Transaction Preview of Apache Pulsar

1 .Transaction Support in Pulsar Penghui Li Apache Pulsar PMC Member Yong Zhang Apache Pulsar Contributor 

2 .What is Apache Pulsar? 

3 .Pub/Sub Messaging 

4 . “Flexible Pub/Sub messaging backed by durable log/stream storage” 

5 .

6 .2012: Pulsar idea started at Yahoo! 5 years on production, 100+ applications, 10+ data centers 2016/09 Yahoo open sourced Pulsar 2017/06 Yahoo donated Pulsar to ASF 2018/09 Pulsar graduated as a Top-Level project 2018/09 InfoWorld Best Open Source Project 

7 .Pulsar Community 

8 .Pulsar Community 

9 .Messaging Semantics • At-most once • At-least once • Exactly once 

10 .Messaging Semantics • At-most once Before 1.20.0-incubating • At-least once • Exactly once 

11 .Messaging Semantics • At-most once • At-least once • Exactly once PIP-6: Guaranteed Message Deduplication 

12 .Revisit Existing Semantics 

13 .Pulsar’s Existing Semantics send(m1) Log Producer Broker 

14 .Pulsar’s Existing Semantics append(m1) Log Producer Broker 

15 .Pulsar’s Existing Semantics m1 Log Producer Broker 

16 .Pulsar’s Existing Semantics m1 ack(m1) Log Producer Broker 

17 .Pulsar’s Existing Semantics m1 ack(m1) Log Producer Broker 

18 .Pulsar’s Existing Semantics m1 send(m2) Log Producer Broker 

19 .Pulsar’s Existing Semantics m1 m2 append(m2) Log Producer Broker 

20 .Pulsar’s Existing Semantics m1 m2 ack(m2) Log Producer Broker 

21 .Pulsar’s Existing Semantics What do we do now? m1 m2 ack(m2) Log Producer Broker 

22 .At Least Once m1 m2 send(m2) Log Producer Broker 

23 .At Least Once m1 m2 m2 append(m2) Log Producer Broker 

24 .At Least Once Duplicates !! m2 m2 m1 append(m2) Log Producer Broker 

25 .Why the duplicates are introduced? • Broker can fail • The request from Producer to Broker can fail • Producer or Consumer can fail 

26 .I want exactly-once 

27 .Message Deduplication • Producer: Idempotent Producer • Broker: Guaranteed Message Deduplication (PIP-6) • Consumer: Reader + Checkpoints (Flink / Spark) 

28 .Idempotent Producer • Producer Name - Identify who is producing the messages • Sequence ID - Identify the message • Producer Name + Sequence ID: The unique identifier for a message 

29 .Guaranteed Message Deduplication • Broker maintains a map between Producer Name and Last- Produced-Sequence-ID • Broker accepts messages if the sequence id of a new message is larger than its last produced sequence id • Broker treats messages whose sequence id are smaller • Broker keeps the map in a de-duplication cursor (stored in bookkeeper)