Merge pull request #526 from michael-loki/context_json_metrics

Make JSON metrics opt-in

llarp/context.cpp

@@ -146,10 +146,13 @@ namespace llarp
           *m_scheduler, m_metricsManager->instance());
     }
 
-    m_metricsManager->instance()->addGlobalPublisher(
+    if(!jsonMetricsPath.native().empty())
-        std::make_shared< metrics::JsonPublisher >(
+    {
-            std::bind(&metrics::JsonPublisher::directoryPublisher,
+      m_metricsManager->instance()->addGlobalPublisher(
-                      std::placeholders::_1, jsonMetricsPath)));
+          std::make_shared< metrics::JsonPublisher >(
+              std::bind(&metrics::JsonPublisher::directoryPublisher,
+                        std::placeholders::_1, jsonMetricsPath)));
+    }
 
     if(!metricTankHost.empty())
     {