Big data beyond the JVM - DDTX 2018
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The document provides an overview of a presentation discussing Apache Spark, focusing on its functionalities, particularly in relation to non-JVM languages like Python. It highlights the challenges and advancements in using PySpark, including serialization costs and the benefits of Spark DataFrames. The presentation also addresses future developments in cross-language interoperability and the integration of new tools like Apache Arrow to enhance performance.
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From https://github.com/holdenk/kafka-streams-python-cthulhu](https://image.slidesharecdn.com/bigdatabeyondthejvm-ddtx2018-180127215307/85/Big-data-beyond-the-JVM-DDTX-2018-43-320.jpg)
Big data beyond the JVM - DDTX 2018
- 1. Big Data Beyond the JVM With a lot of a Spark focus
- 2. Rachel ● My name is Rachel ● Prefered pronouns are she/her ● Data scientist at Salesforce Einstein ● previously at Alpine ● co-author of High Performance Spark ● @warre_n_peace ● Slide share http://www.slideshare.net/rachelbwarren ● Linkedin https://www.linkedin.com/in/rachelbwarren
- 3. Holden: ● My name is Holden Karau ● Prefered pronouns are she/her ● Developer Advocate at Google ● Apache Spark PMC :) ● previously IBM, Alpine, Databricks, Google, Foursquare & Amazon ● co-author of Learning Spark & High Performance Spark ● @holdenkarau ● Slide share http://www.slideshare.net/hkarau ● Linkedin https://www.linkedin.com/in/holdenkarau ● Github https://github.com/holdenk ● Spark Videos http://bit.ly/holdenSparkVideos
- 5. Who is Boo? ● Boo uses she/her pronouns (as I told the Texas house committee) ● Best doge ● Lot’s of experience barking at computers to make them go faster ● Author of “Learning to Bark” & “High Performance Barking” ● On twitter @BooProgrammer
- 6. Who I think you wonderful humans are? ● Nice enough people ● Don’t mind pictures of cats ● Might know some Apache Spark - might not ● Possibly know some Python or R ● Or are tired of scala/ java Lori Erickson
- 7. What is Spark? ● General purpose distributed system ○ With a really nice API including Python :) ● Apache project (one of the most active) ● Must faster than Hadoop Map/Reduce ● Good when problems become too big for a single machine ● Built on top of two abstractions for distributed data: RDDs & Datasets
- 8. Spark specific terms in this talk ● RDD ○ Resilient Distributed Dataset - Like a distributed collection. Supports many of the same operations as Seq’s in Scala but automatically distributed and fault tolerant. Lazily evaluated, and handles faults by recompute. Any* Java or Kyro serializable object. ● DataFrame ○ Spark DataFrame - not a Pandas or R DataFrame. Distributed, supports a limited set of operations. Columnar structured, runtime schema information only. Limited* data types. Sql (ish) API ● Dataset ○ Compile time typed version of DataFrame (generic) skdevitt
- 9. What will be covered? ● A more detailed look at the current state of PySpark ● Why it isn’t good enough ● Why things are finally changing ● A brief tour of options for non-JVM languages in the Big Data space ● My even less subtle attempts to get you to buy my new book ● Pictures of cats & stuffed animals ● tl;dr - We’ve* made some bad** choices historically, and projects like Arrow & friends can save us from some of these (yay!)
- 10. What’s the state of non-JVM big data? Most of the tools are built in the JVM, so how do we play together? ● Pickling, Strings, JSON, XML, oh my! ● Unix pipes ● Sockets What about if we don’t want to copy the data all the time? ● Or standalone “pure”* re-implementations of everything ○ Reasonable option for things like Kafka where you would have the I/O regardless. ○ Also cool projects like dask (pure python) -- but hard to talk to existing ecosystem David Brown
- 11. PySpark: ● The Python interface to Spark ● Same general technique used as the bases for the C#, R, Julia, etc. interfaces to Spark ● Fairly mature, integrates well-ish into the ecosystem, less a Pythonrific API ● Has some serious performance hurdles from the design
- 12. Yes, we have wordcount! :p lines = sc.textFile(src) words = lines.flatMap(lambda x: x.split(" ")) word_count = (words.map(lambda x: (x, 1)) .reduceByKey(lambda x, y: x+y)) word_count.saveAsTextFile(output) No data is read or processed until after this line This is an “action” which forces spark to evaluate the RDD These are still combined and executed in one python executor Trish Hamme
