Hi,
I have a lot of problems with deadlocks and I have tried a lot of different
configuration and none have worked (I will soon post some questions about this). So my
new strategy is to rollback and retry the transactions which fails. However, I have
realized that I do not understand everything about transactions.
Here is the flow of method invocations:
(1) Servlet -> (2) stateful session bean -> (3) several entity beans
First attempt:
(2) has a method request() with transaction type "Required"
I also use context.setRollBackOnly() in the session bean if something other than
deadlock problems happens during the execution.
(1) contains something like the following..
while(!success && k<3)
{
try
{
session.request();
success = true
}
// catch rollback and deadlock exception
catch(Exception e)
{
success = false,
e.printStackTrace();
k++;
}
}
Questions:
Is this the correct way to handle the transaction rollback?
I hope I don't have to call a specific method to actually perform the rollback?
I also read somewhere on this forum that JBoss automatically retries transaction when
deadlock occurs, is that true?
Anyway, the code above seems to work in most cases.
Attempt two:
I don't to want to catch the exceptions in the servlet so I moved the code above to a
new method in the session ejb called testRequest(), which the servlet invokes.
testRequest() then calls the original request() method.
I used "Required" for testRequest() and "RequiresNew() for request(). My thought was
that a new transaction would be created and that would be the transaction that would
be rolled back in case of problems.
(2)
testRequest()
{
while(!success && k<3)
{
try
{
request();
success = true
}
// catch rollback and deadlock exception
catch(Exception e)
{
success = false,
k++;
}
}
}
This didnt work as I expected, the transaction rolled back but it is never restarted ,
instead it stayed in the rollback state. I tried to invoke context.getRollbackOnly()
in testRequest() and it returned "True". So I guess that the transaction which is
started when the servlet calls testRequest() is rolled back as well, I thought that
only the second transaction which is created when request() is called would rollback..
Questions:
Will a rollback propagate all the way back to the original transaction if
"RequiresNew" is used?
Is there a way to catch and retry the transaction rollbacks in the actual session bean
instead of in the servlet?
I hope someone can make some sense of what I wrote above :)
Thanks in advance
/Lars
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