Add AttributesProcessor toString, add attribute filter helper (#5765)

docs/apidiffs/current_vs_latest/opentelemetry-sdk-metrics.txt

@@ -1,2 +1,4 @@
 Comparing source compatibility of  against 
-No changes.
+***  MODIFIED CLASS: PUBLIC FINAL io.opentelemetry.sdk.metrics.ViewBuilder  (not serializable)
+	===  CLASS FILE FORMAT VERSION: 52.0 <- 52.0
+	+++  NEW METHOD: PUBLIC(+) io.opentelemetry.sdk.metrics.ViewBuilder setAttributeFilter(java.util.Set<java.lang.String>)

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/ViewBuilder.java

@@ -5,11 +5,14 @@
 
 package io.opentelemetry.sdk.metrics;
 
+import static io.opentelemetry.sdk.metrics.internal.view.AttributesProcessor.setIncludes;
+
 import io.opentelemetry.sdk.metrics.internal.SdkMeterProviderUtil;
 import io.opentelemetry.sdk.metrics.internal.aggregator.AggregatorFactory;
 import io.opentelemetry.sdk.metrics.internal.state.MetricStorage;
 import io.opentelemetry.sdk.metrics.internal.view.AttributesProcessor;
 import java.util.Objects;
+import java.util.Set;
 import java.util.function.Predicate;
 import javax.annotation.Nullable;
 
@@ -64,6 +67,12 @@ public ViewBuilder setAggregation(Aggregation aggregation) {
     return this;
   }
 
+  /** Sets a filter which retains attribute keys included in {@code keysToRetain}. */
+  public ViewBuilder setAttributeFilter(Set<String> keysToRetain) {
+    Objects.requireNonNull(keysToRetain, "keysToRetain");
+    return setAttributeFilter(setIncludes(keysToRetain));
+  }
+
   /**
    * Sets a filter for attributes keys.
    *
@@ -73,7 +82,8 @@ public ViewBuilder setAggregation(Aggregation aggregation) {
    */
   public ViewBuilder setAttributeFilter(Predicate<String> keyFilter) {
     Objects.requireNonNull(keyFilter, "keyFilter");
-    return addAttributesProcessor(AttributesProcessor.filterByKeyName(keyFilter));
+    this.processor = AttributesProcessor.filterByKeyName(keyFilter);
+    return this;
   }
 
   /**

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/internal/view/AttributesProcessor.java

@@ -8,16 +8,16 @@
 import static io.opentelemetry.sdk.metrics.internal.view.NoopAttributesProcessor.NOOP;
 
 import io.opentelemetry.api.baggage.Baggage;
+import io.opentelemetry.api.common.AttributeKey;
 import io.opentelemetry.api.common.Attributes;
 import io.opentelemetry.api.common.AttributesBuilder;
 import io.opentelemetry.context.Context;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
-import java.util.function.BiFunction;
+import java.util.Set;
 import java.util.function.Predicate;
-import java.util.function.UnaryOperator;
 import javax.annotation.concurrent.Immutable;
 
 /**
@@ -73,11 +73,7 @@ public static AttributesProcessor noop() {
    * @param nameFilter a filter for which attribute keys to preserve.
    */
   public static AttributesProcessor filterByKeyName(Predicate<String> nameFilter) {
-    return simple(
-        incoming ->
-            incoming.toBuilder()
-                .removeIf(attributeKey -> !nameFilter.test(attributeKey.getKey()))
-                .build());
+    return new AttributeKeyFilteringProcessor(nameFilter);
   }
 
   /**
@@ -88,19 +84,7 @@ public static AttributesProcessor filterByKeyName(Predicate<String> nameFilter)
    * @param nameFilter a filter for which baggage keys to select.
    */
   public static AttributesProcessor appendBaggageByKeyName(Predicate<String> nameFilter) {
-    return onBaggage(
-        (incoming, baggage) -> {
-          AttributesBuilder result = Attributes.builder();
-          baggage.forEach(
-              (k, v) -> {
-                if (nameFilter.test(k)) {
-                  result.put(k, v.getValue());
-                }
-              });
-          // Override any baggage keys with existing keys.
-          result.putAll(incoming);
-          return result.build();
-        });
+    return new BaggageAppendingAttributesProcessor(nameFilter);
   }
 
   /**
@@ -111,43 +95,126 @@ public static AttributesProcessor appendBaggageByKeyName(Predicate<String> nameF
    * @param attributes Attributes to append to measurements.
    */
   public static AttributesProcessor append(Attributes attributes) {
-    return simple(incoming -> attributes.toBuilder().putAll(incoming).build());
+    return new AppendingAttributesProcessor(attributes);
   }
 
-  /** Creates a simple attributes processor with no access to context. */
-  static AttributesProcessor simple(UnaryOperator<Attributes> processor) {
-    return new AttributesProcessor() {
+  /** Creates a {@link Predicate} which tests if the {@code set} includes the input. */
+  public static Predicate<String> setIncludes(Set<String> set) {
+    return new SetIncludesPredicate(set);
+  }
 
-      @Override
-      public Attributes process(Attributes incoming, Context context) {
-        return processor.apply(incoming);
-      }
+  /** Predicate which tests if the {@code set} includes the input. */
+  private static class SetIncludesPredicate implements Predicate<String> {
+    private final Set<String> set;
 
