Connect to Cloudant database from SparkR

How to Connect to Cloudant Database from SparkR kernel



Below i will show how to do it from Bluemix but it will apply  Jupyter Notebook running on any environment.

Connecting to Cloudant from IBM Bluemix - Juypter Notebooks on Spark

1. Create an account in bluemix(ibm offers 30 days free trial) - https://console.ng.bluemix.net/registration/


2. Create a spark service (https://www.ng.bluemix.net/docs/services/AnalyticsforApacheSpark/index.html) 
3. Now create notebook with sparkR as language.  
• spark context needs to know which driver to use to connect to Cloudant database. In bluemix spark service enivornment the driver is loaded by default. 
•  https://github.com/cloudant-labs/spark-cloudant
•  Also if you are in different environment, you use binary
• https://github.com/cloudant-labs/spark-cloudant/releases/download/v1.6.3/cloudant-spark-v1.6.3-125.jar
• For ex. use %Addjar -f https://github.com/cloudant-labs/spark-cloudant/releases/download/v1.6.3/cloudant-spark-v1.6.3-125.jar to add it to your spark.
4. Once you have spark-cloudant connector in your spark.
5.  You are going to need to have 3 configuration parameters set for you spark context

• cloudant.host","ACCOUNT.cloudant.com"

  "cloudant.username", "USERNAME"
  "cloudant.password","PASSWORD"

  So in sparkR, you would need to use one of the sparkEnv variable

  to pass your environment variables to all the executors.

  sc <- sparkR.init(sparkEnv = list("cloudant.host"="c8dca934-d2a4-4dcc-9123-2189ce9f5812-bluemix.cloudant.com","cloudant.username"="c8dca934-d2a4-4dcc-9123-2189ce9f5812-bluemix","cloudant.password"="XXXXXXXXXXXXXXXXXXXX")) 

  Once you execute above. Your sparkcontext is ready to use cloudant-connector.

  All you need to do is specify that you are reading using com.cloudant.spark

  people <- read.df(sqlContext, database, header='true', source = "com.cloudant.spark",inferSchema='true') 

  I have complete Notebook published on this github repo. Feel Free to use it.

Difference Between Spark and Hadoop Map-reduce

Difference Between Spark and Hadoop

Difference	Spark	Hadoop Map-reduce
1. Perfomance	Itertaive computations are performed in-memory, the mapper functions just transform one RDD to another RDD, resulting in saving disk io,network io and improving performance	Map and Reduce phases cause every mapper/reducer to write data to disk after mapping and then successive mapper/reducer to read from it, thus resulting in disk io,network io, causing latency
2. Programming Languages	Scala,Java,Python,R	Java
3. Basic Unit of Data	RDD - Resilient Distributed Dataset	Tuples
4. Lines of Code for WordCount	as less as 6 in python code. refer here	as less as 73 in Java code. refer here

Spark 2.0 is out

Spark Summit East Keynote: Apache Spark 2.0


How do you get your hands on Spark 2.0 :-
1. Databricks Community Edition
2. Download and set it up


Major features:-

1.  Tungsten Phase 2 speedups of 5-10x
2. Structured Streaming real-time engine on SQL/DataFrames
3. Unifying Datasets and DataFrames