========= Metrology

A library to easily measure what's going on in your python.

Metrology allows you to add instruments to your python code and hook them to external reporting tools like Graphite so as to better understand what's going on in your running python program.

Installing

To install : ::

pip install metrology

API

Gauge

A gauge is an instantaneous measurement of a value

.. code-block:: python

class JobGauge(metrology.instruments.Gauge):
    def value(self):
        return len(queue)
gauge = Metrology.gauge('pending-jobs', JobGauge())

Counters

A counter is like a gauge, but you can increment or decrement its value

.. code-block:: python

counter = Metrology.counter('pending-jobs')
counter.increment()
counter.decrement()
counter.count

Meters

A meter measures the rate of events over time (e.g., "requests per second"). In addition to the mean rate, you can also track 1, 5 and 15 minutes moving averages

.. code-block:: python

meter = Metrology.meter('requests')
meter.mark()
meter.count

or as a decorator:

.. code-block:: python

@Metrology.meter('requests')
def do_this_again():
    # do something

or with context manager:

.. code-block:: python

with Metrology.meter('requests'):
    # do something

Timers

A timer measures both the rate that a particular piece of code is called and the distribution of its duration

.. code-block:: python

timer = Metrology.timer('responses')
with timer:
    do_something()

or as a decorator:

.. code-block:: python

@Metrology.timer('responses')
def response():
    # do_something

Utilization Timer

A specialized timer that calculates the percentage of wall-clock time that was spent

.. code-block:: python

utimer = Metrology.utilization_timer('responses')
with utimer:
  do_something()

Tagging metrics

All metrics can be tagged if the reporter supports it (currently: Graphite, Librato, Logger. The StatsD reporter supports the Datadog tag format because no official tag standard has been devised by the project). Tags can be arbitrary key-value pairs. Just assign a dict as metric name. A 'name'-entry is required.

.. code-block:: python

counter = Metrology.counter({
  'name': 'pending-jobs',
  'host': 'backend',
  'priority': 'high'
})
counter.increment()
counter.decrement()
counter.count

All metric types support tagging.

Reporters

Logger Reporter

A logging reporter that write metrics to a logger

.. code-block:: python

reporter = LoggerReporter(level=logging.INFO, interval=10)
reporter.start()

Graphite Reporter

A graphite reporter that send metrics to graphite

.. code-block:: python

reporter = GraphiteReporter('graphite.local', 2003)
reporter.start()

Librato Reporter

A librator metric reporter that send metrics to librato API

.. code-block:: python

reporter = LibratoReporter("<email>", "<token>")
reporter.start()

Ganglia Reporter

A ganglia reporter that sends metrics to gmond.

.. code-block:: python

reporter = GangliaReporter("Group Name", "localhost", 8649, "udp", interval=60)
reporter.start()

StatsD Reporter

A statsd reporter that sends metrics to statsd daemon.

.. code-block:: python

reporter = StatsDReporter('localhost', 3333, conn_type='tcp')
reporter.start()

or use default UDP setting:

.. code-block:: python

reporter = StatsDReporter('localhost', 3333)
reporter.start()

Acknowledgement

This is heavily inspired by the awesome metrics <https://github.com/codahale/metrics>_ library.