140 lines
4.3 KiB
Python
140 lines
4.3 KiB
Python
# (C) Copyright 2015-2016 Hewlett Packard Enterprise Development LP
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""" Metric data types
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"""
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import logging
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log = logging.getLogger(__name__)
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class Metric(object):
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"""A base metric class """
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def __init__(self, name, dimensions, tenant):
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self.metric = {'name': name,
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'dimensions': dimensions.copy()}
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self.value_meta = None
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self.value = None
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self.timestamp = None
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self.tenant = tenant
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def measurement(self, value, timestamp):
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measurement = self.metric.copy()
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if self.value_meta:
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measurement['value_meta'] = self.value_meta.copy()
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else:
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measurement['value_meta'] = None
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measurement['value'] = value
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measurement['timestamp'] = timestamp * 1000
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envelope = {'measurement': measurement,
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'tenant_id': self.tenant}
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return envelope
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def sample(self, value, sample_rate, timestamp):
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"""Save a sample. """
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raise NotImplementedError()
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def flush(self):
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if self.timestamp is None:
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return []
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envelope = self.measurement(self.value, self.timestamp)
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self.timestamp = None
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self.value = None
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return [envelope]
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class Gauge(Metric):
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"""A metric that tracks a value at particular points in time. """
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def __init__(self, name, dimensions, tenant=None):
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super(Gauge, self).__init__(name, dimensions, tenant)
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def sample(self, value, sample_rate, timestamp):
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self.value = value
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self.timestamp = timestamp
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class Counter(Metric):
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"""A metric that tracks a counter value. """
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def __init__(self, name, dimensions, tenant=None):
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super(Counter, self).__init__(name, dimensions, tenant)
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def sample(self, value, sample_rate, timestamp):
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try:
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inc = float(value) / sample_rate
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if self.timestamp is None:
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self.value = inc
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else:
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self.value += inc
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self.timestamp = timestamp
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except (TypeError, ValueError):
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log.exception("illegal metric {} value {} sample_rate {}".
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format(self.metric['name'], value, sample_rate))
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# redefine flush method to make counter an integer when sample rates <> 1.0 used
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def flush(self):
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if self.timestamp:
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self.value = int(self.value)
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return super(Counter, self).flush()
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else:
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return []
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class Rate(Metric):
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"""Track the rate of metrics over each flush interval """
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def __init__(self, name, dimensions, tenant=None):
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super(Rate, self).__init__(name, dimensions, tenant)
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self.start_value = None
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self.start_timestamp = None
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def sample(self, value, sample_rate, timestamp):
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# set first value if missing
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if self.start_timestamp is None:
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self.start_timestamp = timestamp
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self.start_value = value
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# set second value otherwise
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else:
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self.timestamp = timestamp
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self.value = value
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# redefine flush method to calculate rate from metrics
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def flush(self):
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# need at least two timestamps to determine rate
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# is the second one is missing then the first is kept as start value for
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# the subsequent interval
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if self.start_timestamp is None or self.timestamp is None:
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return []
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delta_t = self.timestamp - self.start_timestamp
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delta_v = self.value - self.start_value
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try:
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rate = delta_v / float(delta_t)
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except ZeroDivisionError:
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log.warning(
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'Conflicting values reported for metric %s with dimensions %s at time %d: (%f, %f)',
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self.metric['name'],
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self.metric['dimensions'],
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self.timestamp,
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self.start_value,
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self.value)
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# skip this measurement, but keep value for next cycle
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self.start_value = self.value
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return []
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# make it start value for next interval (even if it is None!)
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self.start_value = self.value
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self.start_timestamp = self.timestamp
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envelope = self.measurement(rate, self.timestamp)
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self.timestamp = None
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self.value = None
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return [envelope]
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