Hi Kurt, Thanks! Your link helps me a lot.
I still have some problems after I glance on the document. As you can see from my first email, I tried to implement a mapfunction class in flink. I actually have 3 arraylists to be maintain at this map operator. I think the Using managed keyed state part of the document fits my requirement. But I am still confused about how to maintain my ListStates 1. Does each Array List has its own ListState? 2. I am not clear with the open function on the example given by Flink. I wonder how I can initialize my arraylists with ListStateDescriptor. Desheng Zhang E-mail: gzzhangdesh...@corp.netease.com; > On Jul 13, 2017, at 13:23, Kurt Young <ykt...@gmail.com> wrote: > > Hi, > > I think you can use State to achieve your goal: > https://ci.apache.org/projects/flink/flink-docs-release-1.3/dev/stream/state.html > > <https://ci.apache.org/projects/flink/flink-docs-release-1.3/dev/stream/state.html> > > Best, > Kurt > > On Thu, Jul 13, 2017 at 1:14 PM, ZalaCheung <gzzhangdesh...@corp.netease.com > <mailto:gzzhangdesh...@corp.netease.com>> wrote: > Hi all, > > I am stuck with a problem. I have a stream, I want keyby it and then do a map > function on it. But for each map operator, I want to maintain a variable for > it. Is that possible? I tried a naive version on local IntelliJ IDE and it > works. But I got nullpointerException while trying to run it on a cluster. > > Here is the pseudo code for my naive version, wish it will help you guys > understand my question. > > public class anomalydetection{ > private static List<TimeSeries> queue; > public static void main(String[] args)throws Exception{ > initialize(); > getStreamExecutionEnvironment(); > DataStream input = ... > stream.keyby("some key").map( > MapFunction(){ > if(queue.size() < some_num){ > queue.add() > //do something > } > else{ > //dosomething > } > } > ) > > public void initialize(){ > queue = new ArrayList<>(); > } > } > > when I try to get the size of the arraylist, I get a NullPointerException. > Beside that, I want to maintain a list for each map operator after I group > the stream by some key. > > > Is that possible to do what I want in Flink? > > Desheng Zhang > > E-mail: gzzhangdesh...@corp.netease.com > <mailto:gzzhangdesh...@corp.netease.com>; > >
