attach to existing server instead of trying to start another one on the same display

[Antoine Martin]

See ​im writing a frontend for Xpra that will use ssh to connect... and ​xpra upgrade-or-start --use-display=auto.

Make it possible to start a new session if one does not exist, otherwise upgrade the existing one.
Also adding use-display=auto since the display may have been left behind by a server crash.

[Antoine Martin]

r24791 adds use-display=auto

[Antoine Martin]

See also #2426.

[stdedos]

To get it right: This requires a v4.0 server?

[Antoine Martin]

To get it right: This requires a v4.0 server?

Yes.
And for remote starts via ssh, this is likely to require a v4 client too.
We'll see once that part is implemented.

[Antoine Martin]

Done using a new --use-existing=yes|no|auto flag in r26091.

Usage examples:

xpra start ssh://host/10 --start=xterm --use-existing=yes

Can be repeated any number of times, only the first one will start new server.

xpra shadow ssh://host/ --use-existing=yes

If a server exists it is re-used and the connection succeeds.

EDIT: this syntax is now invalid, see comment:8.

Note: --use-existing=yes will be passed on to the server via the ssh command, if that server is a v3.0 or older then it won't know about this option and the whole thing will fail.

@stdedos: I think you will like this one.

[stdedos]

Replying to Antoine Martin:

@stdedos: I think you will like this one.

I like this one more 😛:

Note: --use-existing=yes will be passed to the server via the ssh command, if that server is a v3.0 or older then it won't know about this option and the whole thing will fail.

[Antoine Martin]

Updates:

• r26096 don't overwrite an existing server logfile until we've checked that the vfb has actually started
• r26097 + r26099 refactoring
• r26098 shortcut and run the client if we find the local server already exists
• r26100 re-use attach
• r26101 minor fixup

Ignore comment:6, I found a way to make it work just by overloading --attach=yes.
The --use-existing option has been removed, the benefit is that this will also degrade well with 3.x servers.

It is now even easier:

xpra start ssh://localhost/3 --start=xterm

Locally:

xpra start :3 --start=xterm --attach=yes

[migration script]

this ticket has been moved to: ​https://github.com/Xpra-org/xpra/issues/2523