How to Mock a Hot Shard Split in Python

import random
from collections import defaultdict


class HotShardMock:
    """Mock implementation of a hot shard split in a distributed database."""

    def __init__(self, shard_id="shard_1", max_entries=5):
        self.shard_id = shard_id
        self.max_entries = max_entries
        self.entries = {}

    def add_entry(self, key, value):
        """Add an entry, triggering a split if the shard becomes hot."""
        self.entries[key] = value
        if len(self.entries) > self.max_entries:
            self.split_shard()

    def split_shard(self):
        """Split the hot shard into two shards by key ranges."""
        keys = sorted(self.entries.keys())
        mid = len(keys) // 2
        left_keys = keys[:mid]
        right_keys = keys[mid:]

        left_shard = HotShardMock(f"{self.shard_id}_left", self.max_entries)
        right_shard = HotShardMock(f"{self.shard_id}_right", self.max_entries)

        for k in left_keys:
            left_shard.entries[k] = self.entries[k]
        for k in right_keys:
            right_shard.entries[k] = self.entries[k]

        self.entries = {}
        self.children = [left_shard, right_shard]
        self.is_split = True
        print(f"{self.shard_id} split into {left_shard.shard_id} and {right_shard.shard_id}")
        print(f"  Left:  {left_shard.entries}")
        print(f"  Right: {right_shard.entries}")

    def __repr__(self):
        status = "SPLIT" if getattr(self, "is_split", False) else "ACTIVE"
        return f"{self.shard_id} ({status}): {self.entries}"


if __name__ == "__main__":
    shard = HotShardMock(max_entries=3)
    for i in range(1, 8):
        shard.add_entry(f"user_{i}", random.randint(100, 999))
    print("\nFinal hierarchy:")
    if hasattr(shard, "children"):
        for child in shard.children:
            print(f"  {child}")
    else:
        print(f"  {shard}")