Adding "driver" and "dangling" filter options to "docker volume ls"

[dani-docker]

volume ls in swarm classic only handles filters with options "node", "name" and "label". This PR adds support for "driver" and "dangling"

Adding "driver" to the filter option is pretty straightforward. The "dangling" filter is a bit more involved as the "volume" struct has no "dangling" property.

2 options to support "dangling": 1- add an extra call to the engine to get the dangling volumes or 2- Iterate through cached "containers" and build a map of volumes that are still referenced by the container, and finally use the delta to delta to determine dangling volumes.

After chatting with @nishanttotla , 1) seems a bit taxing so I decided to go with option 2) Note: I am not caching the map for referenced volumes, so we don't have to maintain it, besides, the calls to filter based on "dangling" should be fast and should not be that frequent.

Repro Steps for driver:

1- Have at least 2 volumes using 2 separate drivers. for ex: docker volume ls

DRIVER	VOLUME NAME
vieux/sshfs:latest	sshvolume
local	testVolume

2- Run docker volume ls --filter=driver=local

3- Expect Results

DRIVER	VOLUME NAME
local	testVolume

Actual Results (all volumes returned)

DRIVER	VOLUME NAME
vieux/sshfs:latest	sshvolume
local	testVolume

Repro Steps for dangling:

1- Have at least 2 volumes with one volume that is dangling (not used). (sshvolume in this example is dangling) docker volume ls

DRIVER	VOLUME NAME
vieux/sshfs:latest	sshvolume
local	testVolume

2- Run docker volume ls --filter=dangling=true

3- Expect Results

DRIVER	VOLUME NAME
vieux/sshfs:latest	sshvolume

Actual Results (all volumes returned)

DRIVER	VOLUME NAME
vieux/sshfs:latest	sshvolume
local	testVolume

Signed-off-by: Dani Louca dani.louca@docker.com

[dani-docker]

had a chat with @thaJeztah and 2 valid use cases were identified:

1. dangling=false has not been handled in my PR, I was under the impression that false means don't do any filtering, but it actually means to return used volumes only . Verified and confirmed the behavior directly on the engine

2. Existing bug that was surfaced with the dangling fix. Currently, we only append the engine name to local volumes, this name uniqueness should be applied to all type of drivers otherwise we can see false/positive results.

I will update the PR shortly. I will wait to see If we can get #2832 in, as the code change here will be much cleaner.

[dani-docker]

While waiting on #2832

• I changed the code to address the below internally without changing the output

Existing bug that was surfaced with the dangling fix. Currently, we only append the engine name to local volumes, this name uniqueness should be applied to all type of drivers otherwise we can see false/positive results.

• added 2 helper methods along with their unit tests

if #2832 is approved, I will update this PR with cleaner/simpler code ping @wsong @nishanttotla

[dani-docker]

PR updated with @wsong suggestions

[dani-docker]

@wsong PR updated with the detailed comment

[dani-docker]

PR updated to address the / in plugin volume names and safeguard check for len of split. Also updated the unit test to cover the above cases.