RATIS-2553. Isolate OpenTelemetry tracing dependencies

[HTHou]

What changes were proposed in this pull request?

This patch isolates OpenTelemetry-specific tracing code behind a TraceProvider facade. The default tracing path uses a no-op provider, so downstream projects can exclude OpenTelemetry jars without loading OTel classes from the default Ratis tracing path.

OpenTelemetry tracing behavior is preserved when tracing is enabled and the OpenTelemetry jars are available. The patch also removes OpenTelemetry SDK and semantic convention dependencies from the main dependency path and keeps SDK testing dependencies in test scope.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/RATIS-2553

How was this patch tested?

• ./mvnw -pl ratis-common,ratis-server,ratis-test -am test-compile -DskipTests
• ./mvnw -pl ratis-server -am -Dtest=RaftServerImplTracingTests -DfailIfNoTests=false test
• ./mvnw -pl ratis-server -am dependency:tree -Dscope=compile -Dincludes=io.opentelemetry,io.opentelemetry.semconv -DskipTests
• Manually verified with a classpath excluding OpenTelemetry jars that TraceUtils.setTracerWhenEnabled(true) falls back to no-op tracing instead of failing with linkage errors.

[szetszwo]

@HTHou , We do plan to make tracing configurable; see #1341 (comment)

Thanks a lot for starting the work! Will review this soon.

Cc @taklwu

[szetszwo]

@HTHou , thanks for working on this! Please see the comments inlined.

[szetszwo]

Let's throw an exception instead of fallback:

  private static TraceProvider newOpenTelemetryTraceProvider() {
    try {
      return new OpenTelemetryTraceProvider();
    } catch (Throwable e) {
      throw new IllegalStateException("OpenTelemetry tracing is enabled but OpenTelemetry is not available; tracing is disabled", e);
    }
  }

[szetszwo]

Let's remove it since it is only used once.

[szetszwo]

Let's check the provider class:

  public static boolean isEnabled() {
    return !(getProvider() instanceof NoOpTraceProvider);
  }

[szetszwo]

Check null for tracer:

  private final Tracer tracer = Objects.requireNonNull(
      GlobalOpenTelemetry.getTracer("org.apache.ratis", VersionInfo.getSoftwareInfoVersion()),
      "tracer == null");

[szetszwo]

Remove isEnabled().

[szetszwo]

Let's keep the javadoc:

  /**
   * This is method is used when you just want to add a listener to the given future. We will call
   * {@link CompletableFuture#whenComplete(BiConsumer)} to register the {@code action} to the
   * {@code future}. Ignoring the return value of a Future is considered as a bad practice as it may
   * suppress exceptions thrown from the code that completes the future, and this method will catch
   * all the exception thrown from the {@code action} to catch possible code bugs.
   * <p/>
   * And the error phone check will always report FutureReturnValueIgnored because every method in
   * the {@link CompletableFuture} class will return a new {@link CompletableFuture}, so you always
   * have one future that has not been checked. So we introduce this method and add a suppression
   * warnings annotation here.
   */
  @SuppressWarnings("FutureReturnValueIgnored")
  private static <T> void addListener(CompletableFuture<T> future,

[szetszwo]

Move it to a new package:

package org.apache.ratis.trace.opentelemetry;

[szetszwo]

Move it to a new package:

package org.apache.ratis.trace.opentelemetry;

[szetszwo]

Add it back to OpenTelemetryTraceUtils and use it.

[HTHou]

Updated the PR to address the inline review comments:

• Moved the OpenTelemetry-specific tracing classes under org.apache.ratis.trace.opentelemetry.
• Removed TraceProvider.isEnabled() and switched TraceUtils.isEnabled() to check the provider type.
• Changed OpenTelemetry provider initialization to throw IllegalStateException when tracing is enabled but OpenTelemetry is unavailable.
• Added Objects.requireNonNull(...) for the global tracer, removed the one-use helper, and restored the addListener javadoc.

Also rebased on the latest master and force-pushed the updated single-commit branch.

Verified with:

• ./mvnw -pl ratis-server -am -Dtest=RaftServerImplTracingTests -DfailIfNoTests=false test

[szetszwo]

+1 the change looks good.