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Introducing Kafka’s Streams API
Stream processing made simple
Target audience: technical staff, developers, architects
Expected duration for full deck: 45 minutes
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0.10 Data processing (Streams API)
0.9 Data integration (Connect API)
Intra-cluster
replication
0.8
Apache Kafka: birthed as a messaging system, now a streaming platform
2012 2014 2015 2016 2017
Cluster mirroring,
data compression
0.7
2013
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Kafka’s Streams API: the easiest way to process data in Apache Kafka
Key Benefits of Apache Kafka’s Streams API
• Build Apps, Not Clusters: no additional cluster required
• Cluster to go: elastic, scalable, distributed, fault-tolerant, secure
• Database to go: tables, local state, interactive queries
• Equally viable for S / M / L / XL / XXL use cases
• “Runs Everywhere”: integrates with your existing deployment
strategies such as containers, automation, cloud
Part of open source Apache Kafka, introduced in 0.10+
• Powerful client library to build stream processing apps
• Apps are standard Java applications that run on client
machines
• https://github.com/apache/kafka/tree/trunk/streams
Streams
API
Your App
Kafka
Cluster
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Kafka’s Streams API: Unix analogy
$  cat  <  in.txt | grep “apache”  | tr a-­‐z  A-­‐Z  > out.txt
Kafka  Cluster
Connect  API Streams  API
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Streams API in the context of Kafka
Streams
API
Your App
Kafka
Cluster
ConnectAPI
ConnectAPI
OtherSystems
OtherSystems
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When to use Kafka’s Streams API
• Mainstream Application Development
• To build core business applications
• Microservices
• Fast Data apps for small and big data
• Reactive applications
• Continuous queries and transformations
• Event-triggered processes
• The “T” in ETL
• <and more>
Use case examples
• Real-time monitoring and intelligence
• Customer 360-degree view
• Fraud detection
• Location-based marketing
• Fleet management
• <and more>
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Some public use cases in the wild & external articles
• Applying Kafka’s Streams API for internal message delivery pipeline at LINE Corp.
• http://developers.linecorp.com/blog/?p=3960
• Kafka Streams in production at LINE, a social platform based in Japan with 220+ million users
• Microservices and reactive applications at Capital One
• https://speakerdeck.com/bobbycalderwood/commander-decoupled-immutable-rest-apis-with-kafka-streams
• User behavior analysis
• https://timothyrenner.github.io/engineering/2016/08/11/kafka-streams-not-looking-at-facebook.html
• Containerized Kafka Streams applications in Scala
• https://www.madewithtea.com/processing-tweets-with-kafka-streams.html
• Geo-spatial data analysis
• http://www.infolace.com/blog/2016/07/14/simple-spatial-windowing-with-kafka-streams/
• Language classification with machine learning
• https://dzone.com/articles/machine-learning-with-kafka-streams
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Do more with less
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Architecture comparison: use case example
Real-time dashboard for security monitoring
“Which of my data centers are under attack?”
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Architecture comparison: use case example
Other
App
Dashboard
Frontend
App
Other
App
1 Capture business
events in Kafka
2 Must process events with
separate cluster (e.g. Spark)
4
Other apps access latest results
by querying these DBs
3 Must share latest results through
separate systems (e.g. MySQL)
Before: Undue complexity, heavy footprint, many technologies, split ownership with conflicting
priorities
Your
“Job”
Other
App
Dashboard
Frontend
App
Other
App
1 Capture business
events in Kafka
2 Process events with standard
Java apps that use Kafka Streams
3 Now other apps can directly
query the latest results
With Kafka Streams: simplified, app-centric architecture, puts app owners in control
Kafka
Streams
Your App
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How do I install the Streams API?
• There is and there should be no “installation” – Build Apps, Not Clusters!
• It’s a library. Add it to your app like any other library.
<dependency>
<groupId>org.apache.kafka</groupId>
<artifactId>kafka-­‐streams</artifactId>
<version>0.10.1.1</version>
</dependency>
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“But wait a minute – where’s THE CLUSTER to process the data?”
• No cluster needed – Build Apps, Not Clusters!
• Unlearn bad habits: “do cool stuff with data ≠ must have cluster”
Ok. Ok. Ok.
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Organizational benefits: decouple teams and roadmaps, scale people
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Organizational benefits: decouple teams and roadmaps, scale people
Infrastructure Team
(Kafka as a shared, multi-tenant service)
Fraud
detection
app
Payments team
Recommenda
tions app
Mobile team
Security
alerts
app
Operations team
...more apps...
...
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How do I package, deploy, monitor my apps? How do I …?
• Whatever works for you. Stick to what you/your company think is the best way.
• No magic needed.
• Why? Because an app that uses the Streams API is…a normal Java app.
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Available APIs
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The API is but the tip of the iceberg
API,  coding
Org.  processes
Reality™
Deployment
Operations
Security
…
Architecture
Debugging
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• API option 1: DSL (declarative)
KStream<Integer,  Integer>  input  =
builder.stream("numbers-­‐topic");
//  Stateless  computation
KStream<Integer,  Integer>  doubled  =
input.mapValues(v  -­‐>  v  *  2);
//  Stateful  computation
KTable<Integer,  Integer>  sumOfOdds =  input
.filter((k,v)  -­‐>  v  %  2  !=  0)
.selectKey((k,  v)  -­‐>  1)
.groupByKey()
.reduce((v1,  v2)  -­‐>  v1  +  v2,  "sum-­‐of-­‐odds");
The preferred API for most use cases.
Particularly appeals to:
• Fans of Scala, functional programming
• Users familiar with e.g. Spark
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• API option 2: Processor API (imperative)
class  PrintToConsoleProcessor
implements  Processor<K,  V>  {
@Override
public  void  init(ProcessorContext context)  {}
@Override
void  process(K  key,  V  value)  {  
System.out.println("Got  value  "  +  value);  
}
@Override
void  punctuate(long  timestamp)  {}
@Override
void  close()  {}
}
Full flexibility but more manual work
Appeals to:
• Users who require functionality that is
not yet available in the DSL
• Users familiar with e.g. Storm, Samza
• Still, check out the DSL!
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When to use Kafka Streams vs. Kafka’s “normal” consumer clients
Kafka Streams
• Basically all the time
• Basically all the time
• Basically all the time
• Basically all the time
• Basically all the time
• Basically all the time
• Basically all the time
• Basically all the time
• Basically all the time
• Basically all the time
• Basically all the time
Kafka consumer clients (Java, C/C++, Python, Go, …)
• When you must interact with Kafka at a very low
level and/or in a very special way
• Example: When integrating your own stream
processing tool (Spark, Storm) with Kafka.
