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.

API Reference

class FakeStatsDClient(prefix='')

Bases: perfmetrics.statsd.StatsdClient

A mock statsd client that tracks sent statsd metrics in memory rather than pushing them over a socket. This class is a drop in replacement for perfmetrics.statsd.StatsdClient that collects statsd packets and Metric that are sent through the client.

clear()

Clears the statsd metrics that have been collected

iter_metrics()

Iterates the Metrics provided to this statsd client.

iter_raw()

Iterates the raw statsd packets provided to the statsd client.

metrics

A list of Metric objects collected by this client.

See also

iter_metrics

packets

A list of raw statsd packets collected by this client.

See also

iter_raw

METRIC_COUNTER_KIND = 'c'

The statsd metric kind for Counters

METRIC_GAUGE_KIND = 'g'

The statsd metric kind for Gauges

METRIC_SET_KIND = 's'

The statsd metric kind for Sets

METRIC_TIMER_KIND = 'ms'

The statsd metric kind for Timers

class Metric(name, value, kind, sampling_rate=None)

Bases: object

The representation of a single statsd metric.

kind = None

The statsd code for the type of metric. e.g. one of the METRIC_*_KIND constants

classmethod make(packet)

Creates a metric from the provided statsd packet.

Raises:ValueError – if packet is a multi metric packet or otherwise invalid.

classmethod make_all(packet)

Makes a list of metrics from the provided statsd packet.

Like make but supports multi metric packets

name = None

The metric name

sampling_rate = None

The rate with which this event has been sampled from (optional)

value = None

The value provided for the metric

Hamcrest Matchers

is_metric(kind=<object object>, name=<object object>, value=<object object>, sampling_rate=<object object>)

A hamcrest matcher that validates the specific parts of a Metric.

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 – A hamcrest matcher or string that matches the value for this metric
• sampling_rate – A hamcrest matcher or number that matches the sampling rate this metric was collected with

is_counter(name=<object object>, value=<object object>, sampling_rate=<object object>)

A hamcrest matcher validating the parts of a Metric of kind METRIC_COUNTER_KIND

See also

is_metric

is_gauge(name=<object object>, value=<object object>, sampling_rate=<object object>)

A hamcrest matcher validating the parts of a Metric of kind METRIC_GAUGE_KIND

See also

is_metric

is_set(name=<object object>, value=<object object>, sampling_rate=<object object>)

A hamcrest matcher validating the parts of a Metric of kind METRIC_SET_KIND

See also

is_metric

is_timer(name=<object object>, value=<object object>, sampling_rate=<object object>)

A hamcrest matcher validating the parts of a Metric of kind METRIC_TIMER_KIND

See also

is_metric

Changes

0.0.2 (2018-10-26)

• Metric kind s is now handled as a distinct type. See issue 6.
• Metric values are now always native strings. See issue 2.
• Restructure and document public objects. See issue 1.
• Add convenience hamcrest matchers. See issue 1.

0.0.1 (2018-10-12)

• First PyPI release.

Indices and tables

• Index
• Module Index
• Search Page