Fix DLQ support for multi-pipelines

Add missing settings to the multi-pipeline settings white list to
allow DLQ to be used with multi-pipelines

Fixes #8069

Fixes #8076

config/pipelines.yml

@@ -67,3 +67,13 @@
 #
 #   # Enable Dead Letter Queueing for this pipeline.
 #   dead_letter_queue.enable: false
+#
+#   If using dead_letter_queue.enable: true, the maximum size of dead letter queue for this pipeline. Entries
+#   will be dropped if they would increase the size of the dead letter queue beyond this setting.
+#   Default is 1024mb
+#   dead_letter_queue.max_bytes: 1024mb
+#
+#   If using dead_letter_queue.enable: true, the directory path where the data files will be stored.
+#   Default is path.data/dead_letter_queue
+#
+#   path.dead_letter_queue:

logstash-core/lib/logstash/pipeline_settings.rb

@@ -12,8 +12,10 @@ module LogStash
       "config.reload.interval",
       "config.string",
       "dead_letter_queue.enable",
+      "dead_letter_queue.max_bytes",
       "metric.collect",
       "path.config",
+      "path.dead_letter_queue",
       "path.queue",
       "pipeline.batch.delay",
       "pipeline.batch.size",

logstash-core/spec/logstash/config/source/multi_local_spec.rb

@@ -155,5 +155,16 @@ describe LogStash::Config::Source::MultiLocal do
         expect { subject.pipeline_configs }.to raise_error(ArgumentError)
       end
     end
+
+    context 'using dead letter queue settings' do
+      let(:retrieved_pipelines) do [
+          { "pipeline.id" => "main", "path.dead_letter_queue" => "/tmp", "dead_letter_queue.max_bytes" => 10000 },
+      ]
+      end
+      it "should not raise an error" do
+        expect { subject.pipeline_configs }.not_to raise_error(ArgumentError)
+      end
+
+    end
   end
 end