Concepts and Patterns for Streaming Services with Kafka
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Cloud Native Night March 2020, Mainz: Talk by Perry Krol (@perkrol, Confluent) === Please download slides if blurred! === Abstract: Proven approaches such as service-oriented and event-driven architectures are joined by newer techniques such as microservices, reactive architectures, DevOps, and stream processing. Many of these patterns are successful by themselves, but they provide a more holistic and compelling approach when applied together. In this session Confluent will provide insights how service-based architectures and stream processing tools such as Apache Kafka® can help you build business-critical systems. You will learn why streaming beats request-response based architectures in complex, contemporary use cases, and explain why replayable logs such as Kafka provide a backbone for both service communication and shared datasets. Based on these principles, we will explore how event collaboration and event sourcing patterns increase safety and recoverability with functional, event-driven approaches, apply patterns including Event Sourcing and CQRS, and how to build multi-team systems with microservices and SOA using patterns such as “inside out databases” and “event streams as a source of truth”.
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Concepts and Patterns for Streaming Services with Kafka
- 1. 1 Concepts and Patterns for Streaming Services Perry Krol, Head of Systems Engineering CEMEA
- 2. 2 Confluent Community Slack Channel Over 10,000 Kafkateers are collaborating every single day on the Confluent Community Slack channel! cnfl.io/community-slack Subscribe to the Confluent blog Get frequent updates from key names in Apache Kafka® on best practices, product updates & more! cnfl.io/read Welcome to the Mainz Cloud Native Night Meetup with Apache Kafka® ! Zoom open at 19:00 19:00PM - 19:10PM Virtual Cheers and Networking 19:10PM - 19:15PM Welcome and Intro 20:00PM - 20:00PM Concepts & Patterns for Streaming Services with Kafka Perry Krol
- 3. 33 Introduction to Apache Kafka® as Event-Driven Streaming Platform
- 5. 55 K V The Truth is in the Log K V K V K V Log of Events Kafka Topic 210 3
- 7. 77 Partitions … … … … Partition 0 Partition 1 Partition 2 Partition 3 • Provides scalable: - Writes - Storage - Consumption • Ordering is within a partition only
- 8. 88 Replicas Broker 1 Broker 2 Broker 3 Broker 4 Topic A Partition 0 Topic A Partition 0 Topic A Partition 1 Topic A Partition 0 Topic A Partition 1 Topic A Partition 2 Topic A Partition 3 Topic A Partition 1 Topic A Partition 2 Topic A Partition 2 Leader Follower
- 9. 99 Replicas Broker 1 Broker 2 Broker 3 Broker 4 Topic A Partition 0 Topic A Partition 0 Topic A Partition 1 Topic A Partition 0 Topic A Partition 1 Topic A Partition 2 Topic A Partition 3 Topic A Partition 1 Topic A Partition 2 Topic A Partition 2
- 10. 1010 Producers … … … … Partition 0 Partition 1 Partition 2 Partition 3 Partitioned Topic Producer
- 11. 1111 Competitive Landscape Non event-streaming (TIBCO, IBM MQ, Solace, ...) Event-streaming Non-Kafka (Kinesis, Pulsar) Kafka Open Source (Apache Kafka) Commercial Offerings Non-Confluent AWS MSK Cloudera Red Hat Aiven ... Confluent DRAFT - For Internal Enablement Only 1414 Record Keys & Ordering Record keys determine the partition with the default kafka partitioner Keys are used in the default partitioning algorithm: partition = hash(key) % numPartitions
- 12. 1212 Consumers … … … … Partition 0 Partition 1 Partition 2 Partition 3 Partitioned Topic Consumer A
- 13. 1313 Consumers … … … … Partition 0 Partition 1 Partition 2 Partition 3 Partitioned Topic Consumer A Consumer B
- 14. 1414 Consumers … … … … Partition 0 Partition 1 Partition 2 Partition 3 Partitioned Topic Consumer A1 Consumer B Consumer A2 Consumer A3 Consumer A4
- 15. 1515 Consumers … … … … Partition 0 Partition 1 Partition 2 Partition 3 Partitioned Topic Consumer A1 Consumer B Consumer A2 Consumer A3 Consumer A4 • A Client Application • Reads Messages from Topics • Horizontally, elastically scalable (if stateless)
- 17. 17 Streaming Integration with Kafka® Connect Kafka® Connect Kafka® Brokers Sources Sinks
- 18. 18 Kafka® Connect Data Pipeline Source Kafka® Connect Kafka® Connector ConverterTransform(s)
- 19. 19 Confluent Hub Online library of pre-packaged and ready-to-install extensions or add-ons for Confluent Platform and Apache Kafka®: ● Connectors ● Transforms ● Converters Easily install the components that suit your needs into your local environment with the Confluent Hub client command line tool . https://hub.confuent.io
- 22. 2222 STREAM PROCESSING Create and store materialized views Filter and join Act and analyze in-flight
- 23. 23 Building blocks for Stream Processing Core Kafka Producer Topic Consumer Kafka Streams State Stores Change Logs Processors Operators Stream Table Persistence Compute Declarative API ksqlDB Push Queries Pull Queries Serverless Topology Durable Pub Sub Transformers
- 24. 24 Runs everywhere Clustering done for you Exactly once processing Event time processing Integrated database Joins, windowing, aggregation S/M/L/XL/XXL/XXXL sizes Things Kafka Streams Does
- 27. 27 CREATE STREAM vip_actions AS SELECT userid, page, action FROM clickstream c LEFT JOIN users u ON c.userid = u.user_id WHERE u.level = 'Platinum’ EMIT CHANGES; Simple SQL syntax for expressing reasoning along and across data streams. You can write user-defined functions in Java Stream Processing with KSQL
- 28. 28 $ cat < in.txt | grep “ksql” | tr a-z A-Z > out.txt Kafka Cluster Stream ProcessingConnect API Connect API Stream Processing Analogy
- 29. @rmoff / Apache Kafka and KSQL in Action : Let’s Build a Streaming Data Pipeline! Do you think that’s a table you are querying?
