def start_worker(channel='tasks', max=None, resources=[]):
"""
channel: Queue from which tasks needs to be executed
max: Maximum number of tasks to be exucuted,
useful when worker is started from another process.
None (default) means all and keep listening for more
resources: List of available CPU and memory for the worker
"""
# initialize worker environment
clear_logs()
count = 0
q = TaskQueue(config_file='config.json')
# start continuously checking queue for tasks
while True:
# check if max tasks are executed
if max is not None:
if count < max:
count += 1
else:
break
task = q.pop()
if task is not None:
task = json.loads(task.decode('utf-8'))
if len(resources) == 2 and \
resources[0] is not None and resources[1] is not None:
req_cpu = int(task['args']['resources']['cpu'])
req_mem = int(task['args']['resources']['mem'])
# wait if enough resources are not available
while resources[0] < req_cpu or resources[1] < req_mem:
print('Waiting for resources ...')
time.sleep(1)
# grab them as soon as they are available
resources[0] -= req_cpu
resources[1] -= req_mem
# execute the task if resources are available
p = threading.Thread(target=execute_task,
args=(task, resources)).start()
else:
# if task queue is empty, wait 1 second before checking again
count -= 1
time.sleep(1)
return 0
# test if task executes with exit status 0
print('Testing docker_task explicitly...')
assert docker_task(args) == 0
print('Done')
# test if task gets enqueued to the queue
assert q.push('test_task', args) == 0
assert q.push('test_task', args) == 0
assert q.push('test_task', args) == 0
assert q.push('test_task', args) == 0
# test if task has enqueued
assert q.q_size() == n + 4
# test if worker executes 3 tasks with given resources and exit with status 0
# since the required cpu of the tasks is 20% and available is 50% only 2 tasks
# should be executed parallely and 3rd will be executed only when one of
# the earlier two is completed. This can be verified through log timestamp.
assert start_worker(max=3, resources=[50, 18000000]) == 0
# test if task has removed from queue
assert q.q_size() == n + 1
# test if pop and front works
assert not q.front() is None
assert not q.pop() is None
# test if pop reduced the size of queue
assert q.q_size() == n
