- The document discusses Spark/Cassandra connector API, best practices, and use cases. - It describes the connector architecture including support for Spark Core, SQL, and Streaming APIs. Data is read from and written to Cassandra tables mapped as RDDs. - Best practices around data locality, failure handling, and cross-region/cluster operations are covered. Locality is important for performance. - Use cases include data cleaning, schema migration, and analytics like joins and aggregation. The connector allows processing and analytics on Cassandra data with Spark.

1. @doanduyhai
Spark/Cassandra connector
API, Best Practices & Use-Cases
DuyHai DOAN, Technical Advocate

2. @doanduyhai
Who Am I ?!
Duy Hai DOAN
Cassandra technical advocate
• talks, meetups, confs
• open-source devs (Achilles, …)
• OSS Cassandra point of contact
☞ duy_hai.doan@datastax.com
☞ @doanduyhai
2

3. @doanduyhai
Datastax!
• Founded in April 2010
• We contribute a lot to Apache Cassandra™
• 400+ customers (25 of the Fortune 100), 200+ employees
• Headquarter in San Francisco Bay area
• EU headquarter in London, offices in France and Germany
• Datastax Enterprise = OSS Cassandra + extra features
3

4. @doanduyhai
Agenda!
• Connector API by example
• Best practices
• Use-cases
• The “Big Data Platform”
4

5. Spark/Cassandra connector API!
Spark Core!
Spark SQL!
Spark Streaming!
!

6. @doanduyhai
Connector architecture!
All Cassandra types supported and converted to Scala types
Server side data filtering (SELECT … WHERE …)
Use Java-driver underneath
!
Scala and Java support
6

7. @doanduyhai
Connector architecture – Core API!
Cassandra tables exposed as Spark RDDs
Read from and write to Cassandra
Mapping of Cassandra tables and rows to Scala objects
• CassandraRow
• Scala case class (object mapper)
• Scala tuples
7

8. Spark Core
https://github.com/doanduyhai/Cassandra-Spark-Demo

9. @doanduyhai
Connector architecture – Spark SQL !
Mapping of Cassandra table to SchemaRDD
• CassandraSQLRow à SparkRow
• custom query plan
• push predicates to CQL for early filtering
SELECT * FROM user_emails WHERE login = ‘jdoe’;
9

10. Spark SQL
https://github.com/doanduyhai/Cassandra-Spark-Demo

11. @doanduyhai
Connector architecture – Spark Streaming !
Streaming data INTO Cassandra table
• trivial setup
• be careful about your Cassandra data model when having an infinite
stream !!!
Streaming data OUT of Cassandra tables (CDC) ?
• work in progress …
11

12. Spark Streaming
https://github.com/doanduyhai/Cassandra-Spark-Demo

13. Q & R
! "!

14. Spark/Cassandra best practices!
Data locality!
Failure handling!
Cross-region operations!

15. @doanduyhai
Cluster deployment!
C*
SparkM
SparkW
C*
SparkW
C*
SparkW
C*
SparkW
C*
SparkW
Stand-alone cluster
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16. @doanduyhai
Remember token ranges ?!
A: ]0, X/8]
B: ] X/8, 2X/8]
C: ] 2X/8, 3X/8]
D: ] 3X/8, 4X/8]
E: ] 4X/8, 5X/8]
F: ] 5X/8, 6X/8]
G: ] 6X/8, 7X/8]
H: ] 7X/8, X]
n1
n2
n3
n4
n5
n6
n7
n8
A
B
C
D
E
F
G
H
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17. @doanduyhai
Data Locality!
C*
SparkM
SparkW
C*
SparkW
C*
SparkW
C*
SparkW
C*
SparkW
Spark partition RDD
Cassandra
tokens ranges
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18. @doanduyhai
Data Locality!
C*
SparkM
SparkW
C*
SparkW
C*
SparkW
C*
SparkW
C*
SparkW
Use Murmur3Partitioner
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19. @doanduyhai
Read data locality!
Read from Cassandra
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20. @doanduyhai
Read data locality!
Spark shuffle operations
20

21. @doanduyhai
Write to Cassandra without data locality!
Async batches fan-out writes to Cassandra
21
Because of shuffle, original data locality is lost

22. @doanduyhai
Or repartition before write !
Write to Cassandra
rdd.repartitionByCassandraReplica("keyspace","table")
22

23. @doanduyhai
Write data locality!
23
• either stream data in Spark layer using repartitionByCassandraReplica()
• or flush data to Cassandra by async batches
• in any case, there will be data movement on network (sorry no magic)

24. @doanduyhai
Joins with data locality!
24
CREATE TABLE artists(name text, style text, … PRIMARY KEY(name));
CREATE TABLE albums(title text, artist text, year int,… PRIMARY KEY(title));
val join: CassandraJoinRDD[(String,Int), (String,String)] =
sc.cassandraTable[(String,Int)](KEYSPACE, ALBUMS)
// Select only useful columns for join and processing
.select("artist","year")
.as((_:String, _:Int))
// Repartition RDDs by "artists" PK, which is "name"
.repartitionByCassandraReplica(KEYSPACE, ARTISTS)
// Join with "artists" table, selecting only "name" and "country" columns
.joinWithCassandraTable[(String,String)](KEYSPACE, ARTISTS, SomeColumns("name","country"))
.on(SomeColumns("name"))

