Github user brkyvz commented on a diff in the pull request:
https://github.com/apache/spark/pull/21220#discussion_r185893837
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/WatermarkTracker.scala
---
@@ -0,0 +1,75 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.execution.streaming
+
+import scala.collection.mutable
+
+import org.apache.spark.internal.Logging
+import org.apache.spark.sql.execution.SparkPlan
+
+class WatermarkTracker extends Logging {
+ private val operatorToWatermarkMap = mutable.HashMap[Int, Long]()
+ private var watermarkMs: Long = 0
+ private var updated = false
+
+ def setWatermark(newWatermarkMs: Long): Unit = synchronized {
+ watermarkMs = newWatermarkMs
+ }
+
+ def updateWatermark(executedPlan: SparkPlan): Unit = synchronized {
+ val watermarkOperators = executedPlan.collect {
+ case e: EventTimeWatermarkExec => e
+ }
+ if (watermarkOperators.isEmpty) return
+
+
+ watermarkOperators.zipWithIndex.foreach {
+ case (e, index) if e.eventTimeStats.value.count > 0 =>
+ logDebug(s"Observed event time stats $index:
${e.eventTimeStats.value}")
+ val newWatermarkMs = e.eventTimeStats.value.max - e.delayMs
+ val prevWatermarkMs = operatorToWatermarkMap.get(index)
+ if (prevWatermarkMs.isEmpty || newWatermarkMs >
prevWatermarkMs.get) {
+ operatorToWatermarkMap.put(index, newWatermarkMs)
+ }
+
+ // Populate 0 if we haven't seen any data yet for this watermark
node.
+ case (_, index) =>
+ if (!operatorToWatermarkMap.isDefinedAt(index)) {
+ operatorToWatermarkMap.put(index, 0)
+ }
+ }
+
+ // Update the global watermark to the minimum of all watermark nodes.
+ // This is the safest option, because only the global watermark is
fault-tolerant. Making
+ // it the minimum of all individual watermarks guarantees it will
never advance past where
+ // any individual watermark operator would be if it were in a plan by
itself.
+ val newWatermarkMs = operatorToWatermarkMap.minBy(_._2)._2
+ if (newWatermarkMs > watermarkMs) {
+ logInfo(s"Updating eventTime watermark to: $newWatermarkMs ms")
+ watermarkMs = newWatermarkMs
+ updated = true
+ } else {
+ logDebug(s"Event time didn't move: $newWatermarkMs < $watermarkMs")
+ updated = false
+ }
+ }
+
+ def watermarkUpdated: Boolean = synchronized { updated }
--- End diff --
is this used anywhere?
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