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

[Wainer dos Santos Moschetta]

On 06/21/2019 11:38 AM, Cleber Rosa wrote:
> 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

It needs a Make target to run those flaky tests (If we ever agree on 
this idea of flaky tests). Other Avocado flags are passed (e.g. -t for 
tags) that can happen to fail tests on their absent. One clear example 
is the spice test on patch 02 of this series...

Side note: check-acceptance seems to get growing in complexity that I 
worry will end up in pitfalls. is a Make target the proper way to 
implement complex test runs (I don't think so). Perhaps Avocado runner 
concept could help somehow?

> > > 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 <address@hidden>
> > > ---
> > >   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.

It seems to me that flaky test is just a case in a broaden scenario: run 
(or not) grouped tests. You may have tests indeed broken or that takes 
considerable time (those tagged "slow") which one may fairly want to 
exclude from `make check-acceptance` as well. Thus some way to group 
tests plus define run inclusion/exclusion patterns seems the ultimate 
goal here.

> > 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.

I agree that all flaky test should have a tracking bug. In the end it 
represents a technical debit that we should address.

- Wainer

> - 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