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require "cabin/namespace"
require "cabin/metrics/gauge"
require "cabin/metrics/meter"
require "cabin/metrics/counter"
require "cabin/metrics/timer"
require "cabin/metrics/histogram"
require "cabin/publisher"
require "cabin/channel"
# 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)
# ------------------------------------------------------------------
# https://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.
class Cabin::Metrics
include Enumerable
include Cabin::Publisher
# Get us a new metrics container.
public
def initialize
@metrics_lock = Mutex.new
@metrics = {}
end # def initialize
private
def create(instance, name, metric_object)
if !instance.is_a?(String)
instance = "#{instance.class.name}<#{instance.object_id}>"
end
if name.nil?
# If no name is given, use the class name of the metric.
# For example, if we invoke Metrics#timer("foo"), the metric
# name will be "foo/timer"
metric_name = "#{instance}/#{metric_object.class.name.split("::").last.downcase}"
else
# Otherwise, use "instance/name" as the name.
metric_name = "#{instance}/#{name}"
end
metric_object.channel = @channel
metric_object.instance = metric_name
if @channel
@channel.debug("Created metric", :instance => instance, :type => metric_object.class)
end
return @metrics_lock.synchronize do
@metrics[metric_name] = metric_object
end
end # def create
# Create a new Counter metric
# 'instance' is usually an object owning this metric, but it can be a string.
# 'name' is the name of the metric.
public
def counter(instance, name=nil)
return create(instance, name, Cabin::Metrics::Counter.new)
end # def counter
# Create a new Meter metric
# 'instance' is usually an object owning this metric, but it can be a string.
# 'name' is the name of the metric.
public
def meter(instance, name=nil)
return create(instance, name, Cabin::Metrics::Meter.new)
end # def meter
# Create a new Histogram metric
# 'instance' is usually an object owning this metric, but it can be a string.
# 'name' is the name of the metric.
public
def histogram(instance, name=nil)
return create(instance, name, Cabin::Metrics::Histogram.new)
end # def histogram
# Create a new Timer metric
# 'instance' is usually an object owning this metric, but it can be a string.
# 'name' is the name of the metric.
public
def timer(instance, name=nil)
return create(instance, name, Cabin::Metrics::Timer.new)
end # def timer
# iterate over each metric. yields identifer, metric
def each(&block)
# delegate to the @metrics hash until we need something fancier
@metrics_lock.synchronize do
@metrics.each(&block)
end
end # def each
end # class Cabin::Metrics
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