Pass the sink from the Logger to each individual Buffer

lib/rackstash/buffer.rb

@@ -28,6 +28,9 @@ module Rackstash
     #   current buffer. It contains frozen strings only.
     attr_reader :tags
 
+    # @return [Sink] the log sink where the buffer is eventually flushed to
+    attr_reader :sink
+
     # @param buffering [Boolean] When set to `true`, this buffer is considered
     #   to be buffering data. When buffering, logged messages will not be
     #   flushed immediately but only with an explicit call to {#flush}.
@@ -37,7 +40,8 @@ module Rackstash
     #   explicit changes to the buffer (e.g. a logged message, added tags or
     #   fields), the buffer will not be flushed to the sink but will be silently
     #   dropped.
-    def initialize(buffering: true, allow_empty: false)
+    def initialize(sink, buffering: true, allow_empty: false)
+      @sink = sink
       @buffering = !!buffering
       @allow_empty = !!allow_empty
 
@@ -60,6 +64,13 @@ module Rackstash
       message
     end
 
+    # When set to `true` in {#initialize}, the data in this buffer will be
+    # flushed to the sink, even if no messages were logged but there were just
+    # added fields or tags. If this is `false` and there were no explicit
+    # changes to the buffer (e.g. a logged message, added tags or fields), the
+    # buffer will not be flushed to the sink but will be silently dropped.
+    #
+    # @return [Boolean]
     def allow_empty?
       @allow_empty
     end

lib/rackstash/buffer_stack.rb

@@ -11,9 +11,16 @@ module Rackstash
   # is used by exactly one BufferedLogger. The responsible {BufferedLogger}
   # ensures that each BufferStack is only accessed from a single `Thread`.
   class BufferStack
+    # @return [Sink] the log sink where the buffers are eventually flushed to
+    attr_reader :sink
+
+    def initialize(sink)
+      @sink = sink
+    end
+
     # TODO: this is only a spike for now
     def with_buffer
-      yield Buffer.new
+      yield Buffer.new(@sink)
     end
   end
 end

lib/rackstash/logger.rb

@@ -242,7 +242,7 @@ module Rackstash
     private
 
     def buffer_stack
-      @buffer_stack ||= Rackstash::BufferStack.new
+      @buffer_stack ||= Rackstash::BufferStack.new(@sink)
     end
   end
 end

spec/rackstash/buffer_spec.rb

@@ -9,7 +9,8 @@ require 'rackstash/buffer'
 
 describe Rackstash::Buffer do
   let(:buffer_options) { {} }
-  let(:buffer) { Rackstash::Buffer.new(**buffer_options) }
+  let(:sink) { instance_double(Rackstash::Sink) }
+  let(:buffer) { Rackstash::Buffer.new(sink, **buffer_options) }
 
   describe '#allow_empty?' do
     it 'defaults to false' do

spec/rackstash/buffer_stack_spec.rb

@@ -8,12 +8,14 @@ require 'spec_helper'
 require 'rackstash/buffer_stack'
 
 describe Rackstash::BufferStack do
-  let(:stack) { Rackstash::BufferStack.new }
+  let(:sink) { instance_double(Rackstash::Sink) }
+  let(:stack) { Rackstash::BufferStack.new(sink) }
 
   describe '#with_buffer' do
     it 'initializes a buffer' do
       stack.with_buffer do |buffer|
         expect(buffer).to be_a Rackstash::Buffer
+        expect(buffer.sink).to equal sink
       end
     end
   end