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Code comparison
Featuring Kafka with Streams API <-> Spark Streaming
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”My WordCount is better than your WordCount” (?)
Kafka
Spark
These isolated code snippets are nice (and actually quite similar) but they are not very meaningful. In practice, we
also need to read data from somewhere, write data back to somewhere, etc.– but we can see none of this here.
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WordCount in Kafka
Word
Count
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Compared to: WordCount in Spark 2.0
1
2
3
Runtime model leaks into
processing logic
(here: interfacing from
Spark with Kafka)
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Compared to: WordCount in Spark 2.0
4
5
Runtime model leaks into
processing logic
(driver vs. executors)
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Key concepts
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Key concepts
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Key concepts
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Key concepts
Kafka Core Kafka Streams
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Streams and Tables
Stream Processing meets Databases
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Key observation: close relationship between Streams and Tables
http://www.confluent.io/blog/introducing-kafka-streams-stream-processing-made-simple
http://docs.confluent.io/current/streams/concepts.html#duality-of-streams-and-tables
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Example: Streams and Tables in Kafka
Word Count
hello 2
kafka 1
world 1
… …
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Example: continuously compute current users per geo-region
4
7
5
3
2
8 4
7
6
3
2
7
Alice
Real-time dashboard
“How many users younger than 30y, per region?”
alice Europe
user-locations
alice Asia, 25y, …
bob Europe, 46y, …
… …
alice Europe, 25y, …
bob Europe, 46y, …
… …
-1
+1
user-locations
(mobile team)
user-prefs
(web team)
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Example: continuously compute current users per geo-region
KTable<UserId,  Location>  userLocations =  builder.table(“user-­‐locations-­‐topic”);
KTable<UserId,  Prefs>        userPrefs =  builder.table(“user-­‐preferences-­‐topic”);
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Example: continuously compute current users per geo-region
alice Europe
user-locations
alice Asia, 25y, …
bob Europe, 46y, …
… …
alice Europe, 25y, …
bob Europe, 46y, …
… …
KTable<UserId,  Location>  userLocations =  builder.table(“user-­‐locations-­‐topic”);
KTable<UserId,  Prefs>        userPrefs =  builder.table(“user-­‐preferences-­‐topic”);
//  Merge  into  detailed  user  profiles  (continuously  updated)
KTable<UserId,  UserProfile>  userProfiles =
userLocations.join(userPrefs,  (loc,  prefs)  -­‐>  new  UserProfile(loc,  prefs));
KTable userProfilesKTable userProfiles
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Example: continuously compute current users per geo-region
KTable<UserId,  Location>  userLocations =  builder.table(“user-­‐locations-­‐topic”);
KTable<UserId,  Prefs>        userPrefs =  builder.table(“user-­‐preferences-­‐topic”);
//  Merge  into  detailed  user  profiles  (continuously  updated)
KTable<UserId,  UserProfile>  userProfiles =
userLocations.join(userPrefs,  (loc,  prefs)  -­‐>  new  UserProfile(loc,  prefs));
//  Compute  per-­‐region  statistics  (continuously  updated)
KTable<UserId,  Long>  usersPerRegion =  userProfiles
.filter((userId,  profile)    -­‐>  profile.age <  30)
.groupBy((userId,  profile)  -­‐>  profile.location)
.count();
alice Europe
user-locations
Africa 3
… …
Asia 8
Europe 5
Africa 3
… …
Asia 7
Europe 6
KTable usersPerRegion KTable usersPerRegion
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Example: continuously compute current users per geo-region
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7
5
3
2
8 4
7
6
3
2
7
Alice
Real-time dashboard
“How many users younger than 30y, per region?”
alice Europe
user-locations
alice Asia, 25y, …
bob Europe, 46y, …
… …
alice Europe, 25y, …
bob Europe, 46y, …
… …
-1
+1
user-locations
(mobile team)
user-prefs
(web team)
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Streams meet Tables – in the DSL
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Streams meet Tables
• Most use cases for stream processing require both Streams and Tables
• Essential for any stateful computations
• Kafka ships with first-class support for Streams and Tables
• Scalability, fault tolerance, efficient joins and aggregations, …
• Benefits include: simplified architectures, less moving pieces, less Do-It-Yourself work
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Key features
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Key features in 0.10
• Native, 100%-compatible Kafka integration
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Native, 100% compatible Kafka integration
Read  from  Kafka
Write  to  Kafka
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Key features in 0.10
• Native, 100%-compatible Kafka integration
• Secure stream processing using Kafka’s security features
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Secure stream processing with the Streams API
• Your applications can leverage all client-side security features in Apache Kafka
• Security features include:
• Encrypting data-in-transit between applications and Kafka clusters
• Authenticating applications against Kafka clusters (“only some apps may talk to the production
cluster”)
• Authorizing application against Kafka clusters (“only some apps may read data from sensitive topics”)
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Configuring security settings
• In general, you can configure both Kafka Streams plus the underlying Kafka clients in your
apps
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Configuring security settings
• Example: encrypting data-in-transit + client authentication to Kafka cluster
Full demo application at https://github.com/confluentinc/examples
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Key features in 0.10
• Native, 100%-compatible Kafka integration
• Secure stream processing using Kafka’s security features
• Elastic and highly scalable
• Fault-tolerant
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Key features in 0.10
• Native, 100%-compatible Kafka integration
• Secure stream processing using Kafka’s security features
• Elastic and highly scalable
• Fault-tolerant
• Stateful and stateless computations
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Stateful computations
• Stateful computations like aggregations (e.g. counting), joins, or windowing require state
• State stores are the backbone of state management
• … are local for best performance
• … are backed up to Kafka for elasticity and for fault-tolerance
• ... are per stream task for isolation – think: share-nothing
• Pluggable storage engines
• Default: RocksDB (a key-value store) to allow for local state that is larger than available RAM
• You can also use your own, custom storage engine
• From the user perspective:
• DSL: no need to worry about anything, state management is automatically being done for you
• Processor API: direct access to state stores – very flexible but more manual work
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Use case: real-time, distributed joins at large scale
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Use case: real-time, distributed joins at large scale
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Use case: real-time, distributed joins at large scale
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Stateful computations
• Use the Processor API to interact directly with state stores
Get  the  store
Use  the  store
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Key features in 0.10
• Native, 100%-compatible Kafka integration
• Secure stream processing using Kafka’s security features
• Elastic and highly scalable
• Fault-tolerant
