blob: cd2c83fff0998f2ccc90d3982f0f1070b548c743 [file] [log] [blame]
#!/usr/bin/env impala-python
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# to you under the Apache License, Version 2.0 (the
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import logging
import os
from contextlib import contextmanager
from multiprocessing import Value
from time import sleep
from tests.stress.util import increment
LOG = logging.getLogger(os.path.splitext(os.path.basename(__file__))[0])
class MemBroker(object):
"""Provides memory usage coordination for clients running in different processes.
The broker fulfills reservation requests by blocking as needed so total memory
used by clients never exceeds the total available memory (including an
'overcommitable' amount).
The lock built in to _available is also used to protect access to other members.
The state stored in this class is actually an encapsulation of part of the state
of the StressRunner class below. The state here is separated for clarity.
def __init__(self, real_mem_mb, overcommitable_mem_mb):
"""'real_mem_mb' memory should be the amount of memory that each impalad is able
to use. 'overcommitable_mem_mb' is the amount of memory that will be dispensed
over the 'real' amount.
self._total_mem_mb = real_mem_mb + overcommitable_mem_mb
self._available = Value("i", self._total_mem_mb)
self._max_overcommitment = overcommitable_mem_mb
# Each reservation will be assigned an id. Ids are monotonically increasing. When
# a reservation crosses the overcommitment threshold, the corresponding reservation
# id will be stored in '_last_overcommitted_reservation_id' so clients can check
# to see if memory was overcommitted since their reservation was made (this is a race
# but an incorrect result will be on the conservative side).
self._next_reservation_id = Value("L", 0)
self._last_overcommitted_reservation_id = Value("L", 0)
def total_mem_mb(self):
return self._total_mem_mb
def overcommitted_mem_mb(self):
return max(self._max_overcommitment - self._available.value, 0)
def available_mem_mb(self):
return self._available.value
def last_overcommitted_reservation_id(self):
return self._last_overcommitted_reservation_id.value
def reserve_mem_mb(self, mem_mb):
"""Blocks until the requested amount of memory is available and taken for the caller.
This function should be used in a 'with' block. The taken memory will
automatically be released when the 'with' context exits. A numeric id is returned
so clients can compare against 'last_overcommitted_reservation_id' to see if
memory was overcommitted since the reservation was obtained.
with broker.reserve_mem_mb(100) as reservation_id:
# Run query using 100 MB of memory
if <query failed>:
# Immediately check broker.was_overcommitted(reservation_id) to see if
# memory was overcommitted.
reservation_id = self._wait_until_reserved(mem_mb)
yield reservation_id
def _wait_until_reserved(self, req):
while True:
with self._available.get_lock():
if req <= self._available.value:
self._available.value -= req
"Reserved %s MB; %s MB available; %s MB overcommitted",
req, self._available.value, self.overcommitted_mem_mb)
reservation_id = self._next_reservation_id.value
if self.overcommitted_mem_mb > 0:
self._last_overcommitted_reservation_id.value = reservation_id
return reservation_id
def _release(self, req):
with self._available.get_lock():
self._available.value += req
"Released %s MB; %s MB available; %s MB overcommitted",
req, self._available.value, self.overcommitted_mem_mb)
def was_overcommitted(self, reservation_id):
"""Returns True if memory was overcommitted since the given reservation was made.
For an accurate return value, this should be called just after the query ends
or while the query is still running.
return reservation_id <= self._last_overcommitted_reservation_id.value