Very misleading error messaging from typo in yaml file.

[endophage]

So I had an errant - in my compose yaml file, and it manifested itself during docker-compose build as the following error:

Couldn't connect to Docker daemon at http+docker://localunixsocket - is it running?

If it's at a non-standard location, specify the URL with the DOCKER_HOST environment variable.

The yml file was bad in the below format (the service name was prefixed with the -):

-test:
    build: .
    dockerfile: Dockerfile

The error docker is returning (dug it out of journalctl) is:

Feb 03 15:51:05 endophage docker[593]: time="2016-02-03T15:51:05.252721921-08:00" level=info msg="POST /v1.19/build?pull=False&nocache=False&q=False&t=david_-test&forcerm=False&rm=True&dockerfile=server.Dockerfile"
Feb 03 15:51:05 endophage docker[593]: time="2016-02-03T15:51:05.252859421-08:00" level=error msg="Handler for POST /v1.19/build returned error: repository name component must match \"[a-z0-9](?:-*[a-z0-9])*(?:[._][a-z0-9](?:-*[a-z0-9])*)*\""
Feb 03 15:51:05 endophage docker[593]: time="2016-02-03T15:51:05.252878753-08:00" level=error msg="HTTP Error" err="repository name component must match \"[a-z0-9](?:-*[a-z0-9])*(?:[._][a-z0-9](?:-*[a-z0-9])*)*\"" statusCode=500

My error in the yaml file is obvious now I've seen it but the error message is very unintuitive and I assume this isn't the only case in which docker returns a reasonable (if technical) error message and compose returns something more obscure.

FYI, when trying to build a similarly badly named thing on docker itself, it returns the expected error:

15:52 $ docker build -t -test .
[sudo] password for david: 
repository name component must match "[a-z0-9](?:-*[a-z0-9])*(?:[._][a-z0-9](?:-*[a-z0-9])*)*"

[dnephin]

That's really strange, our config validation should have noticed this and provided a good error message. What version of compose are you running (docker-compose version)?

The output of docker-compose --verbose build (with the bad config) would also be helpful.

[dnephin]

Ah, I see the problem from the docker log. I assumed it treated -test as a list, but it's reading it as a string with a leading dash.

[dnephin]

@endophage we might be able to work around this from compose, but I think this is actually a bug in docker engine.

An invalid input should be a 400 status code, not a 500.

[endophage]

@dnephin yeah, I believe yaml requires a space between the dash and the following content to treat it as a list.

I'm running 1.4.0, I guess I missed the last update or two. Updated to 1.6.0 RC2 and the error is now:

ERROR: Couldn't connect to Docker daemon - you might need to run `docker-machine start default`.

You're right, this should be a 400, but even a 500 indicates you contacted the server (daemon) so an error message indicating compose couldn't connect seems like something that should be changed on the compose side.

[dnephin]

I think docker-py translates everything into an APIError. It may be that APIError needs to be split up into a few different errors so we can differentiate these failures. I know we have a couple related issues about reporting this same error message for proxy errors, and ssl errors as well.

[endophage]

That makes sense. Should this be closed and the same issue filed over on the docker-py repo? Or will there be some integration work here too?

[dnephin]

We'll often keep the compose issue open to track updating the version of docker-py, so I think it's fine to keep this open.

[dnephin]

@endophage I took another look into these errors in an attempt to fix the behaviour.

I once again believe this is an engine bug. I tried this with docker-py:

client.build('.', '-test')
ConnectionError: ('Connection aborted.', error(104, 'Connection reset by peer')) 

It's not even a 500 error, it a TCP connection error, so I think the error we're responding with is correct.

I also tried the docker build example you gave with docker 1.10, but it's not even sending it to the API, it's being caught during command line flag parsing with:

$ docker build -t -test .
invalid value "-test" for flag -t: Error parsing reference: "-test" is not a valid repository/tag

There's not much we can do here until docker engine responds with a valid HTTP response code. I believe even with a 500 code we would echo the error message and exit properly.

I don't think it's correct to duplicate the tag validation in the client.

[shin-]

Looks like this is working properly now:

$ cat docker-compose.yml 
version: '2'
services:
  -service:
    build:
      context: .
$ docker-compose up
Building -service
ERROR: Error parsing reference: "repro2816_-service" is not a valid repository/tag