Last time I checked there wasn't support for vnodes on in-jvm dtests, which seems an important limitation.
On Mon, 14 Mar 2022 at 12:24, bened...@apache.org <bened...@apache.org> wrote: > I am strongly in favour of deprecating python dtests in all cases where > they are currently superseded by in-jvm dtests. They are environmentally > more challenging to work with, causing many problems on local and remote > machines. They are harder to debug, slower, flakier, and mostly less > sophisticated. > > > > > all focus on getting the in-jvm framework robust enough to cover > edge-cases > > > > Would be great to collect gaps. I think it’s just vnodes, which is by no > means a fundamental limitation? There may also be some stuff to do > startup/shutdown and environmental scripts, that may be a niche we retain > something like python dtests for. > > > > > people aren’t familiar > > > > I would be interested to hear from these folk to understand their concerns > or problems using in-jvm dtests, if there is a cohort holding off for this > reason > > > > > This is going to require documentation work from some of the original > authors > > > > I think a collection of template-like tests we can point people to would > be a cheap initial effort. Cutting and pasting an existing test with the > required functionality, then editing to suit, should get most people off to > a quick start who aren’t familiar. > > > > > Labor and process around revving new releases of the in-jvm dtest API > > > > I think we need to revisit how we do this, as it is currently broken. We > should consider either using ASF snapshots until we cut new releases of C* > itself, or else using git subprojects. This will also become a problem for > Accord’s integration over time, and perhaps other subprojects in future, so > it is worth better solving this. > > > > I think this has been made worse than necessary by moving too many > implementation details to the shared API project – some should be retained > within the C* tree, with the API primarily serving as the shared API itself > to ensure cross-version compatibility. However, this is far from a complete > explanation of (or solution to) the problem. > > > > > > > > *From: *Josh McKenzie <jmcken...@apache.org> > *Date: *Monday, 14 March 2022 at 12:11 > *To: *dev@cassandra.apache.org <dev@cassandra.apache.org> > *Subject: *[DISCUSS] Should we deprecate / freeze python dtests > > I've been wrestling with the python dtests recently and that led to some > discussions with other contributors about whether we as a project should be > writing new tests in the python dtest framework or the in-jvm framework. > This discussion has come up tangentially on some other topics, including > the lack of documentation / expertise on the in-jvm framework > dis-incentivizing some folks from authoring new tests there vs. the > difficulty debugging and maintaining timer-based, sleep-based > non-deterministic python dtests, etc. > > > > I don't know of a place where we've formally discussed this and made a > project-wide call on where we expect new distributed tests to be written; > if I've missed an email about this someone please link on the thread here > (and stop reading! ;)) > > > > At this time we don't specify a preference for where you write new > multi-node distributed tests on our "development/testing" portion of the > site and documentation: > https://cassandra.apache.org/_/development/testing.html > > > > The primary tradeoffs as I understand them for moving from python-based > multi-node testing to jdk-based are: > > Pros: > > 1. Better debugging functionality (breakpoints, IDE integration, etc) > 2. Integration with simulator > 3. More deterministic runtime (anecdotally; python dtests _should_ be > deterministic but in practice they prove to be very prone to environmental > disruption) > 4. Test time visibility to internals of cassandra > > Cons: > > 1. The framework is not as mature as the python dtest framework (some > functionality missing) > 2. Labor and process around revving new releases of the in-jvm dtest > API > 3. People aren't familiar with it yet and there's a learning curve > > > > So my bid here: I personally think we as a project should freeze writing > new tests in the python dtest framework and all focus on getting the in-jvm > framework robust enough to cover edge-cases that might still be causing new > tests to be written in the python framework. This is going to require > documentation work from some of the original authors of the in-jvm > framework as well as folks currently familiar with it and effort from those > of us not yet intimately familiar with the API to get to know it, however I > believe the long-term benefits to the project will be well worth it. > > > > We could institute a pre-commit check that warns on a commit increasing > our raw count of python dtests to help provide process-based visibility to > this change in direction for the project's testing. > > > > So: what do we think? > > >