• Stateful and stateless computations
• Interactive queries
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Interactive Queries: architecture comparison
Kafka
Streams
App
App
App
App
1 Capture business
events in Kafka
2 Process the events
with Kafka Streams
4
Other apps query external
systems for latest results
! Must use external systems
to share latest results
App
App
App
1 Capture business
events in Kafka
2 Process the events
with Kafka Streams
3 Now other apps can directly
query the latest results
Before (0.10.0)
After (0.10.1): simplified, more app-centric architecture
Kafka
Streams
App
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Key features in 0.10
• Native, 100%-compatible Kafka integration
• Secure stream processing using Kafka’s security features
• Elastic and highly scalable
• Fault-tolerant
• Stateful and stateless computations
• Interactive queries
• Time model
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Time
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Time
A
C
B
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Time
• You configure the desired time semantics through timestamp extractors
• Default extractor yields event-time semantics
• Extracts embedded timestamps of Kafka messages (introduced in v0.10)
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Key features in 0.10
• Native, 100%-compatible Kafka integration
• Secure stream processing using Kafka’s security features
• Elastic and highly scalable
• Fault-tolerant
• Stateful and stateless computations
• Interactive queries
• Time model
• Windowing
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Windowing
• Group events in a stream using time-based windows
• Use case examples:
• Time-based analysis of ad impressions (”number of ads clicked in the past hour”)
• Monitoring statistics of telemetry data (“1min/5min/15min averages”)
Input data, where
colors represent
different users events
Rectangles denote
different event-time
windows
processing-time
event-time
windowing
alice
bob
dave
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Windowing in the DSL
TimeWindows.of(3000)
TimeWindows.of(3000).advanceBy(1000)
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Key features in 0.10
• Native, 100%-compatible Kafka integration
• Secure stream processing using Kafka’s security features
• Elastic and highly scalable
• Fault-tolerant
• Stateful and stateless computations
• Interactive queries
• Time model
• Windowing
• Supports late-arriving and out-of-order data
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Out-of-order and late-arriving data
• Is very common in practice, not a rare corner case
• Related to time model discussion
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Out-of-order and late-arriving data: example when this will happen
Users with mobile phones enter
airplane, lose Internet connectivity
Emails are being written
during the 10h flight
Internet connectivity is restored,
phones will send queued emails now
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Out-of-order and late-arriving data
• Is very common in practice, not a rare corner case
• Related to time model discussion
• We want control over how out-of-order data is handled, and handling must be efficient
• Example: We process data in 5-minute windows, e.g. compute statistics
• Option A: When event arrives 1 minute late: update the original result!
• Option B: When event arrives 2 hours late: discard it!
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Key features in 0.10
• Native, 100%-compatible Kafka integration
• Secure stream processing using Kafka’s security features
• Elastic and highly scalable
• Fault-tolerant
• Stateful and stateless computations
• Interactive queries
• Time model
• Windowing
• Supports late-arriving and out-of-order data
• Millisecond processing latency, no micro-batching
• At-least-once processing guarantees (exactly-once is in the works as we speak)
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Roadmap Outlook
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Roadmap outlook for Kafka Streams
• Exactly-Once processing semantics
• Unified API for real-time processing and “batch” processing
• Global KTables
• Session windows
• … and more …
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Wrapping Up
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Where to go from here
• Kafka Streams is available in Confluent Platform 3.1 and in Apache Kafka 0.10.1
• http://www.confluent.io/download
• Kafka Streams demos: https://github.com/confluentinc/examples
• Java 7, Java 8+ with lambdas, and Scala
• WordCount, Interactive Queries, Joins, Security, Windowing, Avro integration, …
• Confluent documentation: http://docs.confluent.io/current/streams/
• Quickstart, Concepts, Architecture, Developer Guide, FAQ
• Recorded talks
• Introduction to Kafka Streams:
http://www.youtube.com/watch?v=o7zSLNiTZbA
• Application Development and Data in the Emerging World of Stream Processing (higher level talk):
https://www.youtube.com/watch?v=JQnNHO5506w
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Thank You
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Appendix: Streams and Tables
A closer look
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Motivating example: continuously compute current users per geo-region
4
7
5
3
2
8
Real-time dashboard
“How many users younger than 30y, per region?”
alice Asia, 25y, …
bob Europe, 46y, …
… …
user-locations
(mobile team)
user-prefs
(web team)
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Motivating example: continuously compute current users per geo-region
4
7
5
3
2
8
Real-time dashboard
“How many users younger than 30y, per region?”
alice Europe
user-locations
alice Asia, 25y, …
bob Europe, 46y, …
… …
user-locations
(mobile team)
user-prefs
(web team)
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Motivating example: continuously compute current users per geo-region
4
7
5
3
2
8
Real-time dashboard
“How many users younger than 30y, per region?”
alice Europe
user-locations
user-locations
(mobile team)
user-prefs
(web team)
alice Asia, 25y, …
bob Europe, 46y, …
… …
alice Europe, 25y, …
bob Europe, 46y, …
… …
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Motivating example: continuously compute current users per geo-region
4
7
5
3
2
8 4
7
6
3
2
7
Alice
Real-time dashboard
“How many users younger than 30y, per region?”
alice Europe
user-locations
alice Asia, 25y, …
bob Europe, 46y, …
… …
alice Europe, 25y, …
bob Europe, 46y, …
… …
-1
+1
user-locations
(mobile team)
user-prefs
(web team)
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Same data, but different use cases require different interpretations
alice San Francisco
alice New York City
alice Rio de Janeiro
alice Sydney
alice Beijing
alice Paris
alice Berlin
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Same data, but different use cases require different interpretations
alice San Francisco
alice New York City
alice Rio de Janeiro
alice Sydney
alice Beijing
alice Paris
alice Berlin
Use  case  1:  Frequent  traveler  status?
Use  case  2:  Current  location?
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Same data, but different use cases require different interpretations
“Alice has been to SFO, NYC, Rio, Sydney,
Beijing, Paris, and finally Berlin.”
“Alice is in SFO, NYC, Rio, Sydney,
Beijing, Paris, Berlin right now.”
⚑ ⚑
⚑⚑
⚑
⚑
⚑ ⚑ ⚑
⚑⚑
⚑
⚑
⚑
Use  case  1:  Frequent  traveler  status? Use  case  2:  Current  location?
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Same data, but different use cases require different interpretations
alice San Francisco
alice New York City
alice Rio de Janeiro
alice Sydney
alice Beijing
alice Paris
alice Berlin
Use  case  1:  Frequent  traveler  status?
Use  case  2:  Current  location?
⚑ ⚑ ⚑⚑
⚑
⚑⚑
⚑
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Same data, but different use cases require different interpretations
alice San Francisco
alice New York City
alice Rio de Janeiro
alice Sydney
alice Beijing
alice Paris
alice Berlin
Use  case  1:  Frequent  traveler  status?
