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From "Christopher James Blythe (JIRA)" <>
Subject [jira] Created: (DAYTRADER-29) Asyc 1-Phase mode should be removed
Date Wed, 06 Dec 2006 21:40:21 GMT
Asyc 1-Phase mode should be removed

                 Key: DAYTRADER-29
             Project: DayTrader
          Issue Type: Improvement
          Components: EJB Tier
    Affects Versions: 1.2, 2.0
            Reporter: Christopher James Blythe

Here are some comments that I added to DT-22...

Since my involvement with Daytrader (and Trade), we've never been all that concerned with
the Async 1-phase mode. Here is the lay of the land to my understanding...

Sync mode
 - Uses JMS topics and TradeTopicMDB to publish changes to the quote prices
 - There is flag in the DDs to disable this but it doesn't seem to apply to direct mode (only
EJB mode)
Async 2-phase mode
 - This mode uses a JMS queue and the TradeBroker to handle order processing
 - Specifically, the buy and sell operations call a queueOrder method to place a message on
the queue
 - The queueOrder is part of an XA transaction because two resource managers (JMS and database)
are involved to create the order in the databse and place a message on the queue
- The MDB starts a new transaction when the message is read from the queue. The MDB then executes
the completeOrder method which updates the order in the database inside the original MDB transaction
Async 1-phase mode
 - Does the same as above, but does not involve an UserTransaction to provide XA
 - Since the MDB is container-managed, TradeEJB is used to complete the order and create a
new transaction (avoiding XA)

My guess is that the Async 1-phase mode was added to messure the overhead associated with
handling the XA transaction.

I have never found that much value in Async 1-phase mode. If you are using two different resources
as part of a logical transaction, you should always use XA to ensure proper rollback handling.
Honestly, I see very little need to keep it around... However, there might be some possiblities
I have not considered. As an added benefit of removing this option, we would remove a dependency
between the TradeDirect and TradeBean code.

I also like the idea of splitting up the modes by category and doing a little renaming to
make them more descriptive.

Persistence Run-time Modes (one has to be selected)
1) Direct (or JDBC)
2) Stateless Session Bean to Direct
3) Full EJB (Stateless Session Bean to Entity Beans)

JMS Support Enablement (any can be selected)
- Publish Quote Updates (Publish quote price changes to a JMS topic)
- Process Buy/Sell Orders using XA (Asychronously process buy/sell orders by placing them
on a JMS queue. An MDB is then responsible for reading a message form the queue and completing
the order)


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