From 271c547f058d4fbbba19d4945bf4e1ab0710d8c9 Mon Sep 17 00:00:00 2001
From: Holger Just <hello@holgerjust.de>
Date: Wed, 2 Aug 2017 17:50:53 +0200
Subject: [PATCH] Initialize monitor and copy internal filters list on
 FilterChain#dup

---
 lib/rackstash/filter_chain.rb       |  9 +++++++++
 spec/rackstash/filter_chain_spec.rb | 10 ++++++++++
 2 files changed, 19 insertions(+)

diff --git a/lib/rackstash/filter_chain.rb b/lib/rackstash/filter_chain.rb
index ff6d7e1..5957d01 100644
--- a/lib/rackstash/filter_chain.rb
+++ b/lib/rackstash/filter_chain.rb
@@ -273,6 +273,15 @@ module Rackstash
 
     private
 
+    def initialize_copy(orig)
+      super
+
+      mon_initialize
+      synchronize do
+        @filters = orig.to_a
+      end
+    end
+
     def index_at(index)
       case index
       when Integer, ->(o) { o.respond_to?(:to_int) }
diff --git a/spec/rackstash/filter_chain_spec.rb b/spec/rackstash/filter_chain_spec.rb
index 8adf6c6..b12cfa7 100644
--- a/spec/rackstash/filter_chain_spec.rb
+++ b/spec/rackstash/filter_chain_spec.rb
@@ -225,6 +225,16 @@ describe Rackstash::FilterChain do
     end
   end
 
+  describe '#dup' do
+    it 'duplicates the filters array' do
+      filter_chain << a_filter
+      dupped = filter_chain.dup
+
+      expect(filter_chain.length).to eql dupped.length
+      expect { filter_chain << a_filter }.not_to change { dupped.length }
+    end
+  end
+
   describe '#each' do
     it 'yields each filter' do
       filter_chain << -> {}