Use  case  2:  Current  location?
⚑ ⚑ ⚑⚑
⚑
⚑⚑
⚑
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Same data, but different use cases require different interpretations
alice San Francisco
alice New York City
alice Rio de Janeiro
alice Sydney
alice Beijing
alice Paris
alice Berlin
Use  case  1:  Frequent  traveler  status?
Use  case  2:  Current  location?
⚑ ⚑ ⚑⚑
⚑
⚑⚑
⚑
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Streams meet Tables
record stream
When you need… so that the topic is
interpreted as a
All the values of a key KStream
then you’d read the
Kafka topic into a
Example
All the places Alice
has ever been to
with messages
interpreted as
INSERT
(append)
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Streams meet Tables
record stream
changelog stream
When you need… so that the topic is
interpreted as a
All the values of a key
Latest value of a key
KStream
KTable
then you’d read the
Kafka topic into a
Example
All the places Alice
has ever been to
Where Alice
is right now
with messages
interpreted as
INSERT
(append)
UPSERT
(overwrite
existing)
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Same data, but different use cases require different interpretations
“Alice has been to SFO, NYC, Rio, Sydney,
Beijing, Paris, and finally Berlin.”
“Alice is in SFO, NYC, Rio, Sydney,
Beijing, Paris, Berlin right now.”
⚑ ⚑
⚑⚑
⚑
⚑
⚑ ⚑ ⚑
⚑⚑
⚑
⚑
⚑
Use  case  1:  Frequent  traveler  status? Use  case  2:  Current  location?
KStream KTable
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Motivating example: continuously compute current users per geo-region
4
7
5
3
2
8 4
7
6
3
2
7
Alice
Real-time dashboard
“How many users younger than 30y, per region?”
alice Europe
user-locations
alice Asia, 25y, …
bob Europe, 46y, …
… …
alice Europe, 25y, …
bob Europe, 46y, …
… …
-1
+1
user-locations
(mobile team)
user-prefs
(web team)
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Motivating example: continuously compute current users per geo-region
KTable<UserId,  Location>  userLocations =  builder.table(“user-­‐locations-­‐topic”);
KTable<UserId,  Prefs>        userPrefs =  builder.table(“user-­‐preferences-­‐topic”);
106Confidential
Motivating example: continuously compute current users per geo-region
alice Europe
user-locations
alice Asia, 25y, …
bob Europe, 46y, …
… …
alice Europe, 25y, …
bob Europe, 46y, …
… …
KTable<UserId,  Location>  userLocations =  builder.table(“user-­‐locations-­‐topic”);
KTable<UserId,  Prefs>        userPrefs =  builder.table(“user-­‐preferences-­‐topic”);
//  Merge  into  detailed  user  profiles  (continuously  updated)
KTable<UserId,  UserProfile>  userProfiles =
userLocations.join(userPrefs,  (loc,  prefs)  -­‐>  new  UserProfile(loc,  prefs));
KTable userProfilesKTable userProfiles
107Confidential
Motivating example: continuously compute current users per geo-region
KTable<UserId,  Location>  userLocations =  builder.table(“user-­‐locations-­‐topic”);
KTable<UserId,  Prefs>        userPrefs =  builder.table(“user-­‐preferences-­‐topic”);
//  Merge  into  detailed  user  profiles  (continuously  updated)
KTable<UserId,  UserProfile>  userProfiles =
userLocations.join(userPrefs,  (loc,  prefs)  -­‐>  new  UserProfile(loc,  prefs));
//  Compute  per-­‐region  statistics  (continuously  updated)
KTable<UserId,  Long>  usersPerRegion =  userProfiles
.filter((userId,  profile)    -­‐>  profile.age <  30)
.groupBy((userId,  profile)  -­‐>  profile.location)
.count();
alice Europe
user-locations
Africa 3
… …
Asia 8
Europe 5
Africa 3
… …
Asia 7
Europe 6
KTable usersPerRegion KTable usersPerRegion
108Confidential
Motivating example: continuously compute current users per geo-region
4
7
5
3
2
8 4
7
6
3
2
7
Alice
Real-time dashboard
“How many users younger than 30y, per region?”
alice Europe
user-locations
alice Asia, 25y, …
bob Europe, 46y, …
… …
alice Europe, 25y, …
bob Europe, 46y, …
… …
-1
+1
user-locations
(mobile team)
user-prefs
(web team)
109Confidential
Another common use case: continuous transformations
• Example: to enrich an input stream (user clicks) with side data (current user profile)
KStream alice /rental/p8454vb, 06:59 PM PDT
user-clicks-topics (at 1M msgs/s)
“facts”
110Confidential
Another common use case: continuous transformations
• Example: to enrich an input stream (user clicks) with side data (current user profile)
KStream alice /rental/p8454vb, 06:59 PM PDT
alice Asia, 25y
bob Europe, 46y
… …
KTable
user-profiles-topic
user-clicks-topics (at 1M msgs/s)
“facts”
“dimensions”
111Confidential
Another common use case: continuous transformations
• Example: to enrich an input stream (user clicks) with side data (current user profile)
KStream
alice /rental/p8454vb, 06:59 PDT, Asia, 25y
stream.JOIN(table)
alice /rental/p8454vb, 06:59 PM PDT
alice Asia, 25y
bob Europe, 46y
… …
KTable
user-profiles-topic
user-clicks-topics (at 1M msgs/s)
“facts”
“dimensions”
112Confidential
Another common use case: continuous transformations
• Example: to enrich an input stream (user clicks) with side data (current user profile)
KStream
alice /rental/p8454vb, 06:59 PDT, Asia, 25y
stream.JOIN(table)
alice /rental/p8454vb, 06:59 PM PDT
alice Asia, 25y
bob Europe, 46y
… …
KTable
alice Europe, 25y
bob Europe, 46y
… …alice Europe
new update for alice from user-locations topic
user-profiles-topic
user-clicks-topics (at 1M msgs/s)
“facts”
“dimensions”
113Confidential
Appendix: Interactive Queries
A closer look
114Confidential
Interactive Queries
115Confidential
Interactive Queries
charlie 3bob 5 alice 2
116Confidential
Interactive Queries
New  API  to  access
local  state  stores  of
an  app  instance
charlie 3bob 5 alice 2
117Confidential
Interactive Queries
New  API  to  discover
running  app  instances
charlie 3bob 5 alice 2
“host1:4460” “host5:5307” “host3:4777”
118Confidential
Interactive Queries
You:  inter-­app  communication  (RPC  layer)

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Introducing Kafka's Streams API

  • 1. 1Confidential Introducing Kafka’s Streams API Stream processing made simple Target audience: technical staff, developers, architects Expected duration for full deck: 45 minutes
  • 2. 2Confidential 0.10 Data processing (Streams API) 0.9 Data integration (Connect API) Intra-cluster replication 0.8 Apache Kafka: birthed as a messaging system, now a streaming platform 2012 2014 2015 2016 2017 Cluster mirroring, data compression 0.7 2013
