Apache Flink Crash Course by Slim Baltagi and Srini Palthepu

Apache Flink Crash Course

Slim Baltagi & Srini Palthepu

with some materials from data-artisans.com

Chicago Apache Flink Meetup

August 4th 2015

“One week of trials and errors can

save you up to half an hour of

reading the documentation.”

Anonymous

For an overview of Apache Flink, see our slides at http://goo.gl/gVOSp8

DataSet (Java/Scala/Python)Batch Processing

DataStream (Java/Scala)

Stream Processing

LocalSingle JVMEmbedded

Docker

ClusterStandalone YARN, Tez, Mesos (WIP)

CloudGoogle’s GCEAmazon’s EC2IBM Docker Cloud, …

RuntimeDistributed Streaming Dataflow

GE Files

LocalHDFS

S3Tachyon

DatabasesMongoDB HBaseSQL …

Streams FlumeKafkaRabbitMQ…

Batch Optimizer Stream Builder

In this talk, we will cover practical steps for: Setup and configuration of your Apache

Flink environment Using Flink tools Learning Flink’s APIs & Domain Specific

Libraries through Some Apache Flink program

examples Free Training from Data Artisans

in Java and Scala Writing, testing, debugging, deploying and

tuning your Flink applications

Agenda1. How to setup and configure your Apache Flink

environment?

2. How to use Apache Flink tools?

3. How to learn Apache Flink’s APIs and its domain specific libraries?

4. How to set up your IDE (IntelliJ IDEA or Eclipse) for Apache Flink?

5. How to write, test and debug your Apache Flink program in an IDE?

6. How to deploy your Apache Flink application in local, in a cluster or in the cloud?

7. How to tune your Apache Flink application?

1. How to setup and configure your Apache Flink environment?

1.1 Local (on a single machine)

1.2 VM image (on a single machine)

1.3 Docker

1.4 Standalone Cluster

1.5 YARN Cluster

1.6 Cloud

Flink runs on Linux, OS X and Windows.In order to execute a program on a running Flink

instance (and not from within your IDE) you need

to install Flink on your machine. The following steps will be detailed for both Unix-

Like (Linux, OS X) as well as Windows

environments: 1.1.1 Verify requirements

1.1.2 Download

1.1.3 Unpack

1.1.4 Check the unpacked archive

1.1.5 Start a local Flink instance

1.1.6 Validate Flink is running

1.1.7 Run a Flink example

1.1.8 Stop the local Flink instance

1.1.1 Verify requirementsThe machine that Flink will run on must have Java

1.6.x or higher installed.In Unix-like environment, the $JAVA_HOME

environment variable must be set. Check the correct

installation of Java by issuing the following

commands: java –version and also check if $Java-

Home is set by issuing: echo $JAVA_HOME. If

needed, follow the instructions for installing Java

and Setting JAVA_HOME here:

http://docs.oracle.com/cd/E19182-01/820-7851/inst_cli_jdk_javahome_t/index.html

In Windows environment, check the correct

installation of Java by issuing the following

commands: java –version. Also, the bin folder of your

Java Runtime Environment must be included in

Window’s %PATH% variable. If needed, follow

this guide to add Java to the path variable.

http://www.java.com/en/download/help/path.xml

1.1.2 Download the latest stable release of Apache

Flink from http://flink.apache.org/downloads.html

For example: In Linux-Like environment, run the

following command:

wget https://www.apache.org/dist/flink/flink-0.9.0/flink-

0.9.0-bin-hadoop2.tgz

1.1.3 Unpack the downloaded .tgz archiveExample:

$ cd ~/Downloads # Go to download directory

$ tar -xvzf flink-*.tgz # Unpack the downloaded archive

1.1.4. Check the unpacked archive $ cd flink-0.9.0

The resulting folder contains a Flink setup that can be locally

executed without any further configuration.

flink-conf.yaml under flink-0.9.0/conf contains the default

configuration parameters that allow Flink to run out-of-the-box

in single node setups.

1.1.5. Start a local Flink instance:

• Given that you have a local Flink installation,

you can start a Flink instance that runs a master

and a worker process on your local machine in a

single JVM. This execution mode is useful for

local testing.• On UNIX-Like system you can start a Flink instance as

follows: cd /to/your/flink/installation ./bin/start-local.sh

1.1.5. Start a local Flink instance:On Windows you can either start with:

• Windows Batch Files by running the following

commands cd C:\to\your\flink\installation .\bin\start-local.bat

• or with Cygwin and Unix Scripts: start the Cygwin

terminal, navigate to your Flink directory and run

the start-local.sh script $ cd /cydrive/c cd flink $ bin/start-local.sh

The JobManager (the master of the distributed system)

automatically starts a web interface to observe program

execution. In runs on port 8081 by default (configured

in conf/flink-config.yml). http://localhost:8081/

1.1.6 Validate that Flink is runningYou can validate that a local Flink instance is running

by:• Issuing the following command: $jps

jps: java virtual machine process status tool• Looking at the log files in ./log/

$tail log/flink-*-jobmanager-*.log • Opening the JobManager’s web interface at

http://localhost:8081

1.1.7 Run a Flink example• On UNIX-Like system you can run a Flink example as follows:

cd /to/your/flink/installation ./bin/flink run ./examples/flink-java-examples-0.9.0-

