Github user zsxwing commented on a diff in the pull request:
https://github.com/apache/spark/pull/11030#discussion_r51662372
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/ContinuousQueryManager.scala ---
@@ -0,0 +1,106 @@
+/*
+ * 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
+
+import scala.collection.mutable
+
+import org.apache.spark.annotation.Experimental
+import org.apache.spark.sql.execution.streaming.{Sink, StreamExecution}
+
+/**
+ * :: Experimental ::
+ * A class to manage all the [[org.apache.spark.sql.ContinuousQuery
ContinuousQueries]] active
+ * on a [[SQLContext]].
+ *
+ * @since 2.0.0
+ */
+@Experimental
+class ContinuousQueryManager {
+
+ private val activeQueries = new mutable.HashMap[String, ContinuousQuery]
+ private val activeQueriesLock = new Object
+ private val awaitTerminationLock = new Object
+
+ @volatile
+ private var lastTerminatedQuery: ContinuousQuery = null
+
+ /** Returns a list of active queries associated with this SQLContext */
+ def active: Array[ContinuousQuery] = activeQueriesLock.synchronized {
+ activeQueries.values.toArray
+ }
+
+ /** Returns an active query from this SQLContext or throws exception if
bad name */
+ def get(name: String): ContinuousQuery = activeQueriesLock.synchronized {
+ activeQueries.get(name).getOrElse {
+ throw new IllegalArgumentException(s"There is no active query with
name $name")
+ }
+ }
+
+ /**
+ * Wait until any of the queries on this SQLContext is terminated, with
or without
+ * exceptions. Returns the query that has been terminated.
+ */
+ def awaitAnyTermination(): ContinuousQuery = {
+ awaitTerminationLock.synchronized {
+ lastTerminatedQuery = null
+ while (lastTerminatedQuery == null) {
+ awaitTerminationLock.wait(10)
+ }
+ lastTerminatedQuery
+ }
+ }
+
+ /**
+ * Wait until any of the queries on this SQLContext is terminated.
+ * Returns the stopped query if any query was terminated.
+ */
+ def awaitAnyTermination(timeoutMs: Long): Option[ContinuousQuery] = {
+ val endTime = System.currentTimeMillis + timeoutMs
+ def timeLeft = math.max(endTime - System.currentTimeMillis, 0)
+
+ awaitTerminationLock.synchronized {
+ lastTerminatedQuery = null
+ while (timeLeft > 0 && lastTerminatedQuery == null) {
+ awaitTerminationLock.wait(10)
--- End diff --
Why use `wait(10)` to wake up every 10 milliseconds? Looks waste a lot of
CPU cycles and unnecessary thread context switches.
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