From 0577a530f7aa86c8ccc03431218792231a210823 Mon Sep 17 00:00:00 2001
From: Justin Howard <jmhoward0@gmail.com>
Date: Thu, 2 Sep 2021 11:43:51 -0700
Subject: [PATCH] Suppress circuit_success for proxy circuits

---
 lib/faulty/cache/circuit_proxy.rb    |  2 +-
 lib/faulty/events.rb                 |  1 +
 lib/faulty/events/filter_notifier.rb | 31 +++++++++++++++++++++++++++
 lib/faulty/storage/circuit_proxy.rb  |  2 +-
 spec/cache/circuit_proxy_spec.rb     |  7 ++++++
 spec/events/filter_notifier_spec.rb  | 32 ++++++++++++++++++++++++++++
 spec/storage/circuit_proxy_spec.rb   |  7 ++++++
 7 files changed, 80 insertions(+), 2 deletions(-)
 create mode 100644 lib/faulty/events/filter_notifier.rb
 create mode 100644 spec/events/filter_notifier_spec.rb

diff --git a/lib/faulty/cache/circuit_proxy.rb b/lib/faulty/cache/circuit_proxy.rb
index f28f3d5..51c1e70 100644
--- a/lib/faulty/cache/circuit_proxy.rb
+++ b/lib/faulty/cache/circuit_proxy.rb
@@ -33,7 +33,7 @@ def finalize
 
           self.circuit ||= Circuit.new(
             Faulty::Storage::CircuitProxy.name,
-            notifier: notifier,
+            notifier: Events::FilterNotifier.new(notifier, exclude: %i[circuit_success]),
             cache: Cache::Null.new
           )
         end
diff --git a/lib/faulty/events.rb b/lib/faulty/events.rb
index ebdd58f..1044888 100644
--- a/lib/faulty/events.rb
+++ b/lib/faulty/events.rb
@@ -26,3 +26,4 @@ module Events
 require 'faulty/events/honeybadger_listener'
 require 'faulty/events/log_listener'
 require 'faulty/events/notifier'
+require 'faulty/events/filter_notifier'
diff --git a/lib/faulty/events/filter_notifier.rb b/lib/faulty/events/filter_notifier.rb
new file mode 100644
index 0000000..8b2b521
--- /dev/null
+++ b/lib/faulty/events/filter_notifier.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+class Faulty
+  module Events
+    # Wraps a Notifier and filters events by name
+    class FilterNotifier
+      # @param notifier [Notifier] The internal notifier to filter events for
+      # @param events [Array, nil] An array of events to allow. If nil, all
+      #   {EVENTS} will be used
+      # @param exclude [Array, nil] An array of events to disallow. If nil,
+      #   no events will be disallowed. Takes priority over `events`.
+      def initialize(notifier, events: nil, exclude: nil)
+        @notifier = notifier
+        @events = Set.new(events || EVENTS)
+        exclude&.each { |e| @events.delete(e) }
+      end
+
+      # Notify all listeners of an event
+      #
+      # If a listener raises an error while handling an event, that error will
+      # be captured and written to STDERR.
+      #
+      # @param (see Notifier)
+      def notify(event, payload)
+        return unless @events.include?(event)
+
+        @notifier.notify(event, payload)
+      end
+    end
+  end
+end
diff --git a/lib/faulty/storage/circuit_proxy.rb b/lib/faulty/storage/circuit_proxy.rb
index e00518b..c89fe5b 100644
--- a/lib/faulty/storage/circuit_proxy.rb
+++ b/lib/faulty/storage/circuit_proxy.rb
@@ -33,7 +33,7 @@ def finalize
 
           self.circuit ||= Circuit.new(
             Faulty::Storage::CircuitProxy.name,
-            notifier: notifier,
+            notifier: Events::FilterNotifier.new(notifier, exclude: %i[circuit_success]),
             cache: Cache::Null.new
           )
         end
diff --git a/spec/cache/circuit_proxy_spec.rb b/spec/cache/circuit_proxy_spec.rb
index bc03207..13e0c4d 100644
--- a/spec/cache/circuit_proxy_spec.rb
+++ b/spec/cache/circuit_proxy_spec.rb
@@ -28,6 +28,13 @@ def respond_to_missing?(*_args)
     expect { proxy.read('foo') }.to raise_error(Faulty::CircuitTrippedError)
   end
 
+  it 'does not notify for circuit sucesses by default' do
+    expect(notifier).not_to receive(:notify)
+    backend = Faulty::Cache::Mock.new
+    proxy = described_class.new(backend, notifier: notifier)
+    proxy.read('foo')
+  end
+
   it 'delegates fault_tolerant? directly' do
     backend = instance_double(Faulty::Cache::Mock)
     marker = Object.new
diff --git a/spec/events/filter_notifier_spec.rb b/spec/events/filter_notifier_spec.rb
new file mode 100644
index 0000000..a90fed0
--- /dev/null
+++ b/spec/events/filter_notifier_spec.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+
+RSpec.describe Faulty::Events::FilterNotifier do
+  let(:backend) { Faulty::Events::Notifier.new }
+
+  it 'forwards all events by default' do
+    filter = described_class.new(backend)
+    expect(backend).to receive(:notify).with(:circuit_success, {})
+    filter.notify(:circuit_success, {})
+  end
+
+  it 'forwards only given events' do
+    filter = described_class.new(backend, events: %i[circuit_failure])
+    expect(backend).to receive(:notify).with(:circuit_failure, {})
+    filter.notify(:circuit_success, {})
+    filter.notify(:circuit_failure, {})
+  end
+
+  it 'forwards all except exluded events' do
+    filter = described_class.new(backend, exclude: %i[circuit_success])
+    expect(backend).to receive(:notify).with(:circuit_failure, {})
+    filter.notify(:circuit_success, {})
+    filter.notify(:circuit_failure, {})
+  end
+
+  it 'forwards given events except excluded' do
+    filter = described_class.new(backend, events: %i[circuit_failure circuit_success], exclude: %i[circuit_success])
+    expect(backend).to receive(:notify).with(:circuit_failure, {})
+    filter.notify(:circuit_success, {})
+    filter.notify(:circuit_failure, {})
+  end
+end
diff --git a/spec/storage/circuit_proxy_spec.rb b/spec/storage/circuit_proxy_spec.rb
index 61c4b2d..f9e913b 100644
--- a/spec/storage/circuit_proxy_spec.rb
+++ b/spec/storage/circuit_proxy_spec.rb
@@ -30,4 +30,11 @@ def respond_to_missing?(*_args)
     expect { proxy.entry(circuit, Faulty.current_time, true) }
       .to raise_error(Faulty::CircuitTrippedError)
   end
+
+  it 'does not notify for circuit sucesses by default' do
+    expect(notifier).not_to receive(:notify)
+    backend = Faulty::Storage::Null.new
+    proxy = described_class.new(backend, notifier: notifier)
+    proxy.entry(circuit, Faulty.current_time, true)
+  end
 end