- 30. 30 Alice + €50 The Stream-Table Duality Stream (payments) Table (balance) time Alice €50 Bob + €18 Alice €50 Alice €50 Bob €18 Alice + €25 Alice €50 Bob €18 Alice €75 Bob €18 Alice – €60 Alice €75 Bob €18 Alice €15 Bob €18
- 31. @rmoff / Apache Kafka and KSQL in Action : Let’s Build a Streaming Data Pipeline! The truth is the log. The database is a cache of a subset of the log. —Pat Helland Immutability Changes Everything http://cidrdb.org/cidr2015/Papers/CIDR15_Paper16.pdf
- 32. 32 KSQL for Real-Time Monitoring 32 • Log data monitoring, tracking and alerting • syslog data • Sensor / IoT data CREATE TABLE error_counts AS SELECT error_code, count(*) FROM monitoring_stream WINDOW TUMBLING (SIZE 1 MINUTE) WHERE type = 'ERROR' GROUP BY error_code;
- 33. 33 KSQL for Streaming ETL 33 CREATE STREAM engine_oil_pressure_readings AS SELECT r.deviceid, r.reading, r.timestamp d.sensor_type, d.uom, d.component FROM sensor_readings r LEFT JOIN device_master d ON r.deviceid = d.id WHERE d.component = ‘Engine’ AND d.sensor_type = ‘Oil Pressure’ EMIT CHANGES; Joining, filtering, and aggregating streams of event data
- 34. 34 Kafka Connect Producer API Elasticsearch Kafka Connect Streaming ETL with Apache Kafka and KSQL er PostgreSQL CDC Debezium
- 35. 35 KSQL is a stream processing technology As such it is not yet a great fit for: Ad-hoc queries ● No indexes yet in KSQL ● Kafka often configured to retain data for only a limited span of time BI reports (Tableau etc.) ● No indexes yet in KSQL ● No JDBC ● Most BI tools don’t understand continuous, streaming results
- 36. 3636 Event Driven Microservices with Apache Kafka® Leveraging a Streaming Platform for Microservices
- 37. 3737 What are microservices? Microservices are a software development technique - a variant of the service-oriented architecture (SOA) architectural style that structures an application as a collection of loosely coupled services. https://en.wikipedia.org/wiki/Microservices
- 38. 3838 structures an application as a collection of loosely coupled services. this is new!
- 39. 39 Making changes is risky
- 40. 40 Handling state is hard Cache? Embedded? Route to right instance?
- 41. 4141 ● Scaling is hard ● Handling state is hard ● Sharing, coordinating is hard ● Run a database in each microservice - is hard What have we learned about microservices?
- 42. 4242 We actually had some of it right
- 44. 4444 What’s the big idea?
- 45. 4545 Event Driven Architectures aren’t new… the world has changed …but…
- 46. 4646 Events Why do you care? Loose coupling, autonomy, evolvability, scalability, resilience, traceability, replayability EVENT-FIRST CHANGES HOW YOU THINK ABOUT WHAT YOU ARE BUILDING ...more importantly...