25. @doanduyhai
Joins pipeline with data locality!
25
LOCAL READ
FROM CASSANDRA

26. @doanduyhai
Joins pipeline with data locality!
26
SHUFFLE DATA
WITH SPARK

27. @doanduyhai
Joins pipeline with data locality!
27
REPARTITION TO MAP
CASSANDRA REPLICA

28. @doanduyhai
Joins pipeline with data locality!
28
JOIN WITH
DATA LOCALITY

29. @doanduyhai
Joins pipeline with data locality!
29
ANOTHER ROUND
OF SHUFFLING

30. @doanduyhai
Joins pipeline with data locality!
30
REPARTITION AGAIN
FOR CASSANDRA

31. @doanduyhai
Joins pipeline with data locality!
31
SAVE TO CASSANDRA
WITH LOCALITY

32. @doanduyhai
Perfect data locality scenario!
32
• read localy from Cassandra
• use operations that do not require shuffle in Spark (map, filter, …)
• repartitionbyCassandraReplica()
• à to a table having same partition key as original table
• save back into this Cassandra table
Sanitize, validate, normalize, transform data
USE CASE

33. @doanduyhai
Failure handling!
Stand-alone cluster
33
C*
SparkM
SparkW
C*
SparkW
C*
SparkW
C*
SparkW
C*
SparkW

34. @doanduyhai
Failure handling!
What if 1 node down ?
What if 1 node overloaded ?
34
C*
SparkM
SparkW
C*
SparkW
C*
SparkW
C*
SparkW
C*
SparkW

35. @doanduyhai
Failure handling!
What if 1 node down ?
What if 1 node overloaded ?
☞ Spark masterwill re-assign
the job to another worker
35
C*
SparkM
SparkW
C*
SparkW
C*
SparkW
C*
SparkW
C*
SparkW

36. @doanduyhai
Failure handling!
Oh no, my data locality !!!
36

37. @doanduyhai
Failure handling!
37

38. @doanduyhai
Data Locality Impl!
38
Remember RDD interface ?
abstract'class'RDD[T](…)'{'
' @DeveloperApi'
' def'compute(split:'Partition,'context:'TaskContext):'Iterator[T]'
'
' protected'def'getPartitions:'Array[Partition]'
' '
' protected'def'getPreferredLocations(split:'Partition):'Seq[String]'='Nil''''''''
}'

39. @doanduyhai
Data Locality Impl!
39
def getPreferredLocations(split: Partition): Cassandra replicas IP address
corresponding to this Spark partition

40. @doanduyhai
Failure handling!
If RF > 1 the Spark master chooses
the next preferred location, which
is a replica 😎
Tune parameters:
① spark.locality.wait
② spark.locality.wait.process
③ spark.locality.wait.node
40
C*
SparkM
SparkW
C*
SparkW
C*
SparkW
C*
SparkW
C*
SparkW

41. @doanduyhai
val confDC1 = new SparkConf(true)
.setAppName("data_migration")
.setMaster("master_ip")
.set("spark.cassandra.connection.host", "DC_1_hostnames")
.set("spark.cassandra.connection.local_dc", "DC_1")
val confDC2 = new SparkConf(true)
.setAppName("data_migration")
.setMaster("master_ip")
.set("spark.cassandra.connection.host", "DC_2_hostnames")
.set("spark.cassandra.connection.local_dc", "DC_2 ")
val sc = new SparkContext(confDC1)
sc.cassandraTable[Performer](KEYSPACE,PERFORMERS)
.map[Performer](???)
.saveToCassandra(KEYSPACE,PERFORMERS)
(CassandraConnector(confDC2),implicitly[RowWriterFactory[Performer]])
Cross-DC operations!
41

42. @doanduyhai
val confCluster1 = new SparkConf(true)
.setAppName("data_migration")
.setMaster("master_ip")
.set("spark.cassandra.connection.host", "cluster_1_hostnames")
val confCluster2 = new SparkConf(true)
.setAppName("data_migration")
.setMaster("master_ip")
.set("spark.cassandra.connection.host", "cluster_2_hostnames")
val sc = new SparkContext(confCluster1)
sc.cassandraTable[Performer](KEYSPACE,PERFORMERS)
.map[Performer](???)
.saveToCassandra(KEYSPACE,PERFORMERS)
(CassandraConnector(confCluster2),implicitly[RowWriterFactory[Performer]])
Cross-cluster operations!
42

43. Q & R
! "!

44. Spark/Cassandra use-cases!
Data cleaning!
Schema migration!
Analytics!
!

45. @doanduyhai
Use Cases!
Load data from various
sources
Analytics (join, aggregate, transform, …)
Sanitize, validate, normalize, transform data
Schema migration,
Data conversion
45

