cluster_mgr.py

#!/usr/bin/env python3
import argparse
import json
import math
import redis
import subprocess
import time

'''
To install: pip install -r requirements.txt
'''


class Node:
    def __init__(self, port):
        self.id = ''
        self.port = port
        self.admin_port = port + 10_000


class Master:
    def __init__(self, port):
        self.node = Node(port)
        self.replicas = []


def start_node(node, threads):
    f = open(f'/tmp/dfly.cluster.node.{node.port}.log', 'w')
    print(
        f'- Log file for node {node.port}: {f.name}')
    subprocess.Popen(['../build-dbg/dragonfly', f'--port={node.port}',
                      f'--admin_port={node.admin_port}', '--cluster_mode=yes', f'--proactor_threads={threads}',
                      '--dbfilename=', f'--logtostderr'], stderr=f)


def send_command(node, command):
    client = redis.Redis(decode_responses=True,
                         host="localhost", port=node.admin_port)

    for i in range(0, 5):
        try:
            result = client.execute_command(*command)
            client.close()
            return result
        except:
            time.sleep(0.1 * i)

    print(
        f'Unable to connect to localhost:{node.admin_port} after 5 attempts!')


def update_id(node):
    id = send_command(node, ['dflycluster', 'myid'])
    node.id = id
    print(f'- ID for {node.port}: {id}')


def build_config_from_list(masters):
    total_slots = 16384
    slots_per_node = math.floor(total_slots / len(masters))

    def build_node(node):
        return {
            "id": node.id,
            "ip": "localhost",
            "port": node.port
        }

    config = []
    for i, master in enumerate(masters):
        c = {
            "slot_ranges": [
                {
                    "start": i * slots_per_node,
                    "end": (i+1) * slots_per_node - 1
                }
            ],
            "master": build_node(master.node),
            "replicas": [build_node(replica) for replica in master.replicas]
        }

        config.append(c)

    config[-1]["slot_ranges"][-1]["end"] += total_slots % len(masters)
    return config


def get_nodes_from_config(config):
    nodes = []
    for shard in config:
        nodes.append(Node(shard["master"]["port"]))
        for replica in shard["replicas"]:
            nodes.append(Node(replica["port"]))
    return nodes


def push_config(config):
    def push_to_node(node, config):
        config_str = json.dumps(config, indent=2)
        response = send_command(node, ['dflycluster', 'config', config_str])
        print(f'- Push to {node.port}: {response}')

    for node in get_nodes_from_config(config):
        push_to_node(node, config)


def create(args):
    print(f'Setting up a Dragonfly cluster:')
    print(f'- Master nodes: {args.num_masters}')
    print(
        f'- Ports: {args.first_port}...{args.first_port + args.num_masters - 1}')
    print(f'- Replicas for each master: {args.replicas_per_master}')
    print()

    next_port = args.first_port
    masters = []
    for i in range(args.num_masters):
        master = Master(next_port)
        next_port += 1
        for j in range(args.replicas_per_master):
            replica = Node(next_port)
            master.replicas.append(replica)
            next_port += 1
        masters.append(master)

    nodes = []
    for master in masters:
        nodes.append(master.node)
        for replica in master.replicas:
            nodes.append(replica)

    print('Starting nodes...')
    for node in nodes:
        start_node(node, args.threads)
    print()

    if args.replicas_per_master > 0:
        print('Configuring replication...')
        for master in masters:
            for replica in master.replicas:
                response = send_command(
                    replica, ['replicaof', 'localhost', master.node.port])
                print(
                    f'- {replica.port} replicating {master.node.port}: {response}')
        print()

    print(f'Getting IDs...')
    for n in nodes:
        update_id(n)
    print()

    config = build_config_from_list(masters)
    print(f'Pushing config:\n{config}\n')
    push_config(config)
    print()


def build_config_from_existing(args):
    def list_to_dict(l):
        return {l[i]: l[i + 1] for i in range(0, len(l), 2)}

    def build_node(node_list):
        d = list_to_dict(node_list)
        return {
            "id": d["id"],
            "ip": d["endpoint"],
            "port": d["port"]
        }

    def build_slots(slot_list):
        slots = []
        for i in range(0, len(slot_list), 2):
            slots.append(
                {
                    "start": slot_list[i],
                    "end": slot_list[i+1]
                }
            )
        return slots

    client = redis.Redis(decode_responses=True,
                         host="localhost", port=args.first_port)
    existing = client.execute_command("cluster", "shards")
    config = []
    for shard_list in existing:
        shard = list_to_dict(shard_list)
        config.append({
            "slot_ranges": build_slots(shard["slots"]),
            "master": build_node(shard["nodes"][0]),
            "replicas": [build_node(replica) for replica in shard["nodes"][1::]]
        })
    return config


