Example usage for org.apache.hadoop.mapreduce TaskAttemptContext getReducerClass

Introduction

In this page you can find the example usage for org.apache.hadoop.mapreduce TaskAttemptContext getReducerClass.

Prototype

public Class<? extends Reducer<?, ?, ?, ?>> getReducerClass() throws ClassNotFoundException;

Source Link

Document

Get the Reducer class for the job.

Usage

From source file:org.apache.tez.mapreduce.processor.reduce.ReduceProcessor.java

License:Apache License

void runNewReducer(JobConf job, final MRTaskReporter reporter, OrderedGroupedInputLegacy input,
        RawComparator comparator, Class keyClass, Class valueClass, final KeyValueWriter out)
        throws IOException, InterruptedException, ClassNotFoundException, TezException {

    // make a task context so we can get the classes
    org.apache.hadoop.mapreduce.TaskAttemptContext taskContext = getTaskAttemptContext();

    // make a reducer
    org.apache.hadoop.mapreduce.Reducer reducer = (org.apache.hadoop.mapreduce.Reducer) ReflectionUtils
            .newInstance(taskContext.getReducerClass(), job);

    // wrap value iterator to report progress.
    final TezRawKeyValueIterator rawIter = input.getIterator();
    TezRawKeyValueIterator rIter = new TezRawKeyValueIterator() {
        public void close() throws IOException {
            rawIter.close();//from   ww w .  j  av a 2 s . c om
        }

        public DataInputBuffer getKey() throws IOException {
            return rawIter.getKey();
        }

        public Progress getProgress() {
            return rawIter.getProgress();
        }

        @Override
        public boolean isSameKey() throws IOException {
            return rawIter.isSameKey();
        }

        public DataInputBuffer getValue() throws IOException {
            return rawIter.getValue();
        }

        public boolean next() throws IOException {
            boolean ret = rawIter.next();
            reporter.setProgress(rawIter.getProgress().getProgress());
            return ret;
        }
    };

    org.apache.hadoop.mapreduce.RecordWriter trackedRW = new org.apache.hadoop.mapreduce.RecordWriter() {

        @Override
        public void write(Object key, Object value) throws IOException, InterruptedException {
            out.write(key, value);
        }

        @Override
        public void close(TaskAttemptContext context) throws IOException, InterruptedException {
        }
    };

    org.apache.hadoop.mapreduce.Reducer.Context reducerContext = createReduceContext(reducer, job,
            taskAttemptId, rIter, reduceInputKeyCounter, reduceInputValueCounter, trackedRW, committer,
            reporter, comparator, keyClass, valueClass);

    reducer.run(reducerContext);

    // Set progress to 1.0f if there was no exception,
    reporter.setProgress(1.0f);

    trackedRW.close(reducerContext);
}

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