@@ -20,7 +20,7 @@
 import io.opencensus.metrics.LabelValue;
 
 /** A helper class that holds OpenCensus's related constants. */
-public class MetricRegistryConstants {
+class MetricRegistryConstants {
 
 // The label keys are used to uniquely identify timeseries.
 private static final LabelKey DATABASE = LabelKey.create("database", "Target database");
@@ -32,22 +32,22 @@ public class MetricRegistryConstants {
 /** The label value is used to represent missing value. */
 private static final LabelValue UNSET_LABEL = LabelValue.create(null);
 
-public static final ImmutableList<LabelKey> SPANNER_LABEL_KEYS =
+static final ImmutableList<LabelKey> SPANNER_LABEL_KEYS =
 ImmutableList.of(DATABASE, INSTANCE_ID, LIBRARY_VERSION);
 
-public static final ImmutableList<LabelValue> SPANNER_DEFAULT_LABEL_VALUES =
+static final ImmutableList<LabelValue> SPANNER_DEFAULT_LABEL_VALUES =
 ImmutableList.of(UNSET_LABEL, UNSET_LABEL, UNSET_LABEL);
 
 /** Unit to represent counts. */
-public static final String COUNT = "1";
+static final String COUNT = "1";
 
 // The Metric name and description
-public static final String ACTIVE_SESSIONS = "cloud.google.com/java/spanner/active_sessions";
-public static final String MAX_SESSIONS = "cloud.google.com/java/spanner/max_sessions";
-public static final String SESSIONS_IN_USE = "cloud.google.com/java/spanner/sessions_in_use";
-public static final String ACTIVE_SESSIONS_DESCRIPTION =
-"Max number of sessions in use during the last 10 minutes";
-public static final String MAX_SESSIONS_DESCRIPTION = "The number of max sessions configured";
-public static final String SESSIONS_IN_USE_DESCRIPTION =
-"The number of sessions checked out from the pool";
+static final String MAX_IN_USE_SESSIONS = "cloud.google.com/java/spanner/max_in_use_session";
+static final String MAX_ALLOWED_SESSIONS = "cloud.google.com/java/spanner/max_allowed_sessions";
+static final String IN_USE_SESSIONS = "cloud.google.com/java/spanner/in_use_sessions";
+static final String MAX_IN_USE_SESSIONS_DESCRIPTION =
+"The max number of sessions in use during the last 10 minutes interval";
+static final String MAX_ALLOWED_SESSIONS_DESCRIPTION =
+"The Maximum number of sessions allowed. Configurable by the user.";
+static final String IN_USE_SESSIONS_DESCRIPTION = "The number of sessions currently in use";
 }

@@ -16,13 +16,13 @@
 
 package com.google.cloud.spanner;
 
-import static com.google.cloud.spanner.MetricRegistryConstants.ACTIVE_SESSIONS;
-import static com.google.cloud.spanner.MetricRegistryConstants.ACTIVE_SESSIONS_DESCRIPTION;
 import static com.google.cloud.spanner.MetricRegistryConstants.COUNT;
-import static com.google.cloud.spanner.MetricRegistryConstants.MAX_SESSIONS;
-import static com.google.cloud.spanner.MetricRegistryConstants.MAX_SESSIONS_DESCRIPTION;
-import static com.google.cloud.spanner.MetricRegistryConstants.SESSIONS_IN_USE;
-import static com.google.cloud.spanner.MetricRegistryConstants.SESSIONS_IN_USE_DESCRIPTION;
+import static com.google.cloud.spanner.MetricRegistryConstants.IN_USE_SESSIONS;
+import static com.google.cloud.spanner.MetricRegistryConstants.IN_USE_SESSIONS_DESCRIPTION;
+import static com.google.cloud.spanner.MetricRegistryConstants.MAX_ALLOWED_SESSIONS;
+import static com.google.cloud.spanner.MetricRegistryConstants.MAX_ALLOWED_SESSIONS_DESCRIPTION;
+import static com.google.cloud.spanner.MetricRegistryConstants.MAX_IN_USE_SESSIONS;
+import static com.google.cloud.spanner.MetricRegistryConstants.MAX_IN_USE_SESSIONS_DESCRIPTION;
 import static com.google.cloud.spanner.MetricRegistryConstants.SPANNER_DEFAULT_LABEL_VALUES;
 import static com.google.cloud.spanner.MetricRegistryConstants.SPANNER_LABEL_KEYS;
 import static com.google.cloud.spanner.SpannerExceptionFactory.newSpannerException;
@@ -1815,36 +1815,36 @@ public void onSessionCreateFailure(Throwable t, int createFailureForSessionCount
 * allows users to monitor client behavior.
 */
 private void initMetricsCollection(MetricRegistry metricRegistry, List<LabelValue> labelValues) {
-DerivedLongGauge activeSessionsGauge =
+DerivedLongGauge maxInUseSessionsMetric =
 metricRegistry.addDerivedLongGauge(
-ACTIVE_SESSIONS,
+MAX_IN_USE_SESSIONS,
 MetricOptions.builder()
-.setDescription(ACTIVE_SESSIONS_DESCRIPTION)
+.setDescription(MAX_IN_USE_SESSIONS_DESCRIPTION)
 .setUnit(COUNT)
 .setLabelKeys(SPANNER_LABEL_KEYS)
 .build());
 
