Add decode_size_limit_bytes option.

CHANGELOG.md

@@ -1,3 +1,6 @@
+## 3.1.0
+  - Add decode_size_limit_bytes option to limit the maximum size of JSON document that can be parsed
+
 ## 3.0.2
   - Relax constraint on logstash-core-plugin-api to >= 1.60 <= 2.99
 

lib/logstash/codecs/json_lines.rb

@@ -28,10 +28,15 @@ class LogStash::Codecs::JSONLines < LogStash::Codecs::Base
   # Change the delimiter that separates lines
   config :delimiter, :validate => :string, :default => "\n"
 
+  # Maximum number of bytes for a single line before a fatal exception is raised
+  # which will stop Logsash.
+  # The default is 20MB which is quite large for a JSON document
+  config :decode_size_limit_bytes, :validate => :number, :default => 20 * (1024 * 1024) # 20MB
+
   public
 
   def register
-    @buffer = FileWatch::BufferedTokenizer.new(@delimiter)
+    @buffer = FileWatch::BufferedTokenizer.new(@delimiter, @decode_size_limit_bytes)
     @converter = LogStash::Util::Charset.new(@charset)
     @converter.logger = @logger
   end

logstash-codec-json_lines.gemspec

@@ -1,7 +1,7 @@
 Gem::Specification.new do |s|
 
   s.name            = 'logstash-codec-json_lines'
-  s.version         = '3.0.2'
+  s.version         = '3.1.0'
   s.licenses        = ['Apache License (2.0)']
   s.summary         = "This codec will decode streamed JSON that is newline delimited."
   s.description     = "This gem is a Logstash plugin required to be installed on top of the Logstash core pipeline using $LS_HOME/bin/logstash-plugin install gemname. This gem is not a stand-alone program"

spec/codecs/json_lines_spec.rb

@@ -117,6 +117,22 @@
       end
     end
 
+    describe "decode_size_limits_bytes" do
+      let(:maximum_payload) { "a" * subject.decode_size_limit_bytes }
+
+      it "should not raise an error if the number of bytes is not exceeded" do
+        expect {
+          subject.decode(maximum_payload)
+        }.not_to raise_error
+      end
+
+      it "should raise an error if the max bytes are exceeded" do
+        expect {
+          subject.decode(maximum_payload << "z")
+        }.to raise_error(RuntimeError, "input buffer full")
+      end
+    end
+
   end
 
   context "#encode" do