1) Akka persistence journal provides an event sourcing API and plugins for various databases like Cassandra and Redis. It stores the full history of events for aggregates. 2) The document discusses using Akka persistence with a Redis journal to remember actor identities and allow persistence queries to the journal from multiple JVMs. 3) It provides an example of using Akka persistence to build a scalable application with thousands of actors across many nodes to handle high volumes of events.

1. Akka Persistence Journal
Ikuo Matsumura
CyberAgent, Inc.
2017-05-14, Scala

2. Akka Persistence
Actor
•
• Actor -> supervisor strategy
• JVM
• JVM
•
2017-05-14, Scala 2

3. Akka Persistence Journal
• Event Sourcing API
• Ka4a, Cassandra, DynamoDB, Redis plugin
• Actor
• Snapshot
2017-05-14, Scala 3

4. "it stores a complete history
of the events associated with
the aggregates in your
domain"
— Reference 3: Introducing Event Sourcing, CQRS
Journey1
1
Dominic Be+s, Julian Dominguez, Grigori Melnik, Fernando Simonazzi, Mani Subramanian,
Exploring CQRS and Event Sourcing, 2012, h+ps://msdn.microsoC.com/en-us/library/
jj554200.aspx
2017-05-14, Scala

5. ( )
• /JVM
•
•
• " " Actor
• , Cameo Pa3ern
2017-05-14, Scala 5

6. : 1 1Actor,
2017-05-14, Scala 6

7. Snapshot
2017-05-14, Scala 7

8. 1. (expire)
• Ka.a, Kinesis, Cassandra, DynamoDB, Redis etc.
2. LRU (evict)
• Redis etc.
2017-05-14, Scala 8

9. 2017-05-14, Scala 9

10. 1 - remember-en))es
akka.cluster.sharding {
remember-entities = on
}
JVM
!
! actor ID
→ (?)
2017-05-14, Scala 10

11. 2 - Persistence Query
val src: Source[String, NotUsed] = // persistenceId
PersistenceQuery(system)
.readJournalFor[ScalaReadJournal](
"akka-persistence-redis.read-journal") // Redis
.currentPersistenceIds
src.mapAsyncUnordered(...)( // Akka Stream
persistenceId => (persistenceId))
.runWith(Sink.ignore)
!
"
2017-05-14, Scala 11

12. : Persistence Query
Redis Journal ,
(JVM) 32GB RAM / 8core
• 15 , Actor
• Cat - Sharding Actor Meow ,
3meout=2
• Sweeper - ID 2
, Cluster Singleton
• : Meow
2
snapshot Redis Journal delete
2017-05-14, Scala 12

13. : Actor 400 9GB (→ 1000 20GB)
2017-05-14, Scala 13

14. : Actor 90 10 (→ 1000 2 )
2017-05-14, Scala 14

15. • Akka Persistence Journal
•
• rememberEn55es, Persistence Query
• Redis Persistence Query
• Actor 1000 ,
• : h?ps://github.com/ikuo/cat-cluster
2017-05-14, Scala 15