Add Null adapter which just swallows any logs

lib/rackstash.rb

@@ -89,3 +89,4 @@ require 'rackstash/logger'
 require 'rackstash/adapters/callable'
 require 'rackstash/adapters/file'
 require 'rackstash/adapters/io'
+require 'rackstash/adapters/null'

lib/rackstash/adapters/null.rb

@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+# Copyright 2017 Holger Just
+#
+# This software may be modified and distributed under the terms
+# of the MIT license. See the LICENSE.txt file for details.
+
+require 'rackstash/adapters/adapter'
+require 'rackstash/encoders/raw'
+
+module Rackstash
+  module Adapters
+    # This adapter swallows all logs sent to it without writing them anywhere.
+    #
+    # It is probably not very useful for production use but can be used to test
+    # the {Flow} pipeline.
+    class Null < Adapter
+      register_for NilClass
+
+      # Create a new black hole adapter. Any logs written to it will be
+      # swallowed and not written anywhere.
+      def initialize(*)
+      end
+
+      # By default, we use a {Rackstash::Encoders::Raw} encoder to encode the
+      # events. Since we are ignoreing them anyway, there is no need for fancy
+      # formatting here.
+      #
+      # @return [Rackstash::Encoders::Raw] a new Raw encoder
+      def default_encoder
+        Rackstash::Encoders::Raw.new
+      end
+
+      # Swallow a log event. It is not written anywhere.
+      #
+      # @param log [Object] the encoded log event
+      # @return [nil]
+      def write_single(log)
+        nil
+      end
+    end
+  end
+end

spec/rackstash/adapters/null_spec.rb

@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+# Copyright 2017 Holger Just
+#
+# This software may be modified and distributed under the terms
+# of the MIT license. See the LICENSE.txt file for details.
+
+require 'spec_helper'
+
+require 'rackstash/adapters/null'
+
+describe Rackstash::Adapters::Null do
+  let(:adapter) { described_class.new }
+
+  describe '#initialize' do
+    it 'accepts and ignores any arguments' do
+      expect { described_class.new }.not_to raise_error
+      expect { described_class.new(:foo, :bar, :baz) }.not_to raise_error
+    end
+  end
+
+  describe '.default_encoder' do
+    it 'returns a Raw encoder' do
+      expect(adapter.default_encoder).to be_instance_of Rackstash::Encoders::Raw
+    end
+  end
+
+  describe '#close' do
+    it 'does nothing' do
+      expect { adapter.close }.not_to raise_error
+    end
+  end
+
+  describe '#reopen' do
+    it 'does nothing' do
+      expect { adapter.reopen }.not_to raise_error
+    end
+  end
+
+  describe '#write_single' do
+    it 'does nothing' do
+      expect { adapter.write('a log line') }.not_to raise_error
+    end
+  end
+end