  • 3. 3Confidential Kafka’s Streams API: the easiest way to process data in Apache Kafka Key Benefits of Apache Kafka’s Streams API • Build Apps, Not Clusters: no additional cluster required • Cluster to go: elastic, scalable, distributed, fault-tolerant, secure • Database to go: tables, local state, interactive queries • Equally viable for S / M / L / XL / XXL use cases • “Runs Everywhere”: integrates with your existing deployment strategies such as containers, automation, cloud Part of open source Apache Kafka, introduced in 0.10+ • Powerful client library to build stream processing apps • Apps are standard Java applications that run on client machines • https://github.com/apache/kafka/tree/trunk/streams Streams API Your App Kafka Cluster
  • 4. 4Confidential Kafka’s Streams API: Unix analogy $  cat  <  in.txt | grep “apache”  | tr a-­‐z  A-­‐Z  > out.txt Kafka  Cluster Connect  API Streams  API
  • 5. 5Confidential Streams API in the context of Kafka Streams API Your App Kafka Cluster ConnectAPI ConnectAPI OtherSystems OtherSystems
  • 6. 6Confidential When to use Kafka’s Streams API • Mainstream Application Development • To build core business applications • Microservices • Fast Data apps for small and big data • Reactive applications • Continuous queries and transformations • Event-triggered processes • The “T” in ETL • <and more> Use case examples • Real-time monitoring and intelligence • Customer 360-degree view • Fraud detection • Location-based marketing • Fleet management • <and more>
  • 7. 7Confidential Some public use cases in the wild & external articles • Applying Kafka’s Streams API for internal message delivery pipeline at LINE Corp. • http://developers.linecorp.com/blog/?p=3960 • Kafka Streams in production at LINE, a social platform based in Japan with 220+ million users • Microservices and reactive applications at Capital One • https://speakerdeck.com/bobbycalderwood/commander-decoupled-immutable-rest-apis-with-kafka-streams • User behavior analysis • https://timothyrenner.github.io/engineering/2016/08/11/kafka-streams-not-looking-at-facebook.html • Containerized Kafka Streams applications in Scala • https://www.madewithtea.com/processing-tweets-with-kafka-streams.html • Geo-spatial data analysis • http://www.infolace.com/blog/2016/07/14/simple-spatial-windowing-with-kafka-streams/ • Language classification with machine learning • https://dzone.com/articles/machine-learning-with-kafka-streams
  • 9. 9Confidential Architecture comparison: use case example Real-time dashboard for security monitoring “Which of my data centers are under attack?”
  • 10. 10Confidential Architecture comparison: use case example Other App Dashboard Frontend App Other App 1 Capture business events in Kafka 2 Must process events with separate cluster (e.g. Spark) 4 Other apps access latest results by querying these DBs 3 Must share latest results through separate systems (e.g. MySQL) Before: Undue complexity, heavy footprint, many technologies, split ownership with conflicting priorities Your “Job” Other App Dashboard Frontend App Other App 1 Capture business events in Kafka 2 Process events with standard Java apps that use Kafka Streams 3 Now other apps can directly query the latest results With Kafka Streams: simplified, app-centric architecture, puts app owners in control Kafka Streams Your App
  • 13. 13Confidential How do I install the Streams API? • There is and there should be no “installation” – Build Apps, Not Clusters! • It’s a library. Add it to your app like any other library. <dependency> <groupId>org.apache.kafka</groupId> <artifactId>kafka-­‐streams</artifactId> <version>0.10.1.1</version> </dependency>
  • 14. 14Confidential “But wait a minute – where’s THE CLUSTER to process the data?” • No cluster needed – Build Apps, Not Clusters! • Unlearn bad habits: “do cool stuff with data ≠ must have cluster” Ok. Ok. Ok.
  • 15. 15Confidential Organizational benefits: decouple teams and roadmaps, scale people
  • 16. 16Confidential Organizational benefits: decouple teams and roadmaps, scale people Infrastructure Team (Kafka as a shared, multi-tenant service) Fraud detection app Payments team Recommenda tions app Mobile team Security alerts app Operations team ...more apps... ...
  • 17. 17Confidential How do I package, deploy, monitor my apps? How do I …? • Whatever works for you. Stick to what you/your company think is the best way. • No magic needed. • Why? Because an app that uses the Streams API is…a normal Java app.
  • 19. 19Confidential The API is but the tip of the iceberg API,  coding Org.  processes Reality™ Deployment Operations Security … Architecture Debugging
  • 20. 20Confidential • API option 1: DSL (declarative) KStream<Integer,  Integer>  input  = builder.stream("numbers-­‐topic"); //  Stateless  computation KStream<Integer,  Integer>  doubled  = input.mapValues(v  -­‐>  v  *  2); //  Stateful  computation KTable<Integer,  Integer>  sumOfOdds =  input .filter((k,v)  -­‐>  v  %  2  !=  0) .selectKey((k,  v)  -­‐>  1) .groupByKey() .reduce((v1,  v2)  -­‐>  v1  +  v2,  "sum-­‐of-­‐odds"); The preferred API for most use cases. Particularly appeals to: • Fans of Scala, functional programming • Users familiar with e.g. Spark
  • 21. 21Confidential • API option 2: Processor API (imperative) class  PrintToConsoleProcessor implements  Processor<K,  V>  { @Override public  void  init(ProcessorContext context)  {} @Override void  process(K  key,  V  value)  {   System.out.println("Got  value  "  +  value);   } @Override void  punctuate(long  timestamp)  {} @Override void  close()  {} } Full flexibility but more manual work Appeals to: • Users who require functionality that is not yet available in the DSL • Users familiar with e.g. Storm, Samza • Still, check out the DSL!
  • 22. 22Confidential When to use Kafka Streams vs. Kafka’s “normal” consumer clients Kafka Streams • Basically all the time • Basically all the time • Basically all the time • Basically all the time • Basically all the time • Basically all the time • Basically all the time • Basically all the time • Basically all the time • Basically all the time • Basically all the time Kafka consumer clients (Java, C/C++, Python, Go, …) • When you must interact with Kafka at a very low level and/or in a very special way • Example: When integrating your own stream processing tool (Spark, Storm) with Kafka.
