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authorStefan Hajnoczi <stefanha@redhat.com>2017-01-06 15:29:30 +0000
committerMichael Roth <mdroth@linux.vnet.ibm.com>2017-03-06 00:54:18 -0600
commit26de229657b943b7a59ad79c387506f6f33ff963 (patch)
treef96ba358e2d31538bd9b57ff7855e6dfe50ec2bd /qga/vss-win32.h
parent17783ac828adc694d986698d2d7014aedfeb48c6 (diff)
qga: add systemd socket activation support
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 <stefanha@redhat.com> Reviewed-by: Daniel P. Berrange <berrange@redhat.com> Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Diffstat (limited to 'qga/vss-win32.h')
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