1. Boston Reactive
Software Meetup

2. Introduction to Reactive
Presented by
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Steven Pember
Principal Consultant , Technical Architect at Cantina
David Fox
Principal Consultant , Technical Architect at Cantina
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3. What is Reactive?
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4. What is Reactive?
A buzzword
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5. What is Reactive?
A popular (comp) science buzzword
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6. The Reactive Manifesto
Written by Jonas Bonér with
contributions by Erik Meijer,
Martin Odersky, Greg Young,
Martin Thompson, Roland Kuhn,
James Ward and Guillaume Bort.
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7. tl;dr
1. WAY more traffic than just a few years ago
2. Users expect immediate response
3. Need 100% uptime
4. Large amounts of data
5. Need better models of concurrency
6. Old models like servlet showing their age
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8. The Four Traits
These are the traits they use to
describe this class of software.
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9. The Four Traits
Note how they play off one
another to form a cohesive whole
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10. changeable
The Missing Traits
There should really be a couple
more traits…
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11. changeable
The Missing Traits
There should really be a couple
more traits…
managable
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12. Reactive Technologies
not just from Typesafe!
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13. These are all “Reactive” technologies
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14. These are all “Reactive” technologies
Reactive isn’t about particular technologies,
it’s a holistic view of application architecture to support
the needs of the current generation of applications
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15. As developers, we need to see the whole picture
of the application, from the front-end to the back-end. It’s
not enough to just use a “reactive framework”.
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16. Spray Framework
HTTP for Akka Actors
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17. Akka
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De-facto Actor implementation for Scala
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Replaced Scala’s actor implementation
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Team wanted to keep Scala smaller
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Better as a separate framework
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Used as basis of Play and Spray and many
other frameworks
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18. Actor
Model
•
Invented in 1973 by Carl Hewitt, Peter
Bishop, and Richard Steiger at MIT's AI lab
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A design pattern for concurrency
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Encapsulates state and behavior
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Alleviates the need for locks
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Allows work to be scheduled fairly
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19. How do actors work?
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20. Actor Receives Message
Message is placed into the
actor’s mailbox
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21. Actor Scheduled
The actor system’s scheduler
schedules the actor to run in a
thread.
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The actor processes a message
according to its behavior
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22. Execution Complete
The actor state is modified.
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The scheduler will continue to
fairly schedule the actor to run
while its mailbox has messages.
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23. Akka’s actors also have supervision
strategies for failure
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24. Supervision
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By default, when an actor crashes, it will
simply be restarted by the system
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Other strategies can be employed such as:
• Resume keeping state
• Resume clearing state
• Terminate the actor permanently
• Escalate, failing the supervising actor
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25. Other
Features
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•
•
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Finite state machine mixin
Typed actor proxy for integration with nonactor-based code
Location transparency / clustering
Support for event/command sourcing
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26. What Are the Drawbacks?
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•
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Programming with actors is more difficult
Type safety is lost
Not as easy to compose
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27. Promises
&
Futures
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Synchronization constructs/patterns
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Allow use of values which will be eventually
available at a later point in time
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Terms sometimes used interchangeably
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A promise is a container to write a value to
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A future is a handle used to read that value
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28. Spray Framework
Live coding demo
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29. Cantina is a digital agency that plans,
designs and builds connected experiences
and product innovations.
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