Redelivery of messages previously consumed.

[fenbers <Ma...@noaa.gov>]

I'm reposting this with updated information.I'm setup to use durable Topics
with retroactive=true.  My application consumes messages, which lights up
certain status indicators.  While this works fine, I have a problem in that
if the user exits and restarts my application, sometimes the messages are
redelivered and sometimes they are not.  I always want all non-expired
messages to be redelivered upon relaunch, no matter how many times the app
is relaunched, but this behavior is inconsistent. If redelivery NEVER
occurs, I'd look at this as a configuration mistake, but redelivery does
occur about 50% of the time.  I cannot figure out why this is inconsistent. 
Does anyone have ideas of what I can try?  I'm using 5.14.2.  Might there be
a way, programmatically, for the app to *manually* request a redelivery of
all unexpired messages (in the order of creation), say, through a "refresh"
button -- even if they have been previously consumed? Mark



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Re: Redelivery of messages previously consumed.

[fenbers <Ma...@noaa.gov>]

OK.  The client app has a durable consumer C has connected to Topic T, and
while it is active, messages X, Y, and Z are eventually delivered by the
broker and consumed by C.  Then, C disconnects and then reconnects
(sometimes immediately).  When C reconnects, sometimes messages X, Y, and Z
are redelivered (and consumed) and sometimes the messages X, Y, and Z
seemingly are *not* redelivered even though other messages U, V, and W are
delivered and consumed properly.

In addition, the same client app has a second durable consumer B connected
to Topic S.

The mystery is why X, Y, and Z are not always redelivered upon C's
reconnection to T, while all messages to Topic S *are* redelivered upon
reconnection of consumer B.  (To clarify, *no* messages at all are
redelivered to C.)  Even stranger, on occasion X, Y, and Z (to clarify,
*all* messages) *do* sometimes get redelivered after a handful of
disconnects/reconnects, but not always.  There are always some offline
subscriptions D and E, and so the messages X, Y, and Z should still be in
the broker until the message expires.  In my case, X, Y, and Z are not yet
close to expiring when this occurs.

There is an overwhelming amount of information in the log files, even
without the highest levels of logging.  Is there something specific in the
log that can tell me anything about the fates of messages X, Y, and Z?  Are
they still in the broker?  If so, why aren't they redelivered on a
reconnect?  If not, what happened to them?  Or maybe the log will say
something about the consumer C rejecting redelivery for some reason?  

To be honest, I am overwhelmed by the logging (most of which I don't
understand) for that to be too helpful in my investigation unless I know
specifically what to search for.
Mark




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Re: Redelivery of messages previously consumed.

[Tim Bain <tb...@alumni.duke.edu>]

There's no mechanism to request that the broker send you everything it has;
if that is going to happen, it happens when the client connects.

In your testing, are you saying that if topic T has messages A, B, and C
that have not yet been consumed by offline durable consumer C1, and
consumer C2 connects and disconnects repeatedly, C2 will sometimes get A,
B, and C, and sometimes will get nothing or some subset of A, B, and C? Can
you please describe in a little more detail exactly what behavior you see?
In particular, redelivery will happen only for messages that are still
unconsumed for at least one other subscription (because once all
subscriptions have consumed it, the broker discards the message), so please
be very specific about which messages are in the topic and which consumers
have consumed which messages at which point.

Tim

On Feb 13, 2017 12:06 PM, "fenbers" <Ma...@noaa.gov> wrote:

> I'm reposting this with updated information.I'm setup to use durable Topics
> with retroactive=true.  My application consumes messages, which lights up
> certain status indicators.  While this works fine, I have a problem in that
> if the user exits and restarts my application, sometimes the messages are
> redelivered and sometimes they are not.  I always want all non-expired
> messages to be redelivered upon relaunch, no matter how many times the app
> is relaunched, but this behavior is inconsistent. If redelivery NEVER
> occurs, I'd look at this as a configuration mistake, but redelivery does
> occur about 50% of the time.  I cannot figure out why this is inconsistent.
> Does anyone have ideas of what I can try?  I'm using 5.14.2.  Might there
> be
> a way, programmatically, for the app to *manually* request a redelivery of
> all unexpired messages (in the order of creation), say, through a "refresh"
> button -- even if they have been previously consumed? Mark
>
>
>
> --
> View this message in context: http://activemq.2283324.n4.
> nabble.com/Redelivery-of-messages-previously-consumed-tp4721929.html
> Sent from the ActiveMQ - User mailing list archive at Nabble.com.