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/*
* 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.util
import org.apache.spark.annotation.Experimental
import org.apache.spark.sql.ContinuousQuery
import org.apache.spark.sql.util.ContinuousQueryListener._
/**
* :: Experimental ::
* Interface for listening to events related to [[ContinuousQuery ContinuousQueries]].
* @note The methods are not thread-safe as they may be called from different threads.
*/
@Experimental
abstract class ContinuousQueryListener {
/**
* Called when a query is started.
* @note This is called synchronously with
* [[org.apache.spark.sql.DataFrameWriter `DataFrameWriter.startStream()`]],
* that is, `onQueryStart` will be called on all listeners before
* `DataFrameWriter.startStream()` returns the corresponding [[ContinuousQuery]]. Please
* don't block this method as it will block your query.
*/
def onQueryStarted(queryStarted: QueryStarted): Unit
/**
* Called when there is some status update (ingestion rate updated, etc.)
*
* @note This method is asynchronous. The status in [[ContinuousQuery]] will always be
* latest no matter when this method is called. Therefore, the status of [[ContinuousQuery]]
* may be changed before/when you process the event. E.g., you may find [[ContinuousQuery]]
* is terminated when you are processing [[QueryProgress]].
*/
def onQueryProgress(queryProgress: QueryProgress): Unit
/** Called when a query is stopped, with or without error */
def onQueryTerminated(queryTerminated: QueryTerminated): Unit
}
/**
* :: Experimental ::
* Companion object of [[ContinuousQueryListener]] that defines the listener events.
*/
@Experimental
object ContinuousQueryListener {
/** Base type of [[ContinuousQueryListener]] events */
trait Event
/** Event representing the start of a query */
class QueryStarted private[sql](val query: ContinuousQuery) extends Event
/** Event representing any progress updates in a query */
class QueryProgress private[sql](val query: ContinuousQuery) extends Event
/** Event representing that termination of a query */
class QueryTerminated private[sql](val query: ContinuousQuery) extends Event
}
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