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Restart the Hadoop cluster and report an error when debugging hdfs api with Eclipse:

[WARNING] java.lang.NullPointerException at org.conan.kafka.HdfsUtil.batchWrite (HdfsUtil.java:50) at org.conan.kafka.SingleTopicConsumer.run (SingleTopicConsumer.java:144) at java.lang.Thread.run (Thread.java:745) at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:617) at java.lang.Thread.run (Thread.java:745)

Find line 50 of HdfsUtil.java

Os.write (buff, 0, buff.length)

I found that I reported an error when I was writing, and then I messed around for a while, but I didn't find the reason. Later, I wondered if it might be a permission problem (the computer is not an administrator, but the hadoop cluster runs as root), but I have previously changed the permissions of the hdfs folder to 777. Anyway, try again, hdfs dfs-chmod-R 777 / input, and then debug again, OK again.

So the question is, does the Hadoop cluster have to modify the permissions of files (folders) after each restart (without namenode format)?

According to practice, it should be.

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