flume taildir 启动异常LifecycleSupervisor$MonitorRunnable.run

1、异常关键信息：

LifecycleSupervisor$MonitorRunnable.run(LifecycleSupervisor.java:251)] Unable to start PollableSourceRunner: { source:Taildir source: { positionFile: /poros/tyxTest/taildir_position.json
java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2

 2、异常全部信息：

[ERROR - org.apache.flume.lifecycle.LifecycleSupervisor$MonitorRunnable.run(LifecycleSupervisor.java:251)] Unable to start PollableSourceRunner: { source:Taildir source: { positionFile: /poros/tyxTest/taildir_position.json, skipToEnd: true, byteOffsetHeader: false, idleTimeout: 120000, writePosInterval: 3000 } counterGroup:{ name:null counters:{} } } - Exception follows.
java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2
    at com.google.gson.stream.JsonReader.expect(JsonReader.java:339)
    at com.google.gson.stream.JsonReader.beginArray(JsonReader.java:306)
    at org.apache.flume.source.taildir.ReliableTaildirEventReader.loadPositionFile(ReliableTaildirEventReader.java:111)
    at org.apache.flume.source.taildir.ReliableTaildirEventReader.(ReliableTaildirEventReader.java:96)
    at org.apache.flume.source.taildir.ReliableTaildirEventReader.(ReliableTaildirEventReader.java:49)
    at org.apache.flume.source.taildir.ReliableTaildirEventReader$Builder.build(ReliableTaildirEventReader.java:355)
    at org.apache.flume.source.taildir.TaildirSource.start(TaildirSource.java:105)
    at org.apache.flume.source.PollableSourceRunner.start(PollableSourceRunner.java:71)
    at org.apache.flume.lifecycle.LifecycleSupervisor$MonitorRunnable.run(LifecycleSupervisor.java:249)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

 3、解决方案（最简单）：

删掉配置文件的
    a1.sources.r1.positionFile = /home/hadoop/taildir_position.json

4、原因： 

上述配置的作用是记录采集文件的读取索引和大小的，是需要flume自动生成和修改的，遇到上面的错，多数是自己创建了此文件，没有细看官网说明（me）

    ~/.flume/taildir_position.json    File in JSON format to record the inode, the absolute path and the last position of each tailing file.