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from __future__ import annotations
import threading
import pytest
from distributed.shuffle._disk import ReadWriteLock
def read(
lock: ReadWriteLock, in_event: threading.Event, block_event: threading.Event
) -> None:
with lock.read():
in_event.set()
block_event.wait()
def write(
lock: ReadWriteLock, in_event: threading.Event, block_event: threading.Event
) -> None:
with lock.write():
in_event.set()
block_event.wait()
def test_basic():
lock = ReadWriteLock()
with lock.write():
pass
# Write after write
with lock.write():
pass
# Read after write
with lock.read():
pass
# Write after read
with lock.write():
pass
with pytest.raises(RuntimeError, match="unlocked read lock"):
lock.release_read()
with pytest.raises(RuntimeError, match="unlocked write lock"):
lock.release_write()
def test_lock_timeout():
lock = ReadWriteLock()
result = lock.acquire_read()
assert result is True
result = lock.acquire_write(timeout=0.1)
assert result is False
# Timed out write does not prevent read
with lock.read():
pass
lock.release_read()
result = lock.acquire_write(timeout=0.1)
assert result is True
result = lock.acquire_read(timeout=0.1)
assert result is False
lock.release_write()
result = lock.acquire_read(timeout=0.1)
assert result is True
def test_concurrent_reads_are_allowed():
in_event = threading.Event()
block_event = threading.Event()
lock = ReadWriteLock()
other = threading.Thread(target=read, args=(lock, in_event, block_event))
try:
other.start()
in_event.wait()
with lock.read():
pass
block_event.set()
finally:
block_event.set()
other.join()
def test_read_blocks_write():
in_event = threading.Event()
block_event = threading.Event()
lock = ReadWriteLock()
other = threading.Thread(target=read, args=(lock, in_event, block_event))
try:
other.start()
in_event.wait()
result = lock.acquire_write(timeout=0.1)
assert result is False
block_event.set()
with lock.write():
pass
finally:
block_event.set()
other.join()
def test_write_blocks_read():
in_event = threading.Event()
block_event = threading.Event()
lock = ReadWriteLock()
other = threading.Thread(target=write, args=(lock, in_event, block_event))
try:
other.start()
in_event.wait()
result = lock.acquire_read(timeout=0.1)
assert result is False
block_event.set()
with lock.read():
pass
finally:
block_event.set()
other.join()
def test_write_blocks_write():
in_event = threading.Event()
block_event = threading.Event()
lock = ReadWriteLock()
other = threading.Thread(target=write, args=(lock, in_event, block_event))
try:
other.start()
in_event.wait()
result = lock.acquire_write(timeout=0.1)
assert result is False
block_event.set()
with lock.write():
pass
finally:
block_event.set()
other.join()
def test_write_preferred_over_read():
in_read_event = threading.Event()
block_read_event = threading.Event()
in_other_read_event = threading.Event()
block_other_read_event = threading.Event()
in_write_event = threading.Event()
block_write_event = threading.Event()
lock = ReadWriteLock()
reader = threading.Thread(target=read, args=(lock, in_read_event, block_read_event))
other_reader = threading.Thread(
target=read, args=(lock, in_other_read_event, block_other_read_event)
)
writer = threading.Thread(
target=write, args=(lock, in_write_event, block_write_event)
)
try:
reader.start()
in_read_event.wait()
writer.start()
result = in_write_event.wait(0.1)
# The write is blocked by the read lock
assert result is False
assert lock._write_pending is True
other_reader.start()
result = in_other_read_event.wait(0.1)
# The read is blocked by the pending write
assert result is False
block_read_event.set()
reader.join()
# The write happens next
in_write_event.wait()
assert in_other_read_event.is_set() is False
block_write_event.set()
writer.join()
in_other_read_event.wait()
block_other_read_event.set()
other_reader.join()
finally:
block_read_event.set()
block_write_event.set()
block_other_read_event.set()
reader.join()
writer.join()
other_reader.join()
|
