Fix Netty deprecation warnings in transport-reactor-netty4 module

[fdesu]

Description

Similar to #20233 this PR fixes some of the deprecation warnings in the transport-reactor-netty4 module.

1. More details on the NioEventLoopGroup -> MultiThreadIoEventLoopGroup migration can be found here https://netty.io/wiki/netty-4.2-migration-guide.html#new-best-practices.
2. A trivial io.netty.handler.codec.http.HttpRequest# getUri -> io.netty.handler.codec.http.HttpRequest#uri

Netty-related deprecation warnings that are left:

1. Usages of reactor.netty.tcp.SslProvider.SslContextSpec#sslContext(reactor.netty.tcp.SslProvider.ProtocolSslContextSpec) e.g. in ReactorHttpClient#createClient. This is fine, since ProtocolSslContextSpec already extends GenericSslContextSpec<SslContextBuilder> and thus, when the SslContextSpec#sslContext(SslProvider.ProtocolSslContextSpec) gets removed, we'll compile against the non-deprecatedreactor.netty.tcp.SslProvider.SslCon1textSpec#sslContext(SslProvider.GenericSslContextSpec<?>).
2. A few usages of deprecated reactor.netty.http.HttpDecoderSpec#maxChunkSize(int) are still in place where the server-side requests decoder gets configured. The deprecation comment says Deprecated as of 1.1.0. This will be removed in 2.0.0 as Netty 5 does not support this configuration., so decoder might need to get a more comprehensive update once the dependency upgrade happens.

Related Issues

N/A

Check List

• Functionality includes testing.
  - [ ] API changes companion pull request created, if applicable.
  - [ ] Public documentation issue/PR created, if applicable.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Fixes Netty deprecation warnings in the transport-reactor-netty4 module by replacing deprecated NioEventLoopGroup with MultiThreadIoEventLoopGroup and adding NioIoHandler.newFactory(). Changes applied to main code and test files with corresponding import updates.

Changes

Cohort / File(s)	Summary
Documentation CHANGELOG.md	Added entry documenting the Netty deprecation fix in the Unreleased 3.x section.
Netty EventLoopGroup Migration plugins/transport-reactor-netty4/src/main/java/org/opensearch/transport/reactor/SharedGroupFactory.java	Replaced NioEventLoopGroup with MultiThreadIoEventLoopGroup, added NioIoHandler.newFactory() factory parameter to constructors for both HTTP and generic transport groups. Updated imports accordingly.
Netty EventLoopGroup Migration plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ReactorHttpClient.java, ...ReactorNetty4HttpServerTransportTests.java, .../ssl/SecureReactorNetty4HttpServerTransportTests.java	Replaced NioEventLoopGroup with generic EventLoopGroup backed by MultiThreadIoEventLoopGroup and NioIoHandler.newFactory(). Updated method signatures and variable types accordingly. Minor API updates (request.uri() instead of request.getUri()).

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• Fix Netty deprecation warnings in transport-netty4 module #20233: Applies the identical NioEventLoopGroup to MultiThreadIoEventLoopGroup migration pattern in the transport-netty4 module.
• Bump reactor-netty to 1.3.2 and reactor to 3.8.2 #20419: Reactor-netty version bump that introduces the newer Netty API and MultiThreadIoEventLoopGroup required by these changes.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 14.29% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: fixing Netty deprecation warnings in the transport-reactor-netty4 module, which matches the primary objective of the PR.
Description check	✅ Passed	The description includes detailed explanation of changes, references to related documentation, notes on remaining deprecations, and confirmation of testing. The Description and Check List sections are properly completed.

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✨ Finishing touches

• 📝 Generate docstrings

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📜 Recent review details

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between ddf20f8 and 13948ce.

📒 Files selected for processing (5)

• CHANGELOG.md
• plugins/transport-reactor-netty4/src/main/java/org/opensearch/transport/reactor/SharedGroupFactory.java
• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ReactorHttpClient.java
• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ReactorNetty4HttpServerTransportTests.java
• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ssl/SecureReactorNetty4HttpServerTransportTests.java

🧰 Additional context used

🧠 Learnings (5)

📓 Common learnings

Learnt from: reta
Repo: opensearch-project/OpenSearch PR: 20017
File: plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ssl/SecureReactorNetty4HttpServerTransportTests.java:256-256
Timestamp: 2025-12-12T18:40:08.452Z
Learning: In the OpenSearch ReactorNetty4 secure HTTP transport tests (plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ssl/SecureReactorNetty4HttpServerTransportTests.java), URI limit validation has been moved from the protocol layer to the transport layer, making it protocol-agnostic. The random protocol selection in ReactorHttpClient.https(settings) is intentional to ensure all tests validate correct behavior across HTTP/1.1, HTTP/2, and HTTP/3.

