Change the "Master" nomenclature

[tlfeng]

Is your feature request related to a problem? Please describe.
OpenSearch repository is going to replace the terminology "master"with "cluster manager".
issue: opensearch-project/OpenSearch#472 (comment), with the plan for its terminology replacement.

Although the existing usages with "master" will be supported in OpenSearch version 2.x to keep the backwards compatibility, please prepare for the nomenclature change in advance, and replace all the usages with "master" terminology in the code base.
All the OpenSearch REST APIs and settings that contain "master" terminology will be deprecated in 2.0, and alternative usages will be added.

Describe the solution you'd like
Replace the terminology "master" with "cluster manager".

When being compatible with OpenSearch 2.0:

• Replace "master" in code comment and internal variable / method name.
• Replace OpenSearh REST API that contains "master" with the provided inclusive REST API:
  replace "master_timeout" with "cluster_manager_timeout"

When being compatible with OpenSearch 3.0:

• Replace "master" in the reference to OpenSearch Java API
  (new APIs are available in version 2.2)
  • DiscoveryNodes.builder().masterNodeId() -> clusterManagerNodeId()
  • DiscoveryNodeRole.MASTER_ROLE -> CLUSTER_MANAGER_ROLE
  • event.localNodeMaster() -> localNodeClusterManager()

Describe alternatives you've considered
None.

Additional context

[dhruv16dhr]

Closing this issue as the changes are merged

[dblock]

I see methods like .localNodeMaster() in the code still. Is this waiting on something in OpenSearch?

[tlfeng]

@dblock That's correct. .localNodeMaster() depends on the change in the OpenSearch class:

asynchronous-search/src/main/java/org/opensearch/search/asynchronous/management/AsynchronousSearchManagementService.java

Line 20 in 1c28a08

import org.opensearch.cluster.ClusterChangedEvent;

The rename is tracked in issue opensearch-project/OpenSearch#1684.
It will be ready before OpenSearch 3.0 and I will complete in advance and keep update.
If the issue is used for pending items for 2.0 release, then the issue is resolved.

[dblock]

I've removed the 2.0 label in favor of 2.1 for the remaining work.

[dhruv16dhr]

@tlfeng I see that opensearch-project/OpenSearch#1684 is still open
@dblock Should we change the label here?

[eirsep]

changed label to v3.0.0 as there are no 2.1 related master deprecation items for the plugin

[anasalkouz]

Java APIs completed and released on 2.2.
@dhruv16dhr Could you please complete the remaining part from your end? let's target 2.3 to remove all usages.

[anasalkouz]

@dhruv16dhr anything remaining? can you close the issue?