JavaCro'15 - Reactive I/O - Ivan Turčinović
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This document provides an overview of Akka I/O, which is a toolkit for building concurrent, fault-tolerant, and scalable applications using message passing and reactive and actor-based APIs. It discusses the basic entities used in Akka I/O like ByteString, and how to create TCP and UDP clients and servers. It also covers lessons learned like how message sending/receiving works, and the importance of heartbeat messages to detect disconnected connections.
JavaCro'15 - Reactive I/O - Ivan Turčinović
- 2. 2 Toolset for building concurrent fault-tolerant scalable applications Core part of Typesafe Platfom
- 3. 3 Actors
- 4. 4 Akka I/O Akka I/O package follows same principles message passing reactive actor based API with immutable data representation Built with collaboration with spray.io team toolkit for building REST/HTTP-based integration layers TCP and UDP implementations available
- 6. 6 Basic entities ByteString actors communicate with immutable objects only ByteString - immutable container for bytes Rope-like data structure TCP messages TCP.connect/TCP.connected/TCP.register TCP.bind/TCP.bound TCP.commandFailed/TCP.connectionClosed/TCP.close TCP write - write, writeFile, compoundWrite UDP messages Unconnected UDP Connected UDP
- 7. 7 TCP Client – creating connection 1. 2. 3. 4. 5.
- 8. 8 TCP Client – send/receive messages, closing connection 1. 2. 3. 4.
- 9. 9 TCP Server – accepting connections 1. 2. 3. 4.
- 10. 10 TCP Server – send/receive messages 1. 2. 3.
- 11. 11 TCP - Throttling Reads and Writes Data congestion needs to be handled at the user level, for both writes and reads. Throttling writes ACK-based NACK-based NACK-based with write suspending Throttling reads Push-reading Pull-reading
- 12. 12 Lessons learned Message sending/receiving is NOT one-by-one onReceive ByteString can have more then one message sent Application is responsible for encoding/decoding messages Client – one connection actor per client is more than enough Server – each connection has one dedicated actor for receiving/sending messages Gives really nice control of clients on server side Authentication, blocking, stats per connection easy to implement Broadcasting message from server to client done really easy Send message to all ServerActor children
- 13. 13 Lessons learned cont’d DON’T rely only on TCP. ConnectionClosed messages for „disconnects” It works OK in „lab” conditions Problems occur in low qualilty network connections + VPN !! Solution: Rely on own heartbeat protocol Simple PingPongMessage Sent frequently – in our case each 5 sec. Gives very little or no overhead App keeps track of heartbeat messages no response message within specified time – something is wrong with connection – kill it!
- 14. 14 Akka – Spring integration Not so much related to akka I/O https://github.com/typesafehub/activator-akka-java-spring SpringExtension - Akka Extension to provide access to Spring managed Actor Beans
- 15. 15 Thank You!