* New metric types: accumulator and delta

* A little bit more debugging info

lib/salus.rb

@@ -129,11 +129,13 @@ def save_state(&block)
     end
 
     def tick
+      log DEBUG, "Tick..."
       lazy_eval
       return if @@_groups.empty?
       pause = (Salus.interval - Salus.tick_timeout - Salus.render_timeout) / 2
       pause = 1 if (pause <= 0)
 
+      log DEBUG, "Starting collection. Top-level groups to spawn: #{@@_groups.count}"
       latch = CountDownLatch.new(@@_groups.count)
       @@_groups.each do |k, v|
         pool.process do
@@ -150,6 +152,7 @@ def tick
       log DEBUG, "Collection finished. Threads: #{pool.spawned} spawned, #{pool.waiting} waiting, #{Thread.list.count} total"
 
       return if @@_renders.empty?
+      log DEBUG, "Starting #{@_renders.count} renderers"
       latch = CountDownLatch.new(@@_renders.count)
       @@_renders.each do |v|
         pool.process do

lib/salus/group.rb

@@ -1,7 +1,9 @@
 require "forwardable"
 require "salus/metric"
 require "salus/metric/absolute"
+require "salus/metric/accumulator"
 require "salus/metric/counter"
+require "salus/metric/delta"
 require "salus/metric/derive"
 require "salus/metric/gauge"
 require "salus/metric/text"

lib/salus/metric.rb

@@ -144,6 +144,15 @@ def to_h
       end
     end
 
+    def clear
+      synchronize do
+        @last_calced_value = nil
+        @last_calced_ts    = nil
+        @needs_update      = true
+        @values.clear
+      end
+    end
+
     protected
     def option(key, *types)
       @attributes[key] = types

lib/salus/metric/accumulator.rb

@@ -0,0 +1,34 @@
+module Salus
+  class Accumulator < Metric
+    STORAGE_DEPTH = 1
+
+    def push(opts={}, &block)
+      opts = {} unless opts.is_a?(Hash)
+
+      synchronize do
+        opts.each do |k, v|
+          validate(k, v)
+          @opts[k] = v unless [:value, :ttl, :timestamp].include?(k)
+        end
+
+        if block_given?
+          v = begin
+            yield
+          rescue Exception => e
+            log DEBUG, e
+            nil
+          end
+          validate(:value, v)
+          opts[:value] = v
+        end
+
+        prev  = @values.empty? ? 0 : (@values.last.value || 0)
+        curr  = opts[:value] || 0
+
+        @values << Value.new(prev+curr, opts[:timestamp] || Time.now.to_f, opts[:ttl] || @opts[:ttl])
+        @needs_update = true
+      end
+    end
+  end
+end
+

lib/salus/metric/delta.rb

@@ -0,0 +1,36 @@
+module Salus
+  class Delta < Metric
+    def initialize(defaults={})
+      super(defaults)
+      option :minimum, Numeric
+      validate(:minimum, @opts[:minimum]) if @opts.key?(:minimum)
+    end
+
+    protected
+    def calc
+      super
+      @last_calced_value = nil
+
+      if @values.length < STORAGE_DEPTH
+        return
+      elsif @values[0].expired?(@values[1].timestamp)
+        return
+      elsif !@values[0].value.is_a?(Numeric)
+        return
+      elsif !@values[1].value.is_a?(Numeric)
+        return
+      end
+
+      @last_calced_value = begin
+        dt = (@values[1].timestamp - @values[0].timestamp)
+        dv = (@values[1].value - @values[0].value)
+        r = (dt == 0) ? nil : dv
+        if @opts.key?(:minimum) && !r.nil? && r < @opts[:minimum]
+          nil
+        else
+          r
+        end
+      end
+    end
+  end
+end

lib/salus/version.rb

@@ -1,3 +1,3 @@
 module Salus
-  VERSION = "0.1.3"
+  VERSION = "0.2.0"
 end

salus.gemspec

@@ -21,9 +21,9 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
-  spec.add_development_dependency "bundler", "~> 1.15"
+  spec.add_development_dependency "bundler", "~> 2.1"
 
-  spec.add_dependency "thor", "~> 0.20"
-  spec.add_development_dependency "rake", "~> 10.0"
+  spec.add_dependency "thor", "~> 1.0"
+  spec.add_development_dependency "rake", ">= 12.3.3"
   spec.add_development_dependency "rspec", "~> 3.0"
 end

spec/salus_accumulator_spec.rb

@@ -0,0 +1,16 @@
+require "spec_helper"
+
+RSpec.describe Salus::Accumulator do
+  context "without ttl" do
+    let(:metric) { Salus::Accumulator.new }
+
+    it "accumulates values as pushed" do
+      metric.push value: 10.0
+      expect(metric.value).to eq(10.0)
+      metric.push value: 20.0
+      expect(metric.value).to eq(30.0)
+      metric.push value: 30.0
+      expect(metric.value).to eq(60.0)
+    end
+  end
+end

spec/salus_delta_spec.rb

@@ -0,0 +1,52 @@
+require "spec_helper"
+
+RSpec.describe Salus::Delta do
+  context "without ttl" do
+    let(:metric) { Salus::Delta.new }
+
+    it "validates types" do
+      expect{metric.push minimum: "just a test"}.to raise_error(ArgumentError)
+    end
+
+    it "counts deltas" do
+      metric.push value: 10, timestamp: 0
+      expect(metric.value).to eq(nil)
+      metric.push value: 20, timestamp: 10
+      expect(metric.value).to eq(10)
+      metric.push value: 100, timestamp: 20
+      expect(metric.value).to eq(80)
+    end
+
+    it "returns nil rate for dt == 0" do
+      metric.push value: 10, timestamp: 10
+      metric.push value: 20, timestamp: 10
+      expect(metric.value).to eq(nil)
+    end
+
+    it "returns nil if one value is nil" do
+      metric.push value: 10, timestamp: 0
+      metric.push value: nil, timestamp: 10
+      expect(metric.value).to eq(nil)
+    end
+
+    it "returns nil if delta is less than minimum" do
+      metric.push value: 200, timestamp: 0, minimum: 0
+      metric.push value: 1000, timestamp: 10
+      expect(metric.value).to eq(800)
+      metric.push value: 1, timestamp: 20
+      expect(metric.value).to eq(nil)
+    end
+  end
+
+  context "with ttl" do
+    let(:metric) { Salus::Delta.new }
+
+    it "returns nil if previous value is expired" do
+      metric.push value: 0, timestamp: 0, ttl: 10
+      metric.push value: 5, timestamp: 5, ttl: 10
+      expect(metric.value).to eq(5)
+      metric.push value: 100, timestamp: 100, ttl: 10
+      expect(metric.value).to eq(nil)
+    end
+  end
+end

spec/salus_metric_spec.rb

@@ -46,6 +46,16 @@
       expect(metric.value).to eq(30)
     end
 
+    it "clears values" do
+      metric.push value: 10
+      expect(metric.value).to eq(10)
+      metric.push value: 20
+      expect(metric.value).to eq(20)
+      metric.clear
+      expect(metric.value).to eq(nil)
+      expect(metric.timestamp).to eq(nil)
+    end
+
     it "takes block" do
       metric.push do
         100 / 10