code review: jaadocs, factory method signature

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

@@ -34,11 +34,16 @@ static <T> Aggregator<T> getAggregator(
   }
 
   static LabelsProcessor getLabelsProcessor(
-      MeterProviderSharedState meterProviderSharedState, InstrumentDescriptor descriptor) {
+      MeterProviderSharedState meterProviderSharedState,
+      MeterSharedState meterSharedState,
+      InstrumentDescriptor descriptor) {
     return meterProviderSharedState
         .getViewRegistry()
         .findView(descriptor)
         .getLabelsProcessorFactory()
-        .create();
+        .create(
+            meterProviderSharedState.getResource(),
+            meterSharedState.getInstrumentationLibraryInfo(),
+            descriptor);
   }
 }

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

@@ -34,7 +34,7 @@ static <T> SynchronousInstrumentAccumulator<T> create(
     return new SynchronousInstrumentAccumulator<>(
         aggregator,
         new InstrumentProcessor<>(aggregator, meterProviderSharedState.getStartEpochNanos()),
-        getLabelsProcessor(meterProviderSharedState, descriptor));
+        getLabelsProcessor(meterProviderSharedState, meterSharedState, descriptor));
   }
 
   SynchronousInstrumentAccumulator(

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/processor/BaggageLabelsProcessor.java

@@ -9,7 +9,11 @@
 import io.opentelemetry.api.metrics.common.LabelsBuilder;
 import io.opentelemetry.context.Context;
 
-public class BaggageLabelsProcessor implements LabelsProcessor {
+/**
+ * A label processor which extracts labels from {@link io.opentelemetry.api.baggage.Baggage}.
+ * Delegates actual extraction implementation to {@link BaggageMetricsLabelsExtractor}
+ */
+public final class BaggageLabelsProcessor implements LabelsProcessor {
   private final BaggageMetricsLabelsExtractor baggageMetricsLabelsExtractor;
 
   public BaggageLabelsProcessor(BaggageMetricsLabelsExtractor baggageMetricsLabelsExtractor) {

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/processor/LabelsProcessor.java

@@ -10,9 +10,14 @@
 
 public interface LabelsProcessor {
   /**
-   * Called when bind() method is called. Allows to manipulate labels which this instrument is bound
-   * to. Particular use case includes enriching lables and/or adding more labels depending on the
-   * Context
+   * Called when bound synchronous instrument is created or metrics are recorded for non-bound
+   * synchronous instrument. Allows to manipulate labels which this instrument is bound to in case
+   * of binding operation or labels used for recording values in case of non-bound synchronous
+   * instrument. Particular use case includes enriching labels and/or adding more labels depending
+   * on the Context
+   *
+   * <p>Please note, this is an experimental API. In case of bound instruments, it will be only
+   * invoked upon instrument binding and not when measurements are recorded.
    *
    * @param ctx context of the operation
    * @param labels immutable labels. When processors are chained output labels of the previous one

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/processor/LabelsProcessorFactory.java

@@ -5,19 +5,27 @@
 
 package io.opentelemetry.sdk.metrics.processor;
 
+import io.opentelemetry.sdk.common.InstrumentationLibraryInfo;
+import io.opentelemetry.sdk.metrics.common.InstrumentDescriptor;
+import io.opentelemetry.sdk.resources.Resource;
+
 public interface LabelsProcessorFactory {
   static LabelsProcessorFactory noop() {
-    return NoopLabelsProcessor::new;
+    return (resource, instrumentationLibraryInfo, descriptor) -> new NoopLabelsProcessor();
   }
 
   static LabelsProcessorFactory baggageExtractor(BaggageMetricsLabelsExtractor labelsExtractor) {
-    return () -> new BaggageLabelsProcessor(labelsExtractor);
+    return (resource, instrumentationLibraryInfo, descriptor) ->
+        new BaggageLabelsProcessor(labelsExtractor);
   }
 
   /**
    * Returns a new {@link LabelsProcessorFactory}.
    *
    * @return new {@link LabelsProcessorFactory}
    */
-  LabelsProcessor create();
+  LabelsProcessor create(
+      Resource resource,
+      InstrumentationLibraryInfo instrumentationLibraryInfo,
+      InstrumentDescriptor descriptor);
 }

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

@@ -30,7 +30,10 @@ public class SynchronousInstrumentAccumulatorTest {
       AggregatorFactory.lastValue()
           .create(
               Resource.getEmpty(), InstrumentationLibraryInfo.create("test", "1.0"), DESCRIPTOR);
-  private final LabelsProcessor labelsProcessor = LabelsProcessorFactory.noop().create();
+  private final LabelsProcessor labelsProcessor =
+      LabelsProcessorFactory.noop()
+          .create(
+              Resource.getEmpty(), InstrumentationLibraryInfo.create("test", "1.0"), DESCRIPTOR);
 
   @Test
   void sameAggregator_ForSameLabelSet() {