The document discusses concurrent programming in Go. It provides an introduction to Go and its characteristics like being statically typed and garbage collected. It then discusses concurrency in Go using goroutines which are lightweight threads, channels for communicating between goroutines, and sync primitives like WaitGroup and Mutex for synchronization. Finally, it provides examples of using concurrency for processing a large CSV file by distributing the work across multiple goroutines.

1. Concurrent Programming in Golang
Jan 7, 2017 @ DILO Surabaya
Noval Agung Prayogo

2. Short about me
• Noval Agung Prayogo
• Surabaya, Indonesia
• Lead Software Engineer @ EACIIT Pte. Ltd.

3. Golang
• Go is an open source programming language that makes it easy to
build simple, reliable, and efficient software – golang.org
• Crafted @ Google @ 2009
• Used on production by many big companies
• Easy to learn, develop, compile, run, deploy
• Rich support for concurrency, and etc …

4. Characteristic
• 99% static type, 1% dynamic
• Garbage collected
• Compiled
• Structural
• Memory safe
• Multiplatform

5. Example: Hello World

6. Another Example: HTTP Server

7. Yet Another
Example: SQL

8. Concurrency
• Concurrency is the composition of independently executing
processes. Concurrency is about dealing with lots of things at once
• Parallelism is the simultaneous execution of (possibly related)
computations. Parallelism is about doing lots of things at once
• Concurrency is about structure, parallelism is about execution
• Concurrency provides a way to structure a solution to solve a problem
that may (but not necessarily) be parallelizable

9. Coffee Machine
Coffee Machine
Coffee Machine
Coffee Machine
Concurrent = Four queues, one coffee machine
Parallel = Three queues, three coffee machine

10. Coffee Machine
Concurrent (not parallel)
Coffee Machine
Concurrent (parallel)
Coffee machine can serve one people at time
I’m not sure if this kind of coffee machine really exists. Maybe it’ll be look like this
Coffee machine can serve
multiple people at time

11. • A goroutine is a lightweight thread managed by the Go runtime
• Not free, but very cheap (4KB ~ 8KB per each goroutine)
• Stacks start small, but grow and shrink as required
Goroutine

12. Channel
• Channels allow you to pass references to data structures between
goroutines

13. sync.WaitGroup
• A WaitGroup waits for a collection of goroutines to finish

14. Race Condition Example
• A race condition is an undesirable situation that occurs when
attempting to perform two or more operations at the same time

15. sync.Mutex
• Mutex used to lock & unlock certain of process

16. Real life Example of Concurrency
• Read then filter csv file (7 million records)
• Implements worker pool technique to do the filter concurrently

17. Open CSV file
Dispatch all workers
Worker 1
Worker 2
Worker 3
Worker 4
Read file line-by-line, then
send data (as job) to workers
Kill worker which is finished doing the jobs
Retreive filtered data
Start
Finish

18. Demo

19. Thank you!
Q&A?

20. Reference
• https://golang.org
• https://tour.golang.org/concurrency/1
• https://talks.golang.org/2012/waza.slide#1
• https://golang.org/doc/codewalk/sharemem
• https://blog.golang.org/share-memory-by-communicating
• https://joearms.github.io/2013/04/05/concurrent-and-parallel-
programming.html
• http://searchstorage.techtarget.com/definition/race-condition