Thread-Safety in Go - An Overlooked Concern (Go Naviro eMeetup)

A talk on learning the fundamentals of thread-safety in Go as presented at Go Naviro eMeetup (https://www.gonaviro.com/blog/2021/05/thread-safety-in-go-thursday-1st-july)

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

Transcript

1. Thread-Safety in Go
   An Overlooked Concern
   P. Mihaylov
   Software Engineer, Tech. Trainer, Speaker
   preslav@pmihaylov.com
   Go Naviro eMeetup, 2021
   

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2. 👋
   🚗 Software Engineer @ Uber
   🎤 Tech. Trainer & Speaker
   ✍ Blogging at pmihaylov.com
   󰞵 Open-sourcing at
   github.com/preslavmihaylov
   

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3. Why not a talk on concurrency?
   

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4. Most courses/books are incomplete…
   

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5. Not enough ❤ for thread-safety
   

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6. Concurrency without thread-safety ->
   200 mp/h 🏎 without safety measures
   

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7. Goals →
   1) Learn the fundamentals
   2) Get guidance on next steps
   

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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?
   

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9. What does “thread-safety” mean?
   

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10. Safe classes →
    behave correctly
    

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11. Thread-safe classes →
    behave correctly
    while bombarded by
    a gazillion goroutines
    

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12. Should you care about it at all?
    

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13. “I don’t need
    thread-safe classes
    as I’m typically
    writing web apps
    without spawning
    any threads…”
    the average web dev
    

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14. You’re already writing
    multi-threaded applications...
    

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15. ...and no.
    Channels can’t save you every time
    

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17. Thread-safety problems & solutions
    

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18. When is there a potential
    thread-safety issue?
    

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20. Is it thread-safe?
    Join at slido.com
    #threadsafe
    

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21. Shared mutable state
    

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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
    

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23. Atomic access to shared state
    

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26. What can go wrong?
    

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28. Using Mutexes is Go’s standard way
    to add critical sections/locks
    

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29. Delegating thread-safety
    

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32. Delegated thread-safety →
    relying on the thread-safetiness of
    objects you use
    

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33. But also (third-party) packages...
    

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34. Atomic compound actions
    

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37. Actions from the
    same invariant need to be
    synchronized together
    

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38. Visibility & stale data
    

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41. Is it thread-safe?
    Join at slido.com
    #threadsafe
    

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42. Thread-safety is not only about
    concurrent writes...
    

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44. Remember 3+1 things
    

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46. Stateless methods →
    thread-safe methods
    

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49. Thread-safety is about
    both reads and writes...
    

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52. Prefer delegation over explicit
    synchronization
    

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55. Be careful with compound actions...
    

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58. Is that all I need to know?
    

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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
    

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61. Get the mats →
    https://bit.ly/thread-safety-go
    

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62. Thread-Safety in Go
    An Overlooked Concern
    P. Mihaylov
    Software Engineer, Tech. Trainer, Speaker
    preslav@pmihaylov.com
    Go Naviro eMeetup, 2021
    

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