C* Summit 2013: Real-time Analytics using Cassandra, Spark and Shark by Evan Chan
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This session covers our experience with using the Spark and Shark frameworks for running real-time queries on top of Cassandra data.We will start by surveying the current Cassandra analytics landscape, including Hadoop and HIVE, and touch on the use of custom input formats to extract data from Cassandra. We will then dive into Spark and Shark, two memory-based cluster computing frameworks, and how they enable often dramatic improvements in query speed and productivity, over the standard solutions today.
![Spark word count example
file = spark.textFile("hdfs://...")
file.flatMap(line => line.split(" "))
.map(word => (word, 1))
.reduceByKey(_ + _)
1 package org.myorg;
2
3 import java.io.IOException;
4 import java.util.*;
5
6 import org.apache.hadoop.fs.Path;
7 import org.apache.hadoop.conf.*;
8 import org.apache.hadoop.io.*;
9 import org.apache.hadoop.mapreduce.*;
10 import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
11 import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
12 import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
13 import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
14
15 public class WordCount {
16
17 public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> {
18 private final static IntWritable one = new IntWritable(1);
19 private Text word = new Text();
20
21 public void map(LongWritable key, Text value, Context context) throws IOException,
InterruptedException {
22 String line = value.toString();
23 StringTokenizer tokenizer = new StringTokenizer(line);
24 while (tokenizer.hasMoreTokens()) {
25 word.set(tokenizer.nextToken());
26 context.write(word, one);
27 }
28 }
29 }
30
31 public static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> {
32
33 public void reduce(Text key, Iterable<IntWritable> values, Context context)
34 throws IOException, InterruptedException {
35 int sum = 0;
36 for (IntWritable val : values) {
37 sum += val.get();
38 }
39 context.write(key, new IntWritable(sum));
40 }
41 }
42
43 public static void main(String[] args) throws Exception {
44 Configuration conf = new Configuration();
45
46 Job job = new Job(conf, "wordcount");
47
48 job.setOutputKeyClass(Text.class);
49 job.setOutputValueClass(IntWritable.class);
50
51 job.setMapperClass(Map.class);
52 job.setReducerClass(Reduce.class);
53
54 job.setInputFormatClass(TextInputFormat.class);
55 job.setOutputFormatClass(TextOutputFormat.class);
56
57 FileInputFormat.addInputPath(job, new Path(args[0]));
58 FileOutputFormat.setOutputPath(job, new Path(args[1]));
59
60 job.waitForCompletion(true);
61 }
62
63 }](https://image.slidesharecdn.com/2evanchan-130619113837-phpapp01/85/C-Summit-2013-Real-time-Analytics-using-Cassandra-Spark-and-Shark-by-Evan-Chan-22-320.jpg)
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C* Summit 2013: Real-time Analytics using Cassandra, Spark and Shark by Evan Chan
- 1. Real-time Analytics with Cassandra, Spark and Shark
- 2. Who is this guy • Staff Engineer, Compute and Data Services, Ooyala • Building multiple web-scale real-time systems on top of C*, Kafka, Storm, etc. • Scala/Akka guy • Very excited by open source, big data projects - share some today • @evanfchan
- 3. Agenda • Ooyala and Cassandra • What problem are we trying to solve? • Spark and Shark • Our Spark/Cassandra Architecture • Demo
- 4. Cassandra at Ooyala Who is Ooyala, and how we use Cassandra
- 5. CONFIDENTIAL—DO NOT DISTRIBUTE OOYALA Powering personalized video experiences across all screens. 5
- 6. CONFIDENTIAL—DO NOT DISTRIBUTE 6CONFIDENTIAL—DO NOT DISTRIBUTE Founded in 2007 Commercially launch in 2009 230+ employees in Silicon Valley, LA, NYC, London, Paris, Tokyo, Sydney & Guadalajara Global footprint, 200M unique users, 110+ countries, and more than 6,000 websites Over 1 billion videos played per month and 2 billion analytic events per day 25% of U.S. online viewers watch video powered by Ooyala COMPANY OVERVIEW
- 7. CONFIDENTIAL—DO NOT DISTRIBUTE 7 TRUSTED VIDEO PARTNER STRATEGIC PARTNERS CUSTOMERS CONFIDENTIAL—DO NOT DISTRIBUTE
- 8. We are a large Cassandra user • 12 clusters ranging in size from 3 to 115 nodes • Total of 28TB of data managed over ~200 nodes • Largest cluster - 115 nodes, 1.92PB storage, 15TB RAM • Over 2 billion C* column writes per day • Powers all of our analytics infrastructure
- 9. What problem are we trying to solve? Lots of data, complex queries, answered really quickly... but how??
