Concurrency on Codrut Constantin Gusoi

Concurrency primitives in Ruby

Mon, 04 Jan 2021 23:30:24 +0000

Note: for parallelism, see Ractors

There’s 3 of them:

Thread
Mutex
Condition Variable

Thread Link to heading

first  = Thread.new { puts 'Thread 1'; sleep 1 }
second = Thread.new { puts 'Thread 2'; sleep 1 }
third  = Thread.new { puts 'Thread 3'; sleep 1 }

puts 'Main Thread'

[first, second, third].map(&:join)

Takeaways:

Blocks execute concurrently, but not in parallel.
Pause a thread for a few seconds with #sleep.
Wait for threads to finish execution with the #join method.
Execution scheduling is non deterministic, output will have a different order over multiple runs.

Mutex Link to heading

Syncronize access to a shared resource with a Mutex: