Remove ANSI color codes from the message in JSON encoder

lib/rackstash/encoders/json.rb

@@ -11,7 +11,8 @@ module Rackstash
   module Encoders
     # The JSON encoder formats the log event as a single-line JSON string. The
     # resulting JSON string contains all data exposed by the buffer. Leading
-    # and trailing whitespace on the `"message"` field will be removed.
+    # and trailing whitespace as well as any ANSI color codes in the `"message"`
+    # field will be removed.
     #
     # The resulting string is in the JSON format native to Logstash. You can
     # thus ship your logs directly to Logstash without further processing by
@@ -23,7 +24,10 @@ module Rackstash
       # @param event [Hash] a log event as produced by the {Flow}
       # @return [String] the event as a single-line JSON string
       def encode(event)
-        event[FIELD_MESSAGE] = event[FIELD_MESSAGE].strip
+        event[FIELD_MESSAGE] = event[FIELD_MESSAGE]
+          .gsub(/\e\[[0-9;]*m/, EMPTY_STRING)
+          .strip
+
         ::JSON.dump(event)
       end
     end

spec/rackstash/encoders/json_spec.rb

@@ -27,5 +27,10 @@ describe Rackstash::Encoders::JSON do
       event = { 'message' => "\n\t \nline1\nline2\n  \n\t\n" }
       expect(encoder.encode(event)).to eql '{"message":"line1\nline2"}'
     end
+
+    it 'removes any ANSI color codes from the message' do
+      event = { 'message' => "Important\n\e[31mRED TEXT\e[0m\nOK" }
+      expect(encoder.encode(event)).to eql '{"message":"Important\nRED TEXT\nOK"}'
+    end
   end
 end