src/borg/testsuite/locking.py
import random
import time
from threading import Thread, Lock as ThreadingLock
from traceback import format_exc
import pytest
from ..platform import get_process_id, process_alive
from ..locking import (
TimeoutTimer,
ExclusiveLock,
Lock,
LockRoster,
ADD,
REMOVE,
SHARED,
EXCLUSIVE,
LockTimeout,
NotLocked,
NotMyLock,
)
ID1 = "foo", 1, 1
ID2 = "bar", 2, 2
RACE_TEST_NUM_THREADS = 40
RACE_TEST_DURATION = 0.4 # seconds
@pytest.fixture()
def free_pid():
"""Return a free PID not used by any process (naturally this is racy)"""
host, pid, tid = get_process_id()
while True:
# PIDs are often restricted to a small range. On Linux the range >32k is by default not used.
pid = random.randint(33000, 65000)
if not process_alive(host, pid, tid):
return pid
class TestTimeoutTimer:
def test_timeout(self):
timeout = 0.5
t = TimeoutTimer(timeout).start()
assert not t.timed_out()
time.sleep(timeout * 1.5)
assert t.timed_out()
def test_notimeout_sleep(self):
timeout, sleep = None, 0.5
t = TimeoutTimer(timeout, sleep).start()
assert not t.timed_out_or_sleep()
assert time.time() >= t.start_time + 1 * sleep
assert not t.timed_out_or_sleep()
assert time.time() >= t.start_time + 2 * sleep
@pytest.fixture()
def lockpath(tmpdir):
return str(tmpdir.join("lock"))
class TestExclusiveLock:
def test_checks(self, lockpath):
with ExclusiveLock(lockpath, timeout=1) as lock:
assert lock.is_locked() and lock.by_me()
def test_acquire_break_reacquire(self, lockpath):
lock = ExclusiveLock(lockpath, id=ID1).acquire()
lock.break_lock()
with ExclusiveLock(lockpath, id=ID2):
pass
def test_timeout(self, lockpath):
with ExclusiveLock(lockpath, id=ID1):
with pytest.raises(LockTimeout):
ExclusiveLock(lockpath, id=ID2, timeout=0.1).acquire()
def test_kill_stale(self, lockpath, free_pid):
host, pid, tid = our_id = get_process_id()
dead_id = host, free_pid, tid
cant_know_if_dead_id = "foo.bar.example.net", 1, 2
dead_lock = ExclusiveLock(lockpath, id=dead_id).acquire()
with ExclusiveLock(lockpath, id=our_id):
with pytest.raises(NotMyLock):
dead_lock.release()
with pytest.raises(NotLocked):
dead_lock.release()
with ExclusiveLock(lockpath, id=cant_know_if_dead_id):
with pytest.raises(LockTimeout):
ExclusiveLock(lockpath, id=our_id, timeout=0.1).acquire()
def test_migrate_lock(self, lockpath):
old_id, new_id = ID1, ID2
assert old_id[1] != new_id[1] # different PIDs (like when doing daemonize())
lock = ExclusiveLock(lockpath, id=old_id).acquire()
assert lock.id == old_id # lock is for old id / PID
old_unique_name = lock.unique_name
assert lock.by_me() # we have the lock
lock.migrate_lock(old_id, new_id) # fix the lock
assert lock.id == new_id # lock corresponds to the new id / PID
new_unique_name = lock.unique_name
assert lock.by_me() # we still have the lock
assert old_unique_name != new_unique_name # locking filename is different now
def test_race_condition(self, lockpath):
class SynchronizedCounter:
def __init__(self, count=0):
self.lock = ThreadingLock()
self.count = count
self.maxcount = count
def value(self):
with self.lock:
return self.count
def maxvalue(self):
with self.lock:
return self.maxcount
def incr(self):
with self.lock:
self.count += 1
if self.count > self.maxcount:
self.maxcount = self.count
return self.count
def decr(self):
with self.lock:
self.count -= 1
return self.count
def print_locked(msg):
with print_lock:
print(msg)
def acquire_release_loop(
id, timeout, thread_id, lock_owner_counter, exception_counter, print_lock, last_thread=None
):
print_locked(
"Thread %2d: Starting acquire_release_loop(id=%s, timeout=%d); lockpath=%s"
% (thread_id, id, timeout, lockpath)
)
timer = TimeoutTimer(timeout, -1).start()
cycle = 0
while not timer.timed_out():
cycle += 1
try:
