Awesome performance numbers! I don't particularly know the logistics of upstreaming a change like this, but optimistically I would suggest upstreaming it to Apache Thrift if possible.
As someone that maintains a fork of a thrift compiler(fork of scrooge), I have to say that it's not that fun. There's a lot of custom code that needs to be maintained and a bunch of work to rebase the code periodically. On Wed, Jan 27, 2016 at 4:51 PM, Bill Farner <wfar...@apache.org> wrote: > Firstly - thanks for the clean organization and delineation of steps in > this change. Top notch work! > > Some of the performance improvements are very nice; and in a particularly > hot code path. I will wager a guess that the majority of the savings is in > avoiding what amounts to copy constructors between mutable and immutable > types. I further wager there are alternative approaches we could weigh to > achieve those performance improvements. As an example - you note above > that we could provide a patch to Apache Thrift. Depending how much > performance inspires our decision here, it will be prudent to evaluate > alternatives. > > I think there are (at least) two major issues worth discussing - code > volume (which you note) and an increase in logical complexity. This will > leave us with a bifurcation in code generation tooling (custom+swift for > Java, Apache Thrift for python and js). It's difficult to quantify the > downside of that, but it seems like an unfortunate state with potential for > compatibility risks. > > > On Wed, Jan 27, 2016 at 2:45 PM, Zameer Manji <zma...@apache.org> wrote: > > > Some high level comments without looking at the code. > > > > I'm in favor from abandoning the thrift generated java code in favor of > > immutable objects. I think it is easier to reason about and will ensure > we > > have less errors in our code. If I understand correctly, the ProtoBuf > > format does this by default, so there some precedent for this style of > code > > generation already. > > > > I think using Facebook's swift is the best approach here. I would be > > hesitant to accept any custom code generation that involved us parsing > > thrift IDL files or thrift formats over the wire because I poses a very > > high maintenance burden. > > > > I also think generating the MyBatis mutable classes is superior to our > > current strategy of manually creating them. > > > > Finally, the performance improvements look fantastic. As an operator of a > > large cluster I am excited to see wholesale performance improvements as I > > am always concerned that my cluster is approaching the limits of what > > Aurora can handle safely. > > > > Overall, I think this change merits a serious discussion from all > > contributors. > > > > On Tue, Jan 26, 2016 at 9:19 PM, John Sirois <jsir...@apache.org> wrote: > > > > > On Tue, Jan 26, 2016 at 8:47 PM, John Sirois <jsir...@apache.org> > wrote: > > > > > > > Context: Aurora uses the official Apache Thrift compiler today plus a > > > > home-grown python code generator [1] for immutable "entity" (I*) > > > wrappers. > > > > > > > > The proposal is to switch from using the Apache Thrift code generator > > to > > > a > > > > home grown generator. The proposal comes with a concrete example in > > the > > > > form of the actual RBs to effect this change: > > > > 1. A custom java thrift code generator: > > > > https://reviews.apache.org/r/42748/ > > > > 2. A custom MyBatis binding code generator powered by 1 above: > > > > https://reviews.apache.org/r/42749/ > > > > 3. Integration of 1 & 2 above into the Aurora codebase: > > > > https://reviews.apache.org/r/42756/ > > > > > > > > Since the RBs are large, I wanted to provide some extra context on > the > > > > idea at a higher level. I provide rationale, pros and cons below for > > > those > > > > interested in the idea but wary of diving in on code review until the > > > idea > > > > itself passes a sniff test. > > > > Thanks in advance for your feedback - and if we get there - for your > > > > review effort. > > > > > > > > > > I just added wfarner and zmanji as reviewers for the 3 RBs above since > > > they've expressed direct interest. Happy to add others, just speak up > or > > > else just comment on the reviews as you see fit. > > > I'll formally only submit if 1st this email thread reaches consensus, > and > > > second, reviews are approved. > > > > > > == > > > > > > > > In the course of an initial run at creating a first-class REST-like > > > > scheduler interface [2] I came to the conclusion generating the json > > API > > > > from the thrift one might be a good path. That idea has been > scrapped > > > with > > > > community feedback, but an initial experiment in custom thrift > code-gen > > > for > > > > java that accompanied that idea seemed worth pursuing for its own > > > > independent benefits, chief among these being 1st class immutable > > thrift > > > > structs and the ability to leverage thrift annotations. > > > > > > > > Immutability: > > > > The benefits of having an immutable by default data model are the > > > standard > > > > ones; namely, its trivial to reason about safety of concurrent > > operations > > > > on the data model, stability of collections containing