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from __future__ import annotations
import asyncio
import math
from collections import defaultdict
import pytest
from dask.utils import parse_bytes
from distributed.shuffle._buffer import ShardsBuffer
from distributed.shuffle._limiter import ResourceLimiter
from distributed.utils_test import gen_test
def gen_bytes(percentage: float, limit: int) -> bytes:
num_bytes = int(math.floor(percentage * limit))
return b"0" * num_bytes
class BufferTest(ShardsBuffer):
def __init__(self, memory_limiter: ResourceLimiter, concurrency_limit: int) -> None:
self.allow_process = asyncio.Event()
self.storage: dict[str, bytes] = defaultdict(bytes)
super().__init__(
memory_limiter=memory_limiter, concurrency_limit=concurrency_limit
)
async def _process(self, id: str, shards: list[bytes]) -> None:
await self.allow_process.wait()
self.storage[id] += b"".join(shards)
def read(self, id: str) -> bytes:
return self.storage[id]
limit = parse_bytes("10.0 MiB")
@pytest.mark.parametrize(
"big_payload",
[
{"big": [gen_bytes(2, limit)]},
{"big": [gen_bytes(0.5, limit)] * 4},
{f"big-{ix}": [gen_bytes(0.5, limit)] for ix in range(4)},
{f"big-{ix}": [gen_bytes(0.5, limit)] * 2 for ix in range(2)},
],
)
@gen_test()
async def test_memory_limit(big_payload):
small_payload = {"small": [gen_bytes(0.1, limit)]}
limiter = ResourceLimiter(limit)
async with BufferTest(
memory_limiter=limiter,
concurrency_limit=2,
) as buf:
# It's OK to write nothing
await buf.write({})
many_small = [asyncio.create_task(buf.write(small_payload)) for _ in range(9)]
buf.allow_process.set()
many_small = asyncio.gather(*many_small)
# Puts that do not breach the limit do not block
await many_small
assert buf.memory_limiter.time_blocked_total == 0
buf.allow_process.clear()
many_small = [asyncio.create_task(buf.write(small_payload)) for _ in range(11)]
assert buf.memory_limiter
while buf.memory_limiter.available():
await asyncio.sleep(0.1)
new_put = asyncio.create_task(buf.write(small_payload))
with pytest.raises(asyncio.TimeoutError):
await asyncio.wait_for(asyncio.shield(new_put), 0.1)
buf.allow_process.set()
many_small = asyncio.gather(*many_small)
await new_put
while not buf.memory_limiter.free():
await asyncio.sleep(0.1)
buf.allow_process.clear()
big = asyncio.create_task(buf.write(big_payload))
small = asyncio.create_task(buf.write(small_payload))
with pytest.raises(asyncio.TimeoutError):
await asyncio.wait_for(asyncio.shield(big), 0.1)
with pytest.raises(asyncio.TimeoutError):
await asyncio.wait_for(asyncio.shield(small), 0.1)
# Puts only return once we're below memory limit
buf.allow_process.set()
await big
await small
# Once the big write is through, we can write without blocking again
before = buf.memory_limiter.time_blocked_total
await buf.write(small_payload)
assert before == buf.memory_limiter.time_blocked_total
class BufferShardsBroken(ShardsBuffer):
def __init__(self, memory_limiter: ResourceLimiter, concurrency_limit: int) -> None:
self.storage: dict[str, bytes] = defaultdict(bytes)
super().__init__(
memory_limiter=memory_limiter, concurrency_limit=concurrency_limit
)
async def _process(self, id: str, shards: list[bytes]) -> None:
if id == "error":
raise RuntimeError("Error during processing")
self.storage[id] += b"".join(shards)
def read(self, id: str) -> bytes:
return self.storage[id]
@gen_test()
async def test_memory_limit_blocked_exception():
limit = parse_bytes("10.0 MiB")
big_payload = {
"shard-1": [gen_bytes(2, limit)],
}
broken_payload = {
"error": ["not-bytes"],
}
limiter = ResourceLimiter(limit)
async with BufferShardsBroken(
memory_limiter=limiter,
concurrency_limit=2,
) as mf:
big_write = asyncio.create_task(mf.write(big_payload))
small_write = asyncio.create_task(mf.write(broken_payload))
# The broken write hits the limit and blocks
await big_write
await small_write
await mf.flush()
# Make sure exception is not dropped
with pytest.raises(RuntimeError, match="Error during processing"):
mf.raise_on_exception()
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