Document blocking SPNEGO hostname lookup#2278
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Canonical-hostname resolution is opt-in but performs a synchronous JVM lookup while deriving the Kerberos service principal. Authentication retries can invoke that lookup on a Netty event-loop thread. Document the blocking behavior and direct users with a known principal to the existing explicit service-principal setting. Codex on behalf of Pavel Ptashyts Co-Authored-By: Codex <codex@openai.com>
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Summary
setServicePrincipalName(...), which avoids hostname canonicalizationMotivation
setUseCanonicalHostname(true)is opt-in, butSpnegoEnginederives the service principal withInetAddress.getByName(...).getCanonicalHostName(). This synchronous lookup can delay unrelated channel work when authentication is retried from an event-loop thread.Changing or bypassing canonicalization can select a different Kerberos service principal and break authentication. Adding an AsyncHttpClient-specific cache would also introduce hostname freshness semantics separate from the JVM DNS cache, while not eliminating the first blocking lookup. This PR therefore documents the risk and the existing behavior-preserving mitigation without changing runtime semantics.
Validation
./mvnw -B -ntp -pl client -DskipTests -Dgpg.skip=true verify(compilation, Javadocs, and Revapi)The required JDK 11
./mvnw clean verifywas not run because JDK 11 is not available in the local environment. This documentation-only change does not alter runtime behavior; CI will exercise the supported JDK matrix.Codex on behalf of Pavel Ptashyts