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https://issues.apache.org/jira/browse/HDFS-14172?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16728581#comment-16728581
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Xiang Li commented on HDFS-14172:
---------------------------------
We met the NPE under the scenario that: we applied the patch of HDFS-7076, to
allow users to add custom storage polices. It will add new section called
"STORAGE_POLICIES" into fsimage. When we fall back to use the code without
HDFS-7076, NameNode could not get started due to NPE, and Offline Image Viewer
has the same error, like:
{code}
DEBUG offlineImageViewer.FSImageHandler: Loading section STORAGE_POLICIES
length: 149
{code}
> Return a default SectionName to avoid NPE
> -----------------------------------------
>
> Key: HDFS-14172
> URL: https://issues.apache.org/jira/browse/HDFS-14172
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Xiang Li
> Assignee: Xiang Li
> Priority: Minor
>
> In FSImageFormatProtobuf.SectionName#fromString(), as follows:
> {code:java}
> public static SectionName fromString(String name) {
> for (SectionName n : values) {
> if (n.name.equals(name))
> return n;
> }
> return null;
> }
> {code}
> When the code meets an unknown section from the fsimage, the function will
> return null. Callers always operates the return value with a "switch" clause,
> like FSImageFormatProtobuf.Loader#loadInternal(), as:
> {code:java}
> switch (SectionName.fromString(n))
> {code}
> NPE will be thrown here.
> Shall we add a default section name in the enum of SectionName, like
> "UNKNOWN", to steer clear of NPE?
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