Raise configuration error when invalid rates are set

lib/logstash/filters/metrics.rb

@@ -142,6 +142,9 @@ class LogStash::Filters::Metrics < LogStash::Filters::Base
     @last_flush = 0 # how many seconds ago the metrics where flushed.
     @last_clear = 0 # how many seconds ago the metrics where cleared.
     @random_key_preffix = SecureRandom.hex
+    unless (@rates - [1, 5, 15]).empty?
+      raise LogStash::ConfigurationError, "Invalid rates configuration. possible rates are 1, 5, 15. Rates: #{rates}."
+    end
     initialize_metrics
   end # def register
 

spec/filters/metrics.rb

@@ -58,6 +58,29 @@ describe LogStash::Filters::Metrics do
         end
       end
     end
+
+    context "when custom rates and percentiles are selected" do
+      context "on the first flush" do
+        subject {
+          config = {
+            "meter" => ["http.%{response}"],
+            "rates" => [1]
+          }
+          filter = LogStash::Filters::Metrics.new config
+          filter.register
+          filter.filter LogStash::Event.new({"response" => 200})
+          filter.filter LogStash::Event.new({"response" => 200})
+          filter.filter LogStash::Event.new({"response" => 404})
+          filter.flush
+        }
+
+        it "should include only the requested rates" do
+          rate_fields = subject.first.to_hash.keys.select {|field| field.start_with?("http.200.rate") }
+          insist { rate_fields.length } == 1
+          insist { rate_fields }.include? "http.200.rate_1m"
+        end
+      end
+    end
   end
 
   context "with multiple instances" do
@@ -175,4 +198,15 @@ describe LogStash::Filters::Metrics do
       insist { filter.flush }.nil?                         # 20s
     end
   end
+
+  context "when invalid rates are set" do
+    subject {
+      config = {"meter" => ["http.%{response}"], "rates" => [90]}
+      filter = LogStash::Filters::Metrics.new config
+    }
+
+    it "should raise an error" do
+      insist {subject.register }.raises(LogStash::ConfigurationError)
+    end
+  end
 end