[GitHub] [flink] zentol commented on a change in pull request #9870: [FLINK-14350][metrics] Introduce dedicated MetricScope

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zentol commented on a change in pull request #9870: [FLINK-14350][metrics] Introduce dedicated MetricScope
URL: https://github.com/apache/flink/pull/9870#discussion_r335431341
 
 

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 File path: flink-runtime/src/main/java/org/apache/flink/runtime/metrics/scope/InternalMetricScope.java
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 @@ -0,0 +1,89 @@
+package org.apache.flink.runtime.metrics.scope;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.metrics.CharacterFilter;
+import org.apache.flink.metrics.MetricScope;
+import org.apache.flink.runtime.metrics.DelimiterProvider;
+
+import java.util.Map;
+import java.util.function.Supplier;
+
+/**
+ * Default scope implementation. Contains additional methods assembling identifiers based on reporter-specific delimiters.
+ */
+@Internal
+public class InternalMetricScope implements MetricScope {
+
+	private final DelimiterProvider delimiterProvider;
+	private final Supplier<Map<String, String>> variablesProvider;
+
+	/**
+	 * The map containing all variables and their associated values, lazily computed.
+	 */
+	protected volatile Map<String, String> variables;
+
+	/**
+	 * The metrics scope represented by this group.
+	 * For example ["host-7", "taskmanager-2", "window_word_count", "my-mapper" ].
+	 */
+	private final String[] scopeComponents;
+
+	/**
+	 * Array containing the metrics scope represented by this group for each reporter, as a concatenated string, lazily computed.
+	 * For example: "host-7.taskmanager-2.window_word_count.my-mapper"
+	 */
+	private final String[] scopeStrings;
+
+	public InternalMetricScope(DelimiterProvider delimiterProvider, String[] scopeComponents, Supplier<Map<String, String>> variablesProvider) {
+		this.delimiterProvider = delimiterProvider;
+		this.variablesProvider = variablesProvider;
+		this.scopeComponents = scopeComponents;
+		this.scopeStrings = new String[delimiterProvider.getNumberReporters()];
+	}
+
+	@Override
+	public Map<String, String> getAllVariables() {
+		if (variables == null) { // avoid synchronization for common case
+			synchronized (this) {
+				if (variables == null) {
+					variables = variablesProvider.get();
+				}
+			}
+		}
+		return variables;
+	}
+
+	public String[] geScopeComponents() {
+		return scopeStrings;
+	}
+
+	@Override
+	public String getMetricIdentifier(String metricName) {
+		return getMetricIdentifier(metricName, s -> s, delimiterProvider.getDelimiter(), -1);
+	}
+
+	@Override
+	public String getMetricIdentifier(String metricName, CharacterFilter filter) {
+		return getMetricIdentifier(metricName, filter, delimiterProvider.getDelimiter(), -1);
+	}
+
+	@Internal
+	public String getMetricIdentifier(String metricName, CharacterFilter filter, int reporterIndex) {
+		return getMetricIdentifier(metricName, filter, delimiterProvider.getDelimiter(reporterIndex), reporterIndex);
 
 Review comment:
   Generally yes, this is more or less a misappropriation of this annotation. This method _shouldn't_ be public, and only is so to enable backwards-compatibility with the deprecated scope-related methods in the `MetricGroup`.
   
   I wanted to mark it in some way, maybe @Deprecated would be more appropriate.

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