08.10.2019 12:24, Daniel P. Berrangé wrote: > On Mon, Oct 07, 2019 at 02:48:40PM -0500, Eric Blake wrote: >> One benefit of --pid-file is that it is easier to probe the file >> system to see if a pid file has been created than it is to probe if a >> socket is available for connection. Document that this is an >> intentional feature. > > I'm not seeing how checking the pid file is better than checking > the socket directly ? I think it is probably actually worse. > > The main problem with the socket is that while we unlink on clean > shutdown, it may still exist in disk if the process has exitted > abnormally. > > With the pidfile though we don't ever unlink it, even on clean > shutdown, as we don't use the pid files existance as a mutual > exclusion check. We instead acquire fcntl locks on it. > > IOW the pidfile could exist already when qemu-nbd starts up and > will still exist when it quits.
Good point. I was just a bit confused, because pid file is something unrelated to socket, and why use one thing to check the existence of another, if we can directly try to connect. > >> Signed-off-by: Eric Blake <ebl...@redhat.com> >> --- >> qemu-nbd.texi | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/qemu-nbd.texi b/qemu-nbd.texi >> index 7f55657722bd..d495bbe8a0ed 100644 >> --- a/qemu-nbd.texi >> +++ b/qemu-nbd.texi >> @@ -118,7 +118,8 @@ in list mode. >> @item --fork >> Fork off the server process and exit the parent once the server is running. >> @item --pid-file=PATH >> -Store the server's process ID in the given file. >> +Store the server's process ID in the given file. The pid file is not >> +created until after the server socket is open. >> @item --tls-authz=ID >> Specify the ID of a qauthz object previously created with the >> --object option. This will be used to authorize connecting users >> -- >> 2.21.0 >> >> > > Regards, > Daniel > -- Best regards, Vladimir
