Annotation of wikisrc/projects/project/pubsub-sockets.mdwn, revision 1.1
1.1 ! dholland 1: [[!template id=project
! 3: title="Publish-subscribe Unix sockets"
! 5: contact="""
! 6: [tech-kern](mailto:tech-kern@NetBSD.org),
! 7: [tech-net](mailto:tech-net@NetBSD.org),
! 8: [David Holland](mailto:dholland@NetBSD.org)
! 9: """
! 11: category="net"
! 12: difficulty="hard"
! 14: description="""
! 15: Add publish-subscribe sockets to AF_UNIX (filesystem sockets).
! 17: The idea of a publish-subscribe socket (as opposed to a traditional
! 18: socket) is that anything written to one end is read out by _all_
! 19: processes reading from the other end.
! 21: This raises some issues that need attention; most notably, if a
! 22: process doesn't read data sent to it, how long do we wait (or how much
! 23: data do we allow to accumulate) before dropping the data or
! 24: disconnecting that process?
! 26: It seems that one would want to be able to have both SOCK_STREAM and
! 27: SOCK_DGRAM publish/subscribe channels, so it isn't entirely clear yet
! 28: how best to graft this functionality into the socket API.
! 29: Or the socket code.
! 30: It might end up needing to be its own thing instead, or needing to
! 31: extend the socket API, which would be unfortunate but perhaps
! 32: unavoidable.
! 34: The goal for these sockets is to provide a principled and robust
! 35: scheme for passing notices around.
! 36: This will allow replacing multiple existing ad hoc callback schemes
! 37: (such as for notices of device insertions) and also to allow various
! 38: signaling schemes among user processes that have never been very
! 39: workable in Unix.
! 40: Those who remember AREXX will recognize the potential; but of course
! 41: it will take time before anything like that can be orchestrated.
! 43: For this reason it's important that it be reasonably easy for one of
! 44: the endpoints to be inside the kernel; but it's also important that
! 45: peer credentials and permissions work.
! 47: Another goal is to be able to use publish/subscribe sockets to provide
! 48: a compatibility library for Linux desktop software that wants to use
! 49: dbus or any successor to dbus.
! 51: I'm marking this project hard as it's still only about half baked.
! 52: """
! 53: ]]
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