[rabbitmq-discuss] Messages Timeout in Queue

[Alexis Richardson]

On Mon, Jul 6, 2009 at 8:17 PM, GAGAN ARORA<gaganarora.itm at gmail.com> wrote:
> Alexis
>
> Actually dropping out messages from queue is another problem I am facing and
> is following it on another thread with you. In this case I am assuming there
> is no dropping  out of messages from queue if there is no consumer is
> listening to the queue and a message is always queued up in queue.

Messages will get dropped by an exchange X instead of being put in a
queue Q, when Q is not bound to X.

So to go through your case:

"Case1: User B sending his message to UserB Exchange which will route
message to User A queue but User A is not connected to any of servers.
 At this point of  all messages sent to Queue A should be dropped."

The property you want is:

* When User A is not connected to any of servers
* Then all messages sent to Queue A should be dropped

This is true IF when User A is not connected to any of the servers,
THEN queue A is not bound to any exchanges.

This has *nothing* to do with consumers or what they are 'listening' to.

So - when User A is not connected then (if above) messages for A get
dropped.  Easy peasy.

alexis





> Thanks
> Gagan
>
> On Tue, Jul 7, 2009 at 12:03 AM, Alexis Richardson
> <alexis.richardson at gmail.com> wrote:
>>
>> Gagan,
>>
>> On Mon, Jul 6, 2009 at 7:02 PM, GAGAN ARORA<gaganarora.itm at gmail.com>
>> wrote:
>> > Alexis
>> >
>> > a) when the User A is not logged into server 1 or server 2, any
>> > messages sent to them by User B are discarded
>> >>> Actually during this case no consumer would be listening to User A
>> >>> queue
>> >>> and hence the messages can't be discarded and would be queued in
>> >>> Queue.
>>
>> In your document you said:
>>
>> "Case1: User B sending his message to UserB Exchange which will route
>> message to User A queue but User A is not connected to any of servers.
>> At this point of  all messages sent to Queue A should be dropped."
>>
>> If this is happening then the messages will be discarded and not
>> queued in Queue.
>>
>> alexis
>>
>>
>>
>> > b) but, when User A is logged in to server 1, any messages sent by
>> > User B that may be routed to User A are queued in Queue A,
>> >>> No of messages increases.
>> >
>> > c) .... delivered when User A logs into server 2.
>> >>> A large no of messages get delieverd.
>> >
>> > It is a constraint in my system that I have to initialize consumer when
>> > User
>> > A connects to Server2.
>> >
>> > On Mon, Jul 6, 2009 at 9:28 PM, Alexis Richardson
>> > <alexis.richardson at gmail.com> wrote:
>> >>
>> >> Gagan
>> >>
>> >> As I understood from your document:
>> >>
>> >> a) when the User A is not logged into server 1 or server 2, any
>> >> messages sent to them by User B are discarded
>> >> b) but, when User A is logged in to server 1, any messages sent by
>> >> User B that may be routed to User A are queued in Queue A, and then
>> >> ...
>> >> c) .... delivered when User A logs into server 2.
>> >>
>> >> Provided that you can implement this efficiently (see other email)
>> >> then the consumer at User A only needs to discard messages that are
>> >> older than one minute, and that were not already discarded due to (a)
>> >> above.  So unless the time interval between A logging into server 1,
>> >> and A logging into server 2, is "quite long" then the 'timestamp'
>> >> method adds very little overhead.
>> >>
>> >> Is that correct or have I missed something?
>> >>
>> >> alexis
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> On Sat, Jul 4, 2009 at 8:28 PM, GAGAN ARORA<gaganarora.itm at gmail.com>
