test(cluster): Add a Cluster Management script (#1390)

This script allows easily setting up a local cluster.

Example invocation:

```
killall dragonfly; ./cluster_mgr.py --num_masters=3 --with_replicas
Setting up a Dragonfly cluster:
- Master nodes: 3
- Ports: 7001...7003
- Admin ports: 8001...8003
- Replicas? True

Starting nodes...
- Log file for node 7001: /tmp/dfly.cluster.node.7001.log
- Log file for node 7002: /tmp/dfly.cluster.node.7002.log
- Log file for node 7003: /tmp/dfly.cluster.node.7003.log
- Log file for node 7004: /tmp/dfly.cluster.node.7004.log
- Log file for node 7005: /tmp/dfly.cluster.node.7005.log
- Log file for node 7006: /tmp/dfly.cluster.node.7006.log

Configuring replication...
- Response for 7004: OK
- Response for 7005: OK
- Response for 7006: OK

Getting IDs...
- ID for 7001: acefdc2da5d397cfcb99239b3c29cbe6ff10d75a
- ID for 7002: a8cc67dfa42e91a94bd7c0903df35d60a39508bd
- ID for 7003: 1ad91af7bd96c89a8da877164b2ebb4cf458cab8
- ID for 7004: d209c3603343e25a18c78bd68304b6d883973bd3
- ID for 7005: bd2b25e95aaf7fdd2b955e50a00093a8272954bf
- ID for 7006: beb5cb07b75c33e3ff938d07725f2688d9bc91e0

Pushing config...
- Push into 7001: OK
- Push into 7002: OK
- Push into 7003: OK
- Push into 7004: OK
- Push into 7005: OK
- Push into 7006: OK
```

tools/cluster_mgr.py

@@ -0,0 +1,163 @@
+#!/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, admin_port):
+        self.id = ''
+        self.port = port
+        self.admin_port = admin_port
+
+
+class Master:
+    def __init__(self, port, admin_port):
+        self.node = Node(port, admin_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)
+
+    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(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 json.dumps(config, indent=2)
+
+
+def push_config(nodes, config):
+    for node in nodes:
+        response = send_command(node, ['dflycluster', 'config', config])
+        print(f'- Push into {node.port}: {response}')
+
+
+def main():
+    parser = argparse.ArgumentParser(description='Local Cluster Manager')
+    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('--first_admin_port', type=int,
+                        default=17_001, help="First master's admin port")
+    parser.add_argument('--threads', type=int, default=2,
+                        help="Threads per node")
+    args = parser.parse_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'- Admin ports: {args.first_admin_port}...{args.first_admin_port + args.num_masters - 1}')
+    print(f'- Replicas for each master: {args.replicas_per_master}')
+    print()
+
+    next_port = args.first_port
+    next_admin_port = args.first_admin_port
+    masters = []
+    for i in range(args.num_masters):
+        master = Master(next_port, next_admin_port)
+        next_port += 1
+        next_admin_port += 1
+        for j in range(args.replicas_per_master):
+            replica = Node(next_port, next_admin_port)
+            master.replicas.append(replica)
+            next_port += 1
+            next_admin_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(masters)
+    print(f'Pushing config...')
+    push_config(nodes, config)
+    print()
+
+
+if __name__ == "__main__":
+    main()