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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

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

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

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

or as a decorator:

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

or with context manager:

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

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

or as a decorator:

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

Utilization Timer

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

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.

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

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

Graphite Reporter

A graphite reporter that send metrics to graphite

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

Librato Reporter

A librator metric reporter that send metrics to librato API

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

Ganglia Reporter

A ganglia reporter that sends metrics to gmond.

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

StatsD Reporter

A statsd reporter that sends metrics to statsd daemon.

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

or use default UDP setting:

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

Acknowledgement

This is heavily inspired by the awesome metrics library.