# This timeout is only for not exceeding the given timeout by more than 5%.
# With sleep<0 it's constantly polling anyway.
with ExclusiveLock(lockpath, id=id, timeout=timeout / 20, sleep=-1):
lock_owner_count = lock_owner_counter.incr()
print_locked(
"Thread %2d: Acquired the lock. It's my %d. loop cycle. "
"I am the %d. who has the lock concurrently." % (thread_id, cycle, lock_owner_count)
)
time.sleep(0.005)
lock_owner_count = lock_owner_counter.decr()
print_locked(
"Thread %2d: Releasing the lock, finishing my %d. loop cycle. "
"Currently, %d colleagues still have the lock." % (thread_id, cycle, lock_owner_count)
)
except LockTimeout:
print_locked("Thread %2d: Got LockTimeout, finishing my %d. loop cycle." % (thread_id, cycle))
except: # noqa
exception_count = exception_counter.incr()
e = format_exc()
print_locked(
"Thread %2d: Exception thrown, finishing my %d. loop cycle. "
"It's the %d. exception seen until now: %s" % (thread_id, cycle, exception_count, e)
)
print_locked("Thread %2d: Loop timed out--terminating after %d loop cycles." % (thread_id, cycle))
if last_thread is not None: # joining its predecessor, if any
last_thread.join()
print("")
lock_owner_counter = SynchronizedCounter()
exception_counter = SynchronizedCounter()
print_lock = ThreadingLock()
thread = None
host_id, process_id = "differenthost", 1234
for thread_id in range(RACE_TEST_NUM_THREADS):
thread = Thread(
target=acquire_release_loop,
args=(
(host_id, process_id, thread_id),
RACE_TEST_DURATION,
thread_id,
lock_owner_counter,
exception_counter,
print_lock,
thread,
),
)
thread.start()
thread.join() # joining the last thread
assert lock_owner_counter.maxvalue() > 0, "Never gained the lock? Something went wrong here..."
assert (
lock_owner_counter.maxvalue() <= 1
), "Maximal number of concurrent lock holders was %d. So exclusivity is broken." % (
lock_owner_counter.maxvalue()
)
assert (
exception_counter.value() == 0
), "ExclusiveLock threw %d exceptions due to unclean concurrency handling." % (exception_counter.value())
class TestLock:
def test_shared(self, lockpath):
lock1 = Lock(lockpath, exclusive=False, id=ID1).acquire()
lock2 = Lock(lockpath, exclusive=False, id=ID2).acquire()
assert len(lock1._roster.get(SHARED)) == 2
assert len(lock1._roster.get(EXCLUSIVE)) == 0
assert not lock1._roster.empty(SHARED, EXCLUSIVE)
assert lock1._roster.empty(EXCLUSIVE)
lock1.release()
lock2.release()
def test_exclusive(self, lockpath):
with Lock(lockpath, exclusive=True, id=ID1) as lock:
assert len(lock._roster.get(SHARED)) == 0
assert len(lock._roster.get(EXCLUSIVE)) == 1
assert not lock._roster.empty(SHARED, EXCLUSIVE)
def test_upgrade(self, lockpath):
with Lock(lockpath, exclusive=False) as lock:
lock.upgrade()
lock.upgrade() # NOP
assert len(lock._roster.get(SHARED)) == 0
assert len(lock._roster.get(EXCLUSIVE)) == 1
assert not lock._roster.empty(SHARED, EXCLUSIVE)
def test_downgrade(self, lockpath):
with Lock(lockpath, exclusive=True) as lock:
lock.downgrade()
lock.downgrade() # NOP
assert len(lock._roster.get(SHARED)) == 1
assert len(lock._roster.get(EXCLUSIVE)) == 0
def test_got_exclusive_lock(self, lockpath):
lock = Lock(lockpath, exclusive=True, id=ID1)
assert not lock.got_exclusive_lock()
lock.acquire()
assert lock.got_exclusive_lock()
lock.release()
assert not lock.got_exclusive_lock()
def test_break(self, lockpath):
lock = Lock(lockpath, exclusive=True, id=ID1).acquire()
lock.break_lock()
assert len(lock._roster.get(SHARED)) == 0
assert len(lock._roster.get(EXCLUSIVE)) == 0
with Lock(lockpath, exclusive=True, id=ID2):
pass
def test_timeout(self, lockpath):
with Lock(lockpath, exclusive=False, id=ID1):
with pytest.raises(LockTimeout):
Lock(lockpath, exclusive=True, id=ID2, timeout=0.1).acquire()
