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Re: [Qemu-devel] [PATCH v2] qga: add systemd socket activation support
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] [PATCH v2] qga: add systemd socket activation support |
Date: |
Fri, 6 Jan 2017 15:34:23 +0000 |
User-agent: |
Mutt/1.7.1 (2016-10-04) |
On Fri, Jan 06, 2017 at 03:29:30PM +0000, Stefan Hajnoczi wrote:
> AF_UNIX and AF_VSOCK listen sockets can be passed in by systemd on
> startup. This allows systemd to manage the listen socket until the
> first client connects and between restarts. Advantages of socket
> activation are that parallel startup of network services becomes
> possible and that unused daemons do not consume memory.
>
> The key to achieving this is the LISTEN_FDS environment variable, which
> is a stable ABI as shown here:
> https://www.freedesktop.org/wiki/Software/systemd/InterfacePortabilityAndStabilityChart/
>
> We could link against libsystemd and use sd_listen_fds(3) but it's easy
> to implement the tiny LISTEN_FDS ABI so that qemu-ga does not depend on
> libsystemd. Some systems may not have systemd installed and wish to
> avoid the dependency. Other init systems or socket activation servers
> may implement the same ABI without systemd involvement.
>
> Test as follows:
>
> $ cat ~/.config/systemd/user/qga.service
> [Unit]
> Description=qga
>
> [Service]
> WorkingDirectory=/tmp
> ExecStart=/path/to/qemu-ga --logfile=/tmp/qga.log --pidfile=/tmp/qga.pid
> --statedir=/tmp
>
> $ cat ~/.config/systemd/user/qga.socket
> [Socket]
> ListenStream=/tmp/qga.sock
>
> [Install]
> WantedBy=default.target
>
> $ systemctl --user daemon-reload
> $ systemctl --user start qga.socket
> $ nc -U /tmp/qga.sock
>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
> v2:
> * Drop libsystemd dependency [danpb]
>
> qga/channel.h | 3 ++-
> qga/channel-posix.c | 66 ++++++++++++++++++++++++++---------------------
> qga/channel-win32.c | 2 +-
> qga/main.c | 74
> +++++++++++++++++++++++++++++++++++++++++++++++++----
> 4 files changed, 109 insertions(+), 36 deletions(-)
Reviewed-by: Daniel P. Berrange <address@hidden>
Regards,
Daniel
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