nti.fakestatsd¶
Warning
This project is deprecated and unmaintained. Its code has moved
into perfmetrics.testing.
The following is for historical information only.
nti.fakestatsd is a testing client for verifying StatsD metrics emitted by perfmetrics.
It’s easy to create a new client for use in testing:
>>> from nti.fakestatsd import FakeStatsDClient
>>> test_client = FakeStatsDClient()
This client exposes the same public interface as
perfmetrics.statsd.StatsdClient. For example we can increment
counters, set gauges, etc:
>>> test_client.incr('request_c')
>>> test_client.gauge('active_sessions', 320)
Unlike perfmetrics.statsd.StatsdClient, FakeStatsDClient simply
tracks the statsd packets that would be sent. This information is
exposed on our test_client both as the raw statsd packet, and for
convenience this information is also parsed and exposed as Metric
objects. For complete details see FakeStatsDClient and Metric.
>>> test_client.packets
['request_c:1|c', 'active_sessions:320|g']
>>> test_client.metrics
[Observation(name='request_c', value='1', kind='c', sampling_rate=None), Observation(name='active_sessions', value='320', kind='g', sampling_rate=None)]
For validating metrics we provide a set of hamcrest matchers for use in test assertions:
>>> from hamcrest import assert_that
>>> from hamcrest import contains
>>> from nti.fakestatsd.matchers import is_metric
>>> from nti.fakestatsd.matchers import is_gauge
We can use both strings and numbers (or any matcher) for the value:
>>> assert_that(test_client,
... contains(is_metric('c', 'request_c', '1'),
... is_gauge('active_sessions', 320)))
>>> assert_that(test_client,
... contains(is_metric('c', 'request_c', '1'),
... is_gauge('active_sessions', '320')))
>>> from hamcrest import is_
>>> assert_that(test_client,
... contains(is_metric('c', 'request_c', '1'),
... is_gauge('active_sessions', is_('320'))))
If the matching fails, we get a descriptive error:
>>> assert_that(test_client,
... contains(is_gauge('request_c', '1'),
... is_gauge('active_sessions', '320')))
Traceback (most recent call last):
...
AssertionError:
Expected: a sequence containing [(an instance of Metric and (an object with a property 'kind' matching 'g' and an object with a property 'name' matching 'request_c' and an object with a property 'value' matching '1')), (an instance of Metric and (an object with a property 'kind' matching 'g' and an object with a property 'name' matching 'active_sessions' and an object with a property 'value' matching '320'))]
but: item 0: was Metric(name='request_c', value='1', kind='c', sampling_rate=None)
For complete details and the changelog, see the documentation.
Hamcrest Matchers¶
-
is_metric(*args, **kwargs)¶ is_observation(*, kind, name, value, sampling_rate) -> matcher
A hamcrest matcher that validates the specific parts of a
Observation. All arguments are optional and can be provided by name or position.Parameters: - kind (str) – A hamcrest matcher or string that matches the kind for this metric
- name (str) – A hamcrest matcher or string that matches the name for this metric
- value (str) – A hamcrest matcher or string that matches the value for this metric
- sampling_rate (float) – A hamcrest matcher or number that matches the sampling rate this metric was collected with
-
is_counter(*, name, value, sampling_rate) → matcher[source]¶ A hamcrest matcher validating the parts of a counter
Observation.See also
-
is_gauge(*, name, value, sampling_rate) → matcher[source]¶ A hamcrest matcher validating the parts of a gauge
ObservationSee also