> Why does majordomo post duplicate copies of the postings all of a
> sudden - when everything was working perfectly all along?
Well, I can tell you what happened to me recently. We use MMDF here,
which certainly colors the picture a little. What was happening here was
that MMDF was verifying the validity of the whole mailing list before
returning from the Submit call. The thing calling the Submit would time
out and close, but the Submit itself would still be running somewhere.
The calling routine would believe that the message had failed in its
delivery, but the Submit would eventually succeed. The calling process
would try again some time later. This, of course, is bad. The larger
the list got, the more addresses there were to verify (verification was
really just a DNS search on the target machine name), the more likely,
under load, that the message would duplicate. We finally got so large,
with so many international addresses (which seem to timeout on DNS
queries much more ofen than US addresses) that we were always
duplicating. Infinitely (until I killed the original submitter).
The solution for us was MMDF-specific. We used a different channel for
submission and delivery, one which deliberately doesn't verify the
addresses before accepting a job. We used the list-processor channel,
and only had to check that the listname-request name was set properly,
because list-processor insists on making listname-request the envelope
"From " header name.
Gunther Anderson
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