from __future__ import unicode_literals
import os
from threading import Lock
from .mmap_dict import mmap_key, MmapedDict
class MutexValue(object):
"""A float protected by a mutex."""
_multiprocess = False
def __init__(self, typ, metric_name, name, labelnames, labelvalues, **kwargs):
self._value = 0.0
self._lock = Lock()
def inc(self, amount):
with self._lock:
self._value += amount
def set(self, value):
with self._lock:
self._value = value
def get(self):
with self._lock:
return self._value
def MultiProcessValue(process_identifier=os.getpid):
"""Returns a MmapedValue class based on a process_identifier function.
The 'process_identifier' function MUST comply with this simple rule:
when called in simultaneously running processes it MUST return distinct values.
Using a different function than the default 'os.getpid' is at your own risk.
"""
files = {}
values = []
pid = {'value': process_identifier()}
# Use a single global lock when in multi-processing mode
# as we presume this means there is no threading going on.
# This avoids the need to also have mutexes in __MmapDict.
lock = Lock()
class MmapedValue(object):
"""A float protected by a mutex backed by a per-process mmaped file."""
_multiprocess = True
def __init__(self, typ, metric_name, name, labelnames, labelvalues, multiprocess_mode='', **kwargs):
self._params = typ, metric_name, name, labelnames, labelvalues, multiprocess_mode
with lock:
self.__check_for_pid_change()
self.__reset()
values.append(self)
def __reset(self):
typ, metric_name, name, labelnames, labelvalues, multiprocess_mode = self._params
if typ == 'gauge':
file_prefix = typ + '_' + multiprocess_mode
else:
file_prefix = typ
if file_prefix not in files:
filename = os.path.join(
os.environ['prometheus_multiproc_dir'],
'{0}_{1}.db'.format(file_prefix, pid['value']))
files[file_prefix] = MmapedDict(filename)
self._file = files[file_prefix]
self._key = mmap_key(metric_name, name, labelnames, labelvalues)
self._value = self._file.read_value(self._key)
def __check_for_pid_change(self):
actual_pid = process_identifier()
if pid['value'] != actual_pid:
pid['value'] = actual_pid
# There has been a fork(), reset all the values.
for f in files.values():
f.close()
files.clear()
for value in values:
value.__reset()
def inc(self, amount):
with lock:
self.__check_for_pid_change()
self._value += amount
self._file.write_value(self._key, self._value)
def set(self, value):
with lock:
self.__check_for_pid_change()
self._value = value
self._file.write_value(self._key, self._value)
def get(self):
with lock:
self.__check_for_pid_change()
return self._value
return MmapedValue
def get_value_class():
# Should we enable multi-process mode?
# This needs to be chosen before the first metric is constructed,
# and as that may be in some arbitrary library the user/admin has
# no control over we use an environment variable.
if 'prometheus_multiproc_dir' in os.environ:
return MultiProcessValue()
else:
return MutexValue
ValueClass = get_value_class()
|