ray/doc/yarn/example.py

from collections import Counter
import sys
import time
import ray


@ray.remote
def gethostname(x):
    import platform
    import time
    time.sleep(0.01)
    return x + (platform.node(), )


def wait_for_nodes(expected):
    # Wait for all nodes to join the cluster.
    while True:
        num_nodes = len(ray.nodes())
        if num_nodes < expected:
            print("{} nodes have joined so far, waiting for {} more.".format(
                num_nodes, expected - num_nodes))
            sys.stdout.flush()
            time.sleep(1)
        else:
            break


def main():
    wait_for_nodes(4)

    # Check that objects can be transferred from each node to each other node.
    for i in range(10):
        print("Iteration {}".format(i))
        results = [
            gethostname.remote(gethostname.remote(())) for _ in range(100)
        ]
        print(Counter(ray.get(results)))
        sys.stdout.flush()

    print("Success!")
    sys.stdout.flush()
    time.sleep(20)


if __name__ == "__main__":
    ray.init(address="localhost:6379")
    main()