Downloaded 11 times
Uploaded byElifTech
Go Concurrency Basics
The document discusses Go's concurrency features including goroutines, channels, and synchronization tools. It explains that goroutines are lightweight threads managed by Go, and channels provide a means of communication between goroutines. The document also covers potential concurrency issues like deadlocks and provides best practices to avoid anti-patterns when using goroutines and channels.
More Related Content
Go Concurrency Basics
- 1. Go Concurrency Basics Goroutines,channels and standard library By Vitalii Perehonchuk, Software Developer
- 2. www.eliftech.com Go provides Concurrent execution Synchronizationand messaging Multi-way concurrent control
- 3. www.eliftech.com Go does NOTprovide direct thread manipulation Go multithreading is fully managed by Go runtime. In Go you use goroutines in place of threads
- 4. www.eliftech.com Go provides arace detector Ran with “-race” flag. It watches for unsynchronized access to shared variables.
- 5. www.eliftech.com Goroutine ▪ A lightweight“thread” of execution managed by Go runtime. ▪ A function ran independently in the same address space as other goroutines. ▪ It’s routine to create thousands of goroutines. ▪ Go web servers usually process each request in a separate goroutine.
- 6. www.eliftech.com Goroutine func sidekick() { //Will be never executed. fmt.Println("Sidekick arrived") } func main() { go sidekick() fmt.Println("Hero arrived") }
- 7. www.eliftech.com Goroutine func sidekick() { //Will be executed this time. fmt.Println("Sidekick arrived") } func main() { go sidekick() runtime.Gosched() fmt.Println("Hero arrived") }
- 8. www.eliftech.com Goroutine anti-pattern Do notcreate functions whose only purpose is to run a goroutine.
- 9. www.eliftech.com Channel Imagine it asa pipe <- <- for communication of goroutines
- 10. www.eliftech.com Channel Imagine it asa pipe for communication of goroutines
- 11. www.eliftech.com Channel A goroutine canwait for a value from a channel
- 12. www.eliftech.com Channel A goroutine canwait for a value from a channel func main() { myChan := make(chan int) <- myChan // deadlock fmt.Println("Hi everyone") }
- 13. www.eliftech.com Channel A goroutine canwait to send a value to a channel func main() { myChan := make(chan int) myChan <- 1 // deadlock fmt.Println("Hi everyone") }
- 14. www.eliftech.com Channel A goroutine canclose a channel func sidekick(mChan chan<- string) { mChan <- "I have not so much to say" mChan <- "Sorry" close(mChan) } func main() { wfm := true var m string mChan := make(chan string) go sidekick(mChan) for { m, wfm = <-mChan if !wfm { break } fmt.Printf("Message from the sidekick: %sn", m) } fmt.Println("Thanks for your attention.") }
- 15. www.eliftech.com Channel A deadlock canoccur when sending into channel func sidekick(taskChannel <-chan string) { task := <- taskChannel fmt.Printf(“Done: %sn”, task) fmt.Println(“Enough work for today”) } func main() { taskChannel := make(chan string) go sidekick(taskChannel) taskChannel <- “Wash the dishes” // deadlock taskChannel <- “Do laundry” }
- 16. www.eliftech.com Channel A channel canhave a buffer func sidekick(taskChannel <-chan string) { task := <- taskChannel fmt.Printf(“Done: %sn”, task) fmt.Println(“Enough work for today”) } func main() { taskChannel := make(chan string, 1) go sidekick(taskChannel) taskChannel <- “Wash the dishes” taskChannel <- “Do laundry” }
- 17. www.eliftech.com Channel “select” waits fora value from a set of channels func sidekick() { task := <-taskChan time.Sleep(2 * time.Second) resChan <- fmt.Sprintf( "Done: %sn", task, ) } func main() { // channels initialization omitted go sidekick(taskChan, resChan) taskChan <- "Wash the dishes" timer := time.NewTimer(1 * time.Second) var res string select { ...
- 18. www.eliftech.com Channel “select” waits fora value from a set of channels func sidekick() { task := <-taskChan time.Sleep(2 * time.Second) resChan <- fmt.Sprintf( "Done: %sn", task, ) } ... select { case res = <- resChan: fmt.Println(res) case <- timer.C: fmt.Println("SIDEKICK!") fmt.Println("What are you doing?") } }
- 19. www.eliftech.com Channel anti-pattern Do notguard channels with mutexes. Channels don’t need concurrency control. They are concurrency control.
- 20.
- 21. www.eliftech.com type sync.Mutex ▪ Mutualexclusion lock. ▪ Zero value is unlocked
- 22. www.eliftech.com type sync.WaitGroup Makes agoroutine block until some work is done
- 23. www.eliftech.com type sync.Mutex, typesync.WaitGroup var c = 0 var cMutex sync.Mutex var waitGroup sync.WaitGroup func sidekick() { cMutex.Lock() c ++ cMutex.Unlock() waitGroup.Done() } func main() { waitGroup.Add(n) for i := 0; i < n; i++ { go sidekick() } waitGroup.Wait() cMutex.Lock() fmt.Printf("Counter's value: %dn", c) cMutex.Unlock() }
- 24. www.eliftech.com type sync.RWMutex Reader /writer mutual exclusion lock. Many readers, single writer simultaneously type sync.Once Performs only one action only once
- 25. www.eliftech.com type sync.Pool typesync.Map type sync.Cond Thread-safe collection of temporary objects Map safe for concurrent use Condition object used to announce an event
- 26. www.eliftech.com runtime.GOMAXPROCS(int) int ▪ Functionto set maximum number of native threads run simultaneously. ▪ Defaults to number of CPUs (since Go 1.6, previously defaulted to 1)
- 27. www.eliftech.com runtime.NumGoroutine() int Returns thenumber of goroutines that currently exist.
- 28. www.eliftech.com runtime.Gosched() Explicitly make Goscheduler switch contexts - let other goroutines run
- 29. www.eliftech.com Conclusion Go concurrency ischeap Go concurrency is complicated (as any concurrency) Go concurrency is powerful
- 30. www.eliftech.com Sources ▪ “Mastering concurrencyin Go” by Nathan Kozyra ▪ Golang.org ▪ “Learning Go’s concurrency through illustrations” by Trevor Forrey ▪ “Go Antipatterns” at hackmongo.com
- 31. www.eliftech.com Don't forget tosubscribe not to miss our next presentations! Find us at eliftech.com Have a question? Contact us: info@eliftech.com