[nidhiii-27]

Summary

Implements Phase 2 (Telemetry, Diagnostics, and Parity Fixes) of DirectPath over Cloud Interconnect (DP over GCI) for google-cloud-storage, achieving cross-SDK parity with C++ PRs googleapis/google-cloud-cpp#16478, googleapis/google-cloud-cpp#16538, googleapis/google-cloud-cpp#16556, googleapis/google-cloud-cpp#16568, and googleapis/google-cloud-cpp#16605.

Key Changes

• GrpcChannelTelemetry:
  • URI and host classification helpers (hasQueryParameter, detectTransportType, c2pTargetHost, authorityHost, isDirectPathInterconnectHost, selectedTransportType, grpcForceXdsIsSupported, isDirectPathInterconnectEnabled, resolveEffectiveTarget) for CloudPath, DirectPath, and DirectPathInterconnect.
  • Two-stage diagnostic logging (logChannelConfiguration and logChannelReady / channelReadyNote) reporting actionable WARNING and INFO messages for DirectPath over Cloud Interconnect configuration, runtime gRPC force-xds support, xDS vs DNS LB fallback, and channel readiness latency.
  • Non-owning async channel[0] readiness watcher (startChannelTelemetry / createChannelPrimer) using WeakReference<ManagedChannel> and notifyWhenStateChanged.
  • OpenTelemetry metric callback (makeChannelMetricsCallback) recording internal/client/channel_creation_latency (in seconds) with transport_type attribute (CloudPath, DirectPath, DirectPathInterconnect).
• OpenTelemetryBootstrappingUtils:
  • Registers the storage.googleapis.com/internal/client/channel_creation_latency histogram view in createMeterProvider.
  • Adds bootstrapGrpcMetrics returning both the ChannelConfigurator and MeterProvider.
  • Updates getCloudMonitoringEndpoint to handle google-c2p:/// / google-c2p-experimental:/// targets, storage-direct.googleapis.com, storage-preprod-direct.sandbox.googleapis.com, and storage-direct.<universeDomain>.
• GrpcStorageOptions:
  • Fixes builder precedence so setAttemptDirectPath(false) disables DirectPath even when setAttemptDirectPathXdsOverInterconnect(true) or GOOGLE_CLOUD_ENABLE_DIRECT_PATH_XDS_OVER_INTERCONNECT=true is set.
  • Wires GrpcChannelTelemetry configuration logging, ChannelPrimer, and OpenTelemetry channel metrics callback into resolveSettingsAndOpts.
• Unit Tests:
  • GrpcChannelTelemetryTest and OpenTelemetryBootstrappingUtilsTest covering URI/host helpers, diagnostic logs and warnings, async state transitions, OpenTelemetry histogram recording, and builder precedence.

(Scoped to java-storage/google-cloud-storage/ to avoid any merge conflict with #14864.)

[gemini-code-assist]

Code Review

This pull request introduces gRPC channel telemetry and diagnostics for Google Cloud Storage, adding the GrpcChannelTelemetry class to support and monitor CloudPath, DirectPath, and DirectPath over Cloud Interconnect. It integrates this telemetry into GrpcStorageOptions and enhances OpenTelemetryBootstrappingUtils to bootstrap gRPC metrics and resolve Cloud Monitoring endpoints. Feedback on the changes highlights critical robustness improvements, including catching Throwable during static class-probing to prevent initialization crashes, calling setAccessible(true) and catching Exception to safely reflect on package-private channel implementations, and adding a defensive null check for credentials to avoid potential null pointer exceptions.

[gemini-code-assist]

In environments where GoogleCloudToProdNameResolver is present but its dependencies or superclasses are missing, Class.forName can throw a LinkageError (such as NoClassDefFoundError). Since this method is called during static initialization of GrpcChannelTelemetry, any uncaught Error will result in an ExceptionInInitializerError, preventing the class from loading and crashing the application. Catching Throwable instead of ReflectiveOperationException | SecurityException ensures robust class-probing without risking initialization failures.

Suggested change

	private static boolean detectGrpcForceXdsSupport() {
	try {
	Class<?> clazz = Class.forName("io.grpc.googleapis.GoogleCloudToProdNameResolver");
	clazz.getDeclaredField("forceXds");
	return true;
	} catch (ReflectiveOperationException | SecurityException e) {
	return false;
	}
	}
	private static boolean detectGrpcForceXdsSupport() {
	try {
	Class<?> clazz = Class.forName("io.grpc.googleapis.GoogleCloudToProdNameResolver");
	clazz.getDeclaredField("forceXds");
	return true;
	} catch (Throwable e) {
	return false;
	}
	}

[gemini-code-assist]

If the runtime class of the ManagedChannel is package-private (such as io.grpc.internal.ManagedChannelImpl), calling Method.invoke on a Method retrieved via getClass().getMethod(...) will throw an IllegalAccessException because the class itself is not accessible, even if the method is public. To bypass this, m.setAccessible(true) should be called. Additionally, on JDK 9+, calling setAccessible(true) on a module-protected class can throw an InaccessibleObjectException (which is a RuntimeException). Since the catch block only catches ReflectiveOperationException and SecurityException, this runtime exception would propagate and crash the application. Catching Exception and calling setAccessible(true) resolves both issues safely.

Suggested change

	private static String defaultExtractLbPolicyName(@Nullable ManagedChannel channel) {
	if (channel == null) {
	return null;
	}
	try {
	Method m = channel.getClass().getMethod("getLoadBalancingPolicyName");
	Object result = m.invoke(channel);
	if (result instanceof String) {
	return (String) result;
	}
	} catch (ReflectiveOperationException | SecurityException ignored) {
	// Standard io.grpc.ManagedChannel does not expose getLoadBalancingPolicyName publicly.
	}
	return null;
	}
	private static String defaultExtractLbPolicyName(@Nullable ManagedChannel channel) {
	if (channel == null) {
	return null;
	}
	try {
	Method m = channel.getClass().getMethod("getLoadBalancingPolicyName");
	m.setAccessible(true);
	Object result = m.invoke(channel);
	if (result instanceof String) {
	return (String) result;
	}
	} catch (Exception ignored) {
	// Standard io.grpc.ManagedChannel does not expose getLoadBalancingPolicyName publicly.
	}
	return null;
	}

References

1. Catching Throwable instead of Exception is acceptable at Future boundaries or during stream cleanup in asynchronous operations to ensure all failures are captured and propagated. For general reflection or runtime exception handling, prefer catching Exception to avoid catching critical JVM Errors.

[gemini-code-assist]

If credentials is null, credentials instanceof NoCredentials evaluates to false, which will lead to calling baseProvider.withCredentials(null). Depending on the GAX provider implementation, passing null to withCredentials might throw a NullPointerException or cause downstream initialization issues. Adding an explicit null check for credentials ensures defensive safety.

Suggested change

	InstantiatingGrpcChannelProvider telemetryProvider =
	credentials instanceof NoCredentials
	? baseProvider
	: (InstantiatingGrpcChannelProvider) baseProvider.withCredentials(credentials);
	InstantiatingGrpcChannelProvider telemetryProvider =
	(credentials == null || credentials instanceof NoCredentials)
	? baseProvider
	: (InstantiatingGrpcChannelProvider) baseProvider.withCredentials(credentials);