Crash protection

David Lee t.d.lee at
Tue Mar 3 10:36:49 GMT 2009

On Mon, 2 Mar 2009, Julian Field wrote:

> On 2/3/09 14:04, David Lee wrote:
>> [...]
>> Given that I was a chief requester, naturally I feel honour-bound to
>> help test it.  Could you give an indication of your production-level
>> confidence in the code?  How high up the inbound MX-priority-tree
>> should I reasonably think of installing it at present?
> Start it off at the bottom (highest number) and intentionally kill it
> during a batch of messages. Do that twice and you should see
> "MailScanner --processing" start to print something. That way it should
> probably only be getting spam anyway, which will be an ideal test
> environment for it.

OK.  Installed on an MX high-value (low-priority) machine.

Testing it with "MailScanner --debug" etc. took a little more than two 
interrupts (perhaps successive "--debug" invocations were picking up 
different emails) but it seems to be OK. "MailScanner --processing" is 
showing some output for two or more attempts.  So looking good!  And in 
the log file I'm seeing messages of the form "Making attempt 2 at ..." 
which (in this controlled-test context) looks promising.


> Cheers for the idea in the first place! (even though I did change it a
> bit as I progressed... :)

You're welcome.  The idea was simply a sketch of a possibility.  Your 
change was to deliver a working product!  Many thanks.

An observation:  "--processing" queries with "SELECT ... count>1".  So on 
a busy, but well-working, server its output is always empty.  Could there 
be a variant "count>0"?  Thus on this same server there would generally be 
output, continually changing, reflecting (more or less) the active part of 
the inbound MS queue.  Don't worry if you would rather not.

Anyway, we have it in service, and I'll keep monitoring it.

Many thanks again.


:  David Lee                                I.T. Service          :
:  Senior Systems Programmer                Computer Centre       :
:  UNIX Team Leader                         Durham University     :
:                                           South Road            :
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