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From artnaseef <>
Subject Re: Persistent message and selectors
Date Tue, 06 Jan 2015 23:00:14 GMT
For Queues, that's right - all messages are stored until consumed (once and
only once consumption).

For Topics, it's a little more complicated.  It's easiest to think of it
this way: topics never store messages themselves; topic subscriptions may
store messages.  Durable subscriptions do store messages for the obvious
reason (need to deliver to the durable subscriber across broker restarts). 
And, since the only messages that go to a subscription are those that match
its selector, those would be the only ones stored.

With that said, durable subscriptions tend to lead to many problems, so
please use them with care.  Any part of the system that relies on a very
specific consumer being active can easily run into slow consumption
problems.  Selectors with Queues also tend to be similarly problematic when
messages that do not match any consumer's selector are sitting around (they
also perform poorly with large numbers of consumers because they are
evaluated in order against every consumer until a match is found).  Camel is
a good tool for handling patterns in which selectors are desirable.

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