46. @doanduyhai
Data cleaning use-cases!
46
Bug in your application ?
Dirty input data ?
☞ Spark job to clean it up! (perfect data locality)
Sanitize, validate, normalize, transform data

47. Data Cleaning
https://github.com/doanduyhai/Cassandra-Spark-Demo

48. @doanduyhai
Schema migration use-cases!
48
Business requirements change with time ?
Current data model no longer relevant ?
☞ Spark job to migrate data !
Schema migration,
Data conversion

49. Data Migration
https://github.com/doanduyhai/Cassandra-Spark-Demo

50. @doanduyhai
Analytics use-cases!
50
Given existing tables of performers and albums, I want:
① top 10 most common music styles (pop,rock, RnB, …) ?
② performer productivity(albums count) by origin country and by
decade ?
☞ Spark job to compute analytics !
Analytics (join, aggregate, transform, …)

51. @doanduyhai
Analytics pipeline!
51
① Read from production transactional tables
② Perform aggregation with Spark
③ Save back data into dedicated tables for fast visualization
④ Repeat step ①

52. Analytics
https://github.com/doanduyhai/Cassandra-Spark-Demo

53. Q & R
! "!

54. The “Big Data Platform”!

55. @doanduyhai
Our vision!
55
We had a dream …
to provide a Big Data Platform …
built for the performance & high availabitly demands
of IoT, web & mobile applications

56. @doanduyhai
Until now in Datastax Enterprise!
Cassandra + Solr in same JVM
Unlock full text search power for Cassandra
CQL syntax extension
56
SELECT * FROM users WHERE solr_query = ‘age:[33 TO *] AND gender:male’;
SELECT * FROM users WHERE solr_query = ‘lastname:*schwei?er’;

57. Cassandra + Solr

58. @doanduyhai
Now with Spark!
Cassandra + Spark
Unlock full analytics power for Cassandra
Spark/Cassandra connector
58

59. @doanduyhai
Tomorrow (DSE 4.7)!
Cassandra + Spark + Solr
Unlock full text search + analytics power for Cassandra
59

60. @doanduyhai
Tomorrow (DSE 4.7)!
Cassandra + Spark + Solr
Unlock full text search + analytics power for Cassandra
60

61. @doanduyhai
The idea!
① Filter the maximum with Cassandra and Solr
② Fetch only small data set in memory
③ Aggregate with Spark
☞ near real time interactive analytics query possible if restrictive criteria
61

62. @doanduyhai
Datastax Entreprise 4.7!
With a 3rd component for full text search …
how to preserve data locality ?
62

63. @doanduyhai
Stand-alone search cluster caveat!
The bad way v1: perform search from the Spark « driver program »
63

64. @doanduyhai
Stand-alone search cluster caveat!
The bad way v2: search from Spark workers with restricted routing
64

65. @doanduyhai
Stand-alone search cluster caveat!
The bad way v3: search from Cassandra nodes with a connector to Solr
65

66. @doanduyhai
Stand-alone search cluster caveat!
The ops won’t be your friend
• 3 clusters to manage: Spark, Cassandra & Solr/whatever
• lots of moving parts
Impacts on Spark jobs
• increased response time due to latency
• the 99.9 percentile can be very slow
66

67. @doanduyhai
Datastax Entreprise 4.7!
The right way, distributed « local search »
67

68. @doanduyhai
val join: CassandraJoinRDD[(String,Int), (String,String)] =
sc.cassandraTable[(String,Int)](KEYSPACE, ALBUMS)
// Select only useful columns for join and processing
.select("artist","year").where("solr_query = 'style:*rock* AND ratings:[3 TO *]' ")
.as((_:String, _:Int))
.repartitionByCassandraReplica(KEYSPACE, ARTISTS)
.joinWithCassandraTable[(String,String)](KEYSPACE, ARTISTS, SomeColumns("name","country"))
.on(SomeColumns("name")).where("solr_query = 'age:[20 TO 30]' ")
Datastax Entreprise 4.7!
① compute Spark partitions using Cassandra token ranges
② on each partition, use Solr for local data filtering (no distributed query!)
③ fetch data back into Spark for aggregations
68

69. @doanduyhai
Datastax Entreprise 4.7!
69
SELECT … FROM …
WHERE token(#partition)> 3X/8
AND token(#partition)<= 4X/8
AND solr_query='full text search expression';
1
2
3
Advantages of same JVM Cassandra + Solr integration
1
Single-pass local full text search (no fan out) 2
Data retrieval
Token Range : ] 3X/8, 4X/8]

70. @doanduyhai
Datastax Entreprise 4.7!
Scalable solution: x2 volume à x2 nodes à constant processing time
70

71. Cassandra + Spark + Solr
https://github.com/doanduyhai/Cassandra-Spark-Demo

72. Q & R
! "!

73. Thank You
@doanduyhai
duy_hai.doan@datastax.com
https://academy.datastax.com/