with Lock(lockpath, exclusive=True, id=ID1):
with pytest.raises(LockTimeout):
Lock(lockpath, exclusive=False, id=ID2, timeout=0.1).acquire()
with Lock(lockpath, exclusive=True, id=ID1):
with pytest.raises(LockTimeout):
Lock(lockpath, exclusive=True, id=ID2, timeout=0.1).acquire()
def test_kill_stale(self, lockpath, free_pid):
host, pid, tid = our_id = get_process_id()
dead_id = host, free_pid, tid
cant_know_if_dead_id = "foo.bar.example.net", 1, 2
dead_lock = Lock(lockpath, id=dead_id, exclusive=True).acquire()
roster = dead_lock._roster
with Lock(lockpath, id=our_id):
assert roster.get(EXCLUSIVE) == set()
assert roster.get(SHARED) == {our_id}
assert roster.get(EXCLUSIVE) == set()
assert roster.get(SHARED) == set()
with pytest.raises(NotLocked):
dead_lock.release()
with Lock(lockpath, id=cant_know_if_dead_id, exclusive=True):
with pytest.raises(LockTimeout):
Lock(lockpath, id=our_id, timeout=0.1).acquire()
def test_migrate_lock(self, lockpath):
old_id, new_id = ID1, ID2
assert old_id[1] != new_id[1] # different PIDs (like when doing daemonize())
lock = Lock(lockpath, id=old_id, exclusive=True).acquire()
assert lock.id == old_id
lock.migrate_lock(old_id, new_id) # fix the lock
assert lock.id == new_id
lock.release()
lock = Lock(lockpath, id=old_id, exclusive=False).acquire()
assert lock.id == old_id
lock.migrate_lock(old_id, new_id) # fix the lock
assert lock.id == new_id
lock.release()
@pytest.fixture()
def rosterpath(tmpdir):
return str(tmpdir.join("roster"))
class TestLockRoster:
def test_empty(self, rosterpath):
roster = LockRoster(rosterpath)
empty = roster.load()
roster.save(empty)
assert empty == {}
def test_modify_get(self, rosterpath):
roster1 = LockRoster(rosterpath, id=ID1)
assert roster1.get(SHARED) == set()
roster1.modify(SHARED, ADD)
assert roster1.get(SHARED) == {ID1}
roster2 = LockRoster(rosterpath, id=ID2)
roster2.modify(SHARED, ADD)
assert roster2.get(SHARED) == {ID1, ID2}
roster1 = LockRoster(rosterpath, id=ID1)
roster1.modify(SHARED, REMOVE)
assert roster1.get(SHARED) == {ID2}
roster2 = LockRoster(rosterpath, id=ID2)
roster2.modify(SHARED, REMOVE)
assert roster2.get(SHARED) == set()
def test_kill_stale(self, rosterpath, free_pid):
host, pid, tid = our_id = get_process_id()
dead_id = host, free_pid, tid
# put a dead local process lock into roster
roster1 = LockRoster(rosterpath, id=dead_id)
roster1.kill_stale_locks = False
assert roster1.get(SHARED) == set()
roster1.modify(SHARED, ADD)
assert roster1.get(SHARED) == {dead_id}
# put a unknown-state remote process lock into roster
cant_know_if_dead_id = "foo.bar.example.net", 1, 2
roster1 = LockRoster(rosterpath, id=cant_know_if_dead_id)
roster1.kill_stale_locks = False
assert roster1.get(SHARED) == {dead_id}
roster1.modify(SHARED, ADD)
assert roster1.get(SHARED) == {dead_id, cant_know_if_dead_id}
killer_roster = LockRoster(rosterpath)
# Active kill_stale_locks here - does it kill the dead_id lock?
assert killer_roster.get(SHARED) == {cant_know_if_dead_id}
killer_roster.modify(SHARED, ADD)
assert killer_roster.get(SHARED) == {our_id, cant_know_if_dead_id}
other_killer_roster = LockRoster(rosterpath)
# Active kill_stale_locks here - must not kill our_id lock since we're alive.
assert other_killer_roster.get(SHARED) == {our_id, cant_know_if_dead_id}
def test_migrate_lock(self, rosterpath):
old_id, new_id = ID1, ID2
assert old_id[1] != new_id[1] # different PIDs (like when doing daemonize())
roster = LockRoster(rosterpath, id=old_id)
assert roster.id == old_id
roster.modify(SHARED, ADD)
assert roster.get(SHARED) == {old_id}
roster.migrate_lock(SHARED, old_id, new_id) # fix the lock
assert roster.id == new_id
assert roster.get(SHARED) == {new_id}