>> >> wrote:
>> >> > Hi Alexis
>> >> >
>> >> > My system is similar to an IM system and is using RabbitMQ for
>> >> > presence
>> >> > updates and have designed it in such a way that a consumer subscribes
>> >> > to
>> >> > a
>> >> > queue only when it comes online.Now the issue is as stated by you
>> >> > there
>> >> > will
>> >> > be a large no of messages ready to be deleivered when a user comes
>> >> > online.
>> >> > Checking timestamp for each message will result in high cost.
>> >> >
>> >> > There can be a solution in which a message can be published using
>> >> > immediate
>> >> > flag. But it is desired by consumer to get all messages which are
>> >> > less
>> >> > than
>> >> > 1 minute old.
>> >> >
>> >> > Can you suggest some other solution for achieving this?
>> >> >
>> >> > Thanks
>> >> > Gagan Arora
>> >> >
>> >> >
>> >> >
>> >> >
>> >> > On Sat, Jul 4, 2009 at 3:32 PM, Alexis Richardson
>> >> > <alexis.richardson at gmail.com> wrote:
>> >> >>
>> >> >> Gagan,
>> >> >>
>> >> >> On Fri, Jul 3, 2009 at 5:08 PM, GAGAN
>> >> >> ARORA<gaganarora.itm at gmail.com>
>> >> >> wrote:
>> >> >> > Hi Alexis
>> >> >> > The problem statement here is I dont want my messages in queue for
>> >> >> > more
>> >> >> > than
>> >> >> > 1 minute.
>> >> >>
>> >> >> The easiest way to do this is for the client to keep consuming the
>> >> >> messages from the queue.
>> >> >>
>> >> >> However: presumably you want messages to be ignored in the case
>> >> >> where
>> >> >> (a) there is no consumer to get the messages from the queue; and (b)
>> >> >> the messages are more than one minute old.
>> >> >>
>> >> >> If so then: Have you considered putting a timestamp on the messages?
>> >> >> That way, when a consumer starts taking messages from the queue, it
>> >> >> can simply check the timestamps and throw away anything 'old'.  This
>> >> >> solution works just fine when (i) you don't need real time accuracy
>> >> >> ie. "about a minute" is just as good as "exactly a minute", and
>> >> >> provided that (ii) there aren't too many messages to throw away.
>> >> >> Judging by the document that you sent, both (i) and (ii) are true.
>> >> >>
>> >> >> Does this help?
>> >> >>
>> >> >> alexis
>> >> >>
>> >> >>
>> >> >> > I have tried expiration property while publishing a message but
>> >> >> > later came to know that it is still not implemented. Can you help
>> >> >> > me
>> >> >> > out
>> >> >> > in
>> >> >> > figuring some alternate approach?
>> >> >> > Thanks
>> >> >> > Gagan Arora
>> >> >> >
>> >> >> > On Fri, Jul 3, 2009 at 8:17 PM, Alexis Richardson
>> >> >> > <alexis.richardson at gmail.com> wrote:
>> >> >> >>
>> >> >> >> Gagan,
>> >> >> >>
>> >> >> >> On Fri, Jul 3, 2009 at 3:10 PM, GAGAN
>> >> >> >> ARORA<gaganarora.itm at gmail.com>
>> >> >> >> wrote:
>> >> >> >> > Hi
>> >> >> >> > Is it possible to set message time out in Java client API, so
>> >> >> >> > that
>> >> >> >> > messages
>> >> >> >> > drop out from queue after some interval of time if nobody
>> >> >> >> > consumes
>> >> >> >> > it?.
>> >> >> >>
>> >> >> >> Not yet but this is a feature have been asking for quite a bit.
>> >> >> >>  It's
>> >> >> >> on our roadmap.
>> >> >> >>
>> >> >> >> There may be other ways to achieve what you want.
>> >> >> >>
>> >> >> >> alexis
>> >> >> >>
>> >> >> >>
>> >> >> >>
>> >> >> >> > Thanks
>> >> >> >> > Gagan Arora
>> >> >> >> > _______________________________________________
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>> >> >> >> >
>> >> >> >> >
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>> >> >> >> >
>> >> >> >> >
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