WordCount.jar• On Windows Batch Files, open a second terminal and run the

following commands”

cd C:\to\your\flink\installation .\bin\flink.bat run .\examples\flink-java-

examples-0.9.0-WordCount.jar

1.1.8 Stop local Flink instance•On UNIX you call ./bin/stop-local.sh•On Windows you quit the running process with Ctrl+C

1.2 VM image (on a single machine)

Download Flink Virtual Machine from: https

://docs.google.com/uc?id=0B-oU5Z27sz1hZ0VtaW5idFViNU0&export=

download

The password is: flinkThis version works with VMware Fusion on

OS X since there is no VMware player for

OSX. https://www.vmware.com/products/fusion/fusion-evaluation.html

1.3 Docker Apache Flink cluster deployment on Docker using

Docker-Compose By Romeo Kienzler. Talk at the Apache

Flink Meetup Berlin planned for August 26, 2015 http

://www.meetup.com/Apache-Flink-Meetup/events/223913365

/The talk will:

• Introduce the basic concepts on container isolation

exemplified on Docker • Explain how Apache Flink is made elastic using

Docker-Compose. • Show how to push the cluster to the cloud exemplified

on the IBM Docker Cloud.

1.4 Standalone Cluster

See quick start - Cluster setuphttps

://ci.apache.org/projects/flink/flink-docs-release-0.9/quickstart/setup_quickstart.html#cluster-

See instructions on how to run Flink in a fully

distributed fashion on a cluster. This involves

two steps:• Installing and configuring Flink • Installing and configuring the Hadoop

Distributed File System (HDFS)https://ci.apache.org/projects/flink/flink-docs-master/setup/cluster_setup.html

1.5 YARN Cluster

You can easily deploy Flink on your

existing YARN cluster.Download the Flink Hadoop2 package: Flink

with Hadoop 2

http://www.apache.org/dyn/closer.cgi/flink/flink-0.9.0/flink-0.9.0-bin-hadoop2.tgz

Make sure

your HADOOP_HOME (or YARN_CONF_DIR or

HADOOP_CONF_DIR) environment

variable is set to read your YARN and HDFS

configuration.

1.5 YARN Cluster

Run the YARN client with:

./bin/yarn-session.shYou can run the client with options -n 10 -tm

8192 to allocate: 10 TaskManagers with 8GB of memory each.

For more detailed instructions, check out the

documentation: https

://ci.apache.org/projects/flink/flink-docs-master/setup/yarn_setup.html

1.6 Cloud

1.6.1 Google Compute Engine (GCE)

1.6.2 Amazon EMR

1.6 Cloud

1.6.1 Google Compute EngineFree trial for Google Cloud Engine: https://cloud.google.com/free-trial/

Enjoy your $300 in GCE for 60 days!Now, how to setup Flink with Hadoop 1 or Hadoop 2 on top of a

Google Compute Engine cluster? Google’s bdutil starts a cluster and

deploys Flink with Hadoop. To get started, just follow the steps here:

https://ci.apache.org/projects/flink/flink-docs-master/setup/gce_setup.html

1.6 Cloud

1.6.2 Amazon EMRAmazon Elastic MapReduce (Amazon EMR) is

a web service providing a managed Hadoop

framework. • http://aws.amazon.com/elasticmapreduce/• http://docs.aws.amazon.com/ElasticMapReduce/latest/DeveloperGuide/emr-what-is

emr.html

•Example: Use Stratosphere with Amazon

Elastic MapReduce, February 18, 2014 by

Robert Metzgerhttps

://flink.apache.org/news/2014/02/18/amazon-elastic-mapreduce-cloud-yarn.html

1.6 Docker

Docker can be used for local developmentOften resource requirements on Data

Processing Clusters exhibit high variation.

Elastic deployments reduce TCO (Total Cost of

Ownership). Container based virtualization; lightweight and

portable; build once, run anywhere; ease of

packaging applications; automated and

scripted; isolatedApache Flink cluster deployment on Docker

using Docker-Compose https://github.com/streamnsight/docker-flink

2. How to use Apache Flink tools?

2.1 Command-Line Interface (CLI)

2.2 Job Client Web Interface

2.3 Job Manager Web Interface

2.4 Interactive Scala Shell

2.5 Zeppelin Notebook

2.1 Command-Line Interface (CLI)

Example:

./bin/flink run ./examples/flink-java-examples-

0.9.0-WordCount.jar bin/flink has 4 major actions

• run #runs a program• info #displays information about a program.• list #lists running and finished programs. -r & -

./bin/flink list -r -s• cancel #cancels a running program. –I

See more examples: https://ci.apache.org/projects/flink/flink-docs-master/apis/cli.html

2.2 Job Client Web InterfaceFlink provides a web interface to:

• Upload jobs• Inspect their execution plans• Execute them• Showcase programs• Debug execution plans• Demonstrate the system as a whole

The web interface runs on port 8080 by default.To specify a custom port set

the webclient.port property in the

./conf/flink.yaml configuration file.

2.2 Job Client Web InterfaceStart the web interface by executing:

./bin/start-webclient.shStop the web interface by executing:

./bin/stop-webclient.sh • Jobs are submitted to the JobManager

specified

by jobmanager.rpc.address and jobmanager.rpc.port

• For more details and further configuration

options, please consult this webpage: https

://ci.apache.org/projects/flink/flink-docs-release-0.9/setup/config.html#webclient

The JobManager (the master of the

distributed system) starts a web interface to

observe program execution. It runs on port 8081 by default (configured

in conf/flink-config.yml). Open the JobManager’s web interface at

http://localhost:8081• jobmanager.rpc.port 6123 • jobmanager.web.port 8081

Overall system status

Job execution details

Task Manager resourceutilization

The JobManager web frontend allows to :• Track the progress of a Flink program as

all status changes are also logged to the

JobManager’s log file.• Figure out why a program failed as it

displays the exceptions of failed tasks

and allow to figure out which parallel task

first failed and caused the other tasks to

cancel the execution.

