Hi all,
I have read on #1, #2 and #3 types of Transaction mechanisms as well as
have gone through the existing transaction source code in MB (Andes
broker).
Regarding the three levels of transactions, AMQP supports three kinds of
transactions [1] [2] as,
- Automatic transactions: Every published message and acknowledgement is
processed as a standalone transaction.
- Server local transactions: Server will buffer published messages and
acknowledgements and commit them on demand from the client.
- Distributed transactions: Server will synchronise its transactions
with an external transaction coordinator, A TransactionManager which
coordinates one of more Resources.
IMO we have already partially implemented AMQP Transactions in MB but
however it is not a full implementation as only transaction commit() and
rollback() operations properly handled for Consuming, and not implemented
for Publishing scenario. The following is an overview of present AMQP
transactions implementation of MB 2.1.0
*(Interface) ServerTransaction
--------------> LocalTransaction
--------------> AutoCommitTransaction : Implementation is
there but it is not used in broker level, as it is not intended to use
autocommit.*
*Local transactions*
Local transactions are applied to message Publish, Acknowledge and
Rejection scenarios. In the consuming side, the acknowledgements are made
transactional, with appropriate Commit/Rollback operations.
When committing a message in Publish mode, basically the transaction should
be completed after the broker gets messages from client application and
successfully writing them into Cassandra storage. Similarly when consuming
messages, the transaction should be committed after the message is received
by client and the Message entry is correctly removed from the Cassandra
storage. When rollbacking the transaction, message needs to be marked as
'Redelivered' and requeue back.
The current code address the Basic.ack and Basic.reject scenarios when
consuming messages in a transacted session [3]. To perform adding/removing
from storage, a CassandraTransation instance is used here.
*Basic Consumer : Commit()*
{
startTxn();
receiveMessage();
dequeMessage (
new Cassandratrnasaction(){
deleteMesageEntryFromStorage();
} );
ackMessage();
endTxn();
}
*Basic Consumer : Rollback()*
{
startTxn();
getUnAckMessage();
setRedelivered();
decrementUnAckMsgCount();
requeueMessage(); or rejectmessage();
endTxn();
}
According to my observation, currently AMQP transactions are not
implemented in Basic.publish mode and therefore we first need to decide on
a common implementation approach to address transaction requirements
described above across both Publish/Acknowledge mechanisms. After that it
is needed to handle JMS Local transactions in the Andes client level.
However AMQP only guarantees atomicity when all transactions involve a
single queue. When there are multiple queues involved, there can be
incidents that, at a broker failure during commit() the effects of the
transaction can only be occurred in some of the queues [4]. To address this
scenario, we need to support distributed transactions. The Java Transaction
API (JTA) [5] provides standard Java interfaces between a
TransactionManager and the Resources involved in distributed transactions
as above.
As our initial requirement is completion of Local transactions properly for
WSO2 MB, at the moment there is no need to using JTA in the implementation.
In addition both AMQP and JMS supports distributed transactions with using
X-Open XA architecture [6], where this can be used when we need to support
distributed transactions.
Please fell free to add your concerns.
Thanks!
Ishara
[1]. http://www.amqp.org/specification/0-10/amqp-org-download
[2].
http://rabbitmq.1065348.n5.nabble.com/Transactions-in-AMQP-td4803.htm<http://rabbitmq.1065348.n5.nabble.com/Transactions-in-AMQP-td4803.html>
l
[3].http://abeykoon.blogspot.com/2013/04/get-jms-local-transactions-to-work-with_21.html
[4]. http://www.rabbitmq.com/amqp-0-9-1-reference.html#class.tx
[5]. http://www.oracle.com/technetwork/java/javaee/jta/index.html
[6].
http://en.wikipedia.org/wiki/Java_Transaction_API#JTA_implementation_of_the_X.2FOpen_XA_architecture
On Mon, Jul 15, 2013 at 4:40 PM, Samisa Abeysinghe <[email protected]> wrote:
> OK, got it. Thanks for the clarification.
>
>
> On Mon, Jul 15, 2013 at 9:13 AM, Srinath Perera <[email protected]> wrote:
>
>> Hi Samisa,
>>
>> AMQP transactions is a subset of JMS transactions we thought that as the
>> starting point.
>>
>> --Srinath
>>
>>
>> On Mon, Jul 15, 2013 at 8:09 AM, Samisa Abeysinghe <[email protected]>wrote:
>>
>>> I was under the impression that JMS transactions are of high priority,
>>> given the industry usage. Why have we picked AMQP over JMS transactions?
>>> Does AMQP get used more than JMS in transactional situations?
>>>
>>>
>>> On Fri, Jul 12, 2013 at 3:02 PM, Srinath Perera <[email protected]>wrote:
>>>
>>>> Ishara and myself chatted about this.
>>>>
>>>> There are 3 levels.
>>>>
>>>> 1. AMQP transactions
>>>> 2. JMS transactions
>>>> 3. JTA transactions
>>>>
>>>> Our first goal is to make AMQP transactions work.
>>>>
>>>> Ishara is working understanding differences of #1, #2, and #3 and
>>>> understanding how #1 should integrating with current MB.
>>>>
>>>> --
>>>> ============================
>>>> Srinath Perera, Ph.D.
>>>> Director, Research, WSO2 Inc.
>>>> Visiting Faculty, University of Moratuwa
>>>> Member, Apache Software Foundation
>>>> Research Scientist, Lanka Software Foundation
>>>> Blog: http://srinathsview.blogspot.com/
>>>> Photos: http://www.flickr.com/photos/hemapani/
>>>> Phone: 0772360902
>>>>
>>>> _______________________________________________
>>>> Architecture mailing list
>>>> [email protected]
>>>> https://mail.wso2.org/cgi-bin/mailman/listinfo/architecture
>>>>
>>>>
>>>
>>>
>>> --
>>>
>>> Thanks,
>>> Samisa...
>>>
>>> Samisa Abeysinghe
>>> VP Engineering
>>> WSO2 Inc.
>>> http://wso2.com
>>> http://wso2.org
>>>
>>
>>
>>
>> --
>> ============================
>> Srinath Perera, Ph.D.
>> Director, Research, WSO2 Inc.
>> Visiting Faculty, University of Moratuwa
>> Member, Apache Software Foundation
>> Research Scientist, Lanka Software Foundation
>> Blog: http://srinathsview.blogspot.com/
>> Photos: http://www.flickr.com/photos/hemapani/
>> Phone: 0772360902
>>
>
>
>
> --
>
> Thanks,
> Samisa...
>
> Samisa Abeysinghe
> VP Engineering
> WSO2 Inc.
> http://wso2.com
> http://wso2.org
>
--
Ishara Premasada
Software Engineer,
WSO2 Inc. http://wso2.com/
*Blog : http://isharapremadasa.blogspot.com/
Twitter : https://twitter.com/ishadil
Mobile : +94 714445832*
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