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On Tue, Aug 23, 2011 at 3:08 PM, Michael Mol <mikemol@×××××.com> wrote: |
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> On Tue, Aug 23, 2011 at 2:57 PM, Canek Peláez Valdés <caneko@×××××.com> wrote: |
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>> On Tue, Aug 23, 2011 at 2:35 PM, Michael Mol <mikemol@×××××.com> wrote: |
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>>> On Tue, Aug 23, 2011 at 1:49 PM, Canek Peláez Valdés <caneko@×××××.com> wrote: |
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>>>> On Tue, Aug 23, 2011 at 1:17 PM, Stroller |
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>>>>> Reading that blog entry I found discouraging the idea that dbus might be required on my servers in the future, if systemd becomes popular with distros. |
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>>>> |
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>>>> I don't see the problem with D-Bus. It's small (the only hard |
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>>>> dependency it has is an XML parser), and it provides the Linux/UNIX |
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>>>> (de facto) standard interprocess communication system. |
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>>> |
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>>> My chief gripe with D-Bus is that I've had X sessions disappear out |
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>>> from under me as a consequence of the daemon being restarted. Having a |
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>>> single point of failure like that is very, very scary. Otherwise, I |
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>>> like what it tries to do. |
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>> |
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>> Restarting or dying? If it's dying, it's a bug and should be reported. |
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>> I haven't had a crash in dbus in years, and I think pretty much |
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>> everyone agrees it's pretty stable nowadays. It even tries to handle |
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>> gracefully thins like out-of-memory errors and things like that. |
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> |
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> I have no doubt a stellar amount of work has been done to gracefully |
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> handle problem scenarios. |
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> |
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>> |
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>> If it's restarting, why on earth will someone restart the system bus |
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>> with active X sessions? If the dbus daemon is restarted, it has to |
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>> kick all the apps from the bus, including the session manager. |
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> |
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> Because I generally update my desktop system while running X, and on |
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> at least two occasions, an update killed my X session by restarting |
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> DBUS on me |
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|
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The update don't restart D-Bus: from the dbus-1.4.14 ebuild: |
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|
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elog "To start the D-Bus system-wide messagebus by default" |
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elog "you should add it to the default runlevel :" |
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elog "\`rc-update add dbus default\`" |
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elog |
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elog "Some applications require a session bus in addition to the system" |
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elog "bus. Please see \`man dbus-launch\` for more information." |
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elog |
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ewarn "You must restart D-Bus \`/etc/init.d/dbus restart\` to run" |
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ewarn "the new version of the daemon." |
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ewarn "Don't do this while X is running because it will restart your X as well." |
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|
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Emphasising: "Don't do this while X is running because it will restart |
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your X as well." So I will assume something went terribly wrong when |
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updating, and again, if that's the case then it's a bug and should be |
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reported. |
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|
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> On the other hand, sshd handles restarts without killing active sessions. |
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|
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Because the daemon state for sshd is tiny compared with the one from |
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D-Bus. Apples and oranges. |
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|
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> These are solvable problems which DBUS hasn't solved yet for itself. |
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> High-availability is one of the best-researched fields in computer |
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> science, but DBUS doesn't handle that case, yet. |
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|
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Because it's not as easy as with systemd (which can also reexecute |
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preserving state) or ssh. The state that D-Bus handles can be really, |
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really big, because is a *generic* IPC. Not like Secure Shell, which |
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only handles one type of session and a very limited set of messages. |
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|
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Regards. |
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-- |
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Canek Peláez Valdés |
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Posgrado en Ciencia e Ingeniería de la Computación |
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Universidad Nacional Autónoma de México |
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