问题描述
我希望将Spark Stream的输出在翻滚窗口的末尾而不是在批处理间隔发送到接收器。
Dataset<Row> sqlResult = session.sql("select window,user,sum(amount) as amount from users where type = 'A' group by window(timestamp,'1 minute','1 minute'),user");
sqlResult = sqlResult.select(to_json(struct("window","user","amount")).as("value"));
StreamingQuery query = sqlResult.writeStream()
.format("kafka")
.option("kafka.bootstrap.servers","localhost:9092")
.option("topic","aggregated-topic")
.option("checkpointLocation","c:/tmp")
.outputMode(OutputMode.Update())
.start();
当我在 1分钟的窗口内为特定用户发送多条记录时,我希望在1分钟结束时将这些事件的总和。
但是我在输出的Kafka流上获得了多个输出,并且写入了间歇性的聚合。
例如
我将在一分钟内以下列间隔发送以下7条记录。
>{ "id" : 123,"type": "A","user": "tukaram","amount": 10}
>{ "id" : 123,"amount": 10}
我得到的输出是这个:
{"window":{"start":"2020-09-18T14:35:00.000+05:30","end":"2020-09-18T14:36:00.000+05:30"},"user":"tukaram","amount":10.0}
{"window":{"start":"2020-09-18T14:35:00.000+05:30","amount":20.0}
{"window":{"start":"2020-09-18T14:35:00.000+05:30","amount":40.0}
{"window":{"start":"2020-09-18T14:35:00.000+05:30","amount":60.0}
{"window":{"start":"2020-09-18T14:35:00.000+05:30","amount":70.0}
我想要的是分钟结束时的单个输出,
{"window":{"start":"2020-09-18T14:35:00.000+05:30","amount":70.0}
我该如何实现?
解决方法
将流写入接收器时,您需要设置处理触发器。
使用具有适当触发值的DataStreamWriter的.trigger(Trigger.ProcessingTime)。
StreamingQuery query = sqlResult.writeStream()
.trigger(Trigger.ProcessingTime("1 minute")) //this