[GitHub] [spark] sarutak commented on a change in pull request #30427: [SPARK-33224][SS] Add watermark gap information into SS UI page

[GitBox]

sarutak commented on a change in pull request #30427:
URL: https://github.com/apache/spark/pull/30427#discussion_r527463165



##########
File path: 
sql/core/src/main/scala/org/apache/spark/sql/streaming/ui/StreamingQueryStatisticsPage.scala
##########
@@ -126,6 +126,53 @@ private[ui] class StreamingQueryStatisticsPage(parent: 
StreamingQueryTab)
     <br />
   }
 
+  def generateWatermark(
+      query: StreamingQueryUIData,
+      minBatchTime: Long,
+      maxBatchTime: Long,
+      jsCollector: JsCollector): Seq[Node] = {
+    // This is made sure on caller side but put it here to be defensive
+    require(query.lastProgress != null)
+    if (query.lastProgress.eventTime.containsKey("watermark")) {
+      val watermarkData = query.recentProgress.flatMap { p =>
+        val batchTimestamp = parseProgressTimestamp(p.timestamp)
+        val watermarkValue = 
parseProgressTimestamp(p.eventTime.get("watermark"))
+        if (watermarkValue > 0L) {
+          // seconds
+          Some((batchTimestamp, ((batchTimestamp - watermarkValue) / 1000.0)))
+        } else {
+          None
+        }
+      }
+      val maxWatermark = watermarkData.maxBy(_._2)._2

Review comment:
       If we access to the UI immediately after starting a streaming query, 
watermarkData can be empty.
   
   ![empty 
maxBy](https://user-images.githubusercontent.com/4736016/99766540-a4590500-2b44-11eb-9113-835dc7debb46.png)
   




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