Misleading Error Message for invalid Image Name

[peterkappelt]

Description of the issue

docker-compose outputs an misleading/ wrong error message, if an invalid image name is specified for an service (e.g. with an uppercase letter in the repository name).

For an invalid name, like

image: pkap/gBridge-redis-worker:latest   #note the uppercase 'B'

docker-compose build outputs:

[...]
Building redis-worker
ERROR: Couldn't connect to Docker daemon at http+docker://localhost - is it running?

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

The build succeeds for

image: pkap/gbridge-redis-worker:latest   #note the lowercase 'b'

This error message seems to be somehow unrelated to the actual issue. Though this is not critical, I'd like to draw attention to this behaviour.

Since I'm a total Docker beginner (and didn't know about image naming conventions), it took me some time to figure out the problem.

Context information (for bug reports)

peter@dev01:~/gBridge-docker$ docker-compose version
docker-compose version 1.21.2, build a133471
docker-py version: 3.3.0
CPython version: 3.6.5
OpenSSL version: OpenSSL 1.0.1t  3 May 2016

peter@dev01:~/gBridge-docker$ docker version
Client:
 Version:      18.03.1-ce
 API version:  1.37
 Go version:   go1.9.5
 Git commit:   9ee9f40
 Built:        Thu Apr 26 07:17:14 2018
 OS/Arch:      linux/amd64
 Experimental: false
 Orchestrator: swarm

Server:
 Engine:
  Version:      18.03.1-ce
  API version:  1.37 (minimum version 1.12)
  Go version:   go1.9.5
  Git commit:   9ee9f40
  Built:        Thu Apr 26 07:15:24 2018
  OS/Arch:      linux/amd64
  Experimental: false

peter@dev01:~/gBridge-docker$ docker-compose config
networks:
  backend:
    driver: bridge
  web_frontend:
    driver: bridge
services:
 [...]
  redis-worker:
    build:
      context: /home/peter/gBridge-docker
      dockerfile: ./docker-redis-worker/Dockerfile
    depends_on:
    - cache
    environment:
      GBRIDGE_REDISWORKER_HOMEGRAPHKEY: ''
      GBRIDGE_REDISWORKER_MQTT: mqtt://
      GBRIDGE_REDISWORKER_REDIS: redis://cache:6379
    image: pkap/g*B*ridge-redis-worker:latest
    links:
    - cache
    networks:
      backend: null
    restart: always
  [...]
version: '3.0'

Steps to reproduce the issue

Use docker-compose.yml with invalid image name:

image: pkap/gBridge-redis-worker:latest   #note the uppercase 'B'

Observed result

[...]
Building redis-worker
ERROR: Couldn't connect to Docker daemon at http+docker://localhost - is it running?

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

Expected result

(Analogous to) "Error: Image name does not comply with the naming restrictions"

[dnephin]

It seems like this may have been fixed in docker engine. I can't reproduce the error anymore with docker-compose 1.21 or master. Using engine 18.05.0-ce

[ericleb010]

It's not fixed. I'm on a fresh install of Docker CE (v19.03.1) and Compose (v1.24.1). A stray colon at the end of our image name, through an environment variable issue on our end, caused this error message to occur. Unfortunately I spent 4 hours debugging my installation before I tried a different and valid Docker Compose file...

image: pkap/gbridge-redis-worker:

...

$ docker-compose build
ERROR: Couldn't connect to Docker daemon at http+docker://localhost - is it running?

[ericleb010]

^ @ijc @shin-