2.4 Interactive Scala ShellFlink comes with an Interactive Scala Shell - REPL ( Read

Evaluate Print Loop ) : ./bin/start-scala-shell.shInteractive queriesLet’s you explore data quicklyComplete Scala API availableIt can be used in a local setup as well as in a cluster

setup. The Flink Shell comes with command history and auto

completion.So far only batch mode is supported. There is plan to

add streaming in the future: https://ci.apache.org/projects/flink/flink-docs-master/scala_shell.html

2.4 Interactive Scala Shellbin/start-scala-shell.sh --host localhost --port 6123

Example 1: Scala-Flink> val input = env.fromElements(1,2,3,4)

Scala-Flink> val doubleInput = input.map(_ *2)

Scala-Flink> doubleInput.print()

Example 2: Scala-Flink> val text = env.fromElements( "To be, or not

to be,--that is the question:--", "Whether 'tis nobler in the

mind to suffer", "The slings and arrows of outrageous

fortune", "Or to take arms against a sea of troubles,")

Scala-Flink> val counts = text.flatMap

{ _.toLowerCase.split("\\W+") }.map { (_,

1) }.groupBy(0).sum(1)

Scala-Flink> counts.print()

Problems with the Interactive Scala Shell:

No visualizationNo saving No replaying of written codeNo assistance as in an IDE

Web-based interactive computation

environment Combines rich text, execution code, plots

and rich media Exploratory data scienceStorytelling

http://localhost:8080/

3. How to learn Flink’s APIs and libraries?

3.1 How to run the examples in the Apache

Flink bundle?

3.2 How to learn Flink Programming APIs?

3.3 How to learn Apache Flink Libraries?

3.1 How to run the examples in the Apache Flink bundle?

3.1.1 Where are the examples?

3.1.2 Where are the related source

codes?

3.1.3 How to re-build these examples?

3.1.4 How to run these examples?

3.1.1 Where are the examples?

The examples provided in the Flink bundle

showcase different applications of Flink from

simple word counting to graph algorithms.They illustrate the use of Flink’s API. They are a very good way to learn how to

write Flink jobs. A good starting point would be to modify

them!Now, where are the related source codes!?

3.1.2 Where are the related source codes?You can find the source code of these

Flink examples in the flink-java-examples or

the flink-scala-examples of the flink-

examples module of the source release of

Flink. You can also access the source (and

hence the examples) through GitHub: https://github.com/apache/flink/tree/master/flink-examples

3.1.2 Where are the related source codes?If you don't want to import the whole Flink project

just for playing around with the examples, you can:• Create an empty maven project. This script will

automatically set everything up for you: $ curl

http://flink.apache.org/q/quickstart.sh | bash• Import the "quickstart" project into Eclipse or

IntelliJ. It will download all dependencies and

package everything correctly. • If you want to use an example there, just copy the

Java file into the "quickstart" project.

3.1.3 How to re-build these examples?

To build the examples, you can run:

"mvn clean package -DskipTests”

in the "flink-examples/flink-java-examples"

directory.

This will re-build them.

3.1.4 How to run these examples?How to display the command line

arguments? ./bin/flink info ./examples/flink-java-

examples-0.9.0-WordCount.jarExample of running an example: ./bin/flink

run ./examples/flink-java-examples-0.9.0-

WordCount.jarMore on the bundled examples: https://ci.apache.org/projects/flink/flink-docs-master/apis/examples.html#running-an-

example

3.2.1 DataSet API

3.2.2 DataStream API

3.2.3 Table API - Relational Queries

3.2.1 DataSet API

https://ci.apache.org/projects/flink/flink-docs-master/apis/programming_guide.html

https://ci.apache.org/projects/flink/flink-docs-master/api/java/

FREE Apache Flink Training by Data Artisans:

DataSet API Basis

•Lecture:

http://dataartisans.github.io/flink-training/dataSetBasics/slides.html Slides

https://www.youtube.com/watch?v=1yWKZ26NQeU Video

•Exercise: http://dataartisans.github.io/flink-training/dataSetBasics/handsOn.html

3.2.1 DataSet API

DataSet API Advanced

• Lecture:

• Slides http://dataartisans.github.io/flink-training/dataSetAdvanced/slides.html

• Video https://www.youtube.com/watch?v=1yWKZ26NQeU

• Exercise: http://dataartisans.github.io/flink-training/dataSetAdvanced/handsOn.html

https://ci.apache.org/projects/flink/flink-docs-master/apis/streaming_guide.html

https://ci.apache.org/projects/flink/flink-docs-master/api/java/

Example 1: Event pattern detection with Apache FlinkThis is a Flink streaming demo given By Data Artisans

on July 17, 2015 titled 'Apache Flink: Unifying batch

and streaming modern data analysis' at the Bay Area

Apache Flink Meetup:

• Related code: https://github.com/StephanEwen/flink-demos/tree/master/streaming-state-

machine

• Related slides: http://www.slideshare.net/KostasTzoumas/first-flink-bay-area-meetup

• Related video recording: https://www.youtube.com/watch?v=BJjGD8ijJcg

Example 2: Fault-Tolerant Streaming with Flink

Slides 16-23 http://www.slideshare.net/AljoschaKrettek/flink-010-upcoming-features

Code https://github.com/aljoscha/flink-fault-tolerant-stream-example

This is a demo to show how Flink can deal with stateful streaming

jobs and fault-tolerance.

