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From "Martyn Taylor (JIRA)" <>
Subject [jira] [Commented] (ARTEMIS-627) Producer Block does work properly on CORE protocol
Date Thu, 14 Jul 2016 09:10:20 GMT


Martyn Taylor commented on ARTEMIS-627:

I don't believe multiple producers sending to the same address is a corner case.  I would
say it's a quite viable pattern that applications may use.  I'm not sure I agree with your
comment about the fix having detrimental impact on performance.  We could just as easily add
a configuration option (or a new AddressFullPolicy.STRICT_BLOCK or similar) that covers the
existing behaviour and the behaviour outlined in the docs.  Any performance implication would
only take affect for those cases where the "STRICT BLOCK" policy is enabled and the impact
could be documented.  Mostly my concern right now is that actual behaviour and what is outlined
in the docs is quite different and misleading to users, in addition to the implications of
doing the flow control on the client side are not obvious to users.  

I'm happy to update the docs to explain how this works right now and what the vunerabilities
are.  I'll update this JIRA to a feature request to implement "STRICT BLOCK" and we can address
it if/when users ask for it.

> Producer Block does work properly on CORE protocol
> --------------------------------------------------
>                 Key: ARTEMIS-627
>                 URL:
>             Project: ActiveMQ Artemis
>          Issue Type: Bug
>            Reporter: Martyn Taylor
> To BLOCK production of messages to an address once it reaches a particular size in memory,
an AddressSetting can be added to the broker that specifies the address size, address match
string and the address full policy "BLOCK".
> This should block messages once the address is full, however the current implementation
uses flow control to allocate producers credits, once the address is full the broker will
not allocate any more credits.
> There are two issues with this approach.
> 1. The main issue is that the credits are not tracked or checked at the broker side.
 The ActiveMQ client takes care of blocking message production when it runs out of credit.
 However, a rogue client could easily allocate it's own credits and continue sending.  I've
tested this by hacking the client and it behaves in this way.
> 2. Even in a non hacked client the size of the address could be pushed over it's limit,
as more credits can be allocated than is available space on the address.  An address can be
full, no more credits are allocated but each producer is able to empty it's credits pushing
the address over its limit.

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