Skip reporting if there are no metrics

We'll still report the first time through the loop. This lets Judoscale know the adapter is set up correctly.

judoscale-ruby/lib/judoscale/reporter.rb

@@ -74,17 +74,26 @@ def stop!
       @_thread&.terminate
       @_thread = nil
       @pid = nil
+      @reported = false
     end
 
     private
 
     def report(config, metrics)
+      # Make sure we report at least once, even if there are no metrics,
+      # so Judoscale knows the adapter is installed and running.
+      if @reported && metrics.empty?
+        logger.debug "No metrics to report - skipping"
+        return
+      end
+
       report = Report.new(Judoscale.adapters, config, metrics)
       logger.info "Reporting #{report.metrics.size} metrics"
       result = AdapterApi.new(config).report_metrics(report.as_json)
 
       case result
       when AdapterApi::SuccessResponse
+        @reported = true
         logger.debug "Reported successfully"
       when AdapterApi::FailureResponse
         logger.error "Reporter failed: #{result.failure_message}"

judoscale-ruby/test/reporter_test.rb

@@ -10,6 +10,7 @@ module Judoscale
       Judoscale.configure do |config|
         config.current_runtime_container = Config::RuntimeContainer.new("web.1")
         config.api_base_url = "http://example.com/api/test-token"
+        config.test_job_config.enabled = true
       end
     }
 
@@ -172,6 +173,19 @@ def stub_reporter_loop
         assert_requested stub
       end
 
+      it "only sends an empty (no metrics) report one time" do
+        metrics_collector = Test::TestEmptyMetricsCollector.new
+
+        expected_body = Report.new(Judoscale.adapters, Config.instance, metrics_collector.collect).as_json
+        stub = stub_request(:post, "http://example.com/api/test-token/v3/reports")
+          .with(body: JSON.generate(expected_body)).to_return({status: 200}).times(1)
+
+        Reporter.instance.run_metrics_collection Config.instance, [metrics_collector]
+        Reporter.instance.run_metrics_collection Config.instance, [metrics_collector]
+
+        assert_requested stub
+      end
+
       it "logs reporting failures" do
         metrics_collector = Test::TestWebMetricsCollector.new
 

judoscale-ruby/test/test_helper.rb

@@ -27,6 +27,12 @@ def collect
         [Metric.new(:qt, 1, Time.now)]
       end
     end
+
+    class TestEmptyMetricsCollector < Judoscale::WebMetricsCollector
+      def collect
+        []
+      end
+    end
   end
 
   add_adapter :test_web, {}, metrics_collector: Test::TestWebMetricsCollector