采用flume的Spooling Directory Source，突然遇到下面的错误

(org.apache.flume.source.SpoolDirectoryExtSource2$SpoolDirectoryRunnable.run:277)  - FATAL: Spool Directory source source1: { spoolDir: /home/work/local/log }: Uncaught exception in SpoolDirectorySource thread. Restart or reconfigure Flume to continue processing.
java.lang.NullPointerException
    at org.apache.avro.io.ResolvingDecoder.readLong(ResolvingDecoder.java:159)
    at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:157)
    at org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:177)
    at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:148)
    at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:139)
    at org.apache.avro.file.DataFileStream.next(DataFileStream.java:233)
    at org.apache.flume.serialization.DurablePositionTracker.initReader(DurablePositionTracker.java:171)
    at org.apache.flume.serialization.DurablePositionTracker.<init>(DurablePositionTracker.java:158)
    at org.apache.flume.serialization.DurablePositionTracker.getInstance(DurablePositionTracker.java:76)
    at org.apache.flume.client.avro.ReliableSpoolingFileEventExtReader2.openFile(ReliableSpoolingFileEventExtReader2.java:561)
    at org.apache.flume.client.avro.ReliableSpoolingFileEventExtReader2.getNextFile(ReliableSpoolingFileEventExtReader2.java:511)
    at org.apache.flume.client.avro.ReliableSpoolingFileEventExtReader2.readEvents(ReliableSpoolingFileEventExtReader2.java:264)
    at org.apache.flume.source.SpoolDirectoryExtSource2$SpoolDirectoryRunnable.run(SpoolDirectoryExtSource2.java:252)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:304)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:178)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)

重启flume 后发现问题依旧。试验把flume 采集的日志放到新目录，重启flume采集新目录发现没问题了。看来是旧目录/home/work/local/log 有文件变动造成的。

例如 有.flumespool隐藏目录，该目录下有文件.flumespool-main.meta隐藏文件，用来记录flume读取文件的位置，发现该记录停止在flume出问题的时间。再查看其它正常运行的机器的相同路径及文件，并没有发现该文件，于是将该文件移到其它目录下，重启flume，此时发现flume成功运行！