[rabbitmq-discuss] Dropping out messages from a queue

[GAGAN ARORA]

Alexis

When are you planning to release version for first option?

Can you explain the second option?

Thanks
Gagan

On Mon, Jul 6, 2009 at 11:06 PM, Alexis Richardson <
alexis.richardson at gmail.com> wrote:

> Gagan
>
> One way to simplify the subscription management and get rid of 'heavy'
> churn, is to use "exchange to exchange" bindings.  These are something
> we have looked at - I am just checking with the guys to find out of
> this solution would work well, and if so then when it will appear.
>
> Another option would be to create a custom exchange which used
> presence to 'show' and 'hide' queue bindings.  This would be quite
> neat, but it would involve some coding.
>
> alexis
>
>
> On Sat, Jul 4, 2009 at 8:07 PM, GAGAN ARORA<gaganarora.itm at gmail.com>
> wrote:
> > Alexis,
> >
> > Thanks for your wonderful support and solutions.
> >
> > Firstly answers to your queries:
> >
> > 1. Are you using fanout exchanges for this (if you want one exchange
> > per user, then the answer should be 'yes').
> >
> >>> No I am using topic exchanges because there will be three type of
> >>> bindings of a queue with an excajnde. One for publishing messages to
> all
> >>> users, another for one to one messaging and third for publishing
> message to
> >>> a set of users.
> >
> > 2. Where is the RabbitMQ server running?  Is it on Server 1 or 2, or
> > is it on a 3rd server?  It may not be that important but it would be
> > good to know.
> >
> >>> RabbitMQ Server is running on 3rd Server.
> >
> >
> > Back to original problem.
> >
> > Actually I thought of the solution provided by you before posting the
> query
> > to you. But if I follow this solution I have to perform following steps
> > whenever a user comes online:
> > 1. Create a queue.
> > 2. Create a binding of newly created queue with all exchanges of other
> users
> > for retrieving messages published by other users.
> > 3. Creating a binding with exchange of all users for one to one
> messaging.
> > 4. Create a binding with exchanges of a set of users.
> >
> > When user goes offline following operation is to be performed:
> > 1. Delete all the existing bindings of a queue.
> > 2. Deleting the queue.
> >
> > Actually I want my online and offline processes light weighted. According
> to
> > me this solution would have a high impact on performance and will
> increase
> > time to come online and offline.
> >
> > Kindly let me know if this can be achieved in some other manner.
> >
> > Thanks
> > Gagan Arora
> >
> >
> >
> >
> >
> > On Sat, Jul 4, 2009 at 3:23 PM, Alexis Richardson
> > <alexis.richardson at gmail.com> wrote:
> >>
> >> Gagan,
> >>
> >> Hi - thank-you for sending the diagram and information which was very
> >> useful.  There are several ways to implement the 'twitter style'
> >> pattern that you have described.  See below for one way to do it that
> >> illustrates the AMQP model.  It may not be the most efficient solution
> >> in terms of performance as I shall point out.
> >>
> >> Two quick questions:
> >>
> >> 1. Are you using fanout exchanges for this (if you want one exchange
> >> per user, then the answer should be 'yes').
> >>
> >> 2. Where is the RabbitMQ server running?  Is it on Server 1 or 2, or
> >> is it on a 3rd server?  It may not be that important but it would be
> >> good to know.
> >>
> >> OK - to your cases -
> >>
> >> 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.
> >>
> >> >>> One way to do this is to identify the lifecycle of Queue A with the
> >> >>> presence of User A on servers 1 and 2.  In other words, when User A
> is not
> >> >>> connected to server 1, and also not connected to server 2, then
> Queue A does
> >> >>> not exist.  Note - This is not the only way to achieve what you want
> but it
> >> >>> may be the least fiddly :-)
> >>
> >> Case2: User A connected to server 1 but UserA consumer is not yet
> >> subscribed to UserA queue. If UserB sends any message to its exchange
> >> which is routed to Queue of UserA. At this moment of time I want all
> >> messages to be stored in queue.
> >>
> >> >>> One way to do this (continuing from the above) is to create Queue A
> >> >>> immediately after UserA connects to server 1.  This is an action
> that server
> >> >>> 1 can initiate on behalf of UserA.  After Queue A has been created,
> then it
> >> >>> should be bound to all exchanges from which it will receive
> messages, such
> >> >>> as UserB's exchange.  This will then have the stated effect you seek
> "If
> >> >>> UserB sends any message to its exchange [it] is routed to Queue of