Example 3: Flink-storm compatibility examplehttps

://github.com/apache/flink/tree/master/flink-contrib/flink-storm-compatibility/flink-storm-compatibility-

examples

Example 4: Data Stream Analytics with Flink

http://net.t-labs.tu-berlin.de/~nsemmler/blog//flink/2015/03/02/Data-Stream-Analysis-with-

flink.html

Example 5: Introducing Flink Streaming

http://flink.apache.org/news/2015/02/09/streaming-example.html

Examples from the code base: flink-streaming-

examples

https://github.com/apache/flink/tree/master/flink-staging/flink-streaming/flink-streaming-examples/src/main/scala/org/apache/flink/streaming/scala/examples

3.2.3 Table API - Relational Queries https

://ci.apache.org/projects/flink/flink-docs-master/libs/table.html

To use the Table API in a project:

• First setup a Flink program: https://ci.apache.org/projects/flink/flink-docs-master/apis/programming_guide.html - linking-with-flink

• Add this to the dependencies section of your pom.xml <dependency>

<groupId>org.apache.flink</groupId>

<artifactId>flink-table</artifactId>

<version>0.10-SNAPSHOT</version>

</dependency>

Table is not currently part of the binary distribution. You need to link it for cluster execution: https://ci.apache.org/projects/flink/flink-docs-master/apis/cluster_execution.html - linking-with-modules-not-contained-in-the-binary-distribution

3.2.3 Table API - Relational Queries

FREE Apache Flink Training by Data Artisans – Table API

• Lecture: http://www.slideshare.net/dataArtisans/flink-table

• Exercise: http://dataartisans.github.io/flink-training/tableApi/

handsOn.html

See also example in slides 36-43 on Log Analysis

http://www.grid.ucy.ac.cy/file/Talks/talks/DeepAnalysiswithApacheFlink_2nd_cloud_workshop.pdf

3.3 Apache Flink Domain Specific Libraries

3.3.1 FlinkML - Machine Learning for Flink

3.3.2 Gelly - Graph Analytics for Flink

3.3 Apache Flink Libraries

3.3.1 FlinkML - Machine Learning for Flinkhttps

://ci.apache.org/projects/flink/flink-docs-master/libs/ml/

FlinkML – Quickstart Guidehttps

://ci.apache.org/projects/flink/flink-docs-master/libs/ml/quickstart.html

To use FlinkML in a project:

• First setup a Flink program: https://ci.apache.org/projects/flink/flink-docs-master/apis/programming_guide.html#linking-with-flink

• Add this to the dependencies section of your pom.xml <dependency>

<artifactId>flink-ml</artifactId>

</dependency>

3.3 Apache Flink Libraries3.3.1 FlinkML - Machine Learning for FlinkQuick Start: Run K-Means Examplehttps

://ci.apache.org/projects/flink/flink-docs-master/quickstart/run_example_quickstart.html

Computing Recommendations at Extreme Scale with

Apache Flink

http://data-artisans.com/computing-recommendations-at-extreme-scale-with-apache-flink/a and

related code: https://github.com/tillrohrmann/flink-perf/blob/ALSJoinBlockingUnified/flink-jobs/src/main/scala/com/github/projectflink/als/

ALSJoinBlocking.scala

Naive Bayes on Apache Flink http://www.itshared.org/2015/03/naive-bayes-on-apache-flink.html

FlinkML is not currently part of the binary distribution.

You need to link it for cluster execution: https://ci.apache.org/projects/flink/flink-docs-master/apis/cluster_execution.html#linking-with-modules-not-contained-in-the-binary-distribution

3.3.2 Gelly: Flink Graph API https://ci.apache.org/projects/flink/flink-docs-master/libs/gelly_guide.html

To use Gelly in a project:

• First setup a Flink program: https://ci.apache.org/projects/flink/flink-docs-master/apis/programming_guide.html#linking-with-flink

• Add this to the dependencies section of your pom.xml

<artifactId>flink-gelly</artifactId>

</dependency>

Gelly Examples: https://github.com/apache/flink/tree/master/flink-staging/flink-gelly/src/main/java/org/apache/flink/graph/

example

Gelly exercise & solution

Gelly API - PageRank on Reply Graphhttp://dataartisans.github.io/flink-training/exercises/replyGraphGelly.html

Gelly is not currently part of the binary distribution.

You need to link it for cluster execution: https://ci.apache.org/projects/flink/flink-docs-master/apis/cluster_execution.html#linking-with-modules-not-contained-in-the-binary-distribution

4. How to set up your IDE (IntelliJ IDEA or Eclipse) for Apache Flink?

4.1 How to set up your IDE (IntelliJ IDEA)?

4.2 How to setup your IDE (Eclipse)?

Flink uses mixed Scala/Java projects, which

pose a challenge to some IDEsMinimal requirements for an IDE are:

• Support for Java and Scala (also mixed projects)

• Support for Maven with Java and Scala

4.1 How to set up your IDE (IntelliJ IDEA)?IntelliJ IDEA supports Maven out of the box

and offers a plugin for Scala development.IntelliJ IDEA Download https

://www.jetbrains.com/idea/download/

IntelliJ Scala Plugin http://plugins.jetbrains.com/plugin/?id=1347

Check out Setting up IntelliJ IDEA guide for

detailshttps://github.com/apache/flink/blob/master/docs/internals/

ide_setup.md#intellij-idea

Screencast: Run Apache Flink WordCount

from IntelliJ https://www.youtube.com/watch?v=JIV_rX-OIQM

4.2 How to setup your IDE (Eclipse)?

• For Eclipse users, Apache Flink committers

recommend using Scala IDE 3.0.3, based on

Eclipse Kepler. • While this is a slightly older version, they

found it to be the version that works most

robustly for a complex project like Flink. One

restriction is, though, that it works only with

Java 7, not with Java 8.• Check out how to setup Eclipse docs:

https://github.com/apache/flink/blob/master/docs/internals/ide_setup.md

#eclipse

5. How to write, test and debug your Apache Flink program in an IDE?

5.1 How to write a Flink program?

5.1.1 How to generate a Flink project with

Maven?

