Ruby check if a thread is "free"

Question

I want to have an array of threads[] such that if a thread is "free" or not working on any program then it will be assigned a new task.

Is there anyway to check if a thread in ruby is "free". Currently I used

if (threads[thread_id].nil? || !threads[thread_id].status)
    # yes thread is free

But doesn't seem to be correct way, some thread still override working other.

Possible duplicate: http://stackoverflow.com/questions/6558828/thread-and-queue — steenslag, Sep 29 '11 at 10:34
@steenslag I didn't see anything similar... in that topic they need a queue to store works. I don't need that, I just want to know whether a threads is free to use — w00d, Sep 29 '11 at 12:24
Maybe test for `alive?` or if you made your mind on a number of threads you want to have at the same time check with `Thread.list.size` — derp, Sep 29 '11 at 14:15

score 2 · Answer 1 · answered Feb 28 '12 at 14:25

threads.each.map {|t| t.alive?}.none?

returns true if all threads are dead

if you have something like this:

threads << Thread.new do
 # do dome work ...
end

and you want to check if all threads are not alive (i.e. dead) you can always use this:

threads.each.map {|t| t.alive?}.none?

We are taking one by one thread from array and checking if it's alive. map method is creating array with true/false values (alive/dead). Finally none? method of enumerable should return true if all members are false (i.e. all threads are dead)

score 1 · Answer 2 · edited May 23 '17 at 12:28

See the answer of Deadlock in ThreadPool for a working threadpool implementation.

With a thread pool, you can do something like this:

pool = ThreadPool.new(10) # up to 10 threads
email_addresses.each do |addr|
  pool.process {send_mail_to addr}
end

ThreadPool#process will block if there are no free threads to complete the work, and continue when one is free.

There are also gems implementing a thread pool, like: http://rubygems.org/gems/work_queue

Ruby check if a thread is "free"

2 Answers2