WPT: Handle flake detection in ServoHandler (#37540)

With this PR ServoHandler will store state of first suite and deal with
subsequent suites as they were run from `--retry-unexpected`, so it will
use results to mark unexpected from first run as flaky. Stats that are
used to display current running tests are still reset per suite. This
allows us to use `--retry-unexpected=1` for flake detection instead of
manual rerunning, which will help with proper subsuites support.

Testing: Manual CI run to ensure end results are still the same:
https://github.com/sagudev/servo/actions/runs/15886712204
Fixes: #37319

---------

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>
This commit is contained in:
sagudev 2025-06-26 10:53:07 +02:00 committed by GitHub
parent 3e1cdacd07
commit b9f9abee91
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2 changed files with 56 additions and 36 deletions

View file

@ -112,7 +112,13 @@ class ServoHandler(mozlog.reader.LogHandler):
"""LogHandler designed to collect unexpected results for use by
script or by the ServoFormatter output formatter."""
def __init__(self):
def __init__(self, detect_flakes=False):
"""
Flake detection assumes first suite is actual run
and rest of the suites are retry-unexpected for flakes detection.
"""
self.detect_flakes = detect_flakes
self.currently_detecting_flakes = False
self.reset_state()
def reset_state(self):
@ -120,6 +126,9 @@ class ServoHandler(mozlog.reader.LogHandler):
self.completed_tests = 0
self.need_to_erase_last_line = False
self.running_tests: Dict[str, str] = {}
if self.currently_detecting_flakes:
return
self.currently_detecting_flakes = False
self.test_output = collections.defaultdict(str)
self.subtest_failures = collections.defaultdict(list)
self.tests_with_failing_subtests = []
@ -146,8 +155,17 @@ class ServoHandler(mozlog.reader.LogHandler):
"PRECONDITION_FAILED": [],
}
def any_stable_unexpected(self) -> bool:
return any(not unexpected.flaky for unexpected in self.unexpected_results)
def suite_start(self, data):
# If there were any unexpected results and we are starting another suite, assume
# that this suite has been launched to detect intermittent tests.
# TODO: Support running more than a single suite at once.
if self.unexpected_results:
self.currently_detecting_flakes = True
self.reset_state()
self.number_of_tests = sum(len(tests) for tests in itervalues(data["tests"]))
self.suite_start_time = data["time"]
@ -171,17 +189,43 @@ class ServoHandler(mozlog.reader.LogHandler):
had_expected_test_result = self.data_was_for_expected_result(data)
subtest_failures = self.subtest_failures.pop(test_path, [])
test_output = self.test_output.pop(test_path, "")
if had_expected_test_result and not subtest_failures:
if not self.currently_detecting_flakes:
self.expected[test_status] += 1
else:
# When `retry_unexpected` is passed and we are currently detecting flaky tests
# we assume that this suite only runs tests that have already been run and are
# in the list of unexpected results.
for unexpected in self.unexpected_results:
if unexpected.path == test_path:
unexpected.flaky = True
break
return None
# If we are currently detecting flakes and a test still had an unexpected
# result, it's enough to simply return the unexpected result. It isn't
# necessary to update any of the test counting data structures.
if self.currently_detecting_flakes:
return UnexpectedResult(
test_path,
test_status,
data.get("expected", test_status),
data.get("message", ""),
data["time"],
"",
subtest_failures,
)
# If the test crashed or timed out, we also include any process output,
# because there is a good chance that the test produced a stack trace
# or other error messages.
stack = data.get("stack", None)
if test_status in ("CRASH", "TIMEOUT"):
stack = f"\n{stack}" if stack else ""
stack = f"{self.test_output[test_path]}{stack}"
stack = f"{test_output}{stack}"
result = UnexpectedResult(
test_path,
@ -285,10 +329,11 @@ class ServoFormatter(mozlog.formatters.base.BaseFormatter, ServoHandler):
def suite_start(self, data):
ServoHandler.suite_start(self, data)
maybe_flakes_msg = " to detect flaky tests" if self.currently_detecting_flakes else ""
if self.number_of_tests == 0:
return "Running tests in %s\n\n" % data["source"]
return f"Running tests in {data['source']}{maybe_flakes_msg}\n\n"
else:
return "Running %i tests in %s\n\n" % (self.number_of_tests, data["source"])
return f"Running {self.number_of_tests} tests in {data['source']}{maybe_flakes_msg}\n\n"
def test_start(self, data):
ServoHandler.test_start(self, data)

View file

@ -93,6 +93,8 @@ def run_tests(default_binary_path: str, **kwargs):
filter_intermittents_output = kwargs.pop("filter_intermittents", None)
unexpected_raw_log_output_file = kwargs.pop("log_raw_unexpected", None)
raw_log_outputs = kwargs.get("log_raw", [])
if filter_intermittents_output and kwargs["retry_unexpected"] <= 0:
kwargs["retry_unexpected"] = 1
wptcommandline.check_args(kwargs)
@ -112,45 +114,18 @@ def run_tests(default_binary_path: str, **kwargs):
else:
logger = wptrunner.setup_logging(kwargs, {"servo": sys.stdout})
handler = ServoHandler()
handler = ServoHandler(detect_flakes=kwargs["retry_unexpected"] >= 1)
logger.add_handler(handler)
wptrunner.run_tests(**kwargs)
return_value = 0 if not handler.unexpected_results else 1
return_value = int(handler.any_stable_unexpected())
# Filter intermittents if that was specified on the command-line.
if handler.unexpected_results and filter_intermittents_output:
# Copy the list of unexpected results from the first run, so that we
# can access them after the tests are rerun (which changes
# `handler.unexpected_results`). After rerunning some tests will be
# marked as flaky but otherwise the contents of this original list
# won't change.
unexpected_results = list(handler.unexpected_results)
# This isn't strictly necessary since `handler.suite_start()` clears
# the state, but make sure that we are starting with a fresh handler.
handler.reset_state()
print(80 * "=")
print(f"Rerunning {len(unexpected_results)} tests with unexpected results to detect flaky tests.")
unexpected_results_tests = [result.path for result in unexpected_results]
kwargs["test_list"] = unexpected_results_tests
kwargs["include"] = unexpected_results_tests
kwargs["pause_after_test"] = False
wptrunner.run_tests(**kwargs)
if filter_intermittents_output:
if github_context:
os.environ["GITHUB_CONTEXT"] = github_context
# Use the second run to mark tests from the first run as flaky, but
# discard the results otherwise.
# TODO: It might be a good idea to send the new results to the
# dashboard if they were also unexpected.
stable_tests = [result.path for result in handler.unexpected_results]
for result in unexpected_results:
result.flaky = result.path not in stable_tests
all_filtered = filter_intermittents(unexpected_results, filter_intermittents_output)
all_filtered = filter_intermittents(handler.unexpected_results, filter_intermittents_output)
return_value = 0 if all_filtered else 1
# Write the unexpected-only raw log if that was specified on the command-line.