5.1.2 How to import the Flink Maven project

into IDE

5.1.3 How to use logging?

5.1.4 FAQs and best practices related to

coding

5.2 How to test your Flink program?

5.3 How to debug your Flink program?

5.1 How to write a Flink program in an IDE?

The easiest way to get a working setup to

develop (and locally execute) Flink programs

is to follow the Quick Start guide:https://ci.apache.org/projects/flink/flink-docs-master/quickstart/java_api_quickstart.html

https://ci.apache.org/projects/flink/flink-docs-master/quickstart/scala_api_quickstart.html

It uses Maven archetype to configure and

generate a Flink Maven project. This will save you time dealing with transitive

dependencies! This Maven project can be imported into your

Generate a skeleton project with Maven to get

started

mvn archetype:generate / -DarchetypeGroupId=org.apache.flink / -DarchetypeArtifactId=flink-quickstart-java / -DarchetypeVersion=0.9.0

you can also put “quickstart-scala” here

or “0.10-SNAPSHOT”or “0.10-SNAPSHOT”

No need for manually downloading any .tgz or .jar files for now

5.1.1 How to generate a skeleton Flink project with Maven?

5.1 How to write a Flink program in an IDE? 5.1.1 How to generate a skeleton Flink project

with Maven?The generated projects are located in a folder

called flink-java-project or flink-scala-project.In order to test the generated projects and to download

all required dependencies run the following commands

(change flink-java-project to flink-scala-project for Scala

projects)• cd flink-java-project

• mvn clean packageMaven will now start to download all required

dependencies and build the Flink quickstart project.

5.1 How to write a Flink program in an IDE? 5.1.2 How to import the Flink Maven project into

IDEThe generated Maven project needs to be imported into

your IDE:IntelliJ:

• Select “File” -> “Import Project”

• Select root folder of your project

• Select “Import project from external model”,

select “Maven”

• Leave default options and finish the importEclipse:

• Select “File” -> “Import” -> “Maven” -> “Existing Maven

Project”

• Follow the import instructions

5.1.3 How to use logging? The logging in Flink is implemented using the slf4j

logging interface. log4j is used as underlying logging

framework. Log4j is controlled using property file usually

called log4j.properties. You can pass to the JVM the

filename and location of this file using

the Dlog4j.configuration= parameter.

The loggers using slf4j are created by callingimport org.slf4j.LoggerFactory

import org.slf4j.Logger

Logger LOG = LoggerFactory.getLogger(Foobar.class)

You can also use logback instead of log4j. https://ci.apache.org/projects/flink/flink-docs-release-0.9/internals/logging.html

5.1 How to write a Flink program?

5.1.4 FAQs & best practices related to codingErrors

http://flink.apache.org/faq.html#errorsUsage

http://flink.apache.org/faq.html#usageBest Practices

https://ci.apache.org/projects/flink/flink-docs-

master/apis/best_practices.html

5.2 How to test your Flink program in an IDE?

Start Flink in your IDE for local development &

debugging.

final ExecutionEnvironment env = ExecutionEnvironment.createLocalEnvironment(); Use Flink’s testing framework

@RunWith(Parameterized.class)class YourTest extends MultipleProgramsTestBase {

@Testpublic void testRunWithConfiguration(){

expectedResult = "1 11\n“; }}

5.3 How to debug your Flink program in an IDE?

Flink programs can be executed and debugged from

within an IDE. This significantly eases the development process and

gives a programming experience similar to working

on a regular Java application. Starting a Flink program in your IDE is as easy as

starting its main()method. Under the hood, the ExecutionEnvironment will start a

local Flink instance within the execution process. Hence it is also possible to put breakpoints

everywhere in your code and debug it.

• Assuming you have an IDE with a Flink quickstart

project imported, you can execute and debug the

example WordCount program which is included in the

quickstart project as follows:• Open the org.apache.flink.quickstart.WordCount class

in your IDE• Place a breakpoint somewhere in the flatMap() method

of the LineSplitter class which is inline defined in

the WordCount class.• Execute or debug the main() method of

the WordCount class using your IDE.

When you start a program locally with

the LocalExecutor, you can place breakpoints

in your functions and debug them like normal

Java/Scala programs.The Accumulators are very helpful in tracking

the behavior of the parallel execution. They

allow you to gather information inside the

program’s operations and show them after the

program execution.

Debugging with the IDE

Debugging on a cluster

Good old system out debugging• Get a logger

– Start logging

• Start logging

private static final Logger LOG = LoggerFactory.getLogger(YourJob.class);

LOG.info("elementCount = {}", elementCount);

• You can also use System.out.println().

Getting logs on a cluster

• Non-YARN (=bare metal installation)–The logs are located in each TaskManager’s

log/ directory.–ssh there and read the logs.

