到目前为止还没有找到解决我的特定问题的方法。它至少不起作用。这让我很疯狂。这个特殊的组合在谷歌空间中似乎并不多。据我所知，我的错误发生在作业进入映射器时。该作业的输入是 avro 模式的输出，虽然我也尝试过未压缩，但它是用 deflate 压缩的。

阿夫罗:1.7.7 Hadoop:2.4.1

我收到此错误，但我不确定原因。这是我的工作，mapper 和 reduce。映射器进来时发生错误。

示例未压缩的 Avro 输入文件(StockReport.SCHEMA 以这种方式定义)

{"day": 3, "month": 2, "year": 1986, "stocks": [{"symbol": "AAME", "timestamp": 507833213000, "dividend": 10.59}]}

工作

@Override
public int run(String[] strings) throws Exception {
    Job job = Job.getInstance();
    job.setJobName("GenerateGraphsJob");
    job.setJarByClass(GenerateGraphsJob.class);

    configureJob(job);

    int resultCode = job.waitForCompletion(true) ? 0 : 1;

    return resultCode;
}

private void configureJob(Job job) throws IOException {
    try {
        Configuration config = getConf();
        Path inputPath = ConfigHelper.getChartInputPath(config);
        Path outputPath = ConfigHelper.getChartOutputPath(config);

        job.setInputFormatClass(AvroKeyInputFormat.class);
        AvroKeyInputFormat.addInputPath(job, inputPath);
        AvroJob.setInputKeySchema(job, StockReport.SCHEMA$);


        job.setMapperClass(StockAverageMapper.class);
        job.setCombinerClass(StockAverageCombiner.class);
        job.setReducerClass(StockAverageReducer.class);

        FileOutputFormat.setOutputPath(job, outputPath);

    } catch (IOException | ClassCastException e) {
        LOG.error("An job error has occurred.", e);
    }
}

映射器:

public class StockAverageMapper extends
        Mapper<AvroKey<StockReport>, NullWritable, StockYearSymbolKey, StockReport> {
    private static Logger LOG = LoggerFactory.getLogger(StockAverageMapper.class);

private final StockReport stockReport = new StockReport();
private final StockYearSymbolKey stockKey = new StockYearSymbolKey();

@Override
protected void map(AvroKey<StockReport> inKey, NullWritable ignore, Context context)
        throws IOException, InterruptedException {
    try {
        StockReport inKeyDatum = inKey.datum();
        for (Stock stock : inKeyDatum.getStocks()) {
            updateKey(inKeyDatum, stock);
            updateValue(inKeyDatum, stock);
            context.write(stockKey, stockReport);
        }
    } catch (Exception ex) {
        LOG.debug(ex.toString());
    }
}

map 输出键的架构:

    {
  "namespace": "avro.model",
  "type": "record",
  "name": "StockYearSymbolKey",
  "fields": [
    {
      "name": "year",
      "type": "int"
    },
    {
      "name": "symbol",
      "type": "string"
    }
  ]
}

堆栈跟踪:

java.lang.Exception: java.lang.IncompatibleClassChangeError: Found interface org.apache.hadoop.mapreduce.TaskAttemptContext, but class was expected
    at org.apache.hadoop.mapred.LocalJobRunner$Job.runTasks(LocalJobRunner.java:462)
    at org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:522)
Caused by: java.lang.IncompatibleClassChangeError: Found interface org.apache.hadoop.mapreduce.TaskAttemptContext, but class was expected
    at org.apache.avro.mapreduce.AvroKeyInputFormat.createRecordReader(AvroKeyInputFormat.java:47)
    at org.apache.hadoop.mapred.MapTask$NewTrackingRecordReader.<init>(MapTask.java:492)
    at org.apache.hadoop.mapred.MapTask.runNewMapper(MapTask.java:735)
    at org.apache.hadoop.mapred.MapTask.run(MapTask.java:340)
    at org.apache.hadoop.mapred.LocalJobRunner$Job$MapTaskRunnable.run(LocalJobRunner.java:243)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)

编辑:这并不重要，但我正在努力将其减少为我可以从中创建 JFreeChart 输出的数据。没有通过映射器，所以不应该相关。

最佳答案

问题是 org.apache.hadoop.mapreduce.TaskAttemptContext 是 class in Hadoop 1但变成了interface in Hadoop 2 .

这就是为什么依赖于 Hadoop 库的库需要为 Hadoop 1 和 Hadoop 2 分别编译 jarfile 的原因之一。根据你的堆栈跟踪，你似乎以某种方式得到了一个 Hadoop1 编译的 Avro jarfile，尽管使用 Hadoop 2.4.1 运行。

download mirrors for Avro为 avro-mapred-1.7.7-hadoop1.jar 提供很好的单独下载对比avro-mapred-1.7.7-hadoop2.jar .

关于java - 找到接口(interface) org.apache.hadoop.mapreduce.TaskAttemptContext，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/29448222/