Apache Flink Crash Course by Slim Baltagi and Srini Palthepu

Apache Flink Crash Course

Slim Baltagi & Srini Palthepuwith some materials from data-artisans.com

Chicago Apache Flink MeetupAugust 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 Docker1.4 Standalone Cluster 1.5 YARN Cluster1.6 Cloud

1.1 Local (on a single machine)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 Local (on a single machine)

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.xml1.1.2 Download the latest stable release of Apache Flink from http://flink.apache.org/downloads.htmlFor 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 Local (on a single machine)1.1.3 Unpack the downloaded .tgz archive

Example: $ 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 Local (on a single machine)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 Local (on a single machine)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

1.1 Local (on a single machine)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 Local (on a single machine)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.jar1.1.8 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-setup

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

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 DockerDocker 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; isolated

Apache 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 Interface2.3 Job Manager Web Interface2.4 Interactive Scala Shell2.5 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 & -

s ./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

2.3 Job Manager Web Interface

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

2.4 Interactive Scala ShellExample 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()

2.4 Interactive Scala Shell

Problems with the Interactive Scala Shell:

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

2.5 Zeppelin Notebook

Web-based interactive computation environment

Combines rich text, execution code, plots and rich media

Exploratory data scienceStorytelling

2.5 Zeppelin Notebookhttp://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?

3.1.1 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 How to run the examples in the Apache Flink bundle?3.1.1 Where are the examples?

3.1 How to run the examples in the Apache Flink bundle?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 How to run the examples in the Apache Flink bundle?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 How to run the examples in the Apache Flink bundle?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 How to learn Flink Programming APIs? 3.2.1 DataSet APIhttps://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

3.2.2 DataStream APIhttps://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 Flinkhttp://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-exampleshttps://github.com/apache/flink/tree/master/flink-staging/flink-streaming/flink-streaming-examples/src/main/scala/org/apache/flink/streaming/scala/examples

3.2 How to learn Flink Programming APIs? 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 How to learn Flink Programming APIs? 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 Libraries3.3.1 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> <groupId>org.apache.flink</groupId> <artifactId>flink-ml</artifactId> <version>0.10-SNAPSHOT</version></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 Apache Flink Libraries3.3.2 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

<groupId>org.apache.flink</groupId> <artifactId>flink-gelly</artifactId> <version>0.10-SNAPSHOT</version></dependency>

3.3 Apache Flink Libraries

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

Gelly exercise & solutionGelly 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 details

https://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 IDE5.1.3 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.htmlhttps://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 IDE.

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”

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 package

Maven 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 import

Eclipse:• 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 calling

import org.slf4j.LoggerFactoryimport org.slf4j.LoggerLogger 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.

5.3 How to debug your Flink program in an IDE?

• 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.

5.3 How to debug your Flink program in an 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: robert11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - JVM: OpenJDK 64-Bit Server VM - Oracle Corporation - 1.7/24.75-b0411:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - Maximum heap size: 736 MiBytes11:42:39,233 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=256m11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - -Xms768m11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - -Xmx768m11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - -Dlog.file=/home/robert/incubator-flink/build-target/bin/../log/flink-robert-jobmanager-robert-da.log11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - -Dlog4j.configuration=file:/home/robert/incubator-flink/build-target/bin/../conf/log4j.properties11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - -Dlogback.configurationFile=file:/home/robert/incubator-flink/build-target/bin/../conf/logback.xml11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - Program Arguments:11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - --configDir11:42:39,233 INFO org.apache.flink.runtime.jobmanager.JobManager - /home/robert/incubator-flink/build-target/bin/../conf11:42:39,234 INFO org.apache.flink.runtime.jobmanager.JobManager - --executionMode11:42:39,234 INFO org.apache.flink.runtime.jobmanager.JobManager - local11:42:39,234 INFO org.apache.flink.runtime.jobmanager.JobManager - --streamingMode11:42:39,234 INFO org.apache.flink.runtime.jobmanager.JobManager - batch11:42:39,234 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/../conf11:42:39,525 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 JobManager11:42:39,527 INFO org.apache.flink.runtime.jobmanager.JobManager - Starting JobManager actor system at localhost:6123.11:42:40,189 INFO akka.event.slf4j.Slf4jLogger - Slf4jLogger started11:42:40,316 INFO Remoting - Starting remoting11:42:40,569 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 actor11:42:40,580 INFO org.apache.flink.runtime.blob.BlobServer - Created BLOB server storage directory /tmp/blobStore-50f75dc9-3001-4c1b-bc2a-6658ac21322b11:42:40,581 INFO org.apache.flink.runtime.blob.BlobServer - Started BLOB server at 0.0.0.0:51194 - max concurrent requests: 50 - max backlog: 100011:42:40,613 INFO org.apache.flink.runtime.jobmanager.JobManager - Starting embedded TaskManager for JobManager's LOCAL execution mode11:42:40,615 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 milliseconds11:42:40,666 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 data

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

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 methods

getIndexOfThisSubtask () / 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 Local6.2 Deploy in Cluster6.3 Deploy in Cloud

6.1 Deploy in LocalPackage 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 CPU7.2 Tuning memory7.3 Tuning I/O7.4 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

Map ReduceMap Reduce

Map Reduce

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 Sink

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 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

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

Reduce SinkSource -> 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 -

> 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

Reduce Source -> flatMap Reduce Source ->

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.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

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.numberOfBuffers

What are these buffers needed for?

TaskManager 1

Slot 2

Map Reduce

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:

What are these buffers needed for?Map Reduce job with a parallelism of 2 and 2 processing slots per Machine

TaskManager 1 TaskManager 2

Reduce

ReduceSl

Network buffer

8 buffers for outgoing data 8 buffers for incoming data

What are these buffers needed for?Map Reduce job with a parallelism of 2 and 2 processing slots per Machine

TaskManager 1 TaskManager 2

Reduce

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/disk2

Use real local disks only (no tmpfs or NAS)

Reader Thread

Disk 1

Writer Thread

Reader Thread

Writer Thread

Disk 2

Task Manager

7. How to tune your Apache Flink application7.4 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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Apache Flink Crash Course by Slim Baltagi and Srini Palthepu

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