- 47. 4747 old world : event-driven architectures new world: event-streaming architectures
- 48. 48 Stream processing Kafka Streams processor input events output events ...temporal reasoning... event-driven microservice
- 49. 49 Scaling state & querying Stream processor Stream processor Stream processor Topic: click-stream Interactive query CDC events from KTable CDC Stream partition partition partition MKleppmann2015: Turningthedatabaseinsideout
- 50. 50 Scaling state: behind the scenes Stream processor topic: click-stream microservice events topic compactionCDC events from KTable (partition level) CDC events Rebuilding state Rocksdb partition
- 51. 5151 Stream processors are uniquely convergent. Data + Processing (sorry dba’s)
- 52. 5252 All of your data is a stream of events
- 53. 5353 stop...where is my database? (you said scaling data was hard)
- 54. 5454 Streams are your persistence model They are also your local database
- 55. 5555 The atomic unit for tackling complexity ...or microservice or whatever... Stream processor input events output events
- 56. 56 It’s pretty powerful Stream processor Stream processor Stream processor Topic: click-stream Interactive query CDC events from KTable CDC Stream partition partition partition CQRS Elastic
- 57. 5757 Stream processor == Single atomic unit It does one thing Like
- 58. 5858 We think in terms of function “Bounded Context” (dataflow - choreography)
- 59. 5959 Let’s build something…. A simple dataflow series of processors “Payment processing”
- 60. 6060 KPay looks like this https://github.com/confluentinc/demo-scene/tree/master/scalable-payment-processing
- 61. 6161 Bounded context “Payments” 1. Payments inflight 2. Account processing [debit/credit] 3. Payments confirmed
- 63. 63 Payments system: bounded context [1] How much is being processed? Expressed as: - Count of payments inflight - Total $ value processed [2&3] Update the account balance Expressed as: - Debit - Credit [4] Confirm successful payment Expressed as: - Total volume today - Total $ amount today
- 64. 64 Payments system: AccountProcessor accountBalanceKTable = inflight.groupByKey() .aggregate( AccountBalance::new, (key, value, aggregate) -> aggregate.handle(key, value), accountStore); KStream<String, Payment>[] branch = inflight .map((KeyValueMapper<String, Payment, KeyValue<String, Payment>>) (key, value) -> { if (value.getState() == Payment.State.debit) { value.setStateAndId(Payment.State.credit); } else if (value.getState() == Payment.State.credit) { value.setStateAndId(Payment.State.complete); } return new KeyValue<>(value.getId(), value); }) .branch(isCreditRecord, isCompleteRecord); branch[0].to(paymentsInflightTopic); branch[1].to(paymentsCompleteTopic); https://github.com/confluentinc/demo-scene/blob/master/scalable-payment-processing/.../AccountProcessor.java KTable state (Kafka Streams)
- 65. 65 Payments system: AccountBalance public AccountBalance handle(String key, Payment value) { this.name = value.getId(); if (value.getState() == Payment.State.debit) { this.amount = this.amount.subtract(value.getAmount()); } else if (value.getState() == Payment.State.credit) { this.amount = this.amount.add(value.getAmount()); } else { // report to dead letter queue via exception handler throw new RuntimeException("Invalid payment received:" + value); } this.lastPayment = value; return this; } https://github.com/confluentinc/demo-scene/.../scalable-payment-processing/.../model/AccountBalance.java
- 66. 66 Payments system: event model https://github.com/confluentinc/demo-scene/.../scalable-payment-processing/.../io/confluent/kpay/payments
- 67. 6767 Bounded context “Payments” Is it enough? no
- 68. 6868 “It’s asynchronous, I don’t trust it” (some developer, 2018)
- 69. 6969 We only have one part of the picture ○ What about failures? ○ Upgrades? ○ How fast is it going? ○ What is happening - is it working?
- 70. 7070 Event-streaming pillars: 1. Business function (payment) 2. Instrumentation plane (trust) 3. Control plane (coordinate) 4. Operational plane (run)
- 71. 7171 Event-streaming provides ● Evolution ● Decoupling ● Bounded context modelling ● Composition (because of SoC)
- 72. 7272 Our mental model: Abstraction as an Art Chained/Orchestrated Bounded contexts Stream processor Stream Event Pillars Business function Control plane Instrumentation Operations Bounded context
- 73. 7373 Key takeaway (state) Event streamingdriven microservices are the new atomic unit: 1. Provide simplicity (and time travel) 2. Handle state (via Kafka Streams) 3. Provide a new paradigm: convergent data and logic processing Stream processor
- 74. 7474 Key takeaway (complexity) ● Event-Streaming apps: model as bounded-context dataflows, handle state & scaling ● Patterns: Build reusable dataflow patterns (instrumentation) ● Composition: Bounded contexts chaining and layering ● Composition: Choreography and Orchestration
- 75. 7575 Questions? “Journey to event driven” blog 1. Event-first thinking 2. Programming models 3. Serverless 4. Pillars of event-streaming ms’s
- 76. 7676 Learn more about Apache Kafka® and Confluent Platform
- 77. 77 Learn Kafka. Start building with Apache Kafka at Confluent Developer. developer.confluent.io
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- 82. 82