data model > > > entities > > > > and it opens up straight-forward optimizations that are easy to > reason > > > > about. > > > > An example optimization is caching hashCodes for the immutable thrift > > > > structs. This was done after comparing jmh benchmarks run against > > master > > > > and then again against the proposal branch. Perf was comparable - > > within > > > > 10% plus and minus depending on the benchmark, but with the > > optimization > > > > added many benchmarks showed pronounced improvement in the proposal > > > branch > > > > [3]. The optimization is clearly safe and was quick and easy to > > > > implement. Further optimizations can be experimented with in a > > > > straightforward way. > > > > > > > > Thrift Annotations: > > > > The thrift IDL grammar has supported these for quite some time, but > > they > > > > are not plumbed to the generated java code. Uses are many and > > varied. I > > > > initially had my eye on annotation of thrift services with REST > verbs, > > > > routes, etc - but immediately we can leverage these annotations to > kill > > > > AnnotatedAuroraAdmin and reduce the amount of MyBatis binding code > that > > > > needs to be maintained. > > > > > > > > There are a few downsides to switching to our own java thrift code > gen: > > > > 1. We own more code to maintain: Even though we have the custom > python > > > > "immutable" wrapper generator [1] today, this new generator - even > with > > > the > > > > python generator removed - represents a 5-6x increase in line count > of > > > > custom code (~4.1k lines of code and tests in the new custom gen, > ~700 > > > > lines in the existing python custom gen) > > > > 2. We conceptually fork from a sibling Apache project. > > > > > > > > The fork could be mitigated by turning our real experience iterating > > the > > > > custom code generator into a well-founded patch back into the Apache > > > Thrift > > > > project, but saying we'll do that is easier than following through > and > > > > actually doing it. > > > > > > > > == > > > > Review guide / details: > > > > > > > > The technology stack: > > > > The thrift IDL parsing and thrift wire parsing are both handled by > the > > > > Facebook swift project [4]. We only implement the middle bit that > > > > generates java code stubs. This gives higher confidence that the > > tricky > > > > bits out at either edge are done right. > > > > The thrift struct code generation is done using Square's javapoet [5] > > in > > > > favor of templating for the purpose of easier to read generator code. > > > This > > > > characterization is debatable though and template are certainly more > > > > flexible the minute you need to gen a second language (say we like > this > > > and > > > > want to do javascript codegen this way too for example). > > > > The MyBatis codegen is forced by the thrift codegen for technical > > > > reasons. In short, there is no simple way to teach MyBatis to read > and > > > > write immutable objects with builders. So the MyBatis code is > > generated > > > > via an annotation processor that runs after thrift code gen, but > > reading > > > > thrift annotations that survive that codegen process. > > > > The codegen unit testing is done with the help of Google's > > compile-tester > > > > [6]. NB that this has an expected output comparison that checks the > > > > generated AST and not the text, so its fairly lenient. Whitepsace > and > > > > comments certainly don't matter. > > > > > > > > Review strategy: > > > > The code generator RBs (#1 & #2 in the 3 part series) are probably > > easier > > > > to review looking at samples of the generated code. Both the thrift > > > > codegen and MyBatis codegen samples are conveniently contained in the > > > > MyBatis codegen RB (#2: https://reviews.apache.org/r/42749/). The > > unit > > > > test uses resource files that contain both the thrift codegen inputs > > the > > > > annotation processor runs over and the annotation processor expected > > > > outputs - the MyBatis peer classes. So have a look there if you > need > > > > something concrete and don't want to patch the RBs in and actually > run > > > the > > > > codegen (`./gradlew api:compileJava`). > > > > The conversion RB (#3) is large but the changes are mainly mechanical > > > > conversions from the current mutable thrift + I* wrappers to pure > > > immutable > > > > thrift mutated via `.toBuilder` and `.with`'er methods. The main > > changes > > > > of note are to the portions of the codebase tightly tied to thrift > as a > > > > technology: > > > > + Gson/thrift converters > > > > + Shiro annotated auth param interception > > > > + Thrift/Servlet binding > > > > > > > > [1] > > > > > > > > > > https://github.com/apache/aurora/blob/master/src/main/python/apache/aurora/tools/java/thrift_wrapper_codegen.py > > > > [2] https://issues.apache.org/jira/browse/AURORA-987 > > > > [3] > > > > > > > > > > https://docs.google.com/spreadsheets/d/1-CYMnEjzknAsY5_r_NVX8r85wxtrEByZ5YRiAbgMhP0/edit#gid=840229346 > > > > [4] https://github.com/facebook/swift > > > > [5] https://github.com/square/javapoet > > > > [6] https://github.com/google/compile-testing > > > > > > > > > > -- > > > Zameer Manji > > > > > > > > >