def move(args):
    config = build_config_from_existing(args)

    new_owner = None
    for shard in config:
        if shard["master"]["port"] == args.target_port:
            new_owner = shard
            break
    else:
        print(
            f"Can't find master with port {args.target_port} (hint: use flag --target_port).")
        exit(-1)

    def remove_slot(slot, from_range, from_shard):
        if from_range["start"] == slot:
            from_range["start"] += 1
            if from_range["start"] > from_range["end"]:
                from_shard["slot_ranges"].remove(from_range)
        elif from_range["end"] == slot:
            from_range["end"] -= 1
            if from_range["start"] > from_range["end"]:
                from_shard["slot_ranges"].remove(from_range)
        else:
            assert slot > from_range["start"] and slot < from_range[
                "end"], f'{slot} {from_range["start"]} {from_range["end"]}'
            from_shard["slot_ranges"].append(
                {"start": slot + 1, "end": from_range["end"]})
            from_range["end"] = slot - 1

    def add_slot(slot, to_shard):
        for slot_range in to_shard["slot_ranges"]:
            if slot == slot_range["start"] - 1:
                slot_range["start"] -= 1
                return
            if slot == slot_range["end"] + 1:
                slot_range["end"] += 1
                return
        to_shard["slot_ranges"].append({"start": slot, "end": slot})

    def find_slot(slot, config):
        for shard in config:
            if shard == new_owner:
                continue
            for slot_range in shard["slot_ranges"]:
                if slot >= slot_range["start"] and slot <= slot_range["end"]:
                    return shard, slot_range
        return None, None

    def pack(slot_ranges):
        new_range = []
        while True:
            changed = False
            new_range = []
            slot_ranges.sort(key=lambda x: x["start"])
            for i, slot_range in enumerate(slot_ranges):
                added = False
                for j in range(i):
                    prev_slot_range = slot_ranges[j]
                    if prev_slot_range["end"] + 1 == slot_range["start"]:
                        prev_slot_range["end"] = slot_range["end"]
                        changed = True
                        added = True
                        break
                if not added:
                    new_range.append(slot_range)
            slot_ranges = new_range
            if not changed:
                break
        return new_range

    for slot in range(args.slot_start, args.slot_end+1):
        shard, slot_range = find_slot(slot, config)
        if shard == None:
            continue
        if shard == new_owner:
            continue
        remove_slot(slot, slot_range, shard)
        add_slot(slot, new_owner)

    for shard in config:
        shard["slot_ranges"] = pack(shard["slot_ranges"])

    print(f'Pushing new config:\n{json.dumps(config, indent=2)}\n')
    push_config(config)


def print_config(args):
    config = build_config_from_existing(args)
    print(json.dumps(config, indent=2))


def shutdown(args):
    config = build_config_from_existing(args)
    for node in get_nodes_from_config(config):
        send_command(node, ["shutdown"])


def main():
    parser = argparse.ArgumentParser(description='''
Local Cluster Manager

Example usage:

Create a 3+3 nodes cluster:
  ./cluster_mgr.py --action=create --num_masters=3 --replicas_per_master=1

Connect to cluster and print current config:
  ./cluster_mgr.py --action=print

Connect to cluster and shutdown all nodes:
  ./cluster_mgr.py --action=shutdown

Connect to cluster and move slots 10-20 to master with port 7002:
  ./cluster_mgr.py --action=move --slot_start=10 --slot_end=20 --new_owner=7002
''')
    parser.add_argument('--action', default='',
                        help='Which action to take? create: start a new instance, move=move slots')
    parser.add_argument('--num_masters', type=int, default=3,
                        help='Number of master nodes in cluster')
    parser.add_argument('--replicas_per_master', type=int, default=0,
                        help='How many replicas for each master')
    parser.add_argument('--first_port', type=int,
                        default=7001, help="First master's port")
    parser.add_argument('--threads', type=int, default=2,
                        help="Threads per node")
    parser.add_argument('--slot_start', type=int,
                        default=0, help="First slot to move (inclusive)")
    parser.add_argument('--slot_end', type=int,
                        default=100, help="Last slot to move (inclusive)")
    parser.add_argument('--target_port', type=int, default=0,
                        help="Master port to take ownership over slots in range "
                        "[--slot_start, --slot_end]")
    args = parser.parse_args()

    actions = {'create': create, 'shutdown': shutdown,
               'move': move, 'print': print_config}
    action = actions.get(args.action.lower())
    if (action):
        action(args)
    else:
        print(f'Error - unknown action "{args.action}"')
        exit(-1)


if __name__ == "__main__":
    main()