• YARN–Make sure YARN log aggregation is enabled–Retrieve logs from YARN (once app is finished)

$ yarn logs -applicationId <application ID>

Flink Logs

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - --------------------------------------------------------------------------------

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - Starting JobManager (Version: 0.9-SNAPSHOT, Rev:2e515fc, Date:27.05.2015 @ 11:24:23 CEST)

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - Current user: robert

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - JVM: OpenJDK 64-Bit Server VM - Oracle Corporation - 1.7/24.75-b04

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - Maximum heap size: 736 MiBytes

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - JAVA_HOME: (not set)

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - JVM Options:

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - -XX:MaxPermSize=256m

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - -Xms768m

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - -Xmx768m

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - -Dlog.file=/home/robert/incubator-flink/build-target/bin/../log/flink-robert-jobmanager-robert-da.log

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - -Dlog4j.configuration=file:/home/robert/incubator-flink/build-target/bin/../conf/log4j.properties

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - -Dlogback.configurationFile=file:/home/robert/incubator-flink/build-target/bin/../conf/logback.xml

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - Program Arguments:

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - --configDir

11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - /home/robert/incubator-flink/build-target/bin/../conf

11:42:39,234 INFO org.apache.flink.runtime.jobmanager.JobManager - --executionMode

11:42:39,234 INFO org.apache.flink.runtime.jobmanager.JobManager - local

11:42:39,234 INFO org.apache.flink.runtime.jobmanager.JobManager - --streamingMode

11:42:39,234 INFO org.apache.flink.runtime.jobmanager.JobManager - batch

11:42:39,234 INFO org.apache.flink.runtime.jobmanager.JobManager - --------------------------------------------------------------------------------

11:42:39,469 INFO org.apache.flink.runtime.jobmanager.JobManager - Loading configuration from /home/robert/incubator-flink/build-target/bin/../conf

11:42:39,525 INFO org.apache.flink.runtime.jobmanager.JobManager - Security is not enabled. Starting non-authenticated JobManager.

11:42:39,525 INFO org.apache.flink.runtime.jobmanager.JobManager - Starting JobManager

11:42:39,527 INFO org.apache.flink.runtime.jobmanager.JobManager - Starting JobManager actor system at localhost:6123.

11:42:40,189 INFO akka.event.slf4j.Slf4jLogger - Slf4jLogger started

11:42:40,316 INFO Remoting - Starting remoting

11:42:40,569 INFO Remoting - Remoting started; listening on addresses :[akka.tcp://flink@127.0.0.1:6123]

11:42:40,573 INFO org.apache.flink.runtime.jobmanager.JobManager - Starting JobManager actor

11:42:40,580 INFO org.apache.flink.runtime.blob.BlobServer - Created BLOB server storage directory /tmp/blobStore-50f75dc9-3001-4c1b-bc2a-6658ac21322b

11:42:40,581 INFO org.apache.flink.runtime.blob.BlobServer - Started BLOB server at 0.0.0.0:51194 - max concurrent requests: 50 - max backlog: 1000

11:42:40,613 INFO org.apache.flink.runtime.jobmanager.JobManager - Starting embedded TaskManager for JobManager's LOCAL execution mode

11:42:40,615 INFO org.apache.flink.runtime.jobmanager.JobManager - Starting JobManager at akka://flink/user/jobmanager#205521910.

11:42:40,663 INFO org.apache.flink.runtime.taskmanager.TaskManager - Messages between TaskManager and JobManager have a max timeout of 100000 milliseconds

11:42:40,666 INFO org.apache.flink.runtime.taskmanager.TaskManager - Temporary file directory '/tmp': total 7 GB, usable 7 GB (100.00% usable)

11:42:41,092 INFO org.apache.flink.runtime.io.network.buffer.NetworkBufferPool - Allocated 64 MB for network buffer pool (number of memory segments: 2048, bytes per segment: 32768).

11:42:41,511 INFO org.apache.flink.runtime.taskmanager.TaskManager - Using 0.7 of the currently free heap space for Flink managed memory (461 MB).

11:42:42,520 INFO org.apache.flink.runtime.io.disk.iomanager.IOManager - I/O manager uses directory /tmp/flink-io-4c6f4364-1975-48b7-99d9-a74e4edb7103 for spill files.

11:42:42,523 INFO org.apache.flink.runtime.jobmanager.JobManager - Starting JobManger web frontend

Build Information

JVM details

Init messages

Get logs of a running YARN application

Debugging on a cluster - Accumulators

Useful to verify your assumptions about the

class Tokenizer extends RichFlatMapFunction<String, String>> { @Override public void flatMap(String value, Collector<String> out) { getRuntimeContext()

.getLongCounter("elementCount").add(1L); // do more stuff. } }

Use “Rich*Functions” to get RuntimeContext Use “Rich*Functions” to get RuntimeContext

Debugging on a cluster - Accumulators

Where can I get the accumulator results?• returned by env.execute()

• displayed when executed with /bin/flink• in the JobManager web frontend

JobExecutionResult result = env.execute("WordCount");long ec = result.getAccumulatorResult("elementCount");

Live Monitoring with Accumulators

In previous versions to Flink 0.10• Accumulators only available after Job finishes

• In Flink 0.10• Accumulators updated while Job is running• System accumulators (number of bytes/records

processed…)

In Flink 0.10, the Job Manager Web Interface displays the accumulators live in the web interface

Excursion: RichFunctions

The default functions are SAMs (Single

Abstract Method). Interfaces with one method

(for Java8 Lambdas)There is a “Rich” variant for each function.

