introducing view (#2956)

* introducing view

* code review

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

@@ -25,6 +25,7 @@ static <T> Aggregator<T> getAggregator(
     return meterProviderSharedState
         .getViewRegistry()
         .findView(descriptor)
+        .getAggregatorFactory()
         .create(
             meterProviderSharedState.getResource(),
             meterSharedState.getInstrumentationLibraryInfo(),

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

@@ -9,10 +9,10 @@
 import io.opentelemetry.api.metrics.MeterProvider;
 import io.opentelemetry.sdk.common.Clock;
 import io.opentelemetry.sdk.internal.ComponentRegistry;
-import io.opentelemetry.sdk.metrics.aggregator.AggregatorFactory;
 import io.opentelemetry.sdk.metrics.data.MetricData;
 import io.opentelemetry.sdk.metrics.export.MetricProducer;
 import io.opentelemetry.sdk.metrics.view.InstrumentSelector;
+import io.opentelemetry.sdk.metrics.view.View;
 import io.opentelemetry.sdk.resources.Resource;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -95,13 +95,14 @@ public static SdkMeterProviderBuilder builder() {
    *   .buildInstrument();
    *
    * // create a specification of how you want the metrics aggregated:
-   * AggregationFactory aggregationFactory = AggregationFactory.minMaxSumCount();
+   * AggregatorFactory aggregatorFactory = AggregatorFactory.minMaxSumCount();
    *
    * //register the view with the MeterSdkProvider
-   * meterProvider.registerView(instrumentSelector, aggregationFactory);
+   * meterProvider.registerView(instrumentSelector, View.builder()
+   *   .setAggregatorFactory(aggregatorFactory).build());
    * }</pre>
    */
-  public void registerView(InstrumentSelector selector, AggregatorFactory aggregatorFactory) {
-    sharedState.getViewRegistry().registerView(selector, aggregatorFactory);
+  public void registerView(InstrumentSelector selector, View view) {
+    sharedState.getViewRegistry().registerView(selector, view);
   }
 }

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

@@ -9,6 +9,7 @@
 import io.opentelemetry.sdk.metrics.common.InstrumentDescriptor;
 import io.opentelemetry.sdk.metrics.common.InstrumentType;
 import io.opentelemetry.sdk.metrics.view.InstrumentSelector;
+import io.opentelemetry.sdk.metrics.view.View;
 import java.util.EnumMap;
 import java.util.LinkedHashMap;
 import java.util.Map;
@@ -23,15 +24,17 @@
  * never blocked.
  */
 final class ViewRegistry {
-  private static final LinkedHashMap<Pattern, AggregatorFactory> EMPTY_CONFIG =
-      new LinkedHashMap<>();
-  static final AggregatorFactory CUMULATIVE_SUM = AggregatorFactory.sum(true);
-  static final AggregatorFactory SUMMARY = AggregatorFactory.minMaxSumCount();
-  static final AggregatorFactory LAST_VALUE = AggregatorFactory.lastValue();
+  private static final LinkedHashMap<Pattern, View> EMPTY_CONFIG = new LinkedHashMap<>();
+  static final View CUMULATIVE_SUM =
+      View.builder().setAggregatorFactory(AggregatorFactory.sum(true)).build();
+  static final View SUMMARY =
+      View.builder().setAggregatorFactory(AggregatorFactory.minMaxSumCount()).build();
+  static final View LAST_VALUE =
+      View.builder().setAggregatorFactory(AggregatorFactory.lastValue()).build();
 
   // The lock is used to ensure only one updated to the configuration happens at any moment.
   private final ReentrantLock lock = new ReentrantLock();
-  private volatile EnumMap<InstrumentType, LinkedHashMap<Pattern, AggregatorFactory>> configuration;
+  private volatile EnumMap<InstrumentType, LinkedHashMap<Pattern, View>> configuration;
 
   ViewRegistry() {
     this.configuration = new EnumMap<>(InstrumentType.class);
@@ -43,27 +46,26 @@ final class ViewRegistry {
     configuration.put(InstrumentType.VALUE_OBSERVER, EMPTY_CONFIG);
   }
 
-  void registerView(InstrumentSelector selector, AggregatorFactory aggregatorFactory) {
+  void registerView(InstrumentSelector selector, View view) {
     lock.lock();
     try {
-      EnumMap<InstrumentType, LinkedHashMap<Pattern, AggregatorFactory>> newConfiguration =
+      EnumMap<InstrumentType, LinkedHashMap<Pattern, View>> newConfiguration =
           new EnumMap<>(configuration);
       newConfiguration.put(
           selector.getInstrumentType(),
           newLinkedHashMap(
               selector.getInstrumentNamePattern(),
-              aggregatorFactory,
+              view,
               newConfiguration.get(selector.getInstrumentType())));
       configuration = newConfiguration;
     } finally {
       lock.unlock();
     }
   }
 
