Class: Cabin::Metrics

Inherits:
Object
  • Object
show all
Includes:
Publisher, Enumerable
Defined in:
lib/cabin/metrics.rb,
lib/cabin/namespace.rb

Overview

What type of metrics do we want?

What metrics should come by default? Per-call/transaction/request metrics like:

- hit (count++ type metrics)
- latencies/timings

Per app or generally long-lifetime metrics like:

- "uptime"
- cpu usage
- memory usage
- count of active/in-flight actions/requests/calls/transactions
- peer metrics (number of cluster members, etc)

github.com/codahale/metrics/tree/master/metrics-core/src/main/java/com/yammer/metrics/core Reading what Coda Hale's “Metrics” stuff has, here's my summary:

gauges (callback to return a number)
counters (.inc and .dec methods)
meters (.mark to track each 'hit')
  Also exposes 1, 5, 15 minute moving averages
histograms: (.update(value) to record a new value)
  like meter, but takes values more than simply '1'
  as a result, exposes percentiles, median, etc.
timers
  a time-observing interface on top of histogram.

With the exception of gauges, all the other metrics are all active/pushed. Gauges take callbacks, so their values are pulled, not pushed. The active metrics can be represented as events since they the update occurs at the time of the change.

These active/push metrics can therefore be considered events.

All metrics (active/passive) can be queried for 'current state', too, making this suitable for serving to interested parties like monitoring and management tools.

Defined Under Namespace

Classes: Counter, Gauge, Histogram, Meter, Timer

Instance Method Summary collapse

Methods included from Publisher

#channel, #channel=, #publish

Constructor Details

#initializeMetrics

Returns a new instance of Metrics.


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# File 'lib/cabin/metrics.rb', line 53

def initialize
  @metrics_lock = Mutex.new
  @metrics = {}
end

Instance Method Details

#counter(instance, name = nil) ⇒ Object


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# File 'lib/cabin/metrics.rb', line 89

def counter(instance, name=nil)
  return create(instance, name, Cabin::Metrics::Counter.new)
end

#each(&block) ⇒ Object

iterate over each metric. yields identifer, metric


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# File 'lib/cabin/metrics.rb', line 118

def each(&block)
  # delegate to the @metrics hash until we need something fancier
  @metrics_lock.synchronize do
    @metrics.each(&block)
  end
end

#histogram(instance, name = nil) ⇒ Object


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# File 'lib/cabin/metrics.rb', line 105

def histogram(instance, name=nil)
  return create(instance, name, Cabin::Metrics::Histogram.new)
end

#meter(instance, name = nil) ⇒ Object


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# File 'lib/cabin/metrics.rb', line 97

def meter(instance, name=nil)
  return create(instance, name, Cabin::Metrics::Meter.new)
end

#timer(instance, name = nil) ⇒ Object


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# File 'lib/cabin/metrics.rb', line 113

def timer(instance, name=nil)
  return create(instance, name, Cabin::Metrics::Timer.new)
end