• RichFlatMapFunction, …• Methods open(Configuration c) & close() getRuntimeContext()

Excursion: RichFunctions & RuntimeContext

The RuntimeContext provides some useful

methodsgetIndexOfThisSubtask () /

getNumberOfParallelSubtasks() – who am I, and

if yes how many?getExecutionConfig() AccumulatorsDistributedCache

Attaching a remote debugger to Flink in a Cluster

Attaching a debugger to Flink in a cluster

Add JVM start option in flink-conf.yaml

env.java.opts: “-agentlib:jdwp=….”Open an SSH tunnel to the machine:

ssh -f -N -L 5005:127.0.0.1:5005 user@host

Use your IDE to start a remote debugging

session

6.1 Deploy in Local

6.2 Deploy in Cluster

6.3 Deploy in Cloud

6.1 Deploy in Local

Package your job in a jar and submit it: • /bin/flink (Command Line Interface)• RemoteExecutionEnvironment (From a

local java app)• Web Frontend (GUI)• Scala Shell

Flink Web Submission Client

Select jobs and preview plan

Understand Optimizer choices

6.2 Deploy in Cluster

• You can start a cluster locally

$ tar xzf flink-*.tgz$ cd flink$ bin/start-cluster.shStarting Job ManagerStarting task manager on host $ jps5158 JobManager5262 TaskManager

6.3 Deploy in Cloud

Google Compute Engine (GCE)

Free trial for Google Cloud Engine: https://cloud.google.com/free-trial/

Enjoy your $300 in GCE for 60 days!

http://ci.apache.org/projects/flink/flink-docs-master/setup/gce_setup.html

./bdutil -e extensions/flink/flink_env.sh deploy

6.3 Deploy in Cloud

Amazon EMR or any other cloud provider with

preinstalled Hadoop YARN http://ci.apache.org/projects/flink/flink-docs-master/setup/yarn_setup.html

wget http://stratosphere-bin.amazonaws.com/flink-0.9-SNAPSHOT-bin-hadoop2.tgztar xvzf flink-0.9-SNAPSHOT-bin-hadoop2.tgzcd flink-0.9-SNAPSHOT/./bin/yarn-session.sh -n 4 -jm 1024 -tm 4096

Install Flink yourself on the machines

7. How to tune your Apache Flink application

7.1 Tuning CPU

7.2 Tuning memory

7.3 Tuning I/O

7.4 Optimizer hints

7. How to tune your Apache Flink application (CPU, Memory, I/O)?

7.1 Tuning CPU Processing slots, threads, …

https://ci.apache.org/projects/flink/flink-docs-master/setup/

config.html#configuring-taskmanager-processing-slots

Tell Flink how many CPUs you have

taskmanager.numberOfTaskSlots in flink-config.yaml:

• number of parallel job instances• number of pipelines per TaskManager

recommended: number of available CPU cores

MapMap ReduceReduceMapMap ReduceReduce

MapMap ReduceReduce

Task Manager 1

Slot 1

Slot 2

Slot 3

Task Manager 2

Slot 1

Slot 2

Slot 3

Task Manager 3

Slot 1

Slot 2

Slot 3

Task Managers: 3

Total number of processing slots: 12

flink-config.yaml:taskmanager.numberOfTaskSlots: 4 or/bin/yarn-session.sh –slots 4 –n 4(Recommended value: Number of CPU cores)

Configuring TaskManager Processing slots

3 machines each with 4 CPU cores gives us a total of 12 processing slots

Slot 4 Slot 4Slot 4

Task Manager 2

Slot 1

Slot 2

Slot 3

Task Manager 3

Slot 1

Slot 2

Slot 3

When no argument are given, parallelism.default from flink-config.yaml is used. Default value = 1

Example 1: WordCount with parallelism = 1

Task Manager 1

Slot 1

Slot 2

Slot 3

Source -> flatMap

Reduce

Slot 4 Slot 4 Slot 4

Example 2: WordCount with parallelism = 2

Task Manager 1

Slot 1

Slot 2

Slot 3

Task Manager 2

Slot 1

Slot 2

Slot 3

Task Manager 3

Slot 1

Slot 2

Slot 3

Source -> flatMap

Reduce SinkSource -> flatMap

Reduce Sink

Places to set parallelism for a job flink-config.yaml parallelism.default: 2 Flink Client:./bin/flink -p 2 ExecutionEnvironment: env.setParallelism(2)

Slot 4 Slot 4 Slot 4

Example 3: WordCount with parallelism = 12 (using all resources)

Task Manager 1

Slot 1

Slot 2

Slot 3

Source -> flatMap

Reduce Sink

Source -> flatMap

Reduce Sink

Source -> flatMap

Reduce Sink

Task Manager 2

Slot 1

Slot 2

Slot 3

Task Manager 3

Slot 1

Slot 2

Slot 3

Source -> flatMap

Reduce Sink

Source -> flatMap Reduce Sink

Source -> flatMap

Reduce Sink

Source -> flatMap

Reduce Sink

Source -> flatMap

Reduce Sink

Source -> flatMap

Example 4: WordCount with parallelism = 12 and sink parallelism = 1

Task Manager 1

Slot 1

Slot 2

Slot 3

Task Manager 2

Slot 1

Slot 2

Slot 3

Task Manager 3

Slot 1

Slot 2

Slot 3

Source -> flatMap Reduce Source -

> flatMapReduce

Source -> flatMap

Reduce

Source -> flatMap

Reduce

Source -> flatMap

Reduce

Source -> flatMap

Reduce

Source -> flatMap

Reduce

Source -> flatMap

Reduce

Source -> flatMap

Reduce

The parallelism of each operator can be set individually in the APIscounts.writeAsCsv(outputPath, "\n", " ").setParallelism(1);

The data is streamed to this Sink from all the other slots on the other TaskManagers

Slot 4 Slot 4 Slot 4Source -> flatMap

ReduceSource -> flatMap

Reduce

7.2 Tuning MemoryHow to adjust memory usage on the

TaskManager?