  • 23. 23Confidential Code comparison Featuring Kafka with Streams API <-> Spark Streaming
  • 24. 24Confidential ”My WordCount is better than your WordCount” (?) Kafka Spark These isolated code snippets are nice (and actually quite similar) but they are not very meaningful. In practice, we also need to read data from somewhere, write data back to somewhere, etc.– but we can see none of this here.
  • 26. 26Confidential Compared to: WordCount in Spark 2.0 1 2 3 Runtime model leaks into processing logic (here: interfacing from Spark with Kafka)
  • 27. 27Confidential Compared to: WordCount in Spark 2.0 4 5 Runtime model leaks into processing logic (driver vs. executors)
  • 32. 32Confidential Streams and Tables Stream Processing meets Databases
  • 35. 35Confidential Key observation: close relationship between Streams and Tables http://www.confluent.io/blog/introducing-kafka-streams-stream-processing-made-simple http://docs.confluent.io/current/streams/concepts.html#duality-of-streams-and-tables
  • 37. 37Confidential Example: Streams and Tables in Kafka Word Count hello 2 kafka 1 world 1 … …
  • 42. 42Confidential Example: continuously compute current users per geo-region 4 7 5 3 2 8 4 7 6 3 2 7 Alice Real-time dashboard “How many users younger than 30y, per region?” alice Europe user-locations alice Asia, 25y, … bob Europe, 46y, … … … alice Europe, 25y, … bob Europe, 46y, … … … -1 +1 user-locations (mobile team) user-prefs (web team)
  • 43. 43Confidential Example: continuously compute current users per geo-region KTable<UserId,  Location>  userLocations =  builder.table(“user-­‐locations-­‐topic”); KTable<UserId,  Prefs>        userPrefs =  builder.table(“user-­‐preferences-­‐topic”);
  • 44. 44Confidential Example: continuously compute current users per geo-region alice Europe user-locations alice Asia, 25y, … bob Europe, 46y, … … … alice Europe, 25y, … bob Europe, 46y, … … … KTable<UserId,  Location>  userLocations =  builder.table(“user-­‐locations-­‐topic”); KTable<UserId,  Prefs>        userPrefs =  builder.table(“user-­‐preferences-­‐topic”); //  Merge  into  detailed  user  profiles  (continuously  updated) KTable<UserId,  UserProfile>  userProfiles = userLocations.join(userPrefs,  (loc,  prefs)  -­‐>  new  UserProfile(loc,  prefs)); KTable userProfilesKTable userProfiles
  • 45. 45Confidential Example: continuously compute current users per geo-region KTable<UserId,  Location>  userLocations =  builder.table(“user-­‐locations-­‐topic”); KTable<UserId,  Prefs>        userPrefs =  builder.table(“user-­‐preferences-­‐topic”); //  Merge  into  detailed  user  profiles  (continuously  updated) KTable<UserId,  UserProfile>  userProfiles = userLocations.join(userPrefs,  (loc,  prefs)  -­‐>  new  UserProfile(loc,  prefs)); //  Compute  per-­‐region  statistics  (continuously  updated) KTable<UserId,  Long>  usersPerRegion =  userProfiles .filter((userId,  profile)    -­‐>  profile.age <  30) .groupBy((userId,  profile)  -­‐>  profile.location) .count(); alice Europe user-locations Africa 3 … … Asia 8 Europe 5 Africa 3 … … Asia 7 Europe 6 KTable usersPerRegion KTable usersPerRegion
  • 46. 46Confidential Example: continuously compute current users per geo-region 4 7 5 3 2 8 4 7 6 3 2 7 Alice Real-time dashboard “How many users younger than 30y, per region?” alice Europe user-locations alice Asia, 25y, … bob Europe, 46y, … … … alice Europe, 25y, … bob Europe, 46y, … … … -1 +1 user-locations (mobile team) user-prefs (web team)
  • 48. 48Confidential Streams meet Tables • Most use cases for stream processing require both Streams and Tables • Essential for any stateful computations • Kafka ships with first-class support for Streams and Tables • Scalability, fault tolerance, efficient joins and aggregations, … • Benefits include: simplified architectures, less moving pieces, less Do-It-Yourself work
  • 50. 50Confidential Key features in 0.10 • Native, 100%-compatible Kafka integration
  • 51. 51Confidential Native, 100% compatible Kafka integration Read  from  Kafka Write  to  Kafka
  • 52. 52Confidential Key features in 0.10 • Native, 100%-compatible Kafka integration • Secure stream processing using Kafka’s security features
  • 53. 53Confidential Secure stream processing with the Streams API • Your applications can leverage all client-side security features in Apache Kafka • Security features include: • Encrypting data-in-transit between applications and Kafka clusters • Authenticating applications against Kafka clusters (“only some apps may talk to the production cluster”) • Authorizing application against Kafka clusters (“only some apps may read data from sensitive topics”)
  • 54. 54Confidential Configuring security settings • In general, you can configure both Kafka Streams plus the underlying Kafka clients in your apps
  • 55. 55Confidential Configuring security settings • Example: encrypting data-in-transit + client authentication to Kafka cluster Full demo application at https://github.com/confluentinc/examples
  • 56. 56Confidential Key features in 0.10 • Native, 100%-compatible Kafka integration • Secure stream processing using Kafka’s security features • Elastic and highly scalable • Fault-tolerant
  • 60. 60Confidential Key features in 0.10 • Native, 100%-compatible Kafka integration • Secure stream processing using Kafka’s security features • Elastic and highly scalable • Fault-tolerant • Stateful and stateless computations
  • 61. 61Confidential Stateful computations • Stateful computations like aggregations (e.g. counting), joins, or windowing require state • State stores are the backbone of state management • … are local for best performance • … are backed up to Kafka for elasticity and for fault-tolerance • ... are per stream task for isolation – think: share-nothing • Pluggable storage engines • Default: RocksDB (a key-value store) to allow for local state that is larger than available RAM • You can also use your own, custom storage engine • From the user perspective: • DSL: no need to worry about anything, state management is automatically being done for you • Processor API: direct access to state stores – very flexible but more manual work
  • 66. 66Confidential Use case: real-time, distributed joins at large scale
  • 67. 67Confidential Use case: real-time, distributed joins at large scale
  • 68. 68Confidential Use case: real-time, distributed joins at large scale
  • 69. 69Confidential Stateful computations • Use the Processor API to interact directly with state stores Get  the  store Use  the  store
