[GitHub] [dubbo] AlbumenJ commented on a diff in pull request #11806: add nop for prometheus metrics

["AlbumenJ (via GitHub)" <gi...@apache.org>]

AlbumenJ commented on code in PR #11806:
URL: https://github.com/apache/dubbo/pull/11806#discussion_r1139781385


##########
dubbo-metrics/dubbo-metrics-prometheus/src/main/java/org/apache/dubbo/metrics/prometheus/PrometheusMetricsReporterFactory.java:
##########
@@ -18,21 +18,48 @@
 package org.apache.dubbo.metrics.prometheus;
 
 import org.apache.dubbo.common.URL;
-import org.apache.dubbo.metrics.report.MetricsReporter;
+import org.apache.dubbo.common.logger.ErrorTypeAwareLogger;
+import org.apache.dubbo.common.logger.LoggerFactory;
 import org.apache.dubbo.metrics.report.AbstractMetricsReporterFactory;
+import org.apache.dubbo.metrics.report.MetricsReporter;
 import org.apache.dubbo.rpc.model.ApplicationModel;
 
+import static org.apache.dubbo.common.constants.LoggerCodeConstants.INTERNAL_ERROR;
+
 /**
  * MetricsReporterFactory to create PrometheusMetricsReporter.
  */
 public class PrometheusMetricsReporterFactory extends AbstractMetricsReporterFactory {
 
+    private final ErrorTypeAwareLogger logger = LoggerFactory.getErrorTypeAwareLogger(PrometheusMetricsReporterFactory.class);
+
     public PrometheusMetricsReporterFactory(ApplicationModel applicationModel) {
         super(applicationModel);
     }
 
     @Override
     public MetricsReporter createMetricsReporter(URL url) {
-        return new PrometheusMetricsReporter(url, getApplicationModel());
+        try {
+            return new PrometheusMetricsReporter(url, getApplicationModel());
+        } catch (NoClassDefFoundError ncde) {
+            String msg = ncde.getMessage();
+            if (messageContainsPrometheusMetricsReporter(msg)) {
+                logger.error(INTERNAL_ERROR, "", "", "Failed to load class \"org.apache.dubbo.metrics.prometheus.PrometheusMetricsReporter\".", ncde);
+                logger.error(INTERNAL_ERROR, "", "", "Defaulting to no-operation (NOP) metricsReporter implementation", ncde);
+                logger.error(INTERNAL_ERROR, "", "", "Introduce the micrometer-core package to use the ability of metrics", ncde);
+                return new NopPrometheusMetricsReporter();
+            } else {
+                logger.error(INTERNAL_ERROR, "", "", "Failed to instantiate PrometheusMetricsReporter", ncde);
+                throw ncde;
+            }
+        }
+    }
+
+    private static boolean messageContainsPrometheusMetricsReporter(String msg) {

Review Comment:
   ```suggestion
       private static boolean dependenciesNotFound(String msg) {
   ```



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