On 5/11/2012 12:45 AM, Adam Heath wrote:
On 05/10/2012 06:40 PM, Adrian Crum wrote:
I wanted to discuss this again.
Some time ago I modified my local copy of OFBiz to execute the the ant
run-install task faster by using multi-threaded entity creation and
data loading. I don't remember what i was working on at the time, but
I needed the process to run much faster.
Adam and I discussed my design and he said it sounded like it was
similar to SEDA (http://www.eecs.harvard.edu/~mdw/proj/seda/).
Actually, my approach was not that sophisticated, I just used a
consumer-provider design pattern based on a FIFO queue.
Anyway, based on that conversation, Adam committed the multi-threaded
entity creation/data loading code
(http://mail-archives.apache.org/mod_mbox/ofbiz-commits/201106.mbox/%3c20110626025049.f302e2388...@eris.apache.org%3E).
The work Adam committed greatly improved the database creation/data
loading time.
In this Jira issue, Adam mentions how transactions are tied to a
single thread. This is due to a fundamental weakness in OFBiz - the
use of ThreadLocal variables. In order to truly remove the bottlenecks
in OFBiz, we need to avoid the use of ThreadLocal variables - because
they prohibit handing off tasks to other threads. The Execution
Context proposed by David Jones some time ago is a step in the right
direction, but it uses ThreadLocal variables too.
My statement has *nothing* to do with ThreadLocal(well, at least not
used by ofbiz). javax.transaction is for the *current* thread. When
an xml import is requested, it *must* be done in the current thread,
in the current transaction. It's not possible to suspend the
transaction for the foreground thread, and resume it in the
background(I tried).
I may not have explained myself fully in the jira issue, or maybe you
didn't understand. In any case, the rest of your explanation seems to
not apply now.
I did not understand that the transaction-to-thread relationship was
required in the javax.transaction API. That is a real problem. It makes
me wonder how SEDA-style designs can work in transaction-based applications.
-Adrian
