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# Copyright (c) 2021 NVIDIA
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import collections
from time import time
from swift.common.utils import node_to_string
class ErrorLimiter(object):
"""
Tracks the number of errors that have occurred for nodes. A node will be
considered to be error-limited for a given interval of time after it has
accumulated more errors than a given limit.
:param suppression_interval: The number of seconds for which a node is
error-limited once it has accumulated more than ``suppression_limit``
errors. Should be a float value.
:param suppression_limit: The number of errors that a node must accumulate
before it is considered to be error-limited. Should be an int value.
"""
def __init__(self, suppression_interval, suppression_limit):
self.suppression_interval = float(suppression_interval)
self.suppression_limit = int(suppression_limit)
self.stats = collections.defaultdict(dict)
def node_key(self, node):
"""
Get the key under which a node's error stats will be stored.
:param node: dictionary describing a node.
:return: string key.
"""
return node_to_string(node)
def is_limited(self, node):
"""
Check if the node is currently error limited.
:param node: dictionary of node to check
:returns: True if error limited, False otherwise
"""
now = time()
node_key = self.node_key(node)
error_stats = self.stats.get(node_key)
if error_stats is None or 'errors' not in error_stats:
return False
if 'last_error' in error_stats and error_stats['last_error'] < \
now - self.suppression_interval:
self.stats.pop(node_key)
return False
return error_stats['errors'] > self.suppression_limit
def limit(self, node):
"""
Mark a node as error limited. This immediately pretends the
node received enough errors to trigger error suppression. Use
this for errors like Insufficient Storage. For other errors
use :func:`increment`.
:param node: dictionary of node to error limit
"""
node_key = self.node_key(node)
error_stats = self.stats[node_key]
error_stats['errors'] = self.suppression_limit + 1
error_stats['last_error'] = time()
def increment(self, node):
"""
Increment the error count and update the time of the last error for
the given ``node``.
:param node: dictionary describing a node.
:returns: True if suppression_limit is exceeded, False otherwise
"""
node_key = self.node_key(node)
error_stats = self.stats[node_key]
error_stats['errors'] = error_stats.get('errors', 0) + 1
error_stats['last_error'] = time()
return error_stats['errors'] > self.suppression_limit
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