-DerivedLongGauge maxSessionsGauge =
+DerivedLongGauge maxAllowedSessionsMetric =
 metricRegistry.addDerivedLongGauge(
-MAX_SESSIONS,
+MAX_ALLOWED_SESSIONS,
 MetricOptions.builder()
-.setDescription(MAX_SESSIONS_DESCRIPTION)
+.setDescription(MAX_ALLOWED_SESSIONS_DESCRIPTION)
 .setUnit(COUNT)
 .setLabelKeys(SPANNER_LABEL_KEYS)
 .build());
 
-DerivedLongGauge sessionsInUseGauge =
+DerivedLongGauge numInUseSessionsMetric =
 metricRegistry.addDerivedLongGauge(
-SESSIONS_IN_USE,
+IN_USE_SESSIONS,
 MetricOptions.builder()
-.setDescription(SESSIONS_IN_USE_DESCRIPTION)
+.setDescription(IN_USE_SESSIONS_DESCRIPTION)
 .setUnit(COUNT)
 .setLabelKeys(SPANNER_LABEL_KEYS)
 .build());
 
 // The value of a maxSessionsInUse is observed from a callback function. This function is
 // invoked whenever metrics are collected.
-activeSessionsGauge.createTimeSeries(
+maxInUseSessionsMetric.createTimeSeries(
 labelValues,
 this,
 new ToLongFunction<SessionPool>() {
@@ -1856,7 +1856,7 @@ public long applyAsLong(SessionPool sessionPool) {
 
 // The value of a maxSessions is observed from a callback function. This function is invoked
 // whenever metrics are collected.
-maxSessionsGauge.createTimeSeries(
+maxAllowedSessionsMetric.createTimeSeries(
 labelValues,
 options,
 new ToLongFunction<SessionPoolOptions>() {
@@ -1868,7 +1868,7 @@ public long applyAsLong(SessionPoolOptions options) {
 
 // The value of a numSessionsInUse is observed from a callback function. This function is
 // invoked whenever metrics are collected.
-sessionsInUseGauge.createTimeSeries(
+numInUseSessionsMetric.createTimeSeries(
 labelValues,
 this,
 new ToLongFunction<SessionPool>() {

@@ -32,11 +32,11 @@
 import java.util.List;
 import java.util.Map;
 
-public class MetricRegistryTestUtils {
+class MetricRegistryTestUtils {
 
-public static class MetricsRecord {
-public final Map<String, Number> metrics;
-public final Map<List<LabelKey>, List<LabelValue>> labels;
+static class MetricsRecord {
+final Map<String, Number> metrics;
+final Map<List<LabelKey>, List<LabelValue>> labels;
 
 private MetricsRecord() {
 this.metrics = Maps.newHashMap();
@@ -78,11 +78,11 @@ public static final class FakeMetricRegistry extends MetricRegistry {
 
 private MetricsRecord record;
 
-public FakeMetricRegistry() {
+FakeMetricRegistry() {
 record = new MetricsRecord();
 }
 
-public MetricsRecord pollRecord() {
+MetricsRecord pollRecord() {
 return record;
 }
 

@@ -1582,11 +1582,11 @@ public void testSessionMetrics() {
 runMaintainanceLoop(clock, pool, pool.poolMaintainer.numClosureCycles);
 
 MetricsRecord record = metricRegistry.pollRecord();
-assertThat(record.metrics).containsEntry(MetricRegistryConstants.ACTIVE_SESSIONS, 0L);
-assertThat(record.metrics).containsEntry(MetricRegistryConstants.SESSIONS_IN_USE, 0L);
+assertThat(record.metrics).containsEntry(MetricRegistryConstants.MAX_IN_USE_SESSIONS, 0L);
+assertThat(record.metrics).containsEntry(MetricRegistryConstants.IN_USE_SESSIONS, 0L);
 assertThat(record.metrics)
 .containsEntry(
-MetricRegistryConstants.MAX_SESSIONS, Long.valueOf(options.getMaxSessions()));
+MetricRegistryConstants.MAX_ALLOWED_SESSIONS, Long.valueOf(options.getMaxSessions()));
 assertThat(record.labels).containsEntry(SPANNER_LABEL_KEYS, labelValues);
 }