"docker node ps" behaves strangely outside swarm mode:
$ docker node ps
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
Error: No such node:
It should explain that the node is not a swarm manager.
The reason this happens is that the argument to "docker node ps" defaults
to "self". The first thing the command does is try to resolve "self" to
a node ID using the /info endpoint. If there is no node ID, it tries to
use the empty string as an ID, and tries to GET /nodes/, which is not a
valid endpoint.
Change the command to check if the node ID is present in the /info
response. If it isn't, a swarm API endpoint can supply a useful error
message.
Also, avoid printing the column headers if the only following text is an
error.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
d59f6d0933