📚 Learning: 2025-12-12T18:40:08.452Z

Learnt from: reta
Repo: opensearch-project/OpenSearch PR: 20017
File: plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ssl/SecureReactorNetty4HttpServerTransportTests.java:256-256
Timestamp: 2025-12-12T18:40:08.452Z
Learning: In the OpenSearch ReactorNetty4 secure HTTP transport tests (plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ssl/SecureReactorNetty4HttpServerTransportTests.java), URI limit validation has been moved from the protocol layer to the transport layer, making it protocol-agnostic. The random protocol selection in ReactorHttpClient.https(settings) is intentional to ensure all tests validate correct behavior across HTTP/1.1, HTTP/2, and HTTP/3.

Applied to files:

• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ReactorNetty4HttpServerTransportTests.java
• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ssl/SecureReactorNetty4HttpServerTransportTests.java
• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ReactorHttpClient.java
• plugins/transport-reactor-netty4/src/main/java/org/opensearch/transport/reactor/SharedGroupFactory.java

📚 Learning: 2025-12-12T13:31:51.234Z

Learnt from: andriyredko
Repo: opensearch-project/OpenSearch PR: 20017
File: plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ssl/SecureReactorNetty4HttpServerTransportTests.java:642-646
Timestamp: 2025-12-12T13:31:51.234Z
Learning: In the OpenSearch ReactorNetty4 secure HTTP transport tests (plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ssl/SecureReactorNetty4HttpServerTransportTests.java), the createBuilderWithPort() helper intentionally uses randomBoolean() for the HTTP/3 enabled setting to ensure all tests validate correct behavior with both HTTP/3 enabled and disabled configurations.

Applied to files:

• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ReactorNetty4HttpServerTransportTests.java
• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ssl/SecureReactorNetty4HttpServerTransportTests.java
• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ReactorHttpClient.java

📚 Learning: 2025-12-13T20:16:15.318Z

Learnt from: reta
Repo: opensearch-project/OpenSearch PR: 20017
File: modules/transport-netty4/src/main/java/org/opensearch/http/netty4/Netty4Http3ServerTransport.java:101-123
Timestamp: 2025-12-13T20:16:15.318Z
Learning: In OpenSearch, only one HTTP transport implementation can be active and loaded at a time, so duplicate setting definitions (such as h3.max_stream_local_length, h3.max_stream_remote_length, and h3.max_streams) across different transport implementations like Netty4Http3ServerTransport and ReactorNetty4HttpServerTransport will not cause setting registration conflicts.

Applied to files:

• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ReactorNetty4HttpServerTransportTests.java
• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ssl/SecureReactorNetty4HttpServerTransportTests.java
• plugins/transport-reactor-netty4/src/main/java/org/opensearch/transport/reactor/SharedGroupFactory.java

📚 Learning: 2025-12-19T21:26:37.090Z

Learnt from: reta
Repo: opensearch-project/OpenSearch PR: 20017
File: modules/transport-netty4/src/main/java/org/opensearch/http/netty4/Netty4QuicServerTransport.java:0-0
Timestamp: 2025-12-19T21:26:37.090Z
Learning: In Netty4QuicServerTransport (modules/transport-netty4/src/main/java/org/opensearch/http/netty4/Netty4QuicServerTransport.java), the secureHttpTransportSettingsProvider parameter is guaranteed to be non-null because the plugin verifies its presence during instantiation, so no explicit null-check is needed in the constructor.

Applied to files:

• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ReactorNetty4HttpServerTransportTests.java
• plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ssl/SecureReactorNetty4HttpServerTransportTests.java

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🔇 Additional comments (12)

CHANGELOG.md (1)

37-37: Changelog entry looks good.

plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ssl/SecureReactorNetty4HttpServerTransportTests.java (2)

70-72: Import-only change.

---

509-548: LGTM.
Test setup and teardown still properly manage the client group lifecycle.

plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ReactorNetty4HttpServerTransportTests.java (2)

78-80: Import-only change.

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502-540: LGTM.
Test remains deterministic with explicit group shutdown in the finally block.

plugins/transport-reactor-netty4/src/main/java/org/opensearch/transport/reactor/SharedGroupFactory.java (3)

29-30: Import-only change.

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91-95: LGTM.

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104-108: LGTM.

plugins/transport-reactor-netty4/src/test/java/org/opensearch/http/reactor/netty4/ReactorHttpClient.java (4)

39-41: Import-only change.

---

204-213: LGTM.

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245-251: LGTM.

---

281-287: LGTM.

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[github-actions]

✅ Gradle check result for 13948ce: SUCCESS

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.23%. Comparing base (ddf20f8) to head (13948ce).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...ensearch/transport/reactor/SharedGroupFactory.java	50.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #20429      +/-   ##
============================================
- Coverage     73.30%   73.23%   -0.08%     
+ Complexity    71832    71760      -72     
============================================
  Files          5792     5792              
  Lines        328639   328641       +2     
  Branches      47311    47311              
============================================
- Hits         240905   240665     -240     
- Misses        68458    68675     +217     
- Partials      19276    19301      +25     

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[reta]

Thank you @fdesu !