start the dbus server automatically

[Antoine Martin]

A number of features rely on having a dbus server running:

• the dbus interface obviously #904
• notifications forwarding
• dbus-forwarding

etc...

The user may also have an existing dbus server running in their desktop session, but using this one can cause serious problems (ie: maybe #1032)

The usual way of working around this is to start the xpra server with:

dbus-launch xpra ..

A better way would be to automatically start the dbus server as part of xpra, through a command line switch and config option which would be enabled by default.

[Antoine Martin]

Done in r11784.

What this changes:

• "xpra start" will start the dbus server for you, no need for "dbus-launch xpra start .."
• "xpra upgrade" will keep track of it, so "xpra stop" will still kill the dbus server after an upgrade
• fewer spurious warnings about pulseaudio and notifications

@afarr: mostly a FYI.

[alas]

Seems to be working as advertised... I'll go ahead and close.

[alas]

Just as a note... after leaving a server running for a few days, when I shut it down with a control-c, I got the following dbus errors:

2016-02-08 10:47:34,840 got signal SIGINT, exiting
2016-02-08 10:47:34,847 Disconnecting client '10.0.11.162:59620':
2016-02-08 10:47:34,847  server shutdown
2016-02-08 10:47:34,874 xpra client disconnected.
2016-02-08 10:47:34,876 child 'xterm' with pid 25094 has terminated
2016-02-08 10:47:34,877 failed to release dbus notification forwarder: org.freedesktop.DBus.Error.NoReply: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.
2016-02-08 10:47:34,877 child 'xterm' with pid 25097 has terminated
Exception dbus.exceptions.DBusException: DBusException('Connection is closed',) in <bound method BusName.__del__ of <dbus.service.BusName org.xpra.Server13 on <dbus._dbus.SessionBus (session) at 0x7f2be9aef650> at 0x7f2bdcc79910>> ignored

The server did shut down ok, and restarted fine though, so maybe it was just the dbus server being shut down before it could respond... Was running a 0.16.2 r11850 win32 client against a 0.16.2 r11850 fedora 23 server.

Reopening the ticket, in case this isn't just an expected signint issue.

[Antoine Martin]

The DBusException from comment:3 is unlikely to be a big problem.
There is a bigger problem though: using xpra exit, the dbus daemon inherits the socket from the parent process so we cannot start a new server using the same port with --use-display.

[Antoine Martin]

That's fixed in r12012 so closing again, we can re-open if something else crops up.

r12018 + r12027 fixes the "xpra upgrade" / "xpra start --use-display" case.
r12019 re-orders initialization so dbus-launch comes after the vfb.

[Antoine Martin]

Since we now have a dbus server started by default, I have enabled dbus in pulseaudio by default: r12139

[migration script]

this ticket has been moved to: ​https://github.com/Xpra-org/xpra/issues/1104