[systemd-devel] how to end a socket activated daemon

[Kok, Auke-jan H]

On Tue, Jun 18, 2013 at 3:04 AM, Łukasz Stelmach <l.stelmach at samsung.com> wrote:
> It was <2013-06-17 pon 20:51>, when Lennart Poettering wrote:
>> On Fri, 14.06.13 14:33, Zbigniew Jędrzejewski-Szmek (zbyszek at in.waw.pl) wrote:
>>
>>> On Fri, Jun 14, 2013 at 10:03:00AM +0200, Łukasz Stelmach wrote:
>>>> We are converting some daemons to socket activation. Most of them
>>>> open unix sockets and manage incoming connections in a main-loop, so
>>>> the easiest way to convert it is to create Accept=false socket with
>>>> systemd.
>>>>
>>>> Now, it is quite well described how to start such daemon, however,
>>>> there is little about shutting it down. Should the daemon close(2)
>>>> the received sockets? Should it unlink(2) them from a filesystem?
>>> close() yes, unlink() no.
>>
>> Strictly speaking you don't even have to do that. The kernel will
>> clean up left-over fds when your process exits, hence you don't have
>> to close it explicitly.
>>
>> But you certainly should not unlink() the socket in the fs, because
>> then the socket will not be accessible anymore.
>
> Maybe I've asked the wrong question. I should rather have asked: Can I
> close? Can I unlink? Because that's what the code does now and we wanted
> to know which parts are common for standalone and
> systemd-socket-activated paths.

The way I think about it is that if you are socket activated, you have
a .socket unit and a .service unit.

The .socket unit controls the socket. The .service unit does NOT
control the socket. Therefore, the .service daemon should NOT unlink
the socket.

Auke