- 13. A quick detour into PySpark’s internals + + JSON
- 14. Spark in Scala, how does PySpark work? ● Py4J + pickling + JSON and magic ○ Py4j in the driver ○ Pipes to start python process from java exec ○ cloudPickle to serialize data between JVM and python executors (transmitted via sockets) ○ Json for dataframe schema ● Data from Spark worker serialized and piped to Python worker --> then piped back to jvm ○ Multiple iterator-to-iterator transformations are still pipelined :) ○ So serialization happens only once per stage ● Spark SQL (and DataFrames) avoid some of this kristin klein
- 15. So what does that look like? Driver py4j Worker 1 Worker K pipe pipe
- 16. So how does that impact PySpark? ● Double serialization cost makes everything more expensive ● Python worker startup takes a bit of extra time ● Python memory isn’t controlled by the JVM - easy to go over container limits if deploying on YARN or similar ● Error messages make ~0 sense ● Spark Features aren’t automatically exposed, but exposing them is normally simple
- 17. Our saviour from serialization: DataFrames ● For the most part keeps data in the JVM ○ Notable exception is UDFs written in Python ● Takes our python calls and turns it into a query plan if we need more than the native operations in Spark’s DataFrames ● be wary of Distributed Systems bringing claims of usability…. Andy Blackledge
- 18. So what are Spark DataFrames? ● More than SQL tables ● Not Pandas or R DataFrames ● Semi-structured (have schema information) ● tabular ● work on expression as well as lambdas ○ e.g. df.filter(df.col(“happy”) == true) instead of rdd.filter(lambda x: x.happy == true)) ● Not a subset of Spark “Datasets” - since Dataset API isn’t exposed in Python yet :( Quinn Dombrowski
- 19. Word count w/Dataframes df = sqlCtx.read.load(src) # Returns an RDD words = df.select("text").flatMap(lambda x: x.text.split(" ")) words_df = words.map( lambda x: Row(word=x, cnt=1)).toDF() word_count = words_df.groupBy("word").sum() word_count.write.format("parquet").save("wc.parquet") Still have the double serialization here :(
- 20. We can see the difference easily: Andrew Skudder * *Vendor benchmark. Trust but verify.
- 21. *For a small price of your fun libraries. Proof-of-Concept.
- 22. That was a bad idea, buuut….. ● Work going on in Scala land to translate simple Scala into SQL expressions - need the Dataset API ○ Maybe we can try similar approaches with Python? ● Very early work going on to use Jython for simple UDFs (e.g. 2.7 compat & no native libraries) - SPARK-15369 ○ Early benchmarking w/word count 5% slower than native Scala UDF, close to 2x faster than regular Python ● Willing to share your Python UDFs for benchmarking? - http://bit.ly/pySparkUDF *The future may or may not have better performance than today. But bun-bun the bunny has some lettuce so its ok!
- 24. The “future”*: faster interchange ● By future I mean availability starting in the next 3-6 months (with more improvements after). ○ Yes much of this code exists, it just isn’t released yet so I’m sure we’ll find all sorts of bugs and ways to improve. ○ Relatedly you can help us test in Spark 2.3 when we start the RC process to catch bug early! ● Unifying our cross-language experience ○ And not just “normal” languages, CUDA counts yo Tambako The Jaguar
- 25. Andrew Skudder *Arrow: likely the future. I really hope so. Spark 2.3 and beyond! * *
- 26. What does the future look like?* *Source: https://databricks.com/blog/2017/10/30/introducing-vectorized-udfs-for-pyspark.html. *Vendor benchmark. Trust but verify.
- 27. Beyond wordcount: depencies? ● Your machines probably already have pandas ○ But maybe an old version ● But they might not have “special_business_logic” ○ Very special business logic, no one wants change fortran code*. ● Option 1: Talk to your vendor** ● Option 2: Try some sketchy open source software from a hack day ● We’re going to focus on option 2! *Because it’s perfect, it is fortran after all. ** I don’t like this option because the vendor I work for doesn’t have an answer.
- 28. coffee_boat to the rescue* # You can tell it's alpha cause were installing from github !pip install --upgrade git+https://github.com/nteract/coffee_boat.git # Use the coffee boat from coffee_boat import Captain captain = Captain(accept_conda_license=True) captain.add_pip_packages("pyarrow", "edtf") captain.launch_ship() sc = SparkContext(master="yarn") # You can now use pyarrow & edtf captain.add_pip_packages("yourmagic") # You can now use yourmagic in transformations!
