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Allow checks to store tagged metrics #79

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merged 4 commits into from
Jun 19, 2012
Merged

Allow checks to store tagged metrics #79

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b758eef
Interim commit.
alq666 Jun 18, 2012
edc0d2a
All tests pass.
alq666 Jun 18, 2012
6c6f87e
Clarified get_samples behavior
alq666 Jun 18, 2012
8a462b7
Updating comment.
clutchski Jun 19, 2012
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62 changes: 34 additions & 28 deletions checks/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -53,12 +53,17 @@ def filter(self, record):
class Check(object):
"""
(Abstract) class for all checks with the ability to:
* store 1 (and only 1) sample for gauges per metric/tag combination
* compute rates for counters
* only log error messages once (instead of each time they occur)

"""
def __init__(self, logger):
# where to store samples, indexed by metric_name
# metric_name: [(ts, value), (ts, value)]
# metric_name: {("sorted", "tags"): [(ts, value), (ts, value)],
# tuple(tags) are stored as a key since lists are not hashable
# None: [(ts, value), (ts, value)]}
# untagged values are indexed by None
self._sample_store = {}
self._counters = {} # metric_name: bool
self.logger = logger
Expand Down Expand Up @@ -92,7 +97,7 @@ def counter(self, metric):
ACHTUNG: Resets previous values associated with this metric.
"""
self._counters[metric] = True
self._sample_store[metric] = []
self._sample_store[metric] = {}

def is_counter(self, metric):
"Is this metric a counter?"
Expand All @@ -103,7 +108,7 @@ def gauge(self, metric):
Treats the metric as a gauge, i.e. keep the data as is
ACHTUNG: Resets previous values associated with this metric.
"""
self._sample_store[metric] = []
self._sample_store[metric] = {}

def is_metric(self, metric):
return metric in self._sample_store
Expand All @@ -116,8 +121,9 @@ def get_metric_names(self):
"Get all metric names"
return self._sample_store.keys()

def save_sample(self, metric, value, timestamp=None):
"""Save a simple sample, evict old values if needed"""
def save_sample(self, metric, value, timestamp=None, tags=None):
"""Save a simple sample, evict old values if needed
"""
if timestamp is None:
timestamp = time.time()
if metric not in self._sample_store:
Expand All @@ -127,21 +133,27 @@ def save_sample(self, metric, value, timestamp=None):
except ValueError, ve:
raise NaN(ve)

# sort tags
if tags is not None:
tags.sort()
tags = tuple(tags)

# Data eviction rules
if self.is_gauge(metric):
self._sample_store[metric] = [(timestamp, value)]
self._sample_store[metric][tags] = ((timestamp, value), )
elif self.is_counter(metric):
if len(self._sample_store[metric]) == 0:
self._sample_store[metric] = [(timestamp, value)]
if self._sample_store[metric].get(tags) is None:
self._sample_store[metric][tags] = [(timestamp, value)]
else:
self._sample_store[metric] = self._sample_store[metric][-1:] + [(timestamp, value)]
self._sample_store[metric][tags] = self._sample_store[metric][tags][-1:] + [(timestamp, value)]
else:
raise CheckException("%s must be either gauge or counter, skipping sample at %s" % (metric, time.ctime(timestamp)))

if self.is_gauge(metric):
assert len(self._sample_store[metric]) in (0, 1), self._sample_store[metric]
# store[metric][tags] = (ts, val) - only 1 value allowd
assert len(self._sample_store[metric][tags]) == 1, self._sample_store[metric]
elif self.is_counter(metric):
assert len(self._sample_store[metric]) in (0, 1, 2), self._sample_store[metric]
assert len(self._sample_store[metric][tags]) in (1, 2), self._sample_store[metric]

@classmethod
def _rate(cls, sample1, sample2):
Expand All @@ -163,28 +175,28 @@ def _rate(cls, sample1, sample2):
except Exception, e:
raise NaN(e)

def get_sample_with_timestamp(self, metric):
def get_sample_with_timestamp(self, metric, tags=None):
"Get (timestamp-epoch-style, value)"
# Never seen this metric
if metric not in self._sample_store:
raise UnknownValue()

# Not enough value to compute rate
elif self.is_counter(metric) and len(self._sample_store[metric]) < 2:
elif self.is_counter(metric) and len(self._sample_store[metric][tags]) < 2:
raise UnknownValue()

elif self.is_counter(metric) and len(self._sample_store[metric]) >= 2:
return self._rate(self._sample_store[metric][-2], self._sample_store[metric][-1])
elif self.is_counter(metric) and len(self._sample_store[metric][tags]) >= 2:
return self._rate(self._sample_store[metric][tags][-2], self._sample_store[metric][tags][-1])

elif self.is_gauge(metric) and len(self._sample_store[metric]) >= 1:
return self._sample_store[metric][-1]
elif self.is_gauge(metric) and len(self._sample_store[metric][tags]) >= 1:
return self._sample_store[metric][tags][-1]

else:
raise UnknownValue()

def get_sample(self, metric):
def get_sample(self, metric, tags=None):
"Return the last value for that metric"
x = self.get_sample_with_timestamp(metric)
x = self.get_sample_with_timestamp(metric, tags)
assert type(x) == types.TupleType and len(x) == 2, x
return x[1]

Expand All @@ -209,21 +221,15 @@ def get_samples(self):
pass
return values

def get_metadata(self):
"""Return a dictionary of key-value pairs with metadata
How these metadata are interpreted and processed is not defined here
"""
return {}

def get_metrics(self):
"""This is the new format to send metrics backs
"""
metrics = []
for m in self._sample_store:
try:
ts, val = self.get_sample_with_timestamp(m)
# FIXME alq - no metadata yet
metrics.append((m, int(ts), val, {}))
for t in self._sample_store[m]:
ts, val = self.get_sample_with_timestamp(m, t)
metrics.append((m, int(ts), val, {"tags": list(t)}))
except:
pass
return metrics
Expand Down
19 changes: 19 additions & 0 deletions tests/test_common.py
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,25 @@ def test_counter(self):
self.c.save_sample("test-counter", -2.0, 3.0)
self.assertRaises(UnknownValue, self.c.get_sample_with_timestamp, "test-counter")

def test_tags(self):
# Test metric tagging
now = int(time.time())
# Tag metrics
self.c.save_sample("test-counter", 1.0, 1.0, tags = ["tag1", "tag2"])
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New syntax to tag metrics.

self.c.save_sample("test-counter", 2.0, 2.0, tags = ["tag1", "tag2"])
# Only 1 point recording for this combination of tags, won't be sent
self.c.save_sample("test-counter", 3.0, 3.0, tags = ["tag1", "tag3"])
self.c.save_sample("test-metric", 3.0, now, tags = ["tag3", "tag4"])
# This is a different combination of tags
self.c.save_sample("test-metric", 3.0, now, tags = ["tag5", "tag3"])
results = self.c.get_metrics()
results.sort()
self.assertEquals(results,
[("test-counter", 2.0, 1.0, {"tags": ["tag1", "tag2"]}),
("test-metric", now, 3.0, {"tags": ["tag3", "tag4"]}),
("test-metric", now, 3.0, {"tags": ["tag3", "tag5"]}),
])

def test_samples(self):
self.assertEquals(self.c.get_samples(), {})
self.c.save_sample("test-metric", 1.0, 0.0) # value, ts
Expand Down