splitting DFS version number
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Key: HADOOP-807
URL: http://issues.apache.org/jira/browse/HADOOP-807
Project: Hadoop
Issue Type: Bug
Components: dfs
Reporter: dhruba borthakur
Assigned To: dhruba borthakur
In the current code, there is a enum named DFS_CURRENT_VERSION. It is being
used for three different purposes:
1. It is stored in the fsimage and represents the format of the fsimage.
2. It is stored in the "storage" file by the Datanodes. Thus, it represents the
format of data on Datanodes.
3. It is used as a version of the Datanode Protocol.
The current implementation makes it difficult to change the fsimage format
without affecting the Datanode Protocol. My proposal is to introduce three new
constants, one for each of the functionality described above.
In the current code, we have:
public static final int DFS_CURRENT_VERSION = -3;
Instead, we can have:
public static final int DFS_FSIMAGE_CURRENT_VERSION = -3;
public static final int DFS_DATANODEPROTOCOL_CURRENT_VERSION = -3;
public static final int DFS_DATASTORAGE_CURRENT_VERSION = -3;
The first one is associated with the format of the fsimage/edits; the second
one is associated with the communication procotol between the namenode and the
datanode; the third one is associated with the format of the datastore on the
datanodes (e.g. directory fanout).
Please comment.
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