Threading and Concurrency in Ruby
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Transcript of Threading and Concurrency in Ruby
Ruby Threads
Ruby Threads
“So… why do I want to work with Ruby’s threads?”
“HN says…”
Synchronization issues crop up everywhere
Mutexes
Easiest way to synchronize things in Ruby
Create a Mutex
Call Mutex.synchronize, and at most one thread will be able to run the content of the block
Condition Variable
Allows us to wait for certain conditions to become true before continuing, rather than burning CPU doing nothing
Allows threads to immediately give up their lock so another thread can make that condition true
Puma::ThreadPool
Puma::ThreadPool
Puma::ThreadPool
Puma::ThreadPool
Puma::ThreadPool
Monitors
Think Mutex + Condition Variable
Provides a better structure
Allows for recursive locking
Threads enter a waiting queue and are signaled by threads that currently have the monitor
Semaphores
Basically variables handled by the runtime/OS
Earliest formulation of synchronization
Two types: counting and binary
Two basic operations: P & V
Ruby doesn’t provide them… for good reason
Software Transactional Memory
No first class support, gems have become stale
Allows writers to take an optimistic view of the world
Onus is on readers to clean up the writers' mess
CelluloidActors for Ruby
MRI's Threads
One pthread for every Thread.new
…but every thread has to obtain a VM-wide Mutex, which is the GIL or Global Interpreter Lock
Better for downloading Tweets while writing ones a user cares about on a Socket, than for mining your Cryptocurrency of choice
Rubinius & jRuby’s Threads
One thread per Thread.new
Rubinius and jRuby have no Global Interpreter Lock, so they’re generally going to be better if your work is CPU bound
The Safest Path to Concurrency
Don't do it
If you must do it, don't share data across threads
If you must share data across threads, don't share mutable data
If you must share mutable data across threads, synchronize access to that data
Source: Working with Ruby Threads - Jesse Stormier
Thanks!@tim_raymond
