dev mailing list
>> [hidden email]
>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>
> --
> Galder Zamarreño
> Sr. Software Engineer
> Infinispan, JBoss Cache
>
>
> _______________________________________________
> infinispan-dev mailing list
> [hidden email]
> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>

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Re: [infinispan-dev] Why DistTxInterceptor in use with Hot Rod ?

Galder Zamarreno

On Sep 14, 2011, at 11:40 AM, Dan Berindei wrote:

> Going back to your original question Galder, the exception is most
> likely thrown because of this sequence of events:
>
> 0. Given a cluster {A, B}, a key k and a node C joining.
> 1. Put acquires the "transaction lock" on node A (blocking rehashing)
> 2. Put acquires lock for key k on node A
> 3. Rehashing starts on node B, blocking transactions
> 4. Put tries to acquire transaction lock on node B
>
> Since it's impossible to finish rehashing while the put operation
> keeps the transaction lock on node A, the best option was to kill the
> put operation by throwing a RehashInProgressException.
>
> I was thinking in the context of transactions when I wrote this code
> (see https://github.com/danberindei/infinispan/commit/6ed94d3b2e184d4a48d4e781db8d404baf5915a3,
> this scenario became just a footnote to the generic case with multiple
> caches), but the scenario also occurs without transactions. Actually I
> renamed it "state transfer lock" and I moved it to a separate
> interceptor in my ISPN-1194 branch.

Right, but it shouldn't happen when transactions are off, right?

>
> Maybe the locking changes in 5.1 will eliminate this scenario, but
> otherwise we could improve the user experience by retrying the command
> after the rehashing finishes.

I'd prefer that, otherwise users are likely to code similar logic which is not nice.

>
> Dan
>
>
> On Tue, Sep 13, 2011 at 8:11 PM, Galder Zamarreño <[hidden email]> wrote:
>>
>> On Sep 13, 2011, at 6:38 PM, Mircea Markus wrote:
>>
>>>
>>> On 13 Sep 2011, at 17:22, Galder Zamarreño wrote:
>>>
>>>> Hi,
>>>>
>>>> I'm looking at this failure http://goo.gl/NQw4h and I'm wondering why "org.infinispan.distribution.RehashInProgressException: Timed out waiting for the transaction lock" is thrown?
>>>>
>>>> This is thrown DistTxInterceptor which is added by the InterceptorChainFactory:
>>>>
>>>>     if (configuration.getCacheMode().isDistributed())
>>>>        interceptorChain.appendInterceptor(createInterceptor(DistTxInterceptor.class));
>>>>     else
>>>>        interceptorChain.appendInterceptor(createInterceptor(TxInterceptor.class));
>>>>
>>>> However, this is a Hot Rod test and the cache is not configured with a transaction manager, so is DistTxInterceptor really needed?
>>>>
>>>> In fact, why a TxInterceptor if no transaction manager is configured? (this kinda goes back to Mircea's email earlier today about a transactions enabled/disabled flag)
>>> All valid concerns, IMO.
>>> 5.1 will clarify this by not adding Tx interceptors for non tx caches.
>>
>> Is this captured in some other JIRA? I'd like to reference the test and the JIRA from ISPN-1123 (stabilising testsuite jira)
>>
>>>
>>>>
>>>> Cheers,
>>>> --
>>>> Galder Zamarreño
>>>> Sr. Software Engineer
>>>> Infinispan, JBoss Cache
>>>>
>>>>
>>>> _______________________________________________
>>>> infinispan-dev mailing list
>>>> [hidden email]
>>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>>>
>>>
>>> _______________________________________________
>>> infinispan-dev mailing list
>>> [hidden email]
>>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>>
>> --
>> Galder Zamarreño
>> Sr. Software Engineer
>> Infinispan, JBoss Cache
>>
>>
>> _______________________________________________
>> infinispan-dev mailing list
>> [hidden email]
>> https://lists.jboss.org/mailman/listinfo/infinispan-dev
>>
>
> _______________________________________________
> infinispan-dev mailing list
> [hidden email]
> https://lists.jboss.org/mailman/listinfo/infinispan-dev

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


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Re: [infinispan-dev] Why DistTxInterceptor in use with Hot Rod ?

