Thread-Safety in Go - An Overlooked Concern (Uber Meetups, Sofia)

A talk on learning the fundamentals of thread-safety in Go as presented at Uber Meetups, Sofia (https://www.meetup.com/Uber-Engineering-Events-Sofia/)

Materials - http://bit.ly/thread-safety-uber

Transcript

1. Thread-Safety in Go An Overlooked Concern P. Mihaylov Software Engineer, Tech. Trainer, Speaker preslav@pmihaylov.com Uber Ungineering Sofia, 2021
2. 👋 🚗 Software Engineer @ Uber 🎤 Tech. Trainer & Speaker ✍ Blogging at pmihaylov.com 󰞵 Open-sourcing at github.com/preslavmihaylov
3. Why not a talk on concurrency?
4. Most courses/books are incomplete…
5. Not enough ❤ for thread-safety
6. Concurrency without thread-safety -> 200 mp/h 🏎 without safety measures
7. Goals → 1) Learn the fundamentals 2) Get guidance on next steps
8. What’s covered 1. What does “thread-safety” mean? 2. Should you care about it at all? 3. Thread-safety problems & solutions a. When is there a potential thread-safety issue? b. Atomic access to shared state c. Delegating thread-safety d. Atomic compound actions e. Visibility & stale data 4. Where to go from here?
9. What does “thread-safety” mean?
10. Safe classes → behave correctly
11. Thread-safe classes → behave correctly while bombarded by a gazillion goroutines
12. Should you care about it at all?
13. “I don’t need thread-safe classes as I’m typically writing web apps without spawning any threads…” the average web dev
14. You’re already writing multi-threaded applications...
15. ...and no. Channels can’t save you every time
17. Thread-safety problems & solutions
18. When is there a potential thread-safety issue?
20. Is it thread-safe? Join at slido.com #thread-safety-uber
21. Shared mutable state
22. Non-shared state Stack #1 Thread #1 Non-shared state #1 Non-shared state #2 Shared memory aka heap Shared state Non-shared state Stack #2 Thread #2
23. Atomic access to shared state
26. What can go wrong?
28. Using Mutexes is Go’s standard way to add critical sections/locks
29. Delegating thread-safety
32. Delegated thread-safety → relying on the thread-safetiness of objects you use
33. But also (third-party) packages...
34. Atomic compound actions
37. Actions from the same invariant need to be synchronized together
38. Visibility & stale data
41. Is it thread-safe? Join at slido.com #thread-safety-uber
42. Thread-safety is not only about concurrent writes...
44. Remember 3+1 things
46. Stateless methods → thread-safe methods
49. Thread-safety is about both reads and writes...
52. Prefer delegation over explicit synchronization
55. Be careful with compound actions...
58. Is that all I need to know?
59. What’s not covered 1. Initialisation safety & Immutable objects 2. Thread-confinement 3. Concurrency tooling - atomic variables/collections, synchronizers 4. Goroutine Management 5. Channels 6. Managing goroutine lifecycle via cancellation/interrupts 7. Dealing with performance/liveness issues (i.e. deadlock, livelock, etc.) 8. The Go Memory Model
61. Get the mats → http://bit.ly/thread-safety-uber
62. Thread-Safety in Go An Overlooked Concern P. Mihaylov Software Engineer, Tech. Trainer, Speaker preslav@pmihaylov.com Uber Ungineering Sofia, 2021