Spark Structured Streaming框架(5)之进程管理

　　Structured Streaming提供一些API来管理Streaming对象。用户可以通过这些API来手动管理已经启动的Streaming，保证在系统中的Streaming有序执行。

1. StreamingQuery

　　在调用DataStreamWriter方法的start启动Streaming后，会返回一个StreamingQuery对象。所以用户就可以通过这个对象来管理Streaming。

如下所示：

val query = df.writeStream.format("console").start() // get the query object

query.id // get the unique identifier of the running query that persists across restarts from checkpoint data

query.runId // get the unique id of this run of the query, which will be generated at every start/restart

query.name // get the name of the auto-generated or user-specified name

query.explain() // print detailed explanations of the query

query.stop() // stop the query

query.awaitTermination() // block until query is terminated, with stop() or with error

query.exception // the exception if the query has been terminated with error

query.recentProgress // an array of the most recent progress updates for this query

query.lastProgress // the most recent progress update of this streaming query

2. StreamingQueryManager

　　Structured Streaming提供了另外一个管理Streaming的接口是：StreamingQueryManager。用户可以通过SparkSession对象的streams方法获得。

如下所示：

val spark: SparkSession = ...

val streamManager = spark.streams()

streamManager.active // get the list of currently active streaming queries

streamManager.get(id) // get a query object by its unique id

streamManager.awaitAnyTermination() // block until any one of them terminates

3. 参考文献

[1]. Structured Streaming Programming Guide.

[2]. Kafka Integration Guide.