HI Kurt, Thanks for you reply! I’ve already solved the problem!
Desheng Zhang E-mail: gzzhangdesh...@corp.netease.com; > On Jul 13, 2017, at 17:10, Kurt Young <ykt...@gmail.com> wrote: > > Hi, > > Regarding 1. State is some kind of value bound with your current key of > KeyedStream. ListState is list like state, it can be used as a List, you can > add value to it, and get a iterator from it. If you have multiple ArrayList > to maintain, you can declare multiple states, each with different names. > > Regarding 2. You should change your MapFunction to RichMapFunction to be able > to declare and use states. > > Best, > Kurt > > On Thu, Jul 13, 2017 at 2:22 PM, ZalaCheung <gzzhangdesh...@corp.netease.com > <mailto:gzzhangdesh...@corp.netease.com>> wrote: > 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 > <mailto:gzzhangdesh...@corp.netease.com>; > >> On Jul 13, 2017, at 13:23, Kurt Young <ykt...@gmail.com >> <mailto: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>; >> >> > >
