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https://issues.apache.org/jira/browse/GEARPUMP-24?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15259884#comment-15259884
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ASF GitHub Bot commented on GEARPUMP-24:
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GitHub user manuzhang opened a pull request:
https://github.com/apache/incubator-gearpump/pull/7
GEARPUMP-24, refactor DataSource API
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/manuzhang/incubator-gearpump data_source
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/incubator-gearpump/pull/7.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #7
----
commit 7d92ad49524c92ac12901c4c73d88ef44617795b
Author: manuzhang <[email protected]>
Date: 2016-03-24T04:05:23Z
GEARPUMP-24, refactor DataSource API
----
> refactor DataSource API
> -----------------------
>
> Key: GEARPUMP-24
> URL: https://issues.apache.org/jira/browse/GEARPUMP-24
> Project: Apache Gearpump
> Issue Type: Improvement
> Components: streaming
> Affects Versions: 0.8.0
> Reporter: Manu Zhang
> Assignee: Manu Zhang
> Fix For: 0.8.1
>
>
> From [https://github.com/gearpump/gearpump/issues/2013]:
> The current DataSource API
> {code}
> trait DataSource extends java.io.Serializable {
> /**
> * open connection to data source
> * invoked in onStart() method of
> [[io.gearpump.streaming.source.DataSourceTask]]
> * @param context is the task context at runtime
> * @param startTime is the start time of system
> */
> def open(context: TaskContext, startTime: Option[TimeStamp]): Unit
> /**
> * read a number of messages from data source.
> * invoked in each onNext() method of
> [[io.gearpump.streaming.source.DataSourceTask]]
> * @param batchSize max number of messages to read
> * @return a list of messages wrapped in [[io.gearpump.Message]]
> */
> def read(batchSize: Int): List[Message]
> /**
> * close connection to data source.
> * invoked in onStop() method of
> [[io.gearpump.streaming.source.DataSourceTask]]
> */
> def close(): Unit
> }
> {code}
> has several issues
> 1. read returns a scala list of Message which is unfriendly to Java
> DataSources. Same for Option parameter in open
> 2. the number of read messages may not be the same as the passed in batchSize
> which leaves uncertainty to users (users may access out of boundary list
> positions)
> 3. to return a list an extra buffer could be needed in read (e.g.
> KafkaSource) which is not best for performance
> Update:
> I'd like to add a "getWatermark" interface that helps to fix GEARPUMP-32
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