-      @Override
-      public boolean usesContext() {
-        return false;
-      }
-    };
+    private SetIncludesPredicate(Set<String> set) {
+      this.set = set;
+    }
+
+    @Override
+    public boolean test(String s) {
+      return set.contains(s);
+    }
+
+    @Override
+    public String toString() {
+      return "SetIncludesPredicate{set=" + set + "}";
+    }
   }
 
-  /** Creates an Attributes processor that has access to baggage. */
-  static AttributesProcessor onBaggage(BiFunction<Attributes, Baggage, Attributes> processor) {
-    return new AttributesProcessor() {
-      @Override
-      public Attributes process(Attributes incoming, Context context) {
-        return processor.apply(incoming, Baggage.fromContext(context));
-      }
+  /**
+   * Processor which filters attributes according to a {@link AttributeKey#getKey()} {@link
+   * Predicate}.
+   */
+  private static class AttributeKeyFilteringProcessor extends AttributesProcessor {
 
-      @Override
-      public boolean usesContext() {
-        return true;
-      }
-    };
+    private final Predicate<String> nameFilter;
+
+    private AttributeKeyFilteringProcessor(Predicate<String> nameFilter) {
+      this.nameFilter = nameFilter;
+    }
+
+    @Override
+    public Attributes process(Attributes incoming, Context context) {
+      return incoming.toBuilder()
+          .removeIf(attributeKey -> !nameFilter.test(attributeKey.getKey()))
+          .build();
+    }
+
+    @Override
+    public boolean usesContext() {
+      return false;
+    }
+
+    @Override
+    public String toString() {
+      return "AttributeKeyFilteringProcessor{nameFilter=" + nameFilter + "}";
+    }
+  }
+
+  /** Processor which appends a static set of {@link Attributes}. */
+  private static class AppendingAttributesProcessor extends AttributesProcessor {
+
+    private final Attributes additionalAttributes;
+
+    private AppendingAttributesProcessor(Attributes additionalAttributes) {
+      this.additionalAttributes = additionalAttributes;
+    }
+
+    @Override
+    public Attributes process(Attributes incoming, Context context) {
+      return additionalAttributes.toBuilder().putAll(incoming).build();
+    }
+
+    @Override
+    public boolean usesContext() {
+      return false;
+    }
+
+    @Override
+    public String toString() {
+      return "AppendingAttributesProcessor{additionalAttributes=" + additionalAttributes + "}";
+    }
+  }
+
+  /** Processor which appends entries from {@link Baggage} with keys that match a predicate. */
+  private static final class BaggageAppendingAttributesProcessor extends AttributesProcessor {
+
+    private final Predicate<String> nameFilter;
+
+    private BaggageAppendingAttributesProcessor(Predicate<String> nameFilter) {
+      this.nameFilter = nameFilter;
+    }
+
+    @Override
+    public Attributes process(Attributes incoming, Context context) {
+      AttributesBuilder result = Attributes.builder();
+      Baggage.fromContext(context)
+          .forEach(
+              (k, v) -> {
+                if (nameFilter.test(k)) {
+                  result.put(k, v.getValue());
+                }
+              });
+      // Override any baggage keys with existing keys.
+      result.putAll(incoming);
+      return result.build();
+    }
+
+    @Override
+    public boolean usesContext() {
+      return true;
+    }
+
+    @Override
+    public String toString() {
+      return "BaggageAppendingAttributesProcessor{nameFilter=" + nameFilter + "}";
+    }
   }
 
   /** A {@link AttributesProcessor} that runs a sequence of processors. */
   @Immutable
-  static final class JoinedAttributesProcessor extends AttributesProcessor {
+  private static final class JoinedAttributesProcessor extends AttributesProcessor {
     private final Collection<AttributesProcessor> processors;
     private final boolean usesContextCache;
 
@@ -188,5 +255,10 @@ AttributesProcessor prepend(AttributesProcessor other) {
       newList.addAll(processors);
       return new JoinedAttributesProcessor(newList);
     }
+
+    @Override
+    public String toString() {
+      return "JoinedAttributesProcessor{processors=" + processors + "}";
+    }
   }
 }

sdk/metrics/src/test/java/io/opentelemetry/sdk/metrics/ViewTest.java

@@ -7,6 +7,8 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+import java.util.Arrays;
+import java.util.HashSet;
 import org.junit.jupiter.api.Test;
 
 class ViewTest {
@@ -26,14 +28,15 @@ void stringRepresentation() {
                 .setDescription("description")
                 .setAggregation(Aggregation.sum())
                 .setCardinalityLimit(10)
+                .setAttributeFilter(new HashSet<>(Arrays.asList("key1", "key2")))
                 .build()
                 .toString())
         .isEqualTo(
             "View{"
                 + "name=name, "
                 + "description=description, "
                 + "aggregation=SumAggregation, "
-                + "attributesProcessor=NoopAttributesProcessor{}, "
+                + "attributesProcessor=AttributeKeyFilteringProcessor{nameFilter=SetIncludesPredicate{set=[key1, key2]}}, "
                 + "cardinalityLimit=10"
                 + "}");
   }