Michael Kjellman created CASSANDRA-14134:
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Summary: Migrate dtests to use pytest and python3
Key: CASSANDRA-14134
URL: https://issues.apache.org/jira/browse/CASSANDRA-14134
Project: Cassandra
Issue Type: Improvement
Components: Testing
Reporter: Michael Kjellman
Assignee: Michael Kjellman
h4. Get the C* dtests running on the pytest framework.
C* DTests currently run using the python test framework nosetest. This
framework has been largely abandoned with no releases since 2015 and a general
strong consensus in the python community that pytest is the future.
h4. Why should we do this.
Currently (and historically) dtests have always been difficult to run, flaky
and unpredictable in CI environments, and almost impossible to debug.
On November 28th, 2017, I proposed on the dev@ list that we move the dtests
from nosetests to pytests. I got replies from Jon Haddad, Philip Thompson, and
kurt greaves with really only "+1" like replies to the proposal.
Since then I've been working pretty much non stop to complete the large
refactor of dtests to pytests. As part of this effort (and due to the migration
tools that exist require it) I also ported the code to python3 (from the
current python 2.7 based code-base).
h4. High-level summary of key changes, improvements, and new features.
* Migrate dtests from executing using the nosetest framework to pytest
* Port the entire code base from Python 2.7 to Python 3.6
* Update run_dtests.py to work with pytest
* Add --dtest-print-tests-only option to run_dtests.py to get easily parsable
list of all available collected tests
* Update README.md for executing the dtests with pytest
* Add new debugging tips section to README.md to help with some basics of
debugging python3 and pytest
* Migrate all existing Enviornment Variable usage as a means to control dtest
operation modes to argparse command line options with documented help on each
toggles intended usage
* Migration of old unitTest and nose based test structure to modern pytest
fixture approach
* Automatic detection of physical system resources to automatically determine
if @pytest.mark.resource_intensive annotated tests should be collected and run
on the system where they are being executed
* new pytest fixture replacements for @since and @pytest.mark.upgrade_test
annotations
* Migration to python logging framework
* Upgrade thrift bindings to latest version with full python3 compatibility
* Remove deprecated cql and pycassa dependencies and migrate any remaining
tests to fully remove those dependencies
* Fixed dozens of tests that would hang the pytest framework forever when run
in CI enviornments
* Ran code nearly 300 times in CircleCI during the migration and to find,
identify, and fix any tests capable of hanging CI
* Upgrade Tests do not yet run in CI and still need additional migration work
(although all upgrade test classes compile successfully)
I started with the *nose2pytest* [https://github.com/pytest-dev/nose2pytest]
migration tool. As this required python 3 language support I found myself down
the 2to3 python migration path. While painful to do this, the benefits of
python3 over python2.7 are numerous and moving to python3 for the additional
debugging tools now available to use when fixing dtests makes the effort worth
it for that reason alone!
After the automated tools did their thing I began what was a much longer and
tedious manual process than I ever could have expected due to the custom many
ways we did things in dtests (frequently to work around nosetest limitations of
missing features that thankfully are now all included with the pytest
framework). I've done nearly 300 test runs of my migration branch with circleci.
The latest CircleCI runs can be found at:
(dtests without vnodes) [https://circleci.com/gh/mkjellman/cassandra/277]
(dtests with vnodes) [https://circleci.com/gh/mkjellman/cassandra/278]
With vnodes, there are currently only 6 remaining dtest test failures.
Without vnodes, there are 12 remaining dtest failures.
It turns out that after the dtests were moved to ASF Jenkins from cassci, the
jobs were misconfigured and we actually haven't been running the dtests in the
non-vnodes configuration. The current most recent trunk dtest job to complete
on ASF Jenkins (with vnodes) was
[https://builds.apache.org/view/A-D/view/Cassandra/job/Cassandra-trunk-dtest/387/].
That test run had 36 test failures.
There are great performance improvements so far with pytests. With a parallism
factor of 90x in CircleCI the dtests-no-vnodes job completed all tests in 16
minutes and 24 seconds and the dtests-with-vnodes job completed all tests in 14
minutes and 22 seconds.. (Compare that to the 8+ hours ASF Jenkins currently
takes!).
A dtest on pytest compatible CircleCI configuration is available at
https://github.com/mkjellman/cassandra/blob/trunk_circle/.circleci/config.yml
A very small patch is required to ccm for 2 places that were not yet python3
compatible. (I didn't do a full audit of ccm, but these appear to be the only
two issues I've found even with a ton of testing when using ccmlib with dtests
and running with python 3).
{code}
--- /home/cassandra/env/src/ccm/ccmlib/node.py 2017-12-13 03:11:13.000000000
+0000-8").splitlines()))
+++ node.py 2017-12-19 09:51:49.083186951 +0000
@@ -57,10 +57,16 @@
message = "Subprocess {} exited with non-zero status; exit status:
{}".format(command, exit_status)
if stdout:
message += "; \nstdout: "
- message += stdout
+ if isinstance(stdout, str):
+ message += stdout
+ else:
+ message += stdout.decode("utf-8")
if stderr:
message += "; \nstderr: "
- message += stderr
+ if isinstance(stderr, str):
+ message += stderr
+ else:
+ message += stderr.decode("utf-8")
Exception.__init__(self, message)
@@ -2009,7 +2015,10 @@
out, _, _ = handle_external_tool_process(p, ["sstableutil", '--type',
'final', ks, table])
- return sorted(filter(lambda s: s.endswith('-Data.db'),
out.splitlines()))
+ if isinstance(out, str):
+ return sorted(filter(lambda s: s.endswith('-Data.db'),
out.splitlines()))
+ else:
+ return sorted(filter(lambda s: s.endswith('-Data.db'),
out.decode("utf-8").splitlines()))
def _get_load_from_info_output(info):
{code}
For the actual dtest work itself: I've squashed all my work down into a single
commit available at
[https://github.com/mkjellman/cassandra-dtest/tree/dtests_on_pytest_v2]
And the actual commit available at
[https://github.com/mkjellman/cassandra-dtest/commit/11201c149d1198c0d6d1a479e08bfb8695f14c9e]
I tried to put a lot of effort into making the end user experience better for
both bootstrapping and running dtests for the first time, but also day to day.
I hope people like the approach! In addition to moving to argparse with
commented command line arguments to control execution, I also updated the
README.md to reflect the new pytest world and also added a new section with a
few tips I learned while I was debugging hundreds of tests during this
migration process that hopefully are helpful to the rest of the community going
forward!
I'm sure the first commit above isn't 100% perfect (although I really have put
a lot of effort into it) but my one request is to hopefully get consensus with
this first revision of changes committed to reduce any chance of further drift
with the codebase as changes are committed into master.
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