gistfile1.txt

lets assume you have array or urls yes ?

urls.each do |url|
 
  check_if_counter < 50

  if yes 
    spawn_thread(url)
  else
    sleep(2)
    retry
  end

end

possibly try_fetch_url needs to be a function with it like this

def try_fetch_url(url)
  if counter < THREAD_CAP
    try_update_counter
    if updated
      spawn_thread(url)
    else
      sleep(2)
      try_fetch_url(url)
    end
  else
    sleep(2)
    try_fetch_url(url)
  end
end

or

def try_fetch_url(url)
  while(true) do
    if counter < COUNTER_CAP
      increment_counter
      spawn_thread(url)
    else
      sleep(1)
    end
  end
end

with spawn thread like this

def spawn_thread(url)
  Thread.new do 
    perform_job
    decrement_counter
  end
end