Go Concurrency Patterns

Examples taken from Rob Pike's talk about concurrency patterns.

Go Concurrency Patterns video:

https://www.youtube.com/watch?v=f6kdp27TYZs

Notes from Rob's talk

"The composition of independently executing computations" -- Rob Pike

Concurrency not parallelism. On a single core, you can't have parallelism.

Concurrency

• Easy To Understand
• Easy To Use
• Easy To Reason
• Work at a Higher Level

Concurrency is not new

Hoare's CSP Paper in 1978

• Occam ('83), Erlang ('86), Newsqueak ('88), Concurrent ML ('93), Alef ('95), Limbo ('96)

Go is a Branch of:

Newsqueak-Alef-Limbo using Channels

Goroutines

• Independently executing function
• Has its own stack which grows and shrinks
• Very Cheap, could have thousands or more
• Not a thread
  • Could have only one thread running thousands of goroutines
• Goroutines are multiplexed dynamically onto threads as needed to keep routines running
• Could think of it as a very cheap thread

Buffered Channels

• Channels can be created with a buffer
• Buffering removes synchronization
• Can be important for some problems but they are more subtle to reason about
• Not using them today

Summary

• Started With
  • Slow, Sequential and Failure-Sensitive code
• Ended With
  • Fast, Concurrent, Replicated and Robust code

Other Patterns

Chatroulette Toy:
http://tinyurl.com/gochatroulette

Load Balancer:
http://tinyurl.com/goloadbalancer

Concurrent Prime Sieve:
http://tinyurl.com/gosieve

Concurrent Power Series (by Mcllroy)
http://tinyurl.com/gopowerseries