[Mailman-Developers] Storing extra data during pipeline processing

[Barry Warsaw]

On May 07, 2015, at 10:51 PM, Juraj Variny wrote:

>I have tried already to use msgdata parameter or adding headers to message
>itself, but was not successful so far. I was thinking about adding external
>database and putting the data there by message ID, but sure there must be a
>better way? I hope to publish the code some day, too.

Can you give some details on what didn't work about using the msgdata
parameter?  This always flows with the message through the pipeline and is
preserved in the pickle files as the message moves from runner to runner.
It's the way handlers are supposed to record information on the message as its
being processed.

This is even more important in Mailman 3 where we've split the pipeline into
rules and handlers.  Rules are run to determine moderation behavior and rules
are never supposed to modify the message.  They communicate state to
(possible) later handlers via the msgdata dictionary.

Cheers,
-Barry