Mahalo endless loop on prepareAndCommit

[Guy Korland]

Hi,

We found out that TransactionManager.commit(long timeout) might stack
forever even if we set a timeout.

It seems like the following code on TxnManagerTransaction is the source
of it (line 680):

  if ((job instanceof PrepareJob) ||

                      (job instanceof PrepareAndCommitJob)) {

                        try {

 Line 680: if
(job.isCompleted(Long.MAX_VALUE)) {

                                result = (Integer)
job.computeResult();


Do you have any suggestions?

Thanks,
Guy

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[Robert Resendes]

Guy Korland wrote:

> Hi,
>
> We found out that TransactionManager.commit(long timeout) might stack
> forever even if we set a timeout.
>
> It seems like the following code on TxnManagerTransaction is the source
> of it (line 680):
>
>   if ((job instanceof PrepareJob) ||
>
>                       (job instanceof PrepareAndCommitJob)) {
>
>                         try {
>
>  Line 680: if
> (job.isCompleted(Long.MAX_VALUE)) {
>
>                                 result = (Integer)
> job.computeResult();
>
>
> Do you have any suggestions?
>

Without more details, I can only guess as to what's happening. One
possibility is that you have a "misbehaving" transaction participant
that is taking a long time to respond to the "prepare" part of the
two-phase commit protocol. If so, then here's what would happen:

- client calls commit() with or without a timeout[1]
- The transaction manager creates a PrepareJob[2] that will "ask" each
participant whether or not it can complete the transaction
- The transaction manager will wait until the PrepareJob provides an
answer before continuing (i.e. abort or commit).

The PrepareJob attempt to call "prepare" on each participant. If any of
those attempts are hanging, then the manager will hang as well (because
it needs an answer).

Hopefully, this helps, but if it doesn't, then please send more details
regarding what you are doing and seeing.

You might also consider sending any follow-up messages to the River User
List (see http://incubator.apache.org/river/RIVER/mailing-lists.html)
because all the new development effort has shifted (from Sun) to that
project under the Apache organization.


Notes:

[1] Note the timeout parameter only states how long the client is
willing to wait for the manager to notify the participants of the
transaction's outcome (i.e. abort/commit). The timeout only applies
after the state of the transaction is determined. See
http://java.sun.com/products/jini/2.0/doc/specs/html/txn-spec.html#7224.

[2] There is also a PrepareAndCommitJob that optimizes for the single
participant case, but the explanation is similar.

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