Merge pull request #10530: [BEAM-9065] Reset MetricsContainerStepMapAccumulator upon initialization of MetricsAccumulator singleton

diff --git a/runners/spark/src/main/java/org/apache/beam/runners/spark/metrics/MetricsAccumulator.java b/runners/spark/src/main/java/org/apache/beam/runners/spark/metrics/MetricsAccumulator.java
index 2d83c3c..8313d73 100644
--- a/runners/spark/src/main/java/org/apache/beam/runners/spark/metrics/MetricsAccumulator.java
+++ b/runners/spark/src/main/java/org/apache/beam/runners/spark/metrics/MetricsAccumulator.java
@@ -74,6 +74,8 @@
         }
       }
       LOG.info("Instantiated metrics accumulator: " + instance.value());
+    } else {
+      instance.reset();
     }
   }
 
diff --git a/runners/spark/src/main/java/org/apache/beam/runners/spark/structuredstreaming/metrics/MetricsAccumulator.java b/runners/spark/src/main/java/org/apache/beam/runners/spark/structuredstreaming/metrics/MetricsAccumulator.java
index f674ef9..e182cf0 100644
--- a/runners/spark/src/main/java/org/apache/beam/runners/spark/structuredstreaming/metrics/MetricsAccumulator.java
+++ b/runners/spark/src/main/java/org/apache/beam/runners/spark/structuredstreaming/metrics/MetricsAccumulator.java
@@ -51,6 +51,8 @@
         }
       }
       LOG.info("Instantiated metrics accumulator: " + instance.value());
+    } else {
+      instance.reset();
     }
   }