introduction to actor model of concurrent and distributed
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Introduction to Actor Model of Concurrent and Distributed Computation
Dmitry Tolpeko, EPAM Systems - January 2015
What is Actor Model?
Design pattern to develop scalable concurrent and distributed applications
Concurrent Models
• Shared Resources
• Actor-based Concurrency
Shared Resources
• Shared Memory
• Locks
Shared Resources - Advantages
• Traditional and well known
• OS and programming language support
• Relatively easy to program (no queues, no messaging i.e.)
Shared Resources - Disadvantages
• Error prone and buggy
• Race conditions and deadlocks
• Over-synchronization that can impact performance
• No distributed processing
Actor Model
• Similar to Object-oriented model but asynchronous, concurrent and distributed
• Actors are processes (threads) that process and send messages
• Shared nothing architecture
Asynchronous
• When an Actor sends a message it is not blocked until the message processed
• Actor is not interrupted when it receives a message
• Every Actor has Mailbox, a task queue to buffer incoming messages
Concurrent and Distributed
• Each Actor runs an infinite loop to read, process and send messages
• Use of messaging allows distributed processing (Multiple Actors running on multiple nodes)
Topology and Life Cycle
• Actors can create other actors, the topology is dynamic
• Actor usually terminates by receiving the application specific “Stop” message
• Actor can also terminate by timeout (no messages in queue) or after completing a message
Advantages of Actor Model
• Scalable
• Clear and reliable design
Thank you!Dmitry_Tolpeko@epam.com
https://twitter.com/dmtolpeko
www.dmtolpeko.com
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