On 2020-01-04 at 05:57, Simon McVittie wrote: > On Fri, 03 Jan 2020 at 19:52:33 -0500, The Wanderer wrote: > >> On 2020-01-03 at 19:33, Simon McVittie wrote: >> >>> D-Bus activation is a D-Bus feature where instead of starting a >>> D-Bus service (another sort of daemon) "eagerly" in case it might >>> be needed, the dbus-daemon starts that D-Bus service "lazily" the >>> first time some other program sends a message to it. >> >> This sounds like the feature I was thinking of. I think I >> understood that the way this message got from the originating >> program to D-Bus (and thence to the service, once running) was by >> way of a socket which would / should be owned by that service, much >> as you describe for systemd's socket-activation feature > > No, part of the purpose of the "message bus" part of D-Bus is that it > provides a hub-and-spoke topology so that connecting n clients and > services together only requires O(n) connections, not O(n**2). > Clients connect to a socket owned by the message bus service, and > send messages through it. Some messages are processed by the message > bus itself. The rest have a header that tells the message bus which > service is the intended destination, and it either: delivers the > message to the destination service immediately; activates (starts) > the destination service (via either traditional or systemd > activation), and then delivers the message when it appears; or > replies with an error message that means "no, I can't do that" (for > example if the requested service isn't installed).
That actually sounds even more like how I originally thought this feature worked, and the name "D-Bus socket activation" makes even more intuitive sense in my mind for the "lazy" activation of services by this method. Still, if that's not what the terminology has been established to mean, then there's no point in belaboring the issue. I certainly have enough of an aversion for unnecessary and unintended ambiguity that I'm not interested in introducing more without good cause. Once again, thanks for the explanation! -- The Wanderer The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man. -- George Bernard Shaw
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