Currently the metrics plugin uses a really hackish host mount with
propagated mounts to get the metrics socket into a plugin after the
plugin is alreay running.
This approach ends up leaking mounts which requires setting the plugin
manager root to private, which causes some other issues.
With this change, plugin subsystems can register a set of modifiers to
apply to the plugin's runtime spec before the plugin is ever started.
This will help to generalize some of the customization work that needs
to happen for various plugin subsystems (and future ones).
Specifically it lets the metrics plugin subsystem append a mount to the
runtime spec to mount the metrics socket in the plugin's mount namespace
rather than the host's and prevetns any leaking due to this mount.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Changes most references of syscall to golang.org/x/sys/
Ones aren't changes include, Errno, Signal and SysProcAttr
as they haven't been implemented in /x/sys/.
Signed-off-by: Christopher Jones <tophj@linux.vnet.ibm.com>
[s390x] switch utsname from unsigned to signed
per 33267e036f
char in s390x in the /x/sys/unix package is now signed, so
change the buildtags
Signed-off-by: Christopher Jones <tophj@linux.vnet.ibm.com>
Allows for a plugin type that can be used to scrape metrics.
This is useful because metrics are not neccessarily at a standard
location... `--metrics-addr` must be set, and must currently be a TCP
socket.
Even if metrics are done via a unix socket, there's no guarentee where
the socket may be located on the system, making bind-mounting such a
socket into a container difficult (and racey, failure-prone on daemon
restart).
Metrics plugins side-step this issue by always listening on a unix
socket and then bind-mounting that into a known path in the plugin
container.
Note there has been similar work in the past (and ultimately punted at
the time) for consistent access to the Docker API from within a
container.
Why not add metrics to the Docker API and just provide a plugin with
access to the Docker API? Certainly this can be useful, but gives a lot
of control/access to a plugin that may only need the metrics. We can
look at supporting API plugins separately for this reason.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