- 10. From mountains of useless data...
- 11. To nuggets of truth...
- 12. To nuggets of truth... • Quickly • Painlessly • At scale?
- 13. Today: Precomputed aggregates • Video metrics computed along several high cardinality dimensions • Very fast lookups, but inflexible, and hard to change • Most computed aggregates are never read • What if we need more dynamic queries? – Top content for mobile users in France – Engagement curves for users who watched recommendations – Data mining, trends, machine learning
- 14. The static - dynamic continuum • Super fast lookups • Inflexible, wasteful • Best for 80% most common queries • Always compute results from raw data • Flexible but slow 100% Precomputation 100% Dynamic
- 15. Where we want to be Partly dynamic • Pre-aggregate most common queries • Flexible, fast dynamic queries • Easily generate many materialized views
- 16. Industry Trends • Fast execution frameworks – Impala • In-memory databases – VoltDB, Druid • Streaming and real-time • Higher-level, productive data frameworks – Cascading, Hive, Pig
- 17. Why Spark and Shark? “Lightning-fast in-memory cluster computing”
- 18. Introduction to Spark • In-memory distributed computing framework • Created by UC Berkeley AMP Lab in 2010 • Targeted problems that MR is bad at: – Iterative algorithms (machine learning) – Interactive data mining • More general purpose than Hadoop MR • Active contributions from ~ 15 companies
- 20. Throughput: Memory is king 0 37500 75000 112500 150000 C*, cold cache C*, warm cache Spark RDD 6-‐node C*/DSE 1.1.9 cluster, Spark 0.7.0
- 21. Developers love it • “I wrote my first aggregation job in 30 minutes” • High level “distributed collections” API • No Hadoop cruft • Full power of Scala, Java, Python • Interactive REPL shell • EASY testing!! • Low latency - quick development cycles
- 22. Spark word count example file = spark.textFile("hdfs://...") file.flatMap(line => line.split(" ")) .map(word => (word, 1)) .reduceByKey(_ + _) 1 package org.myorg; 2 3 import java.io.IOException; 4 import java.util.*; 5 6 import org.apache.hadoop.fs.Path; 7 import org.apache.hadoop.conf.*; 8 import org.apache.hadoop.io.*; 9 import org.apache.hadoop.mapreduce.*; 10 import org.apache.hadoop.mapreduce.lib.input.FileInputFormat; 11 import org.apache.hadoop.mapreduce.lib.input.TextInputFormat; 12 import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat; 13 import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat; 14 15 public class WordCount { 16 17 public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> { 18 private final static IntWritable one = new IntWritable(1); 19 private Text word = new Text(); 20 21 public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { 22 String line = value.toString(); 23 StringTokenizer tokenizer = new StringTokenizer(line); 24 while (tokenizer.hasMoreTokens()) { 25 word.set(tokenizer.nextToken()); 26 context.write(word, one); 27 } 28 } 29 } 30 31 public static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> { 32 33 public void reduce(Text key, Iterable<IntWritable> values, Context context) 34 throws IOException, InterruptedException { 35 int sum = 0; 36 for (IntWritable val : values) { 37 sum += val.get(); 38 } 39 context.write(key, new IntWritable(sum)); 40 } 41 } 42 43 public static void main(String[] args) throws Exception { 44 Configuration conf = new Configuration(); 45 46 Job job = new Job(conf, "wordcount"); 47 48 job.setOutputKeyClass(Text.class); 49 job.setOutputValueClass(IntWritable.class); 50 51 job.setMapperClass(Map.class); 52 job.setReducerClass(Reduce.class); 53 54 job.setInputFormatClass(TextInputFormat.class); 55 job.setOutputFormatClass(TextOutputFormat.class); 56 57 FileInputFormat.addInputPath(job, new Path(args[0])); 58 FileOutputFormat.setOutputPath(job, new Path(args[1])); 59 60 job.waitForCompletion(true); 61 } 62 63 }
