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Subject: Dynamic suspension of JMS producer
From: Baris Acar <baris@acar.org.uk>
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Date: Mon, 30 Sep 2013 21:00:47 +0100
To: users@camel.apache.org
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Hi,

We have two instances of a service, one for low and one for high priority us=
ers. Both post messages to a single shared queue, with the appropriate prior=
ity level set so that high priority requests jump in front.

If the queue is completely full of low priority requests, it's impossible fo=
r high priority requests to arrive. I'd like to prevent this.

One way is to limit the number of low priority messages allowed on the queue=
. We would like to stop the low priority service posting if the (jms) queue i=
s >90% full. This always leaves some headroom on the queue for some high pri=
ority messages. We've had success with this model in other (non-camel) appli=
cations.

How best could I do this with Camel? Also very open to completely alternativ=
e proposals solving the use case.=20

I don't think that there is a JMS-only way to inspect queue depth - we'll ha=
ve to use vendor-specific code to interrogate queue depth (we use IBM MQ and=
 Solace).

The first ideas I had were:
- use a RoutePolicy to suspend the part of the route that's posting - but ca=
sual playing found that suspending in this way caused exceptions rather than=
 blocking behaviour when a route was suspended (I might be doing something w=
rong).
- write a processor which sits just before the "jms:..." endpoint, which ins=
pects the queue and blocks as appropriate. This seems a bit ugly (it needs t=
o know about specific downstream endpoints, which is "weird").=20

Is there something more Camel-y? Any thoughts or ideas most welcome.=20

Bar=C4=B1=C5=9F=