-  AggregatorFactory findView(InstrumentDescriptor descriptor) {
-    LinkedHashMap<Pattern, AggregatorFactory> configPerType =
-        configuration.get(descriptor.getType());
-    for (Map.Entry<Pattern, AggregatorFactory> entry : configPerType.entrySet()) {
+  View findView(InstrumentDescriptor descriptor) {
+    LinkedHashMap<Pattern, View> configPerType = configuration.get(descriptor.getType());
+    for (Map.Entry<Pattern, View> entry : configPerType.entrySet()) {
       if (entry.getKey().matcher(descriptor.getName()).matches()) {
         return entry.getValue();
       }
@@ -72,7 +74,7 @@ AggregatorFactory findView(InstrumentDescriptor descriptor) {
     return getDefaultSpecification(descriptor);
   }
 
-  private static AggregatorFactory getDefaultSpecification(InstrumentDescriptor descriptor) {
+  private static View getDefaultSpecification(InstrumentDescriptor descriptor) {
     switch (descriptor.getType()) {
       case COUNTER:
       case UP_DOWN_COUNTER:
@@ -87,12 +89,10 @@ private static AggregatorFactory getDefaultSpecification(InstrumentDescriptor de
     throw new IllegalArgumentException("Unknown descriptor type: " + descriptor.getType());
   }
 
-  private static LinkedHashMap<Pattern, AggregatorFactory> newLinkedHashMap(
-      Pattern pattern,
-      AggregatorFactory aggregatorFactory,
-      LinkedHashMap<Pattern, AggregatorFactory> parentConfiguration) {
-    LinkedHashMap<Pattern, AggregatorFactory> result = new LinkedHashMap<>();
-    result.put(pattern, aggregatorFactory);
+  private static LinkedHashMap<Pattern, View> newLinkedHashMap(
+      Pattern pattern, View view, LinkedHashMap<Pattern, View> parentConfiguration) {
+    LinkedHashMap<Pattern, View> result = new LinkedHashMap<>();
+    result.put(pattern, view);
     result.putAll(parentConfiguration);
     return result;
   }

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/view/View.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.metrics.view;
+
+import com.google.auto.value.AutoValue;
+import io.opentelemetry.sdk.metrics.aggregator.AggregatorFactory;
+import javax.annotation.concurrent.Immutable;
+
+/** TODO: javadoc. */
+@AutoValue
+@Immutable
+public abstract class View {
+  public abstract AggregatorFactory getAggregatorFactory();
+
+  public static ViewBuilder builder() {
+    return new ViewBuilder();
+  }
+
+  static View create(AggregatorFactory aggregatorFactory) {
+    return new AutoValue_View(aggregatorFactory);
+  }
+}

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

@@ -0,0 +1,24 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.metrics.view;
+
+import io.opentelemetry.sdk.metrics.aggregator.AggregatorFactory;
+import java.util.Objects;
+
+public final class ViewBuilder {
+  private AggregatorFactory aggregatorFactory;
+
+  ViewBuilder() {}
+
+  public ViewBuilder setAggregatorFactory(AggregatorFactory aggregatorFactory) {
+    this.aggregatorFactory = Objects.requireNonNull(aggregatorFactory, "aggregatorFactory");
+    return this;
+  }
+
+  public View build() {
+    return View.create(this.aggregatorFactory);
+  }
+}

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

@@ -32,6 +32,7 @@
 import io.opentelemetry.sdk.metrics.data.MetricData;
 import io.opentelemetry.sdk.metrics.data.ValueAtPercentile;
 import io.opentelemetry.sdk.metrics.view.InstrumentSelector;
+import io.opentelemetry.sdk.metrics.view.View;
 import io.opentelemetry.sdk.resources.Resource;
 import java.util.Arrays;
 import java.util.Collections;
@@ -161,7 +162,7 @@ void collectAllSyncInstruments() {
   void collectAllSyncInstruments_OverwriteTemporality() {
     sdkMeterProvider.registerView(
         InstrumentSelector.builder().setInstrumentType(InstrumentType.COUNTER).build(),
-        AggregatorFactory.sum(false));
+        View.builder().setAggregatorFactory(AggregatorFactory.sum(false)).build());
 
     LongCounter longCounter = sdkMeter.longCounterBuilder("testLongCounter").build();
     longCounter.add(10, Labels.empty());
@@ -671,7 +672,8 @@ private static void registerViewForAllTypes(
       SdkMeterProvider meterProvider, AggregatorFactory factory) {
     for (InstrumentType instrumentType : InstrumentType.values()) {
       meterProvider.registerView(
-          InstrumentSelector.builder().setInstrumentType(instrumentType).build(), factory);
+          InstrumentSelector.builder().setInstrumentType(instrumentType).build(),
+          View.builder().setAggregatorFactory(factory).build());
     }
   }
 }

