SPARK-26285: code review comment fixes

apache · Dec 21, 2018 · 682cfd7 · 682cfd7
1 parent 7f60730
commit 682cfd7
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Showing 2 changed files with 13 additions and 3 deletions.
diff --git a/core/src/main/scala/org/apache/spark/metrics/source/AccumulatorSource.scala b/core/src/main/scala/org/apache/spark/metrics/source/AccumulatorSource.scala
@@ -56,7 +56,9 @@ class DoubleAccumulatorSource extends AccumulatorSource
 
 /**
  * :: Experimental ::
- * Metrics source specifically for LongAccumulators.
+ * Metrics source specifically for LongAccumulators. Accumulators
+ * are only valid on the driver side, so these metrics are reported
+ * only by the driver.
  * Register LongAccumulators using:
  *    LongAccumulatorSource.register(sc, {"name" -> longAccumulator})
  */
@@ -71,7 +73,9 @@ object LongAccumulatorSource {
 
 /**
  * :: Experimental ::
- * Metrics source specifically for DoubleAccumulators.
+ * Metrics source specifically for DoubleAccumulators. Accumulators
+ * are only valid on the driver side, so these metrics are reported
+ * only by the driver.
  * Register DoubleAccumulators using:
  *    DoubleAccumulatorSource.register(sc, {"name" -> doubleAccumulator})
  */

diff --git a/examples/src/main/scala/org/apache/spark/examples/AccumulatorMetricsTest.scala b/examples/src/main/scala/org/apache/spark/examples/AccumulatorMetricsTest.scala
@@ -31,7 +31,9 @@ import org.apache.spark.sql.SparkSession
  *
  * The result is output to stdout in the driver with the values of the accumulators.
  * For the long accumulator, it should equal numElem the double accumulator should be
- * roughly 1.1 x numElem (within double precision.)
+ * roughly 1.1 x numElem (within double precision.) This example also sets up a
+ * ConsoleSink (metrics) instance, and so registered codahale metrics (like the
+ * accumulator source) are reported to stdout as well.
  */
 object AccumulatorMetricsTest {
   def main(args: Array[String]) {
@@ -45,9 +47,13 @@ object AccumulatorMetricsTest {
     val sc = spark.sparkContext
 
     val acc = sc.longAccumulator("my-long-metric")
+    // register the accumulator, the metric system will report as
+    // [spark.metrics.namespace].[execId|driver].AccumulatorSource.my-long-metric
     LongAccumulatorSource.register(sc, List(("my-long-metric" -> acc)).toMap)
 
     val acc2 = sc.doubleAccumulator("my-double-metric")
+    // register the accumulator, the metric system will report as
+    // [spark.metrics.namespace].[execId|driver].AccumulatorSource.my-double-metric
     DoubleAccumulatorSource.register(sc, List(("my-double-metric" -> acc2)).toMap)
 
     val num = if (args.length > 0) args(0).toInt else 1000000