Memory in Flink - Theory

Memory Management (Batch API) https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=53741525

taskmanager.network.numberOfBufferstaskmanager.network.numberOfBuffers

relative: taskmanager.memory.fractionabsolute: taskmanager.memory.size

Memory in Flink - Configuration

taskmanager.heap.mb or „-tm“ argument for bin/yarn-session.sh

Memory in Flink - OOM2015-02-20 11:22:54 INFO JobClient:345 - java.lang.OutOfMemoryError: Java heap space at org.apache.flink.runtime.io.network.serialization.DataOutputSerializer.resize(DataOutputSerializer.java:249) at org.apache.flink.runtime.io.network.serialization.DataOutputSerializer.write(DataOutputSerializer.java:93) at org.apache.flink.api.java.typeutils.runtime.DataOutputViewStream.write(DataOutputViewStream.java:39) at com.esotericsoftware.kryo.io.Output.flush(Output.java:163) at com.esotericsoftware.kryo.io.Output.require(Output.java:142) at com.esotericsoftware.kryo.io.Output.writeBoolean(Output.java:613) at com.twitter.chill.java.BitSetSerializer.write(BitSetSerializer.java:42) at com.twitter.chill.java.BitSetSerializer.write(BitSetSerializer.java:29) at com.esotericsoftware.kryo.Kryo.writeClassAndObject(Kryo.java:599) at org.apache.flink.api.java.typeutils.runtime.KryoSerializer.serialize(KryoSerializer.java:155) at org.apache.flink.api.scala.typeutils.CaseClassSerializer.serialize(CaseClassSerializer.scala:91) at org.apache.flink.api.scala.typeutils.CaseClassSerializer.serialize(CaseClassSerializer.scala:30) at org.apache.flink.runtime.plugable.SerializationDelegate.write(SerializationDelegate.java:51) at org.apache.flink.runtime.io.network.serialization.SpanningRecordSerializer.addRecord(SpanningRecordSerializer.java:76) at org.apache.flink.runtime.io.network.api.RecordWriter.emit(RecordWriter.java:82) at org.apache.flink.runtime.operators.shipping.OutputCollector.collect(OutputCollector.java:88) at org.apache.flink.api.scala.GroupedDataSet$$anon$2.reduce(GroupedDataSet.scala:262) at org.apache.flink.runtime.operators.GroupReduceDriver.run(GroupReduceDriver.java:124) at org.apache.flink.runtime.operators.RegularPactTask.run(RegularPactTask.java:493) at org.apache.flink.runtime.operators.RegularPactTask.invoke(RegularPactTask.java:360) at org.apache.flink.runtime.execution.RuntimeEnvironment.run(RuntimeEnvironment.java:257) at java.lang.Thread.run(Thread.java:745)

Memory is missing here

Reduce managed memory

reduce taskmanager.memory.fraction

Reduce managed memory

reduce taskmanager.memory.fraction

Memory in Flink – Network buffers

Memory is missing here

Managed memory will shrink automatically

Error: java.lang.Exception: Failed to deploy the task CHAIN Reduce(org.okkam.flink.maintenance.deduplication.blocking.RemoveDuplicateReduceGroupFunction) -> Combine(org.apache.flink.api.java.operators.DistinctOperator$DistinctFunction) (15/28) - execution #0 to slot SubSlot 5 (cab978f80c0cb7071136cd755e971be9 (5) - ALLOCATED/ALIVE): org.apache.flink.runtime.io.network.InsufficientResourcesException: okkam-nano-2.okkam.it has not enough buffers to safely execute CHAIN Reduce(org.okkam.flink.maintenance.deduplication.blocking.RemoveDuplicateReduceGroupFunction) -> Combine(org.apache.flink.api.java.operators.DistinctOperator$DistinctFunction) (36 buffers missing)

Increase

taskmanager.network.numberOfBuffersIncrease

taskmanager.network.numberOfBuffers

What are these buffers needed for?

TaskManager 1

Slot 2

MapMap ReduceReduce

Slot 1

TaskManager 2

Slot 2

Slot 1

A small Flink cluster with 4 processing slots (on 2 Task Managers)

A simple MapReduce Job in Flink:

Map Reduce job with a parallelism of 2 and 2 processing slots per Machine

TaskManager 1 TaskManager 2

MapMap

ReduceReduce

MapMap

ReduceReduce

MapMap

ReduceReduce

MapMap

ReduceReduce

ReduceReduceS

Network bufferNetwork buffer

8 buffers for outgoing data

8 buffers for outgoing data 8 buffers for incoming data8 buffers for incoming data

Map Reduce job with a parallelism of 2 and 2 processing slots per Machine

TaskManager 1 TaskManager 2

MapMap

ReduceReduce

MapMap

ReduceReduce

MapMap

ReduceReduce

MapMap

ReduceReduce

Each mapper has a logical connection to

a reducer

Each mapper has a logical connection to

a reducer

7.3 Tuning I/OSpecifying temporary directories for

spilling

Disk I/O

Sometimes your data doesn’t fit into main

memory, so we have to spill to disk:

taskmanager.tmp.dirs:

/mnt/disk1,/mnt/disk2Use real local disks only (no tmpfs or NAS)

Reader ThreadReader Thread

Disk 1Disk 1

Writer ThreadWriter Thread

Reader ThreadReader Thread

Writer ThreadWriter Thread

Disk 2Disk 2

Task Manager

7. How to tune your Apache Flink application

7.4 Optimizer hints Examples: DataSet.join(DataSet other,

JoinHint.BROADCAST_HASH_SECOND) DataSet.join(DataSet other, JoinHint.BROADCAST_HASH_FIRST)

http://stackoverflow.xluat.com/questions/31484856/the-difference-and-benefit-

of-joinwithtiny-joinwithhuge-and-joinhint

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