[ https://issues.apache.org/jira/browse/SPARK-20928?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Reynold Xin updated SPARK-20928: -------------------------------- Attachment: (was: Continuous Processing in Structured Streaming Design Sketch.pdf) > SPIP: Continuous Processing Mode for Structured Streaming > --------------------------------------------------------- > > Key: SPARK-20928 > URL: https://issues.apache.org/jira/browse/SPARK-20928 > Project: Spark > Issue Type: Improvement > Components: Structured Streaming > Affects Versions: 2.2.0 > Reporter: Michael Armbrust > Labels: SPIP > Attachments: Continuous Processing in Structured Streaming Design > Sketch.pdf > > > Given the current Source API, the minimum possible latency for any record is > bounded by the amount of time that it takes to launch a task. This > limitation is a result of the fact that {{getBatch}} requires us to know both > the starting and the ending offset, before any tasks are launched. In the > worst case, the end-to-end latency is actually closer to the average batch > time + task launching time. > For applications where latency is more important than exactly-once output > however, it would be useful if processing could happen continuously. This > would allow us to achieve fully pipelined reading and writing from sources > such as Kafka. This kind of architecture would make it possible to process > records with end-to-end latencies on the order of 1 ms, rather than the > 10-100ms that is possible today. > One possible architecture here would be to change the Source API to look like > the following rough sketch: > {code} > trait Epoch { > def data: DataFrame > /** The exclusive starting position for `data`. */ > def startOffset: Offset > /** The inclusive ending position for `data`. Incrementally updated > during processing, but not complete until execution of the query plan in > `data` is finished. */ > def endOffset: Offset > } > def getBatch(startOffset: Option[Offset], endOffset: Option[Offset], > limits: Limits): Epoch > {code} > The above would allow us to build an alternative implementation of > {{StreamExecution}} that processes continuously with much lower latency and > only stops processing when needing to reconfigure the stream (either due to a > failure or a user requested change in parallelism. -- This message was sent by Atlassian JIRA (v6.4.14#64029) --------------------------------------------------------------------- To unsubscribe, e-mail: issues-unsubscr...@spark.apache.org For additional commands, e-mail: issues-h...@spark.apache.org