  • 70. 70Confidential Key features in 0.10 • Native, 100%-compatible Kafka integration • Secure stream processing using Kafka’s security features • Elastic and highly scalable • Fault-tolerant • Stateful and stateless computations • Interactive queries
  • 72. 72Confidential Interactive Queries: architecture comparison Kafka Streams App App App App 1 Capture business events in Kafka 2 Process the events with Kafka Streams 4 Other apps query external systems for latest results ! Must use external systems to share latest results App App App 1 Capture business events in Kafka 2 Process the events with Kafka Streams 3 Now other apps can directly query the latest results Before (0.10.0) After (0.10.1): simplified, more app-centric architecture Kafka Streams App
  • 73. 73Confidential Key features in 0.10 • Native, 100%-compatible Kafka integration • Secure stream processing using Kafka’s security features • Elastic and highly scalable • Fault-tolerant • Stateful and stateless computations • Interactive queries • Time model
  • 76. 76Confidential Time • You configure the desired time semantics through timestamp extractors • Default extractor yields event-time semantics • Extracts embedded timestamps of Kafka messages (introduced in v0.10)
  • 77. 77Confidential Key features in 0.10 • Native, 100%-compatible Kafka integration • Secure stream processing using Kafka’s security features • Elastic and highly scalable • Fault-tolerant • Stateful and stateless computations • Interactive queries • Time model • Windowing
  • 78. 78Confidential Windowing • Group events in a stream using time-based windows • Use case examples: • Time-based analysis of ad impressions (”number of ads clicked in the past hour”) • Monitoring statistics of telemetry data (“1min/5min/15min averages”) Input data, where colors represent different users events Rectangles denote different event-time windows processing-time event-time windowing alice bob dave
  • 79. 79Confidential Windowing in the DSL TimeWindows.of(3000) TimeWindows.of(3000).advanceBy(1000)
  • 80. 80Confidential Key features in 0.10 • Native, 100%-compatible Kafka integration • Secure stream processing using Kafka’s security features • Elastic and highly scalable • Fault-tolerant • Stateful and stateless computations • Interactive queries • Time model • Windowing • Supports late-arriving and out-of-order data
  • 81. 81Confidential Out-of-order and late-arriving data • Is very common in practice, not a rare corner case • Related to time model discussion
  • 82. 82Confidential Out-of-order and late-arriving data: example when this will happen Users with mobile phones enter airplane, lose Internet connectivity Emails are being written during the 10h flight Internet connectivity is restored, phones will send queued emails now
  • 83. 83Confidential Out-of-order and late-arriving data • Is very common in practice, not a rare corner case • Related to time model discussion • We want control over how out-of-order data is handled, and handling must be efficient • Example: We process data in 5-minute windows, e.g. compute statistics • Option A: When event arrives 1 minute late: update the original result! • Option B: When event arrives 2 hours late: discard it!
  • 84. 84Confidential Key features in 0.10 • Native, 100%-compatible Kafka integration • Secure stream processing using Kafka’s security features • Elastic and highly scalable • Fault-tolerant • Stateful and stateless computations • Interactive queries • Time model • Windowing • Supports late-arriving and out-of-order data • Millisecond processing latency, no micro-batching • At-least-once processing guarantees (exactly-once is in the works as we speak)
  • 86. 86Confidential Roadmap outlook for Kafka Streams • Exactly-Once processing semantics • Unified API for real-time processing and “batch” processing • Global KTables • Session windows • … and more …
  • 88. 88Confidential Where to go from here • Kafka Streams is available in Confluent Platform 3.1 and in Apache Kafka 0.10.1 • http://www.confluent.io/download • Kafka Streams demos: https://github.com/confluentinc/examples • Java 7, Java 8+ with lambdas, and Scala • WordCount, Interactive Queries, Joins, Security, Windowing, Avro integration, … • Confluent documentation: http://docs.confluent.io/current/streams/ • Quickstart, Concepts, Architecture, Developer Guide, FAQ • Recorded talks • Introduction to Kafka Streams: http://www.youtube.com/watch?v=o7zSLNiTZbA • Application Development and Data in the Emerging World of Stream Processing (higher level talk): https://www.youtube.com/watch?v=JQnNHO5506w
  • 90. 90Confidential Appendix: Streams and Tables A closer look
  • 91. 91Confidential Motivating example: continuously compute current users per geo-region 4 7 5 3 2 8 Real-time dashboard “How many users younger than 30y, per region?” alice Asia, 25y, … bob Europe, 46y, … … … user-locations (mobile team) user-prefs (web team)
  • 92. 92Confidential Motivating example: continuously compute current users per geo-region 4 7 5 3 2 8 Real-time dashboard “How many users younger than 30y, per region?” alice Europe user-locations alice Asia, 25y, … bob Europe, 46y, … … … user-locations (mobile team) user-prefs (web team)
  • 93. 93Confidential Motivating example: continuously compute current users per geo-region 4 7 5 3 2 8 Real-time dashboard “How many users younger than 30y, per region?” alice Europe user-locations user-locations (mobile team) user-prefs (web team) alice Asia, 25y, … bob Europe, 46y, … … … alice Europe, 25y, … bob Europe, 46y, … … …
  • 94. 94Confidential Motivating example: continuously compute current users per geo-region 4 7 5 3 2 8 4 7 6 3 2 7 Alice Real-time dashboard “How many users younger than 30y, per region?” alice Europe user-locations alice Asia, 25y, … bob Europe, 46y, … … … alice Europe, 25y, … bob Europe, 46y, … … … -1 +1 user-locations (mobile team) user-prefs (web team)
  • 95. 95Confidential Same data, but different use cases require different interpretations alice San Francisco alice New York City alice Rio de Janeiro alice Sydney alice Beijing alice Paris alice Berlin
  • 96. 96Confidential Same data, but different use cases require different interpretations alice San Francisco alice New York City alice Rio de Janeiro alice Sydney alice Beijing alice Paris alice Berlin Use  case  1:  Frequent  traveler  status? Use  case  2:  Current  location?
  • 97. 97Confidential Same data, but different use cases require different interpretations “Alice has been to SFO, NYC, Rio, Sydney, Beijing, Paris, and finally Berlin.” “Alice is in SFO, NYC, Rio, Sydney, Beijing, Paris, Berlin right now.” ⚑ ⚑ ⚑⚑ ⚑ ⚑ ⚑ ⚑ ⚑ ⚑⚑ ⚑ ⚑ ⚑ Use  case  1:  Frequent  traveler  status? Use  case  2:  Current  location?
