Mark Chavez
References:
Idiomatic Ruby code is most often thread-safe Ruby code.
Global objects are implicitly shared between all threads. Not thread-safe!
$counter = 0
puts "Hey threads, go ahead and increment me at will!"
class RainyCloudFactory
def self.generate
cloud = Cloud.new
cloud.rain!
cloud
end
end
class RainyCloudFactory
def self.generate
cloud = Cloud.new
@@clouds << cloud
cloud
end
end
A thread-local lets you define a variable that is global to the scope of the current thread. It’s a global variable that is locally scoped on a per-thread basis.
Example
# Instead of
$redis = Redis.new
# Use
Thread.current[:redis] = Redis.new
If your program is running N threads, it will open N connections to redis as well.
The same heuristic is applicable to a background job processor. Each job will be handled by a separate thread. A thread may process multiple jobs in its lifetime, but a job will only be processed by a single thread in its lifecycle.
Again, the path to thread safety is clear: create the necessary objects that you need in the body of the job, rather than sharing any global state.