Another consideration ... but this may be outside the scope of what you are working on.
I assume that by "graceful shutdown for ejb transactions" you
mean a feature to allow ejb transactions, which have been
initiated before a shutdown, to be given a reasonable chance to
complete after shutdown has been initiated, and so avoiding
aborting a transaction just because a shutdown was initiated at an
inappropriate time. In other words, the feature is specific to the
case of when the server is being shutdown cleanly/gracefully. It's
worht mentioning that in addition to shutdown of the server,
undeploying a deployment containing ejbs (in the middle of a
transaction) is going to have a similar negative impact on ejb
transactions as initiating a shutdown. Also, if the deployment is
clustered, there are possibilities for retrying on another
available node; but as I mentioned before, there are issues with
that too.
Just to say that "graceful shutdown" has different meanings in
different deployment contexts.
Hi Flavia
Is there any overall design for this feature available to browse? For example, there has long been a problem (and still is) with remotely initiated transactions and the EJB client retry mechanism (both of them) which associates an XA resource with one node at the beginning of the transaction and then retries on another, completes on the other, then tries to commit on the original XA node which has shutdown. This is anything but clean.
Richard
On 02/12/16 11:56 AM, Flavia Rainone wrote:
Hi,
I'm creating this thread to discuss the remaining details of graceful shutdown for ejb transactions.
This is more or less what I've done so far:
https://github.com/fl4via/wildfly/commit/7017146522af9a979a8a8e0c92039e6a5fb18760
While discussing this in the hip chat yesterday, Stuart mentioned that maybe we could have the transactions subsystem responsible for keeping track of how many active transactions we have, instead of putting that code in EjbRemoteTransactionsRepository.
Stuart, does that include having the suspend callback being done at transactions subsystem as well? I'm thinking maybe not, because there are two points in the ejb subsystem we need to know if transactions suspension is over:
- at EjbSuspendInterceptor if it is over, no request is allowed, if it is not over, we need to check if current invocation contains a reference to an active transaction
- at some point, we need to let control point notify that the ejb module is no longer available to ejb client after transaction suspension is over, i.e., we need to do that when suspend has been requested and there are no remaining active transactions available.
On the other hand, it is hard to draw the line between what should be in the transactions subsystem and what shouldn't. If the callback is done at transactions subsystem, we need a way of having ejb3 notified that it is done. If it is not done at transactions subsystem, ejb3 has to be notified of the active transactions going to zero, which seems a lot of overhead, so from this point of view maybe the callback should be in the transactions system after all.
Stuart and Gytis, any thoughts?
-- Flavia Rainone Principal Software Engineer JBoss EAP/WildFly Team M: (+55) 11 981-225-466 Red Hat. Better technology. Faster innovation. Powered by community collaboration.
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