- 23. The Spark Ecosystem Bagel -‐ Pregel on Spark HIVE on Spark Spark Streaming -‐ discreRzed stream processing Spark Tachyon -‐ in-‐memory caching DFS
- 24. Shark - HIVE on Spark • 100% HiveQL compatible • 10-100x faster than HIVE, answers in seconds • Reuse UDFs, SerDe’s, StorageHandlers • Can use DSE / CassandraFS for Metastore • Easy Scala/Java integration via Spark - easier than writing UDFs
- 25. Our new analytics architecture How we integrate Cassandra and Spark/Shark
- 26. From raw events to fast queries IngesRon C* event store Raw Events Raw Events Raw Events Spark Spark Spark View 1 View 2 View 3 Spark Shark Predefined queries Ad-‐hoc HiveQL
- 27. Our Spark/Shark/Cassandra Stack Node1 Cassandra InputFormat SerDe Spark Worker Shark Node2 Cassandra InputFormat SerDe Spark Worker Shark Node3 Cassandra InputFormat SerDe Spark Worker Shark Spark Master Job Server
- 28. Event Store Cassandra schema t0 t1 t2 t3 t4 2013-‐04-‐05T00: 00Z#id1 {event0: a0} {event1: a1} {event2: a2} {event3: a3} {event4: a4} ipaddr:10.20.30.40:t1 videoId:45678:t1 providerId:500:t0 2013-‐04-‐05T00: 00Z#id1 Event CF EventAfr CF
- 29. Unpacking raw events t0 t1 2013-‐04-‐05T00: 00Z#id1 {video: 10, type:5} {video: 11, type:1} 2013-‐04-‐05T00: 00Z#id2 {video: 20, type:5} {video: 25, type:9} UserID Video Type id1 10 5
- 30. Unpacking raw events t0 t1 2013-‐04-‐05T00: 00Z#id1 {video: 10, type:5} {video: 11, type:1} 2013-‐04-‐05T00: 00Z#id2 {video: 20, type:5} {video: 25, type:9} UserID Video Type id1 10 5 id1 11 1
- 31. Unpacking raw events t0 t1 2013-‐04-‐05T00: 00Z#id1 {video: 10, type:5} {video: 11, type:1} 2013-‐04-‐05T00: 00Z#id2 {video: 20, type:5} {video: 25, type:9} UserID Video Type id1 10 5 id1 11 1 id2 20 5
- 32. Unpacking raw events t0 t1 2013-‐04-‐05T00: 00Z#id1 {video: 10, type:5} {video: 11, type:1} 2013-‐04-‐05T00: 00Z#id2 {video: 20, type:5} {video: 25, type:9} UserID Video Type id1 10 5 id1 11 1 id2 20 5 id2 25 9
- 33. Tips for InputFormat Development • Know which target platforms you are developing for – Which API to write against? New? Old? Both? • Be prepared to spend time tuning your split computation – Low latency jobs require fast splits • Consider sorting row keys by token for data locality • Implement predicate pushdown for HIVE SerDe’s – Use your indexes to reduce size of dataset
- 34. Example: OLAP processing t0 2013-‐04-‐0 5T00:00Z#i d1 {video: 10, type:5} 2013-‐04-‐0 5T00:00Z#i d2 {video: 20, type:5} C* events OLAP Aggregates OLAP Aggregates OLAP Aggregates Cached Materialized Views Spark Spark Spark Union Query 1: Plays by Provider Query 2: Top content for mobile
- 35. Performance numbers Spark: C* -‐> OLAP aggregates cold cache, 1.4 million events 130 seconds C* -‐> OLAP aggregates warmed cache 20-‐30 seconds OLAP aggregate query via Spark (56k records) 60 ms 6-‐node C*/DSE 1.1.9 cluster, Spark 0.7.0
- 36. Spark: Under the hood Map DatasetReduce Map Driver Map DatasetReduce Map Map DatasetReduce Map One executor process per node Driver
- 37. Fault Tolerance • Cached dataset lives in Java Heap only - what if process dies? • Spark lineage - automatic recomputation from source, but this is expensive! • Can also replicate cached dataset to survive single node failures • Persist materialized views back to C*, then load into cache -- now recovery path is much faster • Persistence also enables multiple processes to hold cached dataset
- 38. Demo time
- 39. Shark Demo • Local shark node, 1 core, MBP • How to create a table from C* using our inputformat • Creating a cached Shark table • Running fast queries
- 40. Backup Slides • THE NEXT FEW SLIDES ARE STRICTLY BACKUP IN CASE LIVE DEMO DOESN’T WORK
- 41. Creating a Shark Table from InputFormat
- 42. Creating a cached table
- 43. Doing a row count ... don’t try in HIVE!
- 44. Top k providerId query
- 45. THANK YOU