This presentation was delivered to engineering students from Computer, IT, Electronics background. This was lab hands on session on Apache Apex. The lab session was conducted after having lecture on introduction to Apex. Advanced users of Apex/experts may not find this relevant.

1. © 2015 DataTorrent
Akshay Gore, Bhupesh Chawda
DataTorrent
Apex Hands-on Lab - Into the code!
Getting started with your first Apex Application!

2. © 2015 DataTorrent
Operators
• Input Adaptor Vs
Generic Operators ?
• What are streams?
• What are ports?

3. © 2015 DataTorrent
Apex Operator Lifecycle

4. © 2015 DataTorrent
Apex Streaming Application
public class Application implements StreamingApplication
{
populateDAG(DAG dag, Configuration conf)
{
// Add Operators to dag - dag.addOperator(args)
// Add Streams between operators - dag.addStream(args)
// Additional config + Hints to YARN - Optional
}
}

5. © 2015 DataTorrent
Apex Application - FilterWords
Apex Application DAG
• Problem statement - Filter words in the file
ᵒ Read a file located on HDFS
ᵒ Split each line into words, check if it is not one of the forbidden words and write it
down to HDFS
HDFS
Lines Filtered Words
HDFS

6. © 2015 DataTorrent
FilterWords Application DAG
Reader Tokenize Processor Writter
Input
Operator
(Adapter)
Output
Operator
(Adapter)
Generic
Operators
HDFS HDFS
Lines Words
Filtered
Words

7. © 2015 DataTorrent
Prerequisites
• JAVA 1.7 or above
• Maven 3.0 or above
• Apache Apex projects:
ᵒ Apache Apex Core: core platform, engine
ᵒ Apache Apex Malhar: operators library
• Hadoop cluster in running state
• Your favourite IDE - Eclipse / vi

8. © 2015 DataTorrent
Demo time!
• Apex application structure
• Application code walk through
• How to execute the application
• Assignment

9. © 2015 DataTorrent
Assignment - WordCount
Apex Application DAG
• Problem statement - Count occurrences of words in a file
ᵒ Read a file located on HDFS
ᵒ Emit count at the end of the every window and writes into HDFS
HDFS
Lines <Word, Count>
HDFS

10. © 2015 DataTorrent
Assignment - Word Count Application DAG
Reader Tokenize
Counter
Output
HDFS HDFS
Lines Words
<Word,
count>

11. © 2015 DataTorrent
Assignment - What you need to do
Reader Tokenizer Processor Writer
String String String
Line Words Words’
Counter Writer
Map
{Word: Count}
Assignment

12. © 2015 DataTorrent
Assignment - Hints
• Create copy of Processor.java. Name it Counter.java
• Modify Counter.java as follows:
ᵒ Define a data structure which can hold counts for words
ᵒ Process method of input port must count the occurrences
ᵒ Clear the counts in beginWindow() call
ᵒ Emit the counts in endWindow() call

13. © 2015 DataTorrent
Solution - Changes to Counter.java
• Need to define a data structure which can hold counts for words
private HashMap<String, Integer> counts = new HashMap<>();
• Process method of input port must count the occurrences
if(counts.containsKey(refinedWord)) {
counts.put(refinedWord, counts.get(refinedWord) + 1);
} else {
counts.put(refinedWord, 1);
}
● Clear the counts in beginWindow call
counts.clear();
● Emit the counts in endWindow call
output.emit(counts.toString());
● Run Application Test

14. © 2015 DataTorrent
Assignment - Are we done yet?
• Change the DAG
ᵒ Replace Processor operator with the newly created operator - Counter

15. © 2015 DataTorrent
Assignment - Slight change
• We are emitting a Map. However it is still a string.
ᵒ Change type of output port of Counter to type Map
ᵒ Change type of input port of Writer to Map
ᵒ Make appropriate changes to Writer to read a Map and write in a format such
that each line belongs to a single word.

16. © 2015 DataTorrent
Assignment - Final change
• Change the code such that each count is the overall count, not just for each
window?

17. © 2015 DataTorrent
Summary - Recap
• Writing Apache Apex operators
• Chaining the operators into an Apache Apex application
• Executing the application on the Apache Apex platform

18. © 2015 DataTorrent
Where to go from here?
Apache Apex Documentation - http://apex.incubator.apache.org/docs.html
Apache Apex Core Git - https://github.com/apache/incubator-apex-core
Apache Apex Malhar Git - https://github.com/apache/incubator-apex-malhar
Join Users Mailing List - users-subscribe@apex.incubator.apache.org
Join Dev Mailing List - dev-subscribe@apex.incubator.apache.org
Send queries to Users Mailing List - users@apex.incubator.apache.org
Send queries to Dev Mailing List - dev@apex.incubator.apache.org

19. © 2015 DataTorrent
Thank You