[reactor-optional] Implement trace context propagation without hard dependency on Reactor

[atakavci]

Introduces a new getTraceContextAsync method on TraceContextProvider that accepts a plain Map<Object, Object> instead of relying on Reactor's Mono-based deferred resolution. This removes the hard dependency on Reactor from the TraceContextProvider interface while still supporting trace context propagation in reactive command flows. A lightweight ContextViewMapAdapter bridges Reactor's ContextView to the Map interface at the call site.

Changes

• TraceContextProvider – Added getTraceContextAsync(Map<Object, Object>) default method that returns a Supplier<TraceContext>. Deprecated the existing getTraceContextLater() method.
• BraveTracing – Implemented getTraceContextAsync to look up Span or TraceContext from the provided map, intentionally skipping ThreadLocal fallback in async contexts.
• MicrometerTracing – Implemented getTraceContextAsync to look up Observation, TraceContext, or ObservationThreadLocalAccessor.KEY from the provided map, with the same ThreadLocal-skip policy.
• AbstractRedisReactiveCommands – Added ContextViewMapAdapter (a read-only AbstractMap backed by Reactor's ContextView) and replaced withTraceContext() with an implementation that uses deferContextual + getTraceContextAsync for non-blocking trace context resolution.

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Note

Medium Risk
Changes how reactive tracing context is resolved and propagated (new async context API and updated withTraceContext()), which can affect span parentage/trace continuity across reactive flows. Scope is contained to tracing integration, with new integration tests reducing regression risk.

Overview
Updates trace-context propagation to avoid a hard Reactor dependency by introducing TraceContextProvider#getTraceContextAsync(Map) (returning a Supplier<TraceContext>) and deprecating getTraceContextLater().

Reactive command tracing now resolves parent context via Reactor ContextView using a lightweight ContextViewMapAdapter, calling getTraceContextAsync during deferContextual in AbstractRedisReactiveCommands#withTraceContext().

Adds async-context implementations for Brave and Micrometer providers (explicitly not falling back to ThreadLocals when an async context map is present), plus new integration tests covering async (connection.async()) and reactive (contextWrite) tracing flows and verifying emitted spans/tags and parent/trace IDs.

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[Copilot]

Pull request overview

This PR refactors reactive trace-context propagation to avoid relying on Reactor ContextView/Mono-based resolution at the TraceContextProvider call site by introducing a Map-based async context lookup and adapting Reactor context to that interface.

Changes:

• Add TraceContextProvider.getTraceContextAsync(Map<Object, Object>) (returns Supplier<TraceContext>) and deprecate getTraceContextLater().
• Implement getTraceContextAsync for Brave and Micrometer tracing providers to resolve trace context from the provided map (with deliberate no-ThreadLocal fallback when async context is present).
• Update reactive command tracing (AbstractRedisReactiveCommands.withTraceContext) to resolve trace context via deferContextual + ContextViewMapAdapter.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 7 comments.

File	Description
src/main/java/io/lettuce/core/tracing/TraceContextProvider.java	Introduces Map-based async context lookup API and deprecates Reactor-Mono method.
src/main/java/io/lettuce/core/tracing/BraveTracing.java	Adds getTraceContextAsync implementation for Brave context lookup.
src/main/java/io/lettuce/core/tracing/MicrometerTracing.java	Adds getTraceContextAsync implementation for Micrometer context lookup.
src/main/java/io/lettuce/core/AbstractRedisReactiveCommands.java	Adapts Reactor ContextView to Map and switches reactive trace context resolution to the new API.

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[tishun]

LGTM

[a-TODO-rov]

The approach LGTM - this is the way !
I think we should follow the same approach on all public APIs, directly exposing reactive - simple plain java foundation (async based) for the reactive implementation to adapt.
Minor comments to become production ready:

• javadoc
• tests

[a-TODO-rov]

LGTM

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

There are 2 total unresolved issues (including 1 from previous review).

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