Postfix snapshot 20090123 provides support for managing multiple
Postfix instances. It was designed, implemented and documented
during this week (implementation taking about 1/6 of that time).
Citing from the RELEASE_NOTES:
This can automatically apply your "postfix start" etc. command to
multiple Postfix instances, including upgrades to new Postfix
versions.
Multi-instance support allows you to do the following and more:
- Simplify post-queue content filter configuration by using separate
Postfix instances before and after the filter. This simplifies
trouble shooting and performance tuning.
- Implement per-user content filters (or no filter) via transport
map lookups instead of content_filter settings. Mail for some
users can be sent directly from the before-filter instance to
the after-filter instance.
- Test new configuration settings (on a different server IP address
or TCP port) without disturbing production instances.
- Each additional Postfix instance uses a few files and directories,
plus memory for an extra master daemon and queue manager. The
pickup daemon is needed only if you use local submission or
"postsuper -r".
Best of all, nothing changes when you use only one Postfix instance.
The postfix-wrapper script (in the daemon directory) implements a
simple but useful multi-instance manager, with instructions. The
plug-in API itself is described in the postfix-wrapper(5) manpage.
A more sophisticated multi-instance manager called postmulti(1) is
approaching completion. A prototype version has been used internally
at Morgan Stanley. This version will be adapted to the new plug-in
API which makes some simplification possible.
Wietse
