Wrapping C++ Arrow Why and How? – Yoni Davidson

Transcript

1. Wrapping C++ Arrow Why and How? Yoni Davidson Bond
2. About me! Married + 1 + 4 Data Architect and SW engineer at Bond. Before: Sears Israel. Eyesight mobile. Alvarion.
3. Motivation Moving data around is expensive (Serialization and Deserialization) - IO between Services and languages is expensive.
4. What is Apache Arrow? Apache Arrow is a cross-language development platform for in-memory data. zero-copy streaming messaging and interprocess communication. Languages currently supported include C, C++, C#, Go, Java, JavaScript, MATLAB, Python, R, Ruby, and Rust.
5. What is Apache Arrow? Advantages of a Common Data Layer
6. What is Apache Arrow? Performance Advantage of Columnar In-Memory
7. What is Apache Arrow?
8. Apache Arrow Flight: A Framework for Fast Data Transport
9. Snowflake DWH with Arrow
10. Moving data around
11. Who is leading the work on Apache Arrow?
12. What is Language Binding?
13. Where do we find language bindings ?
14. Language bindings - Kafka
15. Apache Arrow Language bindings status
16. Apache Arrow Python bindings Based on the C++ project. Built with Cython. Allows integration with the massive Python ecosystem.
17. Possible Awesome Usages Sharing table with Python in same memory space. 0 serialization Sharing table with Python in between services. 0 serialization
18. Pros: 1. “Closed problem”. 2. It gives you all the advantages of Arrow (to date). 3. Go allows us to improve the implementation. Implement spec in pure Go Cons: 1. Hard to follow up the changes. 2. Harder to maintain. 3. Hard to insert improvements back to the C++.
19. Implement spec in pure Go
20. carrow - Go bindings to Apache Arrow via C++ API https://github.com/353solutions/carrow
21. Go bindings to Apache Arrow via C++ Pros: 1. This project enjoys all the C++ main branch improvements. 2. Any addition that we create using the Go project we can export back to Python/C++ project. Cons: 1. It's much harder ...
22. Challenge 1 - Go and C++ - don’t link C++ compilers do symbols mangling CGo doesn’t support it and a C wrapper is needed.
23. Challenge 1 - Go and C++ - don’t link #ifndef _CARROW_H_ #define _CARROW_H_ #ifdef __cplusplus extern "C" { #endif void *table_new(void *sp, void *cp); #ifdef __cplusplus } #endif // extern "C" #endif // #ifdef _CARROW_H_
24. Challenge 2 - Building a C++/Go project C++ libs and headers are required, this means that the dev env’ is more complex than a Go project. Solution is a Dockerfile that has Native C++ and Python bindings for E2E tests.
25. FROM ubuntu:18.04 # Tools RUN apt-get update && apt-get install -y \ gdb \ git \ ... # Go installation ... Challenge 2 - Building a C++/Go project
26. Challenge 2 - Building a C++/Go project # Python bindings RUN cd /tmp && \ wget https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh && \ bash Miniconda3-latest-Linux-x86_64.sh -b -p /miniconda && \ rm Miniconda3-latest-Linux-x86_64.sh ENV PATH="/miniconda/bin:${PATH}" RUN conda install -y \ Cython \ conda-forge::compilers \ conda-forge::pyarrow=0.14 \ ... ENV LD_LIBRARY_PATH=/miniconda/lib WORKDIR /src/carrow
27. Challenge 3 - Wrapper for each type Since this is a wrapper lib, there is a need to do a lot of “copy pasta” code to wrap each type. Solution was to use go template and generate some of the code.
28. Challenge 3 - Wrapper for each type func main() { arrowTypes := []string{"Bool", "Float64", "Integer64", "String", "Timestamp"} . . . // Supported data types var( {{- range $val := .ArrowTypes}} {{$val}}Type = DType(C.{{$val | ToUpper }}_DTYPE) {{- end}} )
29. Challenge 4 - Logger Do we send all our errors up the stream to the Go package for logging ? We can also create a Go logger and throw it down to the C++ code for logging.
30. Challenge 5 - Error handling Where are errors handled ? Where is the best place to log and handle them? For now - every call returns this result_t typedef struct { const char *err; void *ptr; int64_t i; } result_t
31. Challenge 666 - Memory management 2 memory managers. 1. Go runtime - Automatic memory management. 2. C++ runtime - Apache arrow uses std::shared_ptr extensively.
32. Wrap std::shared_ptr with a struct - so we know who owns the memory. Challenge 666 - Memory management struct Table { std::shared_ptr<arrow::Table> table; };
33. Use finalizer to free memory. Challenge 666 - Memory management // NewSchema creates a new schema func NewSchema(fields []*Field) (*Schema, error) { fieldsList, err := NewFieldList() if err != nil { return nil, fmt.Errorf("can't create schema,failed creating fields list") } . . . schema := &Schema{ptr} runtime.SetFinalizer(schema, func(s *Schema) { C.schema_free(s.ptr) }) return schema, nil }
34. Challenge 7 - cgo is FFI FFI - Foreign function interface https://github.com/dyu/ffi-overhead Results (500M calls) c: 1182 1182 c++: 1182 1183 Go: 37975 37879
35. Try and reduce unneeded cgo calls - Builder pattern: Challenge 7 - cgo is FFI func TestAppendInt64(t *testing.T) { bld := NewInteger64ArrayBuilder() const size = 20913 for i := int64(0); i < size; i++ { err := bld.Append(i) require.NoErrorf(err, "append %d", i) } arr, err := bld.Finish() }
36. Challenge 8 - Making package Go getable This lib is linked to a specific Arrow version in a specific OS (Linux AMD64 for example). Do we precompile for each OS? Add to Readme what packages need to be installed alongside?
37. Challenge 8 - Making package Go getable package carrow import ( "fmt" "runtime" "time" "unsafe" ) /* #cgo pkg-config: arrow plasma #cgo LDFLAGS: -lcarrow #cgo linux LDFLAGS: -L./bindings/linux-x86_64 #cgo CXXFLAGS: -I/src/arrow/cpp/src #include "carrow.h" #include <stdlib.h> */ import "C" //go:generate go run gen.go //go:generate go fmt
38. carrow status Adding more features (More data types). Building good use-cases, Flight! Adding our project to main Apache Arrow Repo.
39. Questions?
40. Thank you https://github.com/yonidavidson https://www.linkedin.com/in/yoni-davidson-35b53222/ https://twitter.com/yonidavidson https://github.com/353solutions/carrow
41. How fast is it - https://ursalabs.org/blog/2019-10-columnar-perf/