Re: [Qemu-devel] [PATCH 1/2] Acceptance tests: exclude "flaky" tests

[Cleber Rosa <crosa@redhat.com>]

On Fri, Jun 21, 2019 at 09:03:33AM +0200, Philippe Mathieu-Daudé wrote:
> On 6/21/19 8:09 AM, Cleber Rosa wrote:
> > It's a fact that some tests may not be 100% reliable in all
> > environments.  While it's a tough call to remove a useful test that
> > from the tree because it may fail every 1/100th time (or so), having
> > human attention drawn to known issues is very bad for humans and for
> > the projects they manage.
> > 
> > As a compromise solution, this marks tests that are known to have
> > issues, or that exercises known issues in QEMU or other components,
> > and excludes them from the entry point.  As a consequence, tests
> > marked as "flaky" will not be executed as part of "make
> > check-acceptance".
> > 
> > Because such tests should be forgiven but never be forgotten, it's
> > possible to list them with (assuming "make check-venv" or "make
> > check-acceptance" has already initiatilized the venv):
> > 
> >   $ ./tests/venv/bin/avocado list -t flaky tests/acceptance
> > 
> > The current list of tests marked as flaky are a result of running
> > the entire set of acceptance tests around 20 times.  The results
> > were then processed with a helper script[1].  That either confirmed
> > known issues (in the case of aarch64 and arm)[2] or revealed new
> > ones (mips).
> > 
> > This also bumps the Avocado version to one that includes a fix to the
> > parsing of multiple and mix "key:val" and simple tag values.
> > 
> > [1] https://raw.githubusercontent.com/avocado-framework/avocado/master/contrib/scripts/summarize-job-failures.py
> > [2] https://bugs.launchpad.net/qemu/+bug/1829779
> > 
> > Signed-off-by: Cleber Rosa <crosa@redhat.com>
> > ---
> >  docs/devel/testing.rst                   | 17 +++++++++++++++++
> >  tests/Makefile.include                   |  6 +++++-
> >  tests/acceptance/boot_linux_console.py   |  2 ++
> >  tests/acceptance/linux_ssh_mips_malta.py |  2 ++
> >  tests/requirements.txt                   |  2 +-
> >  5 files changed, 27 insertions(+), 2 deletions(-)
> > 
> > diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst
> > index da2d0fc964..ff4d8e2e1c 100644
> > --- a/docs/devel/testing.rst
> > +++ b/docs/devel/testing.rst
> > @@ -574,6 +574,23 @@ may be invoked by running:
> >  
> >    tests/venv/bin/avocado run $OPTION1 $OPTION2 tests/acceptance/
> >  
> > +Tagging tests
> > +-------------
> > +
> > +flaky
> > +~~~~~
> > +
> > +If a test is known to fail intermittently, even if only every one
> > +hundredth time, it's highly advisable to mark it as a flaky test.
> > +This will prevent these individual tests from failing much larger
> > +jobs, will avoid human interaction and time wasted to verify a known
> > +issue, and worse of all, can lead to the discredit of automated
> > +testing.
> > +
> > +To mark a test as flaky, add to its docstring.::
> > +
> > +  :avocado: tags=flaky
> 
> I certainly disagree with this patch, failing tests have to be fixed.
> Why not tag all the codebase flaky and sing "happy coding"?
>

That's a great idea! :)

Now, seriously, I also resisted this for quite a long time.  The
reality, though, is that intermittent failures will continue to
appear, and letting tests (and jobs, and CI pipelines, and whatnot)
fail is a very bad idea.  We all agree that real fixes are better than
this, but many times they don't come quickly.

> Anyway if this get accepted, 'flaky' tags must have the intermittent
> failure well described, and a Launchpad/Bugzilla tracking ticket referenced.
>

And here you have a key point that I absolutely agree with.  The
"flaky" approach can either poison a lot of tests, and be seen as
quick way out of a difficult issue revealed by a test.  Or, it can
serve as an effective tool to keep track of these very important
issues.

If we add:

   # https://bugs.launchpad.net/qemu/+bug/1829779
   :avocado: flaky

Topped with some human, I believe this can be very effective.  This goes
without saying, but comments here are very much welcome.

