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Re: [Libguestfs] [PATCH] v2v: rhv-upload-plugin: Use BrokenPipeError



On Tue, Aug 28, 2018 at 11:55 PM Richard W.M. Jones <rjones redhat com> wrote:
On Tue, Aug 28, 2018 at 11:50:56PM +0300, Nir Soffer wrote:
> With python 3, we have a nicer way to handle socket.error with errno set
> to EPIPE (or ESHUTDOWN).
>
> This is also more correct since in some cases (that I could not
> reproduce yet with v2v), using e[0] with BrokenPipeError will fail with:
>
> >>> OSError(errno.EPIPE, "Broken pipe")[0]
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> TypeError: 'BrokenPipeError' object is not subscriptable
>
> For python 2 e[0] seems to work, but is leftover from historic python
> version that used to raise a tuple instead of socket.error instance.
> In python 2.7 library code e.args[0] is used. If we ever port this to
> python 2 this is the best form.

Unfortunately we do have to port this to Python 2, at least while RHEL 7
is a thing we have to deal with:

https://github.com/libguestfs/libguestfs/commit/866d303bce0fee88b118768d1b7b36c87da6200b

Do you know what exactly will work with Python 2?

Yes - this should be equivalent of "except BrokenPipeError":

    expect socket.error as e:
        if e.args[0] not in (errno.EPIPE, errno.ESHUTDOWN):
            raise

See this for reference:
https://github.com/python/cpython/blob/491740f116755e220135e596ec802ea3a0f65596/Lib/asyncore.py#L115

This also works for hybrid code based that works on both python 2 and 3, see:
https://gerrit.ovirt.org/c/93278/

As for upstream / Python 3, the patch looks fine so I'll push it shortly.

Rich.

>  v2v/rhv-upload-plugin.py | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/v2v/rhv-upload-plugin.py b/v2v/rhv-upload-plugin.py
> index b5dd5521d..5cd6d5cab 100644
> --- a/v2v/rhv-upload-plugin.py
> +++ b/v2v/rhv-upload-plugin.py
> @@ -17,7 +17,6 @@
>  # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

>  import builtins
> -import errno
>  import json
>  import logging
>  import socket
> @@ -361,9 +360,8 @@ def pwrite(h, buf, offset):

>      try:
>          http.send(buf)
> -    except socket.error as e:
> -        if e[0] != errno.EPIPE:
> -            raise
> +    except BrokenPipeError:
> +        pass

>      r = http.getresponse()
>      if r.status != 200:
> @@ -425,9 +423,8 @@ def emulate_zero(h, count, offset):
>                  http.send(buf)
>                  count -= len(buf)
>              http.send(buffer(buf, 0, count))
> -        except socket.error as e:
> -            if e[0] != errno.EPIPE:
> -                raise
> +        except BrokenPipeError:
> +            pass

>          r = http.getresponse()
>          if r.status != 200:
> --
> 2.17.1

--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines.  Supports shell scripting,
bindings from many languages.  http://libguestfs.org

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