[exim-dev] [Bug 956] spamd fallback only for connect(). Lack…

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Author: Phil Pennock
Date:  
To: exim-dev
Subject: [exim-dev] [Bug 956] spamd fallback only for connect(). Lack of fallback for other types of errors.
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http://bugs.exim.org/show_bug.cgi?id=956




--- Comment #1 from Phil Pennock <exim-dev@???> 2010-01-25 21:20:55 ---
Beware, here lies the potential for major chaos.

The spam-scanning server code is failing to return an expected response. That
means it's buggy. If the bug is triggered by the message being processed, then
your farm of scanners can be taken out in quick succession by one bad message.

If Exim behaves as it currently does, then a second attempt later will knock
out another server, but the first server should be up again. If Exim is
changed as you suggest, then one message knocks them all out.

"Could not connect to server" does not imply a bug, it means we couldn't reach
it and trying another server increases reliability, by making a pool of
resources available. This is an expected part of the flow.

Servers which fail to return an expected error are not an expected part of the
flow.

I personally am opposed to your suggested change, as it currently stands.
[Note: I'm not a committer, so that that's not all that bad] If you can refine
the proposal to address my concerns, enumerating what should happen in which
circumstances and why it's safe, that would be good.


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