This is handled by the ActiveMQ failover transport (the default in 5.1
onwards).
It replays messages on your behalf that haven't been acknowledged -
there is duplicate detection built in to the broker and the clients
too ...
cheers,
Rob
cheers,
Rob
Rob Davies
http://fusesource.com
http://rajdavies.blogspot.com/
On 28 Nov 2008, at 13:09, thabach wrote:
Hey everyone
I have a conceptual question regarding reconciliation after a JMS
server
crash. According to the JMS specification (paragraph 4.4.13, see
below)
there is room for some ambiguity leaving a producer in doubt if a
message
successfully made it to the server or not in case of server failure.
The [X] part is what disquiets me: "It is up to a JMS application to
deal
with this ambiguity."
A producer in doubt can only resend the original message. In what
way does
ActiveMQ support me in doing so ? Are there any means of having
ActiveMQ
sort out potential duplicates sent by the application layers after
server
recovery and publisher reconnect ? Or do downstream consumers have
to cope
with these kind of duplicate messages somehow ?
Regards and thanks for any insights, Christian.
== JMS spec excerpt ============================================
4.4.13 Duplicate Production of Messages
JMS providers must never produce duplicate messages. This means that a
client that produces a message can rely on its JMS provider to
insure that
consumers of the message will receive it only once. No client error
can
cause a
provider to duplicate a message.
If a failure occurs between the time a client commits its work on a
Session
and
the commit method returns, the client cannot determine if the
transaction
was
committed or rolled back. The same ambiguity exists when a failure
occurs
between the non-transactional send of a PERSISTENT message and the
return
from the sending method.
[X] It is up to a JMS application to deal with this ambiguity. In some
cases, this
may cause a client to produce functionally duplicate messages.
A message that is redelivered due to session recovery is not
considered a
duplicate message.
======================================================
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