Increase visibility of some Metrics methods

runners/core-java/src/main/java/org/apache/beam/runners/core/metrics/CounterCell.java

@@ -21,8 +21,10 @@
 import java.util.concurrent.atomic.AtomicLong;
 import org.apache.beam.sdk.annotations.Experimental;
 import org.apache.beam.sdk.annotations.Experimental.Kind;
+import org.apache.beam.sdk.annotations.Internal;
 import org.apache.beam.sdk.metrics.Counter;
 import org.apache.beam.sdk.metrics.MetricName;
+import org.apache.beam.sdk.metrics.MetricsContainer;
 
 /**
  * Tracks the current value (and delta) for a Counter metric for a specific context and bundle.
@@ -40,10 +42,12 @@ public class CounterCell implements Counter, MetricCell<Long> {
   private final MetricName name;
 
   /**
-   * Package-visibility because all {@link CounterCell CounterCells} should be created by
-   * {@link MetricsContainerImpl#getCounter(MetricName)}.
+   * Generally, runners should construct instances using the methods in
+   * {@link MetricsContainerImpl}, unless they need to define their own version of
+   * {@link MetricsContainer}. These constructors are *only* public so runners can instantiate.
    */
-  CounterCell(MetricName name) {
+  @Internal
+  public CounterCell(MetricName name) {
     this.name = name;
   }
 

runners/core-java/src/main/java/org/apache/beam/runners/core/metrics/DirtyState.java

@@ -22,6 +22,7 @@
 import java.util.concurrent.atomic.AtomicReference;
 import org.apache.beam.sdk.annotations.Experimental;
 import org.apache.beam.sdk.annotations.Experimental.Kind;
+import org.apache.beam.sdk.annotations.Internal;
 
 /**
  * Atomically tracks the dirty-state of a metric.
@@ -42,7 +43,8 @@
  * completed.
  */
 @Experimental(Kind.METRICS)
-class DirtyState implements Serializable {
+@Internal
+public class DirtyState implements Serializable {
   private enum State {
     /** Indicates that there have been changes to the MetricCell since last commit. */
     DIRTY,

runners/core-java/src/main/java/org/apache/beam/runners/core/metrics/DistributionCell.java

@@ -21,8 +21,10 @@
 import java.util.concurrent.atomic.AtomicReference;
 import org.apache.beam.sdk.annotations.Experimental;
 import org.apache.beam.sdk.annotations.Experimental.Kind;
+import org.apache.beam.sdk.annotations.Internal;
 import org.apache.beam.sdk.metrics.Distribution;
 import org.apache.beam.sdk.metrics.MetricName;
+import org.apache.beam.sdk.metrics.MetricsContainer;
 
 /**
  * Tracks the current value (and delta) for a Distribution metric.
@@ -41,10 +43,12 @@ public class DistributionCell implements Distribution, MetricCell<DistributionDa
   private final MetricName name;
 
   /**
-   * Package-visibility because all {@link DistributionCell DistributionCells} should be created by
-   * {@link MetricsContainerImpl#getDistribution(MetricName)}.
+   * Generally, runners should construct instances using the methods in
+   * {@link MetricsContainerImpl}, unless they need to define their own version of
+   * {@link MetricsContainer}. These constructors are *only* public so runners can instantiate.
    */
-  DistributionCell(MetricName name) {
+  @Internal
+  public DistributionCell(MetricName name) {
     this.name = name;
   }
 

runners/core-java/src/main/java/org/apache/beam/runners/core/metrics/GaugeCell.java

@@ -20,8 +20,10 @@
 
 import java.util.concurrent.atomic.AtomicReference;
 import org.apache.beam.sdk.annotations.Experimental;
+import org.apache.beam.sdk.annotations.Internal;
 import org.apache.beam.sdk.metrics.Gauge;
 import org.apache.beam.sdk.metrics.MetricName;
+import org.apache.beam.sdk.metrics.MetricsContainer;
 
 /**
  * Tracks the current value (and delta) for a {@link Gauge} metric.
@@ -39,10 +41,12 @@ public class GaugeCell implements Gauge, MetricCell<GaugeData> {
   private final MetricName name;
 
   /**
-   * Package-visibility because all {@link GaugeCell GaugeCells} should be created by
-   * {@link MetricsContainerImpl#getGauge(MetricName)}.
+   * Generally, runners should construct instances using the methods in
+   * {@link MetricsContainerImpl}, unless they need to define their own version of
+   * {@link MetricsContainer}. These constructors are *only* public so runners can instantiate.
    */
-  GaugeCell(MetricName name) {
+  @Internal
+  public GaugeCell(MetricName name) {
     this.name = name;
   }
 
@@ -70,7 +74,6 @@ public GaugeData getCumulative() {
     return gaugeValue.get();
   }
 
-
   @Override
   public MetricName getName() {
     return name;

runners/core-java/src/main/java/org/apache/beam/runners/core/metrics/MetricsContainerImpl.java

@@ -31,7 +31,9 @@
 import org.apache.beam.sdk.metrics.MetricsContainer;
 
 /**
- * Holds the metrics for a single step and unit-of-commit (bundle).
+ * Holds the metrics for a single step and uses metric cells that allow extracting the cumulative
+ * value. Generally, this implementation should be used for a specific unit of commitment (bundle)
+ * that wishes to report the values since the start of the bundle (eg., for committed metrics).
  *
  * <p>This class is thread-safe. It is intended to be used with 1 (or more) threads are updating
  * metrics and at-most 1 thread is extracting updates by calling {@link #getUpdates} and

sdks/java/core/src/main/java/org/apache/beam/sdk/metrics/MetricsContainer.java

@@ -23,7 +23,8 @@
 import org.apache.beam.sdk.annotations.Experimental.Kind;
 
 /**
- * Holds the metrics for a single step and unit-of-commit (bundle).
+ * Holds the metrics for a single step. Each of the methods should return an implementation of the
+ * appropriate metrics interface for the "current" step.
  */
 @Experimental(Kind.METRICS)
 public interface MetricsContainer extends Serializable {