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

@@ -12,25 +12,27 @@
 import io.opentelemetry.sdk.metrics.common.InstrumentType;
 import io.opentelemetry.sdk.metrics.common.InstrumentValueType;
 import io.opentelemetry.sdk.metrics.view.InstrumentSelector;
+import io.opentelemetry.sdk.metrics.view.View;
 import org.junit.jupiter.api.Test;
 
 class ViewRegistryTest {
   @Test
   void selection_onType() {
     AggregatorFactory factory = AggregatorFactory.lastValue();
+    View view = View.builder().setAggregatorFactory(factory).build();
 
     ViewRegistry viewRegistry = new ViewRegistry();
     viewRegistry.registerView(
         InstrumentSelector.builder()
             .setInstrumentType(InstrumentType.COUNTER)
             .setInstrumentNameRegex(".*")
             .build(),
-        factory);
+        view);
     assertThat(
             viewRegistry.findView(
                 InstrumentDescriptor.create(
                     "", "", "", InstrumentType.COUNTER, InstrumentValueType.LONG)))
-        .isEqualTo(factory);
+        .isEqualTo(view);
     // this one hasn't been configured, so it gets the default still.
     assertThat(
             viewRegistry.findView(
@@ -42,19 +44,20 @@ void selection_onType() {
   @Test
   void selection_onName() {
     AggregatorFactory factory = AggregatorFactory.lastValue();
+    View view = View.builder().setAggregatorFactory(factory).build();
 
     ViewRegistry viewRegistry = new ViewRegistry();
     viewRegistry.registerView(
         InstrumentSelector.builder()
             .setInstrumentType(InstrumentType.COUNTER)
             .setInstrumentNameRegex("overridden")
             .build(),
-        factory);
+        view);
     assertThat(
             viewRegistry.findView(
                 InstrumentDescriptor.create(
                     "overridden", "", "", InstrumentType.COUNTER, InstrumentValueType.LONG)))
-        .isSameAs(factory);
+        .isSameAs(view);
     // this one hasn't been configured, so it gets the default still.
     assertThat(
             viewRegistry.findView(
@@ -66,56 +69,59 @@ void selection_onName() {
   @Test
   void selection_LastAddedViewWins() {
     AggregatorFactory factory1 = AggregatorFactory.lastValue();
+    View view1 = View.builder().setAggregatorFactory(factory1).build();
     AggregatorFactory factory2 = AggregatorFactory.minMaxSumCount();
+    View view2 = View.builder().setAggregatorFactory(factory2).build();
 
     ViewRegistry viewRegistry = new ViewRegistry();
     viewRegistry.registerView(
         InstrumentSelector.builder()
             .setInstrumentType(InstrumentType.COUNTER)
             .setInstrumentNameRegex(".*")
             .build(),
-        factory1);
+        view1);
     viewRegistry.registerView(
         InstrumentSelector.builder()
             .setInstrumentType(InstrumentType.COUNTER)
             .setInstrumentNameRegex("overridden")
             .build(),
-        factory2);
+        view2);
 
     assertThat(
             viewRegistry.findView(
                 InstrumentDescriptor.create(
                     "overridden", "", "", InstrumentType.COUNTER, InstrumentValueType.LONG)))
-        .isEqualTo(factory2);
+        .isEqualTo(view2);
     assertThat(
             viewRegistry.findView(
                 InstrumentDescriptor.create(
                     "default", "", "", InstrumentType.COUNTER, InstrumentValueType.LONG)))
-        .isEqualTo(factory1);
+        .isEqualTo(view1);
   }
 
   @Test
   void selection_regex() {
     AggregatorFactory factory = AggregatorFactory.lastValue();
+    View view = View.builder().setAggregatorFactory(factory).build();
 
     ViewRegistry viewRegistry = new ViewRegistry();
     viewRegistry.registerView(
         InstrumentSelector.builder()
             .setInstrumentNameRegex("overrid(es|den)")
             .setInstrumentType(InstrumentType.COUNTER)
             .build(),
-        factory);
+        view);
 
     assertThat(
             viewRegistry.findView(
                 InstrumentDescriptor.create(
                     "overridden", "", "", InstrumentType.COUNTER, InstrumentValueType.LONG)))
-        .isEqualTo(factory);
+        .isEqualTo(view);
     assertThat(
             viewRegistry.findView(
                 InstrumentDescriptor.create(
                     "overrides", "", "", InstrumentType.COUNTER, InstrumentValueType.LONG)))
-        .isEqualTo(factory);
+        .isEqualTo(view);
     // this one hasn't been configured, so it gets the default still..
     assertThat(
             viewRegistry.findView(