- Cleber.

> > +
> >  Manual Installation
> >  -------------------
> >  
> > diff --git a/tests/Makefile.include b/tests/Makefile.include
> > index db750dd6d0..4c97da2878 100644
> > --- a/tests/Makefile.include
> > +++ b/tests/Makefile.include
> > @@ -1125,7 +1125,11 @@ TESTS_RESULTS_DIR=$(BUILD_DIR)/tests/results
> >  # Any number of command separated loggers are accepted.  For more
> >  # information please refer to "avocado --help".
> >  AVOCADO_SHOW=app
> > -AVOCADO_TAGS=$(patsubst %-softmmu,-t arch:%, $(filter %-softmmu,$(TARGET_DIRS)))
> > +
> > +# Additional tags that are added to each occurence of "--filter-by-tags"
> > +AVOCADO_EXTRA_TAGS := ,-flaky
> > +
> > +AVOCADO_TAGS=$(patsubst %-softmmu,--filter-by-tags=arch:%$(AVOCADO_EXTRA_TAGS), $(filter %-softmmu,$(TARGET_DIRS)))
> >  
> >  ifneq ($(findstring v2,"v$(PYTHON_VERSION)"),v2)
> >  $(TESTS_VENV_DIR): $(TESTS_VENV_REQ)
> > diff --git a/tests/acceptance/boot_linux_console.py b/tests/acceptance/boot_linux_console.py
> > index 32159503e9..6bd5c1ab53 100644
> > --- a/tests/acceptance/boot_linux_console.py
> > +++ b/tests/acceptance/boot_linux_console.py
> > @@ -249,6 +249,7 @@ class BootLinuxConsole(Test):
> >          """
> >          :avocado: tags=arch:aarch64
> >          :avocado: tags=machine:virt
> > +        :avocado: tags=flaky
> >          """
> >          kernel_url = ('https://download.fedoraproject.org/pub/fedora/linux/'
> >                        'releases/29/Everything/aarch64/os/images/pxeboot/vmlinuz')
> > @@ -270,6 +271,7 @@ class BootLinuxConsole(Test):
> >          """
> >          :avocado: tags=arch:arm
> >          :avocado: tags=machine:virt
> > +        :avocado: tags=flaky
> >          """
> >          kernel_url = ('https://download.fedoraproject.org/pub/fedora/linux/'
> >                        'releases/29/Everything/armhfp/os/images/pxeboot/vmlinuz')
> > diff --git a/tests/acceptance/linux_ssh_mips_malta.py b/tests/acceptance/linux_ssh_mips_malta.py
> > index aafb0c39f6..ae70b658e0 100644
> > --- a/tests/acceptance/linux_ssh_mips_malta.py
> > +++ b/tests/acceptance/linux_ssh_mips_malta.py
> > @@ -208,6 +208,7 @@ class LinuxSSH(Test):
> >          :avocado: tags=machine:malta
> >          :avocado: tags=endian:big
> >          :avocado: tags=device:pcnet32
> > +        :avocado: tags=flaky
> >          """
> >          kernel_url = ('https://people.debian.org/~aurel32/qemu/mips/'
> >                        'vmlinux-3.2.0-4-5kc-malta')
> > @@ -222,6 +223,7 @@ class LinuxSSH(Test):
> >          :avocado: tags=machine:malta
> >          :avocado: tags=endian:little
> >          :avocado: tags=device:pcnet32
> > +        :avocado: tags=flaky
> >          """
> >          kernel_url = ('https://people.debian.org/~aurel32/qemu/mipsel/'
> >                        'vmlinux-3.2.0-4-5kc-malta')
> > diff --git a/tests/requirements.txt b/tests/requirements.txt
> > index 3ae0e29ad7..58d63d171f 100644
> > --- a/tests/requirements.txt
> > +++ b/tests/requirements.txt
> > @@ -1,5 +1,5 @@
> >  # Add Python module requirements, one per line, to be installed
> >  # in the tests/venv Python virtual environment. For more info,
> >  # refer to: https://pip.pypa.io/en/stable/user_guide/#id1
> > -avocado-framework==68.0
> > +avocado-framework==69.1
> >  paramiko
> > 
>