Орхан Гасимов: "Reactive Applications in Java with Akka"
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This document provides an overview of reactive applications in Java using Akka. It discusses the reactive manifesto which outlines principles of responsive, resilient, elastic and message-driven systems. The actor model and Akka framework are introduced as ways to build such reactive systems. Key concepts covered include actors, message passing, concurrency vs parallelism. Akka features for scaling systems through dispatchers, mailboxes and routers are described. Other Akka modules for futures, agents, remote communication and more are also listed.
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Mailboxes
Akka comes shipped with a number of mailbox implementations
- Unbounded (default)
- Bounded
- [U/B] Non-Blocking
- [U/B] Priority
- [U/B] Stable Priority (FIFO)
- [U/B] Control Aware
- Unbounded Single Consumer Only](https://image.slidesharecdn.com/gasimovppt-160606085912/85/Reactive-Applications-in-Java-with-Akka-36-320.jpg)
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Орхан Гасимов: "Reactive Applications in Java with Akka"
- 1. www.luxoft.com Reactive Applications in Java with Akka by Orkhan Gasimov
- 2. www.luxoft.com About author Orkhan Gasimov Software Developer Over 13 years in software development field Participated in full-cycle application development, leading development groups with hands-on experience in a variety of programming languages and technologies including solution design and architecture Applied practical usage of Java, C#, C/C++, Perl, PHP, JavaScript and other programming languages. Designed desktop, mobile and web applications from consumer products to N-tier systems
- 3. www.luxoft.com Evolution of the Programming Model
- 4. www.luxoft.com Scaling up Scaling out • More price with each step • Greater risk of hardware failure causing bigger outages • Limited upgradeability in the future • One unit for everything • Much cheaper than scaling vertically • Easier to run fault-tolerance • Easy to upgrade • Parallel units enable parallel execution Scaling
- 5. www.luxoft.com Reactive Applications in Java with Akka Reactive Manifesto Actor Model Load Balancing & Scaling Other Features & Available Modules
- 7. www.luxoft.com Reactive Manifesto Application requirements have changed dramatically in recent years A few years ago a large application had - tens of servers - seconds of response time - hours of offline maintenance - gigabytes of data Today - applications are deployed on everything from mobile devices to cloud-based clusters - users expect millisecond response times and 100% uptime - data is measured in Petabytes
- 8. www.luxoft.com Reactive Manifesto Today's demands are simply not met by yesterday’s software architectures A coherent approach to systems architecture is needed All necessary aspects are already recognized individually We want systems that are - Responsive - Resilient - Elastic - Message Driven We call these Reactive Systems
- 9. www.luxoft.com Reactive Manifesto Responsive: The system responds in a timely manner if at all possible. Responsiveness means that problems may be detected quickly and dealt with effectively. Resilient: The system stays responsive in the face of failure. Any system that is not resilient will be unresponsive after a failure. Elastic: The system stays responsive under varying workload. Reactive Systems can react to changes in the input rate by increasing or decreasing the resources allocated to service these inputs. Message Driven: Reactive Systems rely on asynchronous message-passing to establish a boundary between components that ensures loose coupling, isolation and location transparency. This boundary also provides the means to delegate failures as messages.
- 10. www.luxoft.com Reactive Manifesto Large systems are composed of smaller ones and therefore depend on the Reactive properties of their constituents. This means that Reactive Systems apply design principles so these properties apply at all levels of scale, making them composable.
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- 13. www.luxoft.com Akka vs JavaEE No application server is required Vanilla JVM and core Java is enough JVMs can be stacked up to a Cluster Akka offers Actor Model instead of Object Oriented Model - Actors are workers - Objects are objects Actors are parallelized by default
- 14. www.luxoft.com Concepts Let’s review some base concepts before the deep dive
- 23. www.luxoft.com Progress Condition We want so called Progress Condition. These are actual non- blocking guarantees. We want applications to behave - Parallel - Asynchronous - Non-blocking - Without deadlocks, starvation and live-locks - Without race conditions
- 24. www.luxoft.com Akka What is Akka? What does Akka bring?
- 25. www.luxoft.com Actor Model An actor is a computational entity that, in response to a message it receives, can concurrently: - send a finite number of messages to other actors; - create a finite number of new actors; - designate the behavior to be used for the next message it receives. There is no assumed sequence to the above actions. They could be parallel! The Actor Model philosophy says ”everything is an actor”. This is similar to the ”everything is an object” philosophy, but object-oriented software is typically executed sequentially, while the Actor Model is inherently concurrent.
- 26. www.luxoft.com
- 27. www.luxoft.com Actor Model Actors are objects which encapsulate state and behavior They communicate exclusively by exchanging messages which are placed into the recipient’s mailbox View them as persons While modeling a solution with actors - envision a group of people and assign sub-tasks to them, - arrange their functions into an organizational structure - and think about how to escalate failure
- 28. www.luxoft.com Actor System Actors come in systems and never alone Actors form hierarchies Actor can start child actors and supervise them Splitting tasks brings in smaller and more manageable tasks
- 29. www.luxoft.com Actor Systems as a single Cluster
- 32. www.luxoft.com API is very easy Create the ActorSystem Actor is a class extending UntypedActor and overriding onReceive method Use ActorSystem::actorOf method to create actors - Each actor can create child actor using getContext().actorOf method To send a message to Actor ActorRef::tell method is used - you should have ActorRef (actor reference) which you will get on actor creation or you can lookup/search for it by path
- 33. www.luxoft.com Load Balancing & Scaling Dispatchers Mailboxes Routers
- 36. www.luxoft.com Mailboxes Akka comes shipped with a number of mailbox implementations - Unbounded (default) - Bounded - [U/B] Non-Blocking - [U/B] Priority - [U/B] Stable Priority (FIFO) - [U/B] Control Aware - Unbounded Single Consumer Only
- 38. www.luxoft.com Other Features & Available Modules Futures – functional promises that are used to retrieve the result of some concurrent operation Agents – provide asynchronous change of individual locations Remote – enable remote actor messaging between actor systems over the network Cluster – turn actor systems into a single cluster over the network I/O – module carries API for the implementation of network protocols and building higher abstractions Camel – actors can now exchange messages with other systems over large number of protocols & APIs such as HTTP, SOAP, TCP, FTP, SMTP or JMS, to mention a few Streams – stream processing API HTTP – a full server- and client-side HTTP stack on top of akka-actor and akka-stream. It's not a web-framework but rather a more general toolkit for providing and consuming HTTP-based services.
- 39. www.luxoft.com R e a c t i v e Thank You!