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# Copyright 2010-present Basho Technologies, Inc.
#
# 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 math
import time
from threading import RLock
class Decaying(object):
"""
A float value which decays exponentially toward 0 over time. This
is used internally to select nodes for new connections that have
had the least errors within the recent period.
"""
def __init__(self, p=0.0, e=math.e, r=None):
"""
Creates a new decaying error counter.
:param p: the initial value (defaults to 0.0)
:type p: float
:param e: the exponent base (defaults to math.e)
:type e: float
:param r: timescale factor (defaults to decaying 50% over 10
seconds, i.e. log(0.5) / 10)
:type r: float
"""
self.p = p
self.e = e
self.r = r or (math.log(0.5) / 10)
self.lock = RLock()
self.t0 = time.time()
def incr(self, d):
"""
Increases the value by the argument.
:param d: the value to increase by
:type d: float
"""
with self.lock:
self.p = self.value() + d
def value(self):
"""
Returns the current value (adjusted for the time decay)
:rtype: float
"""
with self.lock:
now = time.time()
dt = now - self.t0
self.t0 = now
self.p = self.p * (math.pow(self.e, self.r * dt))
return self.p
class RiakNode(object):
"""
The internal representation of a Riak node to which the client can
connect. Encapsulates both the configuration for the node and
error tracking used for node-selection.
"""
def __init__(self, host='127.0.0.1', http_port=8098, pb_port=8087,
**unused_args):
"""
Creates a node.
:param host: an IP address or hostname
:type host: string
:param http_port: the HTTP port of the node
:type http_port: integer
:param pb_port: the Protcol Buffers port of the node
:type pb_port: integer
"""
self.host = host
self.http_port = http_port
self.pb_port = pb_port
self.error_rate = Decaying()