Author: ceridwen
The 0.1 alpha release of reprotest has been accepted into Debian
unstable and is available for install at
packages.debian.org or
through apt.
I've been working on redesigning reprotest so that it runs commands
through autopkgtest's adt_testbed interface. For the most part, I
needed to replace explicit calls to Python standard library functions
for copying files and directories with calls to
adt_testbed.Testbed.command() with
copyup and
copydown, and to
use
Testbed.execute() and
Testbed.check_exec() to run commands
instead of
subprocess.
To test reprotest on the actual containers requires having containers
constructed for this purpose. autopkgtest has a test that builds a
minimal chroot. I considered doing something like this approach or
using BusyBox. However, I have a Python script that mocks a build
process, which requires having Python available in the container, and
while I looked into
busybox-python and
MicroPython to keep the
footprint small, I decided that for now this would take too much work
and decided to go straight to the autopkgtest recommendations for
building containers,
mk-sbuild
and
vmdebootstrap. (I also
ended up discovering a
bug
in debootstrap.) This means that to get the tests run requires some
manual setup at the moment. In the long run, I'd like to improve
that, but it's not an immediate priority. While working on adding
tests for the other containers supported by autopkgtest, I also
converted to
py.test so that I
could use
fixtures and
parametrization to run
the Cartesian product of each variation with each container.
With tests written, I started trying to verify that my new code
worked. One problem I encountered while trying to debug was that I
wasn't getting full error output. In
VirtSubproc.check_exec(),
execute_timeout() acts something like a
Popen() call:
(status, out, err) = execute_timeout(None, timeout, real_argv,
stdout=stdout, stderr=subprocess.PIPE)
if status:
bomb("%s%s failed (exit status %d)" %
((downp and "(down) " or ""), argv, status))
if err:
bomb("%s unexpectedly produced stderr output %s'" %
(argv, err))
The problem with this is that if the call returns a non-zero exit
code, which is typical for program failures, stderr doesn't get
included in the error message.
I changed the first if-block to:
if status:
bomb("%s%s failed (exit status %d)\n%s" %
((downp and "(down) " or ""), argv, status, err))
Another example is that autopkgtest calls
schroot with the
--quiet
flag, which in one case was making
schroot fail without any output
due to a misconfiguration. I'm still trying to find and eliminate
more places where errors are silenced.
autopkgtest was designed to be installed with Debian's packaging
system, which handles arbitrary files and directory layouts.
Unfortunately, setuptools is
completely different in a way that
doesn't work well with autopkgtest's design. (I'm sure this is partly
because setuptools has to support all the different major OSes that
run Python, including Windows.) As I discussed
last
week,
autopkgtest has Python scripts in
virt/ that are executed by
subprocess calls in
adt_testbed. Because these scripts import
files from
lib/, there needs to be an
__init__.py in
virt/ to
make it into a package and a
sys.path hack in each script to allow
it to find modules in
lib/. Unfortunately, setuptools
will not
install this structure. First, setuptools will not install any file
without a
.py extension into a package. Theoretically, this is
fixable, the files in
virt/ are Python scripts so I could rename
them. (Theoretically, there's supposed to be some workaround
involving
MANIFEST.in or
package_data in
setup.py, but I have
yet to find any documentation or explanation giving a method for
installing non-Python files inside a Python package.) Second,
however, setuptools does not preserve the executable bit when
installing package files. The obvious workaround, changing the
subprocess calls so that they invoke
python virt/foo.py rather
than
virt/foo.py requires changing all the internal calls in the
autopkgtest code, which I'm loathe to do for fear of breaking it.
(It's not clear to me I can easily find all of the calls, for
starters.)
There are about three solutions to this I see at the moment, all of
them difficult. The first involves using either the
scripts keyword
or
console_scripts entry point in
setup.py, as explained
here.
The
scripts keyword is supposed to preserve the executable bit
according to
this StackExchange
question,
but I haven't verified this myself, and like everything to do with
setuptools I don't trust anything anyone says about it without testing
it myself. It also has the disadvantage of dumping them all into the
common scripts directory. Using
console_scripts involves rewriting
all of them to have an executable function I can refer to in
setup.py. I worry that this would be both fragile and break
existing expectations in the rest of the autopkgtest code, but it
might be the best solution. The third solution involves refactoring
of all the autopkgtest code to import the code in the scripts rather
than running it through
subprocess calls. I'm reluctant to do this
because I think it's almost certain to break things that will require
significant work to fix.
Getting setuptools to install the autopkgtest code correctly is one
blocker for the next release. Another is that autopkgtest's handling
of errors during the build process involves closing the
adt_testbed.Testbed so it won't take further commands.
Unfortunately, this handling runs
before any cleanup code I write to
run outside it, which means that at the moment errors during the build
will result in things like disorderfs being left mounted.
The last release blocker is that
adt_testbed doesn't have any way to
set a working directory when running commands. For instance, the
virt/schroot script always calls
schroot with
--directory=/. I
thought about trying to use absolute paths, but decided this was
unintuitive and impractical. For the user, this would mean that
instead of running something simple like
make in the correct
directory, they would have to run
make
--file=/absolute/path/to/Makefile or something similar, making all
paths absolute. I worry that some build scripts wouldn't handle this
correctly, either: for instance, running
python setup.py from a
different directory can have different effects because Python's path
is initialized to contain the current directory. Changing this is
going to require going deeper into the autopkgtest code than I'd
hoped.
I intend to try to resolve these three issues over the next week and
then prepare the next release, though how much progress I make depends
on how thorny they turn out to be.
For a long time I ve wanted an ssh-agent setup that would ask me before every use, so I could slightly more comfortably forward authentication over SSH without worrying that my session might get hijacked somewhere at the remote end (I often find myself wanting to pull authenticated git repos on remote hosts). I m at DebConf this week, which is an ideal time to dig further into these things, so I did so today. As is often the case it turns out this is already possible, if you know how.
I began with a setup that was using GNOME Keyring to manage my SSH keys. This isn t quite what I want (eventually I want to get to the point that I can sometimes forward a GPG agent to remote hosts for signing purposes as well), so I set about setting up gpg-agent. I used Chris excellent guide to GnuPG/SSH Agent setup as a starting point and ended up doing the following:
Last week, I posted about 
My monthly report covers a large part of what I have been doing in the free software world. I write it for 
Here is my monthly update covering a large part of what I have been doing in the free software world (
I had planned to do some work on NBD while here at debcamp. Here's a progress report:
This isn't actually answering the question, but it's close. It's also horrible, so whoever adopts
I am mourning for the UK. I feel so much pain and pity for all my good friends over there. Stupidity has won again. Good bye UK, your long reign has found its end. The rest is silence.
RIP.
(Graphic from The Guardian