srowen commented on a change in pull request #27046:
[SPARK-29348][SQL][FOLLOWUP] Fix slight bug on streaming example for
Dataset.observe
URL: https://github.com/apache/spark/pull/27046#discussion_r362011825
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File path: sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala
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@@ -1891,14 +1891,34 @@ class Dataset[T] private[sql](
* [[org.apache.spark.sql.util.QueryExecutionListener]] to the spark session.
*
* {{{
- * // Observe row count (rc) and error row count (erc) in the streaming
Dataset
+ * // Monitor the metrics for batch query using a listener.
+ * spark.listenerManager.register(new QueryExecutionListener() {
+ * override def onSuccess(funcName: String, qe: QueryExecution,
durationNs: Long): Unit = {
+ * qe.observedMetrics.get("my_event").foreach { row =>
+ * // Trigger if the number of errors exceeds 5 percent
+ * val num_rows = row.getAs[Long]("rc")
+ * val num_error_rows = row.getAs[Long]("erc")
+ * val ratio = num_error_rows.toDouble / num_rows
+ * if (ratio > 0.05) {
+ * // Trigger alert
+ * }
+ * }
+ * }
+ * override def onFailure(funcName: String, qe: QueryExecution, error:
Throwable): Unit = {
+ * // No-op
+ * }
+ * }
+ *
+ * // Observe row count (rc) and error row count (erc) in the batch Dataset
* val observed_ds = ds.observe("my_event", count(lit(1)).as("rc"),
count($"error").as("erc"))
- * observed_ds.writeStream.format("...").start()
+ * observed_ds.collect()
+ * }}}
*
- * // Monitor the metrics using a listener.
+ * {{{
+ * // Monitor the metrics for streaming query using a listener.
* spark.streams.addListener(new StreamingQueryListener() {
* override def onQueryProgress(event: QueryProgressEvent): Unit = {
- * event.progress.observedMetrics.get("my_event").foreach { row =>
+ * event.progress.observedMetrics.asScala.get("my_event").foreach { row
=>
Review comment:
Sounds fine. The alternative is to wrap it in `Option(....get(...)).foreach`
but that's messier
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