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https://issues.apache.org/jira/browse/HDFS-17463?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17837678#comment-17837678
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ASF GitHub Bot commented on HDFS-17463:
---------------------------------------
XbaoWu commented on code in PR #6736:
URL: https://github.com/apache/hadoop/pull/6736#discussion_r1567198629
##########
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/AclEntryStatusFormat.java:
##########
@@ -47,7 +47,7 @@ public enum AclEntryStatusFormat implements
LongBitFormat.Enum {
private static final AclEntryType[] ACL_ENTRY_TYPE_VALUES =
AclEntryType.values();
- private final LongBitFormat BITS;
Review Comment:
Because the “private” BITS cannot be import by FSImageFormatPBINode. This
change may not be appropriate, I will write a getter for BITS is a better
solution.
> Support the switch StringTable Split ID feature
> -----------------------------------------------
>
> Key: HDFS-17463
> URL: https://issues.apache.org/jira/browse/HDFS-17463
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Affects Versions: 3.2.0, 3.3.5, 3.3.3, 3.3.4
> Reporter: wangzhihui
> Priority: Major
> Labels: pull-request-available
> Attachments: Image_struct.png, error.png
>
>
> desc:
> *
> Hadoop 3.2 introduced optimization features for HDFS StringTable
> (b60ca37914b22550e3630fa02742d40697decb3), It resulted in lower versions of
> Hadoop upgraded to 3.2 and later versions not supporting downgrade
> operations.
> !error.png!
> * This issue has also been discussed in HDFS-14831, and it is recommended to
> revert the feature, but it cannot fundamentally solve the problem。
> *
> Therefore, we have added an optimization to support downgrading
>
> Solution:
> * First, we will add the "dfs. image. save. splitId. stringTable" conf
> switch "StringTable optimization feature" is enabled
> * When the conf value is false, an Image file compatible with lower versions
> of HDFS is generated to support downgrading.
> *
> The difference in HDFS Image file format between Hadoop 3.1.1 and Hadoop 3.2
> is shown in the following figure.
> * With the sub-sections feature introduced in HDFS-14617, Protobuf can
> support compatible reading.
> *
> The data structure causing incompatible differences is mainly StringTable.
> !Image_struct.png|width=396,height=163!
> * In "dfs.image.save.splitId.stringTable = false " the Id generation order
> of StringTable starts from 0 to Integer.Max. When true, the Id value range
> follows the latest rules.
>
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