Haohui Mai created HDFS-8249:
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Summary: Separate HdfsConstants into the client and the server
side class
Key: HDFS-8249
URL: https://issues.apache.org/jira/browse/HDFS-8249
Project: Hadoop HDFS
Issue Type: Sub-task
Reporter: Haohui Mai
Assignee: Haohui Mai
The constants in {{HdfsConstants}} are used by both the client side and the
server side. There are two types of constants in the class:
1. Constants that are used internally by the servers or not part of the APIs.
These constants are free to evolve without breaking compatibilities. For
example, {{MAX_PATH_LENGTH}} is used by the NN to enforce the length of the
path does not go too long. Developers are free to change the name of the
constants and to move it around if necessary.
1. Constants that are used by the clients, but not parts of the APIs. For
example, {{QUOTA_DONT_SET}} represents an unlimited quota. The value is part of
the wire protocol but the value is not. Developers are free to rename the
constants but are not allowed to change the value of the constants.
1. Constants that are parts of the APIs. For example, {{SafeModeAction}} is
used in {{DistributedFileSystem}}. Changing the name / value of the constant
will break binary compatibility, but not source code compatibility.
This jira proposes to separate the above three types of constants into
different classes:
* Creating a new class {{HdfsConstantsServer}} to hold the first type of
constants.
* Move {{HdfsConstants}} into the {{hdfs-client}} package. The work of
separating the second and the third types of constants will be postponed in a
separate jira.
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