[META] Breaking changes in 3.0

[reta]

This is a meta issue which lists down all breaking changes in OpenSearch 3.0

Deprecated code in 3.0+

• Cleanup deprecated thread pool settings [REMOVE] Cleanup deprecated thread pool settings #2595
• Replace 'whitelist' terminology in Java API Replace "blacklist/whitelist" terminology in Java APIs #1683
• Removed deprecated methods from JodaCompatibleZonedDateTime [Remove] Remove deprecated methods from JodaCompatibleZonedDateTime which are called by scripts #3346
• Rename Class ending with Plugin to Module under modules dir Rename Class ending with Plugin to Module under modules dir  #4042
• Migrate client transports to Apache HttpClient / Core 5.x #4459
• Block access to system indices from REST APIs #7936
• [BUG] Indexing a document through the bulk api bypasses the 512 byte _id size limit #6595
• [BUG] OpenSearch app is not able to pick up empty node.roles= environment variable to run as coordinating node. #3412 (Treat Setting value with empty array string as empty array #10625)
• Deprecate CamelCase PathHierarchy tokenizer name #10894
• Ensure Jackson default maximums introduced in 2.16.0 do not conflict with OpenSearch settings #11811 - content limits in XContent / Jackson
• Introduce index.query.max_nested_depth. fix #3268 #11670

Removed code in 3.0+

• List of deprecated code removal in 3.0 #2773

Major updates:

• COMPAT locale provider will be removed in a future release #13988 (COMPAT locale provider will be removed in a future release #11550)
• [PROPOSAL] Set OpenSearch 3.0.0 baseline JDK version to JDK-21 #10745
• [FEATURE] Explore the update route to Apache Lucene 10 for 3.0.0 #11415
• [META] Set OpenSearch 3.0.0 baseline JDK version to JDK-21 #14011

[reta]

@saratvemulapalli fyi, meta for 3.0 breaking changes, thanks!

[saratvemulapalli]

@CEHENKLE could you help add this to 3.0 roadmap?

[CEHENKLE]

Done.

[saratvemulapalli]

Looks like this is getting stale.
@andrross /@reta do you think we can use Changelog for this ?

[reta]

@andrross /@reta do you think we can use Changelog for this ?

We probably would have to, but what are other breaking changes to mention? I think @nknize is doing some large refactorings but so far I think it was non breaking.

[andrross]

I did some searching and couldn't find any open issues, but we have deprecation warning about blocking direct access to system indices. @reta is implementing the block for direct access to system indices something we should track for 3.0?

This came up in discussion in #7778.

[reta]

@andrross I think we should track it, thanks!

[andrross]

Created issue #7936 and added to the list here. Thanks!

[msfroh]

@reta -- is this a good place to build a wishlist for breaking changes in 3.0? Do you know if we have an existing good place to do that?

(For example, #1029 is a longstanding issue that would be nice to address in a 3.0 release, since otherwise I think it would need to wait for 4.0. I don't want to clutter up this issue with more wishlist items, but that one would be near the top of my list.)

[reta]

@reta -- is this a good place to build a wishlist for breaking changes in 3.0? Do you know if we have an existing good place to do that?

@msfroh I think this is the designated place for breaking changes which are going to be in 3.0, regarding wishlist - I don't think we have any lists for that besides targeting issues / pull requests as v3.0.0