> UserA.".
> >> >>>  Also, because UserA's consumer has not yet started consuming
> messages from
> >> >>> Queue A, the messages will all remain stored in the queue.
> >>
> >> >>> In addition, if instead of proceeding to Case 3, we revert to Case
> 1,
> >> >>> for example User A disconnects from Server 1, then Queue A can
> simply be
> >> >>> deleted (along with its contents).  (See also Case 5 below)
> >>
> >> >>> However - while simple, the above is possibly not the most
> performant
> >> >>> solution if (a) you are running RabbitMQ in clustered mode and (b)
> your
> >> >>> Users generally follow a lot of other Users and (c) they connect and
> >> >>> disconnect frequently.  This is because the effect of (c) is to
> frequuently
> >> >>> update the routing table, possibly with a lot of binding/routing
> data (b),
> >> >>> and then replicating it across the cluster (a).
> >>
> >> >>> Let us know if you want more info about other ways to do this.
> >>
> >>
> >> Case3: User A is connected to both servers and UserA consumer is
> >> subscribed to UserA queue. If UserB sends any message to its exchange
> >> which is routed to Queue of UserA. At this moment of time I want all
> >> messages stored in queue to be delievered plus any other incoming
> >> message should also be routed.
> >>
> >> >>> In any case, to achieve this, just start consuming messages from
> Queue
> >> >>> A.
> >>
> >> >>> I assume by 'delivered', you mean 'delivered to UserA's consumer'.
> >> >>>  Where is that running?
> >>
> >>
> >>
> >>
> >> Case4: User A is connected to both servers and UserA consumer is
> >> subscribed to UserA queue. Now User disconnects from Server 2. If
> >> UserB sends any message to its exchange which is routed to Queue of
> >> UserA. Again I want to store all messages.
> >>
> >> >>> To achieve this, just stop consuming messages from Queue A.  They
> will
> >> >>> be stored in Queue A.
> >>
> >>
> >>
> >> Case5: If user A is disconnected from both servers. Initial state is
> >> achieved again.
> >>
> >> >>> When User A disconnects from Server 1, then Server 1 can tell
> RabbitMQ
> >> >>> to delete Queue A (along with its contents)
> >>
> >> Cheers,
> >>
> >> alexis
> >>
> >>
> >>
> >>
> >>
> >>
> >> On Fri, Jul 3, 2009 at 5:05 PM, GAGAN ARORA<gaganarora.itm at gmail.com>
> >> wrote:
> >> > Hi Alexis
> >> > Attaching a doc having architecture diagram and cases desired. Hope
> this
> >> > would make things more clear to you.
> >> > Thanks
> >> > Gagan Arora
> >> >
> >> > On Fri, Jul 3, 2009 at 8:23 PM, Alexis Richardson
> >> > <alexis.richardson at gmail.com> wrote:
> >> >>
> >> >> Gagan,
> >> >>
> >> >> I'm a bit confused about what you are trying to do.  I think what you
> >> >> describe is possible but I am not sure what role is being played by
> >> >> your two servers.  Is RabbitMQ running on both of them, one of them,
> >> >> or neither?  You may find it easier to just use one RabbitMQ server.
> >> >>
> >> >> Can you send a drawing of what your desired configuration is?
> >> >>
> >> >> alexis
> >> >>
> >> >>
> >> >>
> >> >>
> >> >> On Fri, Jul 3, 2009 at 3:08 PM, GAGAN ARORA<gaganarora.itm at gmail.com
> >
> >> >> wrote:
> >> >> > Hi
> >> >> > I am developing a system in which a user will connect to two
> servers.
> >> >> > On
> >> >> > connecting to first server he will become online and will send his
> >> >> > presence
> >> >> > update but he will receive presence updates only once he is
> connected
> >> >> > to
> >> >> > other server as his consumer subscribes to his queue after
> connecting
> >> >> > to
> >> >> > second server.
> >> >> > I am using one exchange and one queue per user. So if one user
> comes
> >> >> > online
> >> >> > then he will send his presence update to his exchange and users
> bound
> >> >> > to
> >> >> > that will receive updates.
> >> >> > I need to configure a queue which would hold messages for user who
> >> >> > has
> >> >> > just
> >> >> > came online until he is connected to other server. After connecting
> >> >> > to
> >> >> > second server all messages will be consumed. All messages sent to
> >> >> > queue
> >> >> > will
> >> >> > be dropped once user goes offline.
> >> >> > Is it possible?
> >> >> > Thanks
> >> >> > Gagan Arora
> >> >> > _______________________________________________
> >> >> > rabbitmq-discuss mailing list
> >> >> > rabbitmq-discuss at lists.rabbitmq.com
> >> >> >
> http://lists.rabbitmq.com/cgi-bin/mailman/listinfo/rabbitmq-discuss
> >> >> >
> >> >> >
> >> >
> >> >
> >
> >
>
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