Dan Berindei
On Thu, Sep 15, 2011 at 12:25 PM, Galder Zamarreño <[hidden email]> wrote:

>
> On Sep 14, 2011, at 11:40 AM, Dan Berindei wrote:
>
>> Going back to your original question Galder, the exception is most
>> likely thrown because of this sequence of events:
>>
>> 0. Given a cluster {A, B}, a key k and a node C joining.
>> 1. Put acquires the "transaction lock" on node A (blocking rehashing)
>> 2. Put acquires lock for key k on node A
>> 3. Rehashing starts on node B, blocking transactions
>> 4. Put tries to acquire transaction lock on node B
>>
>> Since it's impossible to finish rehashing while the put operation
>> keeps the transaction lock on node A, the best option was to kill the
>> put operation by throwing a RehashInProgressException.
>>
>> I was thinking in the context of transactions when I wrote this code
>> (see https://github.com/danberindei/infinispan/commit/6ed94d3b2e184d4a48d4e781db8d404baf5915a3,
>> this scenario became just a footnote to the generic case with multiple
>> caches), but the scenario also occurs without transactions. Actually I
>> renamed it "state transfer lock" and I moved it to a separate
>> interceptor in my ISPN-1194 branch.
>
> Right, but it shouldn't happen when transactions are off, right?
>

It will still happen with transactions off, because state transfer
will acquire the state transfer lock in exclusive mode and
WriteCommands will acquire the state transfer lock in shared mode
instead of PrepareCommands with transactions on.

If we don't acquire the state transfer lock than we run the risk of
pushing stale data to other nodes, are you saying that without
transactions enabled this risk is acceptable?

>>
>> Maybe the locking changes in 5.1 will eliminate this scenario, but
>> otherwise we could improve the user experience by retrying the command
>> after the rehashing finishes.
>
> I'd prefer that, otherwise users are likely to code similar logic which is not nice.
>

After looking at the scenario again it became clear that step 2. is
not necessary at all and the locking enhancements will not change
anything.

We could change DistributionInterceptor to not hold the state transfer
lock during remote calls, which will allow rehashing to proceed on the
origin. But then the ownership of the keys might change during the
call, so we'll need a retry phase anyway.

Dan

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Re: [infinispan-dev] Why DistTxInterceptor in use with Hot Rod ?

Galder Zamarreno

On Sep 15, 2011, at 1:31 PM, Dan Berindei wrote:

> On Thu, Sep 15, 2011 at 12:25 PM, Galder Zamarreño <[hidden email]> wrote:
>>
>> On Sep 14, 2011, at 11:40 AM, Dan Berindei wrote:
>>
>>> Going back to your original question Galder, the exception is most
>>> likely thrown because of this sequence of events:
>>>
>>> 0. Given a cluster {A, B}, a key k and a node C joining.
>>> 1. Put acquires the "transaction lock" on node A (blocking rehashing)
>>> 2. Put acquires lock for key k on node A
>>> 3. Rehashing starts on node B, blocking transactions
>>> 4. Put tries to acquire transaction lock on node B
>>>
>>> Since it's impossible to finish rehashing while the put operation
>>> keeps the transaction lock on node A, the best option was to kill the
>>> put operation by throwing a RehashInProgressException.
>>>
>>> I was thinking in the context of transactions when I wrote this code
>>> (see https://github.com/danberindei/infinispan/commit/6ed94d3b2e184d4a48d4e781db8d404baf5915a3,
>>> this scenario became just a footnote to the generic case with multiple
>>> caches), but the scenario also occurs without transactions. Actually I
>>> renamed it "state transfer lock" and I moved it to a separate
>>> interceptor in my ISPN-1194 branch.
>>
>> Right, but it shouldn't happen when transactions are off, right?
>>
>
> It will still happen with transactions off, because state transfer
> will acquire the state transfer lock in exclusive mode and
> WriteCommands will acquire the state transfer lock in shared mode
> instead of PrepareCommands with transactions on.
>
> If we don't acquire the state transfer lock than we run the risk of
> pushing stale data to other nodes, are you saying that without
> transactions enabled this risk is acceptable?

Hmmm, at first glance no, it does not look acceptable. Refactoring though, as you did, is in order though to move it somewhere else, cos clearly it's logic that's required by both transactional and non-transactional caches.

>
>>>
>>> Maybe the locking changes in 5.1 will eliminate this scenario, but
>>> otherwise we could improve the user experience by retrying the command
>>> after the rehashing finishes.
>>
>> I'd prefer that, otherwise users are likely to code similar logic which is not nice.
>>
>
> After looking at the scenario again it became clear that step 2. is
> not necessary at all and the locking enhancements will not change
> anything.
>
> We could change DistributionInterceptor to not hold the state transfer
> lock during remote calls, which will allow rehashing to proceed on the
> origin. But then the ownership of the keys might change during the
> call, so we'll need a retry phase anyway.
>
> Dan
>
> _______________________________________________
> infinispan-dev mailing list
> [hidden email]
> https://lists.jboss.org/mailman/listinfo/infinispan-dev

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


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