One point toward seperate repositories, vendoring Arrow for C++ project with git submodules becomes awkward if it's a multi-lang monorepo.
On Tue, Oct 16, 2018 at 9:22 PM Wes McKinney <wesmck...@gmail.com> wrote: > I would also add -- Krisztian's recent work Dockerizing the project is > setting us up to be able to decouple ourselves from Travis CI. We need > build hosts where we can use Docker to be able to do this, though. > Preferably the build hosts would have NVIDIA GPUs so we can use > nvidia-docker to test our GPU functionality > On Tue, Oct 16, 2018 at 9:09 PM Wes McKinney <wesmck...@gmail.com> wrote: > > > > hi Antoine, > > > > Some small critiques to the listing of implementations: > > > > * The Java library predates the C++ library (it originated in Apache > Drill) > > * Python and C++ both interact with the Java library in different > > ways. There's JNI for Gandiva and Plasma, and Python uses Java via > > JPype in unit tests > > > > There's some critical questions to answer here: > > > > 1. Is there such a thing as an "independent implementation"? > > 2. What's the best way to manage changesets / patches? > > 3. What is the best way to manage the burgeoning complexity of testing > > and verification of the entire project? > > 4. How much longer will public CI services be adequate for our needs? > > > > This may be a bit long winded so bear with me > > > > 1. Is there such a thing as an "independent implementation"? > > > > My answer to this is actually "not really". The reasons are as follows: > > > > * The integration tests are one of the most important parts of the > > project. While C++, Java, and JavaScript are the only participants, we > > eventually need Rust, Go, and C# to be in the matrix. This will > > include integration testing for RPC / Flight in addition to the > > current IPC tests. > > * By the nature of Arrow, any implementation may build in-memory or > > RPC-based bindings to computational libraries that are in C++ or use > > LLVM, such as Gandiva and Plasma. This is already the case in Java, > > and may expand beyond Java. I could see Go or Rust or C# using Gandiva > > or Plasma. The scope of what kinds of shared infrastructure might be > > used in multiple languages will only expand over time > > > > 2. What's the best way to manage changesets / patches? > > > > * Because no two implementations can be guaranteed to be independent, > > in a non-monorepo setup, changes may require multiple patches. > > Verifying "joint patches" is likely to require manual / human > > intervention in ways that are a non-issue for a monorepo > > * Splitting development up into multiple repositories will decrease > > visibility into the patch queues in the less active subprojects. I'm > > strongly in support not only of a single codebase but a single patch > > queue. I admit that seeing ~70 open pull requests on Arrow stresses me > > out a bit, but having 70 patches spread across 5 repos would be more > > stressful for me at least > > * Broken builds in any part of the project should be a concern to the > > entire community -- we should not have broken builds. I'd be concerned > > about having any part of the project becoming a "ghetto" if the > > plurality of developers are working elsewhere with an "out of sight, > > out of mind" mindset > > > > To play devil's advocate, some web applications could be developed to > > create the appearance of a unified patch queue across many repos. > > > > That being said, our patch queue pales in comparison to some larger / > > more mature ASF projects: > > > > * Spark has 523 open PRs: https://github.com/apache/spark/pulls > > * Airflow has 218 open PRs: > https://github.com/apache/incubator-airflow/pulls > > * Hadoop 195 open PRs: https://github.com/apache/hadoop/pulls > > > > 3. What is the best way to manage the burgeoning complexity of testing > > and verification of the entire project? > > 4. How much longer will public CI services be adequate for our needs? > > > > I think we are already reaching the limits of what we can reasonably > > accomplish with public CI services. Apache Arrow is a project with > > sophistication and scope that is destined to outgrow what Travis CI > > can provide within the scope of a single implementation, i.e. > > C++/Python. For example, we're going to be past the 50 minute time > > limit before too long. I think that continuing to constrain ourselves > > by the 50 minute time limit will also limit the scope of what kinds of > > automated testing we can employ, to our long term detriment. We also > > have things (like GPU support) that we cannot test there. > > > > Considering more mature data projects in the ASF that I'm familiar > > with: Kudu, Impala, Spark: none of these projects use Travis CI. Their > > testing uses Jenkins build slaves and run much longer than our CI > > jobs. If we used beefier build slaves, our builds would also run much > > faster. > > > > So, what should we do? Well, part of why I have recently created an > > organization (https://ursalabs.org/) dedicated to Arrow development is > > to have the financial means and the engineering resources to actually > > do something about problems like these. I would propose to make an > > investment of hardware and engineering time to augment our ability to > > test the repository to make sure we can manage 5-10x the current test > > runtime that we have now. If I have to personally halt feature > > development and focus on build and development tooling for a while, so > > be it. We've already spent many months this year on packaging > > automation but we are still coming up short in development tooling. If > > anyone reading has funds to invest in hardware resources, please let > > me know. > > > > As Clint Eastwood's character said in "The Good, The Bad, and The > > Ugly", "$200,000 is a lot of money. We're gonna have to earn it." > > > > FWIW: I am not sure Parquet is a good example of a better way to be. > > Parquet lacks automated integration tests (terrifying to me) and > > failed to grow a community outside of the Java world until 2016 when a > > few of us started building out the C++ library. > > > > - Wes > > On Tue, Oct 16, 2018 at 1:02 PM Antoine Pitrou <anto...@python.org> > wrote: > > > > > > > > > Hello, > > > > > > We are quickly growing the number of Arrow implementations. Soon we'll > > > have: > > > - C++: the most mature, reference, and historical implementation > > > - Python: linked with Arrow C++ > > > - C/GLib: linked with Arrow C++ > > > - Ruby: linked with Arrow C++ (indirectly through C/GLib) > > > - R: linked with Arrow C++ > > > - Matlab: linked with Arrow C++ > > > - Java: independent implementation > > > - Rust: independent implementation > > > - Go: independent implementation > > > - Javascript: independent implementation > > > - .Net (C#): independent implementation > > > > > > This creates various kinds of issues. Technical issues such as CI > > > matrices being more and more large and complex. Social issues such as > > > different implementations having different development speeds and > > > maturity, and the fact that development teams are effectively disjoint > > > (for example, whoever develops on the C++ codebase usually doesn't > > > develop on the Rust codebase, and vice-versa). > > > > > > I'm not proposing anything concrete here, but would like to ask what > > > people think of moving independent implementations (those that don't > > > depend on Arrow C++) into independent repositories. This would let > them > > > define their own workflow, permissions, teams, CI configurations and > > > whatnot. This would also allow growing the CI matrix for the main repo > > > without reaching humongous sizes. The implementations would still be > > > under the umbrella of the Apache Arrow project; but they would exist as > > > independent GitHub projects (this is a bit how Parquet implementations > > > are handled, AFAIK). > > > > > > To start with, Wes expressed opposition to the idea: > > > """ > > > I am against breaking up the monorepo -- I think that we should scale > > > our process using tools that we develop rather than conforming to the > > > objectively crude affordances of Travis CI and Appveyor. > Implementations > > > that are independent now may not be so in the future by the nature of > > > the project -- any implementation could integrate with Gandiva, for > > > example, and that would become much more difficult to develop if the > > > code is fragmented in multiple repositories. > > > """ > > > > > > (https://github.com/apache/arrow/pull/2765#issuecomment-430224701) > > > > > > Regards > > > > > > Antoine. > -- Sent from my jetpack.