- 29. Hadoop “streaming” (Python/R) ● Unix pipes! ● Involves a data copy, formats get sad ● But the overhead of a Map/Reduce task is pretty high anyways... Lisa Larsson
- 30. Kafka: re-implement all the things ● Multiple options for connecting to Kafka from outside of the JVM (yay!) ● They implement the protocol to talk to Kafka (yay!) ● This involves duplicated client work, and sometimes the clients can be slow (solution, FFI bindings to C instead of Java) ● Buuuut -- we can’t access all of the cool Kafka business (like Kafka Streams) and features depend on client libraries implementing them (easy to slip below parity) Smokey Combs
- 31. Dask: a new beginning? ● Pure* python implementation ● Provides real enough DataFrame interface for distributed data ● Also your standard-ish distributed collections ● Multiple backends ● Primary challenge: interacting with the rest of the big data ecosystem ○ Arrow & friends might make this better with time too, buuut…. ● See https://dask.pydata.org/en/latest/ & http://dask.pydata.org/en/latest/spark.html Lisa Zins
- 32. BEAM Beyond the JVM ● Non JVM BEAM doesn’t work outside of Google’s environment yet, so I’m going to skip the details. ● tl;dr : uses grpc / protobuf ● But exciting new plans to unify the runners and ease the support of different languages (called SDKS) ○ See https://beam.apache.org/contribute/portability/ ● If this is exciting, you can come join me on making BEAM work in Python3 ○ Yes we still don’t have that :( ○ But we're getting closer!
- 33. Why now? ● There’s been better formats/options for a long time ● JVM devs want to use libraries in other languages with lots of data ○ e.g. startup + Deep Learning + ? => profit ● Arrow has solved the chicken-egg problem by building not just the chicken & the egg, but also a hen house Andrew Mager
- 34. References ● Apache Arrow: https://arrow.apache.org/ ● Brian (IBM) on initial Spark + Arrow https://arrow.apache.org/blog/2017/07/26/spark-arrow/ ● Li Jin (two sigma) https://databricks.com/blog/2017/10/30/introducing-vectorized-udfs-for-pyspar k.html ● Bill Maimone https://blogs.nvidia.com/blog/2017/06/27/gpu-computation-visualization/
- 35. Learning Spark Fast Data Processing with Spark (Out of Date) Fast Data Processing with Spark (2nd edition) Advanced Analytics with Spark Spark in Action High Performance SparkLearning PySpark
- 36. High Performance Spark! You can buy it today! Only one chapter on non-JVM stuff, I’m sorry. Cats love it* *Or at least the box it comes in. If buying for a cat, get print rather than e-book.
- 37. Spark Videos ● Apache Spark Youtube Channel ● My Spark videos on YouTube - ○ http://bit.ly/holdenSparkVideos ● Spark Summit 2014 training ● Paco’s Introduction to Apache Spark
- 38. And some upcoming talks: ● Feb ○ FOSDEM - One on testing one on scaling ○ JFokus in Stockholm - Adding deep learning to Spark ○ I disappear for a week and pretend computers work ● March ○ Strata San Jose - Big Data Beyond the JVM ■ You can give us feedback so that one rocks more
- 39. k thnx bye :) If you care about Spark testing and don’t hate surveys: http://bit.ly/holdenTestingSpark I need to give a testing talk next month, help a “friend” out. Will tweet results “eventually” @holdenkarau Do you want more realistic benchmarks? Share your UDFs! http://bit.ly/pySparkUDF Pssst: Have feedback on the presentation? Give me a shout ([email protected]) if you feel comfortable doing so :)
- 40. Bonus Slides Maybe you ask a question and we go here :)
- 41. We can do that w/Kafka streams.. ● Why bother learning from our mistakes? ● Or more seriously, the mistakes weren’t that bad...
- 42. Our “special” business logic def transform(input): """ Transforms the supplied input. """ return str(len(input)) Pargon
- 43. Let’s pretend all the world is a string: override def transform(value: String): String = { // WARNING: This may summon cuthuluhu dataOut.writeInt(value.getBytes.size) dataOut.write(value.getBytes) dataOut.flush() val resultSize = dataIn.readInt() val result = new Array[Byte](resultSize) dataIn.readFully(result) // Assume UTF8, what could go wrong? :p new String(result) } From https://github.com/holdenk/kafka-streams-python-cthulhu
- 44. Then make an instance to use it... val testFuncFile = "kafka_streams_python_cthulhu/strlen.py" stream.transformValues( PythonStringValueTransformerSupplier(testFuncFile)) // Or we could wrap this in the bridge but thats effort. From https://github.com/holdenk/kafka-streams-python-cthulhu
- 45. Let’s pretend all the world is a string: def main(socket): while (True): input_length = _read_int(socket) data = socket.read(input_length) result = transform(data) resultBytes = result.encode() _write_int(len(resultBytes), socket) socket.write(resultBytes) socket.flush() From https://github.com/holdenk/kafka-streams-python-cthulhu
- 46. What does that let us do? ● You can add a map stage with your data scientists Python code in the middle ● You’re limited to strings* ● Still missing the “driver side” integration (e.g. the interface requires someone to make a Scala class at some point)
- 47. What about things other than strings? Use another system ● Like Spark! (oh wait) or BEAM* or FLINK*? Write it in a format Python can understand: ● Pickling (from Java) ● JSON ● XML Purely Python solutions ● Currently roll-your-own (but not that bad) *These are also JVM based solutions calling into Python. I’m not saying they will also summon Cuthulhu, I’m just saying hang onto