PS Improvements: ignore linked names and image lookup cache.

[calavera]

• Ignore linked container names in the api when they are not necessary.
  This avoids an O(N) traversal of the container tree when we're not
  going to display the linked names for containers. docker ps ignores
  those names by default, so we don't need them in 99% of the cases.
• Cache image name lookup. Same image names are going to be resolved
  to the same id for a given list of containers. We can cache the result
  of the first operation avoiding an O(N) lookup of images.

Signed-off-by: David Calavera david.calavera@gmail.com

[LK4D4]

Why not use trunc here too. For me it sounds good.

[calavera]

I actually implemented this at the beginning with trunc, but I think having a dedicated flag is better because we're not using it for anything else but ignoring the links.

[LK4D4]

I dunno, trunc sounds pretty fit for this and doesn't add anything to API. And it means same things from cli point of view. I'd better to try to keep it same if possible and now I don't see any requests for separate flag.

[calavera]

we're not sending the trunc flag to the api currently, we need a new flag regardless. All truncating is client side.

[LK4D4]

Hmm, funny. Okay.

[calavera]

Some timings with a few big images:

root@docker-flames:~# time sh -c "./docker ps -a --format '{{.Image}}' | sort | uniq"
alpine
golang
quay.io/coreos/etcd
ubuntu

real    0m0.063s
user    0m0.076s
sys     0m0.004s

218 containers in that previous list:

root@docker-flames:~# time sh -c "./docker ps -a  | wc -l"
218

real    0m0.079s
user    0m0.100s
sys     0m0.028s

[cpuguy83]

If we do #16032 then link lookup will be fast anyway.

[LK4D4]

@cpuguy83 yeah, maybe we should try to merge it :)

[calavera]

@cpuguy83 I know. There is still no need to look for links when we don't even display those names by default.

[LK4D4]

sounds ok for me

[tiborvass]

@calavera instead of having ignoreLinks, we could also have a Name field returned by the API, and if people want all the names then they use --format to return .Names explicitly. WDYT?

[calavera]

@tiborvass we currently have that .Names field. The default ps format ignore the link names, the --no-trunc flag makes those names to show up. There is still no need to gather the names unless you explicitly want them. We make that explicit in our cli with --no-trunc.

[tiborvass]

@calavera I was suggesting Name in addition to Names

I see what you mean. The right solution here would be to allow API clients to specify filters, a bit like --format in the CLI. But instead of using the go template for API filters something like a comma-separated list parameter (e.g. fields=id,name) would be more appropriate.

[calavera]

closing this until new order.

[LK4D4]

@calavera Cache fix still can be used I think.