[jira] [Created] (HDFS-13313) FSEditLogOp.toString() throws NullPointerException

["Tianyi Wang (JIRA)" <ji...@apache.org>]

Tianyi Wang created HDFS-13313:
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             Summary: FSEditLogOp.toString() throws NullPointerException
                 Key: HDFS-13313
                 URL: https://issues.apache.org/jira/browse/HDFS-13313
             Project: Hadoop HDFS
          Issue Type: Bug
    Affects Versions: 3.0.2
            Reporter: Tianyi Wang


In some subclasses of FSEditLogOp, toString() [uses dot (.) operator on some could-be-null fields|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java#L3896]. Those fields could be set to null by [resetSubFields()|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogOp.java#L3857]. This error can be hit by turning on debug logging: toString() is called in [FSEditLogAsync.logSync()|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogAsync.java#L128] with debug logging and reset() is called in [doEditTransaction()|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLog.java#L484] when the operation is executed asynchronously.

Proposed change: Avoid "field of field" access in toString() and use StringBuilder.append(field) because those fields have toString() themselves, and it would append "null" to the string if 'field' is null. 

 



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