  • 98. 98Confidential Same data, but different use cases require different interpretations alice San Francisco alice New York City alice Rio de Janeiro alice Sydney alice Beijing alice Paris alice Berlin Use  case  1:  Frequent  traveler  status? Use  case  2:  Current  location? ⚑ ⚑ ⚑⚑ ⚑ ⚑⚑ ⚑
  • 99. 99Confidential Same data, but different use cases require different interpretations alice San Francisco alice New York City alice Rio de Janeiro alice Sydney alice Beijing alice Paris alice Berlin Use  case  1:  Frequent  traveler  status? Use  case  2:  Current  location? ⚑ ⚑ ⚑⚑ ⚑ ⚑⚑ ⚑
  • 100. 100Confidential Same data, but different use cases require different interpretations alice San Francisco alice New York City alice Rio de Janeiro alice Sydney alice Beijing alice Paris alice Berlin Use  case  1:  Frequent  traveler  status? Use  case  2:  Current  location? ⚑ ⚑ ⚑⚑ ⚑ ⚑⚑ ⚑
  • 101. 101Confidential Streams meet Tables record stream When you need… so that the topic is interpreted as a All the values of a key KStream then you’d read the Kafka topic into a Example All the places Alice has ever been to with messages interpreted as INSERT (append)
  • 102. 102Confidential Streams meet Tables record stream changelog stream When you need… so that the topic is interpreted as a All the values of a key Latest value of a key KStream KTable then you’d read the Kafka topic into a Example All the places Alice has ever been to Where Alice is right now with messages interpreted as INSERT (append) UPSERT (overwrite existing)
  • 103. 103Confidential Same data, but different use cases require different interpretations “Alice has been to SFO, NYC, Rio, Sydney, Beijing, Paris, and finally Berlin.” “Alice is in SFO, NYC, Rio, Sydney, Beijing, Paris, Berlin right now.” ⚑ ⚑ ⚑⚑ ⚑ ⚑ ⚑ ⚑ ⚑ ⚑⚑ ⚑ ⚑ ⚑ Use  case  1:  Frequent  traveler  status? Use  case  2:  Current  location? KStream KTable
  • 104. 104Confidential Motivating example: continuously compute current users per geo-region 4 7 5 3 2 8 4 7 6 3 2 7 Alice Real-time dashboard “How many users younger than 30y, per region?” alice Europe user-locations alice Asia, 25y, … bob Europe, 46y, … … … alice Europe, 25y, … bob Europe, 46y, … … … -1 +1 user-locations (mobile team) user-prefs (web team)
  • 105. 105Confidential Motivating example: continuously compute current users per geo-region KTable<UserId,  Location>  userLocations =  builder.table(“user-­‐locations-­‐topic”); KTable<UserId,  Prefs>        userPrefs =  builder.table(“user-­‐preferences-­‐topic”);
  • 106. 106Confidential Motivating example: continuously compute current users per geo-region alice Europe user-locations alice Asia, 25y, … bob Europe, 46y, … … … alice Europe, 25y, … bob Europe, 46y, … … … KTable<UserId,  Location>  userLocations =  builder.table(“user-­‐locations-­‐topic”); KTable<UserId,  Prefs>        userPrefs =  builder.table(“user-­‐preferences-­‐topic”); //  Merge  into  detailed  user  profiles  (continuously  updated) KTable<UserId,  UserProfile>  userProfiles = userLocations.join(userPrefs,  (loc,  prefs)  -­‐>  new  UserProfile(loc,  prefs)); KTable userProfilesKTable userProfiles
  • 107. 107Confidential Motivating example: continuously compute current users per geo-region KTable<UserId,  Location>  userLocations =  builder.table(“user-­‐locations-­‐topic”); KTable<UserId,  Prefs>        userPrefs =  builder.table(“user-­‐preferences-­‐topic”); //  Merge  into  detailed  user  profiles  (continuously  updated) KTable<UserId,  UserProfile>  userProfiles = userLocations.join(userPrefs,  (loc,  prefs)  -­‐>  new  UserProfile(loc,  prefs)); //  Compute  per-­‐region  statistics  (continuously  updated) KTable<UserId,  Long>  usersPerRegion =  userProfiles .filter((userId,  profile)    -­‐>  profile.age <  30) .groupBy((userId,  profile)  -­‐>  profile.location) .count(); alice Europe user-locations Africa 3 … … Asia 8 Europe 5 Africa 3 … … Asia 7 Europe 6 KTable usersPerRegion KTable usersPerRegion
  • 108. 108Confidential Motivating example: continuously compute current users per geo-region 4 7 5 3 2 8 4 7 6 3 2 7 Alice Real-time dashboard “How many users younger than 30y, per region?” alice Europe user-locations alice Asia, 25y, … bob Europe, 46y, … … … alice Europe, 25y, … bob Europe, 46y, … … … -1 +1 user-locations (mobile team) user-prefs (web team)
  • 109. 109Confidential Another common use case: continuous transformations • Example: to enrich an input stream (user clicks) with side data (current user profile) KStream alice /rental/p8454vb, 06:59 PM PDT user-clicks-topics (at 1M msgs/s) “facts”
  • 110. 110Confidential Another common use case: continuous transformations • Example: to enrich an input stream (user clicks) with side data (current user profile) KStream alice /rental/p8454vb, 06:59 PM PDT alice Asia, 25y bob Europe, 46y … … KTable user-profiles-topic user-clicks-topics (at 1M msgs/s) “facts” “dimensions”
  • 111. 111Confidential Another common use case: continuous transformations • Example: to enrich an input stream (user clicks) with side data (current user profile) KStream alice /rental/p8454vb, 06:59 PDT, Asia, 25y stream.JOIN(table) alice /rental/p8454vb, 06:59 PM PDT alice Asia, 25y bob Europe, 46y … … KTable user-profiles-topic user-clicks-topics (at 1M msgs/s) “facts” “dimensions”
  • 112. 112Confidential Another common use case: continuous transformations • Example: to enrich an input stream (user clicks) with side data (current user profile) KStream alice /rental/p8454vb, 06:59 PDT, Asia, 25y stream.JOIN(table) alice /rental/p8454vb, 06:59 PM PDT alice Asia, 25y bob Europe, 46y … … KTable alice Europe, 25y bob Europe, 46y … …alice Europe new update for alice from user-locations topic user-profiles-topic user-clicks-topics (at 1M msgs/s) “facts” “dimensions”
  • 116. 116Confidential Interactive Queries New  API  to  access local  state  stores  of an  app  instance charlie 3bob 5 alice 2
  • 117. 117Confidential Interactive Queries New  API  to  discover running  app  instances charlie 3bob 5 alice 2 “host1:4460” “host5:5307” “host3:4777”
  • 118. 118Confidential Interactive Queries You:  inter-­app  communication  (RPC  layer)