[META] Deprecate REST client

[dblock]

Is your feature request related to a problem? Please describe.

In opensearch-project/opensearch-java#262 we are removing the dependency on OpenSearch (this repo). I propose to loudly deprecate REST client code in this repo and require users to migrate to a dependency on opensearch-java. This would significantly reduce the amount of projects that depend on OpenSearch core by all the ones that depend on the REST APIs.

Describe the solution you'd like

1. Deprecate a large portion of/all org.opensearch.client namespace in 2.x.
2. Keep it in 3.0.0 but make the respective transport optional in opensearch-java
3. Remove it in 4.0.

Dependencies:

• Remove documentation for High Level Rest Client [DOC] documentation-website#2010
• [FEATURE] Get rid of the dependency on OpenSearch core opensearch-java#262
• [FEATURE] Reimplement BulkProcessor opensearch-java#181
• [FEATURE] Deprecate RestClientTransport opensearch-java#326

Related:

• [PROPOSAL] Restore support for Java 8 opensearch-java#156
• [DISCUSS] Client implementation (Rest High LevelClient vs OpenSearch Java client) for Extensibility opensearch-sdk-java#294
• [FEATURE] Create OpenSearchClient implementation in SDK Client and deprecate it opensearch-sdk-java#302

[reta]

@dblock Regarding the suggested plan, it might be a bit aggressive:

• Deprecate a large portion of/all org.opensearch.client namespace in 2.x
• Keep it in 3.0.0 but make the respective transport optional in opensearch-java (giving a time to migrate since it could be a short notice, might be a good start for 2.0 but we are at 2.4 already)
• Remove it in 4.0.0

[dblock]

@reta I think it's a sensible plan. thank you.

[wbeckler]

I've proposed removing documentation of the high-level rest client from the organization documentation. There hasn't been any feedback on the proposal: opensearch-project/documentation-website#2010

[manirudh78]

Hello all,
Hope all is well.
Based on the comments in this ticket
The Opensearch-Hadoop will support the scala client for opensearch? Yes

Response is highly appreciated.
Thanks

[wbeckler]

@manirudh78 I'm not sure I understand your comment. Is it possibly in the wrong repo?

[dblock]

I think it was meant for https://github.com/opensearch-project/opensearch-hadoop. I don't see why that wouldn't work in Scala.