Reputation: 1951
I'm using threads in a program that uploads files over sftp. The number of files that could be upload can potentially be very large or very small. I'd like to be able to have 5 or less simultaneous uploads, and if there's more have them wait. My understanding is usually a conditional variable would be used for this, but it looks to me like that would only allow for 1 thread at a time.
cv = ConditionVariable.new
t2 = Thread.new {
mutex.synchronize {
cv.wait(mutex)
upload(file)
cv.signal
}
}
I think that should tell it to wait for the cv to be available the release it when done. My question is how can I do this allowing more than 1 at a time while still limiting the number?
edit: I'm using Ruby 1.8.7 on Windows from the 1 click installer
Upvotes: 0
Views: 1347
Reputation: 9225
A word of caution -- there is no real concurrency in Ruby unless you are using JRuby. Also, exception in thread will freeze main loop unless you are in debug mode.
require "thread"
POOL_SIZE = 5
items_to_process = (0..100).to_a
message_queue = Queue.new
start_thread =
lambda do
Thread.new(items_to_process.shift) do |i|
puts "Processing #{i}"
message_queue.push(:done)
end
end
items_left = items_to_process.length
[items_left, POOL_SIZE].min.times do
start_thread[]
end
while items_left > 0
message_queue.pop
items_left -= 1
start_thread[] unless items_left < POOL_SIZE
end
Upvotes: 1
Reputation: 80128
Use a ThreadPool instead. See Deadlock in ThreadPool (the accepted answer, specifically).
Upvotes: 2