CODEWITHSUNDEEP
rubymultithreading
JohnMerlino
JohnMerlino

Reputation: 3928

creating infinite loop in main thread while having infinite loops in spawned threads

I am trying to create an infinite loop in the main ruby thread, while having infinite loops in spawned threads, but this doesn't work:

my_threads = []
for i in 1..2 do
    puts "Creating thread #{i}"
    my_threads << Thread.new(i) do |j|
        loop do
            sleep(1)
            puts "work in #{Thread.current.object_id}"
        end
    end
end

my_threads.each do |t|
    t.join
end

loop do
    sleep(1)
    puts 'work in main thread'
end

I need it this way because in my Rails app, I cannot use ActiveRecord objects inside of a thread, as explained here:

https://stackoverflow.com/questions/24903230/activerecord-object-freezes-thread-in-multi-threaded-script

so I need a main thread that runs a loop, while having spawned threads run their own loops all concurrently.

The code above however does this:

work in 79515570work in 79515510

work in 79515510work in 79515570

work in 79515510work in 79515570

work in 79515570work in 79515510

work in 79515570work in 79515510

work in 79515570
work in 79515510
work in 79515570
work in 79515510
work in 79515570work in 79515510

It never reaches the main thread loop. How can I accomplish this?

Upvotes: 2

Views: 1744

Answers (1)

Uri Agassi
Uri Agassi

Reputation: 37409

The code in your main thread is stopped here:

my_threads.each do |t|
    t.join
end

What join does is make the current thread wait until the the thread object it is called on finishes its run.

To resolve this, simply skip the above block:

my_threads = []
for i in 1..2 do
    puts "Creating thread #{i}"
    my_threads << Thread.new(i) do |j|
        loop do
            sleep(1)
            puts "work in #{Thread.current.object_id}"
        end
    end
end

loop do
    sleep(1)
    puts 'work in main thread'
end

# work in 84665270
# work in 84665760
# work in main thread
# work in 84665270
# work in 84665760
# work in main thread
# work in 84665270
# work in 84665760
# work in main thread
# work in 84665270
# work in 84665760

Upvotes: 3

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