HDDS-4491. Deprecate raft.server.rpcslowness.timeout config key

[wycccccc]

What changes were proposed in this pull request?

Add old config key rpcslowness.timeout to handle deprecated configs

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-4491

How was this patch tested?

Added unit test.

[adoroszlai]

Thanks @wycccccc for working on this. Unfortunately the patch is not enough to handle deprecated configs.

1. rpc.slowness.timeout is only part of the config key name. It is defined in

   ozone/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/conf/DatanodeRatisServerConfig.java

   Line 91 in a4cd12c

   @Config(key = "rpc.slowness.timeout",

   and should be used together with its prefix, which comes from

   ozone/hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/conf/DatanodeRatisServerConfig.java

   Lines 34 to 35 in a4cd12c

   	@ConfigGroup(prefix = HDDS_DATANODE_RATIS_PREFIX_KEY + "."
   	+ RaftServerConfigKeys.PREFIX)

2. The ConfigurationProvider changed in this patch is for Recon, but the config key belongs to Datanode, another component of Ozone. The DeprecationDelta should be added somewhere in org.apache.hadoop.hdds.conf in hadoop-hdds. (Sidenote: I think DatanodeRatis*Config classes belong to hadoop-hdds/container-service, not hadoop-hdds/framework.)

[wycccccc]

Thank @adoroszlai for your suggestion, I will try to modify it correctly.

[adoroszlai]

Thanks @wycccccc for updating the patch. The change looks good to achieve the desired goal. I think cohesion might be improved by adding the deprecation in RaftServerConfigKeys instead of OzoneConfiguration, but it may have downsides, too, so I'm OK with the current version.

Can you please fix checkstyle violations?

[wycccccc]

I have fixed checkstyle violations.Thanks @adoroszlai for your suggestion, it helped me a lot.

[adoroszlai]

Thanks @wycccccc for the contribution.