Data Stream Processing with Apache Flink

Fabian Hueske@fhueske

Apache Flink Meetup Madrid, 25.02.2016

What is Apache Flink?Apache Flink is an open source platform for scalable stream and batch processing.

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• The core of Flink is a distributed streaming dataflow engine.• Executes dataflows in

parallel on clusters• Provides a reliable

backend for various workloads

• DataStream and DataSet programming abstractions are the foundation for user programs and higher layers

What is Apache Flink?

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Streaming topologies

Long batch pipelines

Machine Learning at scale

A stream processor with many faces

Graph Analysis

resource utilization iterative algorithms

Mutable state

low-latency processing

History & Community of Flink

From incubation until now

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Apr ‘14 Jun ‘15Dec ‘14

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Nov ‘15

Top level

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Mar ‘15

1.0!

Growing and Vibrant Community

Flink is one of the largest and most active Apache big data projects:• more than 150 contributors• more than 600 forks• more than 1000 Github stars (since yesterday)

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Flink Meetups around the Globe

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Flink Meetups around the Globe

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✔

Organizations at Flink Forward

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The streaming eraComing soon…

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What is Stream Processing? Today, most data is continuously produced

• user activity logs, web logs, sensors, database transactions, …

The common approach to analyze such data so far• Record data stream to stable storage (DBMS, HDFS,

…)• Periodically analyze data with batch processing

engine (DBMS, MapReduce, ...)

Streaming processing engines analyze data while it arrives

Why do Stream Processing? Decreases the overall latency to obtain results

• No need to persist data in stable storage• No periodic batch analysis jobs

Simplifies the data infrastructure• Fewer moving parts to be maintained and

coordinated

Makes time dimension of data explicit• Each event has a timestamp• Data can be processed based on timestamps

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What are the Requirements? Low latency

• Results in millisecond

High throughput• Millions of events per second

Exactly-once consistency• Correct results in case of failures

Out-of-order events• Process events based on their associated time

Intuitive APIs13

OS Stream Processors so far Either low latency or high throughput

Exactly-once guarantees only with high latency

Lacking time semantics• Processing by wall clock time only• Events are processed in arrival order, not in the order

they were created

Shortcomings lead to complicated system designs• Lambda architecture

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Stream Processing with Flink

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Stream Processing with Flink Low latency

• Pipelined processing engine

High throughput• Controllable checkpointing overhead

Exactly-once guarantees• Distributed snapshots

Support for out-of-order streams• Processing semantics based on event-time

Programmability • APIs similar to those known from the batch world

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Flink in Streaming Architectures

Flink

Flink Flink

Elasticsearch, Hbase, Cassandra, …

HDFS

Kafka

Analytics on static dataData ingestion

and ETL

Analytics on data in motion

The DataStream APIConcise and easy-to-grasp code

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The DataStream API

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case class Event(location: Location, numVehicles: Long)

val stream: DataStream[Event] = …;

stream .filter { evt => isIntersection(evt.location) }

The DataStream API

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case class Event(location: Location, numVehicles: Long)

val stream: DataStream[Event] = …;

stream .filter { evt => isIntersection(evt.location) } .keyBy("location") .timeWindow(Time.minutes(15), Time.minutes(5)) .sum("numVehicles")

The DataStream API

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case class Event(location: Location, numVehicles: Long)

val stream: DataStream[Event] = …;

stream .filter { evt => isIntersection(evt.location) } .keyBy("location") .timeWindow(Time.minutes(15), Time.minutes(5)) .sum("numVehicles")

.keyBy("location") .mapWithState { (evt, state: Option[Model]) => { val model = state.orElse(new Model()) (model.classify(evt), Some(model.update(evt))) }}

Event-time processingConsistent and sound results

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Event-time Processing Most data streams consist of events

• log entries, sensor data, user actions, …• Events have an associated timestamp

Many analysis tasks are based on time• “Average temperature every minute”• “Count of processed parcels per hour”• ...

Events often arrive out-of-order at processor• Distributed sources, network delays, non-synced clocks, …

Stream processor must respect time of events for consistent and sound results• Most stream processors use wall clock time

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Event Processing

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Events occur on devices

Queue / Log

Events analyzed in a

stream processor

Stream Analysis

Events stored in a log

Event Processing

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Event Processing

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Event Processing

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Event Processing

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Out of order!!!

First burst of eventsSecond burst of events

Event Processing

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Event time windows

Arrival time windows

Instant event-at-a-time

Flink supports out-of-order streams (event time) windows,arrival time windows (and mixtures) plus low latency processing.

First burst of eventsSecond burst of events

Event-time Processing Event-time processing decouples job

semantics from processing speed

Analyze events from static data store and online stream using the same program

Semantically sound and consistent results

Details:http://data-artisans.com/how-apache-flink-enables-new-streaming-applications-part-1

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Operational FeaturesRunning Flink 24*7*52

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Monitoring & Dashboard Many metrics exposed via REST

interface Web dashboard• Submit, stop, and cancel jobs• Inspect running and completed jobs• Analyze performance• Check exceptions• Inspect configuration• …

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Highly-available Cluster Setup Stream applications run for weeks, months, …

• Application must never fail!• No single-point-of-failure component allowed

Flink supports highly-available cluster setups• Master failures are resolved using Apache Zookeeper• Worker failures are resolved by master

Stand-alone cluster setup• Requires (manually started) stand-by masters and workers

YARN cluster setup• Masters and workers are automatically restarted

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A save point is a consistent snapshot of a job• Includes source offsets and operator state• Stop job• Restart job from save point

What can I use it for?• Fix or update your job• A/B testing• Update Flink• Migrate cluster• …

Details:http://data-artisans.com/how-apache-flink-enables-new-streaming-applications

Save Points

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Performance: Summary

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Continuousstreaming

Latency-boundbuffering

DistributedSnapshots

High Throughput &Low Latency

With configurable throughput/latency tradeoff

Details: http://data-artisans.com/high-throughput-low-latency-and-exactly-once-stream-processing-with-apache-flink

Integration (picture not complete)

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POSIX Java/ScalaCollections

POSIX

Post v1.0 RoadmapWhat’s coming next?

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Stream SQL and Table API Structured queries over data streams

• LINQ-style Table API• Stream SQL

Based on Apache Calcite • SQL Parser and optimizer

“Compute every hour the number of orders and number ordered units for each product.”

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SELECT STREAM productId, TUMBLE_END(rowtime, INTERVAL '1' HOUR) AS rowtime, COUNT(*) AS cnt, SUM(units) AS units FROM Orders GROUP BY TUMBLE(rowtime, INTERVAL '1' HOUR), productId;

Complex Event Processing Identify complex patterns in event streams

• Correlations & sequences

Many applications• Network intrusion detection via access patterns• Item tracking (parcels, devices, …)• …

CEP depends on low latency processing• Most CEP system are not distributed

CEP in Flink• Easy-to-use API to define CEP patterns• Integration with Table API for structured analytics• Low-latency and high-throughput engine

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Dynamic Job Parallelism Adjusting parallelism of tasks without

(significantly) interrupting the program

Initial version based on save points• Trigger save point• Stop job• Restart job with adjusted parallelism

Later change parallelism while job is running

Vision is automatic adaption based on throughput

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Wrap up! Flink is a kick-ass stream processor…• Low latency & high throughput• Exactly-once consistency• Event-time processing• Support for out-of-order streams• Intuitive API

with lots of features in the pipeline…

and a reliable batch processor as well!41

I ♥ Squirrels, do you? More Information at

• http://flink.apache.org/

Free Flink training at• http://dataartisans.github.io/flink-training

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