This patch adds a new "prune" event type to indicate that pruning of a resource
type completed.
This event-type can be used on systems that want to perform actions after
resources have been cleaned up. For example, Docker Desktop performs an fstrim
after resources are deleted (https://github.com/linuxkit/linuxkit/tree/v0.7/pkg/trim-after-delete).
While the current (remove, destroy) events can provide information on _most_
resources, there is currently no event triggered after the BuildKit build-cache
is cleaned.
Prune events have a `reclaimed` attribute, indicating the amount of space that
was reclaimed (in bytes). The attribute can be used, for example, to use as a
threshold for performing fstrim actions. Reclaimed space for `network` events
will always be 0, but the field is added to be consistent with prune events for
other resources.
To test this patch:
Create some resources:
for i in foo bar baz; do \
docker network create network_$i \
&& docker volume create volume_$i \
&& docker run -d --name container_$i -v volume_$i:/volume busybox sh -c 'truncate -s 5M somefile; truncate -s 5M /volume/file' \
&& docker tag busybox:latest image_$i; \
done;
docker pull alpine
docker pull nginx:alpine
echo -e "FROM busybox\nRUN truncate -s 50M bigfile" | DOCKER_BUILDKIT=1 docker build -
Start listening for "prune" events in another shell:
docker events --filter event=prune
Prune containers, networks, volumes, and build-cache:
docker system prune -af --volumes
See the events that are returned:
docker events --filter event=prune
2020-07-25T12:12:09.268491000Z container prune (reclaimed=15728640)
2020-07-25T12:12:09.447890400Z network prune (reclaimed=0)
2020-07-25T12:12:09.452323000Z volume prune (reclaimed=15728640)
2020-07-25T12:12:09.517236200Z image prune (reclaimed=21568540)
2020-07-25T12:12:09.566662600Z builder prune (reclaimed=52428841)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
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