[GitHub] [flink] tillrohrmann commented on a change in pull request #9697: [FLINK-14094] [runtime] [metric] Fix OperatorIOMetricGroup repeat register problem

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tillrohrmann commented on a change in pull request #9697: [FLINK-14094] [runtime] [metric] Fix OperatorIOMetricGroup repeat register problem
URL: https://github.com/apache/flink/pull/9697#discussion_r326051179
 
 

 ##########
 File path: flink-runtime/src/main/java/org/apache/flink/runtime/metrics/groups/TaskMetricGroup.java
 ##########
 @@ -143,20 +143,17 @@ public OperatorMetricGroup getOrAddOperator(OperatorID operatorID, String name)
 			LOG.warn("The operator name {} exceeded the {} characters length limit and was truncated.", name, METRICS_OPERATOR_NAME_MAX_LENGTH);
 			name = name.substring(0, METRICS_OPERATOR_NAME_MAX_LENGTH);
 		}
-		OperatorMetricGroup operator = new OperatorMetricGroup(this.registry, this, operatorID, name);
+
 		// unique OperatorIDs only exist in streaming, so we have to rely on the name for batch operators
 		final String key = operatorID + name;
+		if (operators.containsKey(key)) {
+			return operators.get(key);
+		}
 
+		OperatorMetricGroup operator = new OperatorMetricGroup(this.registry, this, operatorID, name);
 		synchronized (this) {
-			OperatorMetricGroup previous = operators.put(key, operator);
-			if (previous == null) {
-				// no operator group so far
-				return operator;
-			} else {
-				// already had an operator group. restore that one.
-				operators.put(key, previous);
-				return previous;
-			}
+			operators.put(key, operator);
+			return operator;
 
 Review comment:
   I'd suggest to do it the following way:
   
   ```
   public OperatorMetricGroup getOrAddOperator(OperatorID operatorID, String name) {
   		final String metricName;
   		if (name != null && name.length() > METRICS_OPERATOR_NAME_MAX_LENGTH) {
   			LOG.warn("The operator name {} exceeded the {} characters length limit and was truncated.", name, METRICS_OPERATOR_NAME_MAX_LENGTH);
   			metricName = name.substring(0, METRICS_OPERATOR_NAME_MAX_LENGTH);
   		} else {
   			metricName = name;
   		}
   		// unique OperatorIDs only exist in streaming, so we have to rely on the name for batch operators
   		final String key = operatorID + metricName;
   
   		synchronized (this) {
   			return operators.computeIfAbsent(key, ignored -> new OperatorMetricGroup(this.registry, this, operatorID, metricName));
   		}
   	}
   ```

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