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# Copyright (c) 2018 Uber 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 json
import logging
import random
from threading import Lock
from typing import Any, Optional
from tornado.ioloop import PeriodicCallback
from .constants import DEFAULT_THROTTLER_REFRESH_INTERVAL
from .metrics import Metrics, MetricsFactory
from .utils import ErrorReporter
MINIMUM_CREDITS = 1.0
default_logger = logging.getLogger('jaeger_tracing')
class Throttler(object):
def set_client_id(self, client_id: int) -> None:
"""
Called by tracer to set client ID of throttler.
"""
pass
def is_allowed(self, operation: str) -> bool:
raise NotImplementedError()
def close(self) -> None:
pass
class RemoteThrottler(Throttler):
"""
RemoteThrottler controls the flow of spans emitted from client to prevent
flooding. RemoteThrottler requests credits from the throttling service
periodically. These credits determine the amount of debug spans a client
may emit for a particular operation without receiving more credits.
:param channel: channel for communicating with jaeger-agent
:param service_name: name of this application
:param kwargs: optional parameters
- refresh_interval: interval in seconds for requesting more credits
- logger: Logger instance
- metrics_factory: factory to create throttler-specific metrics
- error_reporter: ErrorReporter instance
"""
def __init__(self, channel: Any, service_name: str, **kwargs: Any) -> None:
self.channel = channel
self.service_name = service_name
self.client_id: Optional[int] = None
self.refresh_interval = \
kwargs.get('refresh_interval', DEFAULT_THROTTLER_REFRESH_INTERVAL)
self.logger = kwargs.get('logger', default_logger)
metrics_factory = kwargs.get('metrics_factory', MetricsFactory())
self.metrics = ThrottlerMetrics(metrics_factory)
self.error_reporter = kwargs.get('error_reporter', ErrorReporter(Metrics()))
self.credits: dict = {}
self.lock = Lock()
self.running = True
self.periodic = None
if not self.channel.io_loop:
self.logger.error(
'Cannot acquire IOLoop, throttler will not be updated')
else:
self.channel.io_loop.add_callback(self._init_polling)
def is_allowed(self, operation: str) -> bool:
with self.lock:
if operation not in self.credits:
self.credits[operation] = 0.0
self.metrics.throttled_debug_spans(1)
return False
value = self.credits[operation]
if value < MINIMUM_CREDITS:
self.metrics.throttled_debug_spans(1)
return False
self.credits[operation] = value - MINIMUM_CREDITS
return True
def set_client_id(self, client_id: int) -> None:
with self.lock:
if self.client_id is None:
self.client_id = client_id
def _init_polling(self):
"""
Bootstrap polling for throttler.
To avoid spiky traffic from throttler clients, we use a random delay
before the first poll.
"""
with self.lock:
if not self.running:
return
r = random.Random()
delay = r.random() * self.refresh_interval
self.channel.io_loop.call_later(
delay=delay, callback=self._delayed_polling)
self.logger.info(
'Delaying throttling credit polling by %d sec', delay)
def _operations(self):
with self.lock:
return self.credits.keys()
def _delayed_polling(self):
def callback():
self._fetch_credits(self._operations())
periodic = PeriodicCallback(
callback=callback,
# convert interval to milliseconds
callback_time=self.refresh_interval * 1000)
self._fetch_credits(self._operations())
with self.lock:
if not self.running:
return
self.periodic = periodic
self.periodic.start()
self.logger.info(
'Throttling client started with refresh interval %d sec',
self.refresh_interval)
def _fetch_credits(self, operations):
if not operations:
return
self.logger.debug('Requesting throttling credits')
fut = self.channel.request_throttling_credits(
self.service_name, self.client_id, operations)
fut.add_done_callback(self._request_callback)
def _request_callback(self, future):
exception = future.exception()
if exception:
self.metrics.throttler_update_failure(1)
self.error_reporter.error(
'Failed to get throttling credits from jaeger-agent: %s',
exception)
return
response = future.result()
# In Python 3.5 response.body is of type bytes and json.loads() does only support str
# See: https://github.com/jaegertracing/jaeger-client-python/issues/180
if hasattr(response.body, 'decode') and callable(response.body.decode):
response_body = response.body.decode('utf-8')
else:
response_body = response.body
try:
throttling_response = json.loads(response_body)
self.logger.debug('Received throttling response: %s',
throttling_response)
self._update_credits(throttling_response)
self.metrics.throttler_update_success(1)
except Exception as e:
self.metrics.throttler_update_failure(1)
self.error_reporter.error(
'Failed to parse throttling credits response '
'from jaeger-agent: %s [%s]', e, response_body)
return
def _update_credits(self, response):
with self.lock:
for op_balance in response['balances']:
op = op_balance['operation']
balance = op_balance['balance']
if op not in self.credits:
self.credits[op] = 0
self.credits[op] += balance
self.logger.debug('credits = %s', self.credits)
def close(self) -> None:
with self.lock:
self.running = False
if self.periodic:
self.periodic.stop()
class ThrottlerMetrics(object):
"""
Metrics specific to throttler.
"""
def __init__(self, metrics_factory: MetricsFactory) -> None:
self.throttled_debug_spans = \
metrics_factory.create_counter(name='jaeger:throttled_debug_spans')
self.throttler_update_success = \
metrics_factory.create_counter(name='jaeger:throttler_update',
tags={'result': 'ok'})
self.throttler_update_failure = \
metrics_factory.create_counter(name='jaeger:throttler_update',
tags={'result': 'err'})
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