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>
Container state counts are used for reporting in the `/info` endpoint.
Currently when `/info` is called, each container is iterated over and
the containers 'StateString()' is called. This is not very efficient
with lots of containers, and is also racey since `StateString()` is not
using a mutex and the mutex is not otherwise locked.
We could just lock the container mutex, but this is proven to be
problematic since there are frequent deadlock scenarios and we should
always have the `/info` endpoint available since this endpoint is used
to get general information about the docker host.
Really, these metrics on `/info` should be deprecated. But until then,
we can just keep a running tally in memory for each of the reported
states.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
This adds a metrics packages that creates additional metrics. Add the
metrics endpoint to the docker api server under `/metrics`.
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
Add metrics to daemon package
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
api: use standard way for metrics route
Also add "type" query parameter
Signed-off-by: Alexander Morozov <lk4d4@docker.com>
Convert timers to ms
Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
