Re: [Qemu-devel] [PATCH] docker: Handle exceptions when looking for docker command

[Fam Zheng <famz@redhat.com>]

On Tue, 09/20 08:05, Eduardo Habkost wrote:
> When trying to run docker tests on a host without the docker
> command,  we get the following Python backtrace:
> 
>   $ make docker-test-quick@centos6 V=1
>   .../qemu/tests/docker/docker.py build qemu:centos6 .../qemu/tests/docker/dockerfiles/centos6.docker
>   Traceback (most recent call last):
>     File ".../qemu/tests/docker/docker.py", line 339, in <module>
>       sys.exit(main())
>     File ".../qemu/tests/docker/docker.py", line 336, in main
>       return args.cmdobj.run(args, argv)
>     File ".../qemu/tests/docker/docker.py", line 231, in run
>       dkr = Docker()
>     File ".../qemu/tests/docker/docker.py", line 98, in __init__
>       self._command = _guess_docker_command()
>     File ".../qemu/tests/docker/docker.py", line 41, in _guess_docker_command
>       stdout=DEVNULL, stderr=DEVNULL) == 0:
>     File "/usr/lib64/python2.7/subprocess.py", line 523, in call
>       return Popen(*popenargs, **kwargs).wait()
>     File "/usr/lib64/python2.7/subprocess.py", line 711, in __init__
>       errread, errwrite)
>     File "/usr/lib64/python2.7/subprocess.py", line 1343, in _execute_child
>       raise child_exception
>   OSError: [Errno 2] No such file or directory
>   .../qemu/tests/docker/Makefile.include:47: recipe for target 'docker-image-centos6' failed
>   make: *** [docker-image-centos6] Error 1
> 
> Change _guess_docker_command() to handle OSError exceptions
> raised by subprocess.call(), so we will keep looking for other
> commands and print a better error message.
> 
> New output will be:
> 
>   $ make docker-test-quick@centos6 V=1
>   .../qemu/tests/docker/docker.py build qemu:centos6 .../qemu/tests/docker/dockerfiles/centos6.docker
>   Traceback (most recent call last):
>     File ".../qemu/tests/docker/docker.py", line 343, in <module>
>       sys.exit(main())
>     File ".../qemu/tests/docker/docker.py", line 340, in main
>       return args.cmdobj.run(args, argv)
>     File ".../qemu/tests/docker/docker.py", line 235, in run
>       dkr = Docker()
>     File ".../qemu/tests/docker/docker.py", line 102, in __init__
>       self._command = _guess_docker_command()
>     File ".../qemu/tests/docker/docker.py", line 49, in _guess_docker_command
>       commands_txt)
>   Exception: Cannot find working docker command. Tried:
>     docker
>     sudo -n docker
>   .../qemu/tests/docker/Makefile.include:47: recipe for target 'docker-image-centos6' failed
>   make: *** [docker-image-centos6] Error 1
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
>  tests/docker/docker.py | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/tests/docker/docker.py b/tests/docker/docker.py
> index b85c165..daff340 100755
> --- a/tests/docker/docker.py
> +++ b/tests/docker/docker.py
> @@ -13,6 +13,7 @@
>  
>  import os
>  import sys
> +import exceptions
>  import subprocess
>  import json
>  import hashlib
> @@ -37,9 +38,12 @@ def _guess_docker_command():
>      """ Guess a working docker command or raise exception if not found"""
>      commands = [["docker"], ["sudo", "-n", "docker"]]
>      for cmd in commands:
> -        if subprocess.call(cmd + ["images"],
> -                           stdout=DEVNULL, stderr=DEVNULL) == 0:
> -            return cmd
> +        try:
> +            if subprocess.call(cmd + ["images"],
> +                               stdout=DEVNULL, stderr=DEVNULL) == 0:
> +                return cmd
> +        except exceptions.OSError:
> +            pass
>      commands_txt = "\n".join(["  " + " ".join(x) for x in commands])
>      raise Exception("Cannot find working docker command. Tried:\n%s" % \
>                      commands_txt)
> -- 
> 2.7.4
> 

Looks good, except that like exceptions.Exception, OSError is also magically
addressable as "OSError", saving us one import. _copy_with_mkdir below already
does that. Fixing that for consistency and queued for next PULL, thanks!

Fam