[HUDI-1326] Added an API to force publish metrics and flush them. (#2152)

* [HUDI-1326] Added an API to force publish metrics and flush them.

Using the added API, publish metrics after each level of the DAG completed in hudi-test-suite.

* Code cleanups

Co-authored-by: Vinoth Chandar <vinoth@apache.org>

hudi-client/hudi-client-common/src/main/java/org/apache/hudi/metrics/Metrics.java

@@ -38,13 +38,15 @@ public class Metrics {
   private static final Logger LOG = LogManager.getLogger(Metrics.class);
 
   private static volatile boolean initialized = false;
-  private static Metrics metrics = null;
+  private static Metrics instance = null;
+
   private final MetricRegistry registry;
   private MetricsReporter reporter;
+  private final String commonMetricPrefix;
 
   private Metrics(HoodieWriteConfig metricConfig) {
     registry = new MetricRegistry();
-
+    commonMetricPrefix = metricConfig.getTableName();
     reporter = MetricsReporterFactory.createReporter(metricConfig, registry);
     if (reporter == null) {
       throw new RuntimeException("Cannot initialize Reporter.");
@@ -68,13 +70,24 @@ public class Metrics {
     }
   }
 
+  private void reportAndFlushMetrics() {
+    try {
+      LOG.info("Reporting and flushing all metrics");
+      this.registerHoodieCommonMetrics();
+      this.reporter.report();
+      this.registry.getNames().forEach(this.registry::remove);
+    } catch (Exception e) {
+      LOG.error("Error while reporting and flushing metrics", e);
+    }
+  }
+
   private void registerHoodieCommonMetrics() {
-    registerGauges(Registry.getAllMetrics(true, true), Option.empty());
+    registerGauges(Registry.getAllMetrics(true, true), Option.of(commonMetricPrefix));
   }
 
   public static Metrics getInstance() {
     assert initialized;
-    return metrics;
+    return instance;
   }
 
   public static synchronized void init(HoodieWriteConfig metricConfig) {
@@ -82,7 +95,7 @@ public class Metrics {
       return;
     }
     try {
-      metrics = new Metrics(metricConfig);
+      instance = new Metrics(metricConfig);
     } catch (Exception e) {
       throw new HoodieException(e);
     }
@@ -93,10 +106,17 @@ public class Metrics {
     if (!initialized) {
       return;
     }
-    metrics.reportAndCloseReporter();
+    instance.reportAndCloseReporter();
     initialized = false;
   }
 
+  public static synchronized void flush() {
+    if (!Metrics.initialized) {
+      return;
+    }
+    instance.reportAndFlushMetrics();
+  }
+
   public static void registerGauges(Map<String, Long> metricsMap, Option<String> prefix) {
     String metricPrefix = prefix.isPresent() ? prefix.get() + "." : "";
     metricsMap.forEach((k, v) -> registerGauge(metricPrefix + k, v));