nti.fakestatsd¶
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
conveninece 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
[<nti.fakestatsd.metric.Metric object at ...>, <nti.fakestatsd.metric.Metric object at ...>]
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
>>> assert_that(test_client,
... contains(is_metric('c', 'request_c', '1'),
... is_gauge('active_sessions', '320')))
>>> 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 [Metric of form <request_c:1|g>, Metric of form <active_sessions:320|g>]
but: item 0: was <request_c:1|c>
For complete details and the changelog, see the documentation.