It is not reflection that is the issue here but use of an RDD
transformation "featureKeyClassPair.map" inside "lines.mapToPair".
>From the code snippet you have sent it is not very clear if
getFeatureScore(id,data)
invokes executeFeedFeatures, but if that is the case it is not very obvious
that “data” is a supposed to be huge and thus need to be PairRDD and if it
is not you do not need to use the JavaPairRDD<String, String>, instead use
a Map<String, String> and return a List<Double>.
If it data is huge and has to be PairRDD pull out the logic to build the
data PairRDD and then invoke map function on that RDD.
- Ankur
On Mon, Sep 14, 2015 at 12:43 PM, <rachana.srivast...@thomsonreuters.com>
wrote:
> Thanks so much Ajay and Ankur for your input.
>
>
>
> What we are trying to do is following: I am trying to invoke a class
> using Java reflection to get the result
>
>
>
> *THIS WORKS FINE*
>
> public static void main(String[] args) throws Exception {
>
> final JavaSparkContext jsc = new JavaSparkContext(sparkConf);
>
> ...
>
> METHOD THAT I AM TRYING TO INVOKE USING REFLECTION
>
> JavaPairDStream<String, String> urlFeatureScore = lines.mapToPair( new
> PairFunction<String, String, String>() {
>
> public Tuple2<String, String> call(final String urlString) throws
> Exception {
>
> String featureScore = getFeatureScore(id,data);
>
> return new Tuple2<String, String>(urlString, featureScore);
>
> }
>
> });
>
> ...
>
> *REPLACED WITH METHOD INVOKED USING REFLECTION DOES NOT WORK ERROR MESSAGE
> BELOW.*
>
> > executeFeedFactories2(featureClassName, featureParam, featureData)
>
> jssc.start();
>
> jssc.awaitTermination();
>
> }
>
>
>
> *Splitting the same work to Class using Reflection does not work:*
>
>
>
> private static JavaRDD<Double> executeFeedFactories2(String
> featureClassName, Map<String, String> featureParam,JavaPairRDD<String,
> String> featureData) throws Exception {
>
> Class featureClass = Class.forName(MyClass);
>
> Method m = featureClass.getMethod("executeFeedFeatures",
> Map.class, JavaPairRDD.class);
>
> JavaRDD<Double> score = ( JavaRDD<Double> )
> m.invoke(featureClass.newInstance(), featureParam,featureData);
>
> return score;
>
> }
>
>
>
> public class MyClass{
>
> public static JavaRDD<Double> executeFeedFeatures(*Map*
> featureParamMap,JavaPairRDD<String,
> String> featureKeyClassPair ){
>
> featureScoreRDD = featureKeyClassPair.map(new Function<Tuple2<String,
> String>, Double>() {
>
> public Double call(Tuple2<String, String> keyValue) {
>
> …
>
> }
>
> });
>
> return featureScoreRDD;
>
> }
>
>
>
> }
>
>
>
> Thanks again for all your help and advice.
>
>
>
> Regards,
>
>
>
> Rachana
>
>
>
> *From:* Ajay Singal [mailto:asinga...@gmail.com]
> *Sent:* Monday, September 14, 2015 12:20 PM
> *To:* Rachana Srivastava; Ankur Srivastava
> *Cc:* u...@spark.apache.org; dev@spark.apache.org; Ajay Singal
> *Subject:* Re: JavaRDD using Reflection
>
>
>
> Hello Rachana,
>
>
>
> The easiest way would be to start with creating a 'parent' JavaRDD and run
> different filters (based on different input arguments) to create respective
> 'child' JavaRDDs dynamically.
>
>
>
> Notice that the creation of these children RDDs is handled by the
> application driver.
>
>
>
> Hope this helps!
>
> Ajay
>
>
>
> On Mon, Sep 14, 2015 at 1:21 PM, Ankur Srivastava <
> ankur.srivast...@gmail.com> wrote:
>
> Hi Rachana
>
>
>
> I didn't get you r question fully but as the error says you can not
> perform a rdd transformation or action inside another transformation. In
> your example you are performing an action "rdd2.values.count()" in side
> the "map" transformation. It is not allowed and in any case this will be
> very inefficient too.
>
>
>
> you should do something like this:
>
>
>
> final long rdd2_count = rdd2.values.count()
>
> rdd1.map(x => rdd2_count * x)
>
>
>
> Hope this helps!!
>
>
>
> - Ankur
>
>
>
> On Mon, Sep 14, 2015 at 9:54 AM, Rachana Srivastava <
> rachana.srivast...@markmonitor.com> wrote:
>
> Hello all,
>
>
>
> I am working a problem that requires us to create different set of JavaRDD
> based on different input arguments. We are getting following error when we
> try to use a factory to create JavaRDD. Error message is clear but I am
> wondering is there any workaround.
>
>
>
> *Question: *
>
> How to create different set of JavaRDD based on different input arguments
> dynamically. Trying to implement something like factory pattern.
>
>
>
> *Error Message: *
>
> RDD transformations and actions can only be invoked by the driver, not
> inside of other transformations; for example, rdd1.map(x =>
> rdd2.values.count() * x) is invalid because the values transformation and
> count action cannot be performed inside of the rdd1.map transformation. For
> more information, see SPARK-5063.
>
>
>
> Thanks,
>
>
>
> Rachana
>
>
>
>
>
