fix(trace context propagation): Fix context loss propagation issues

[thrivikram-karur-g]

Description

Fix context loss and propagation issues to ensure trace context is propagated in gcsx client readers.

Link to the issue in case of a bug fix.

b/473678121

Testing details

1. Manual - NA
2. Unit tests - NA
3. Integration tests - NA

Any backward incompatible change? If so, please explain.

[gemini-code-assist]

Summary of Changes

Hello @thrivikram-karur-g, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses critical issues related to trace context propagation within the GCSFuse client readers. By introducing a dedicated tracing package and integrating its utilities across various file system and GCS interaction components, it ensures that OpenTelemetry trace information is consistently carried through operations, even when new Go contexts are spawned. This enhancement is crucial for maintaining end-to-end visibility and accurate monitoring of request flows, particularly in scenarios involving background reads and interrupt handling.

Highlights

• Centralized Tracing Utilities: Introduced a new tracing package with a shared OpenTelemetry tracer and a utility function (MaybePropagateTraceContext) for consistent context propagation.
• Improved Context Propagation: Modified internal/fs, internal/gcsx/client_readers, internal/gcsx/multi_range_downloader_wrapper, and internal/gcsx/random_reader to correctly propagate trace contexts, especially when new contexts are created (e.g., for interruptless operations or background reads).
• Standardized Span Naming: Replaced hardcoded string literals for FUSE operation names in internal/fs/wrappers/tracing.go with constants defined in the new tracing/span_names.go file, promoting consistency and reducing potential for typos.

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[gemini-code-assist]

Code Review

This pull request effectively addresses trace context propagation issues by introducing a centralized tracing package and refactoring existing code to use it. This improves maintainability by using constants for span names and ensuring trace context is not lost, especially in background operations within GCS client readers.

I've found one area for improvement regarding context cancellation handling in the multi_range_downloader_wrapper, where the IgnoreInterrupts flag is not being respected, potentially making an operation non-cancellable. My specific comment provides a suggestion to align its behavior with the rest of the codebase.

[gemini-code-assist]

The current implementation creates a new non-cancellable context for NewMultiRangeDownloader, effectively ignoring cancellation from the parent context regardless of the IgnoreInterrupts flag. This is inconsistent with how interrupts are handled elsewhere (e.g., in fs.go#getInterruptlessContext or in other readers like range_reader.go), which respect the FileSystem.IgnoreInterrupts config flag. If NewMultiRangeDownloader is a long-running operation (e.g., due to network issues), it will not be cancellable.

The context for NewMultiRangeDownloader should be cancellable if IgnoreInterrupts is false. You can achieve this by conditionally creating a new background context only when IgnoreInterrupts is true.

	if mrdWrapper.config != nil && mrdWrapper.config.FileSystem.IgnoreInterrupts {
		ctx = tracing.MaybePropagateTraceContext(context.Background(), ctx, cfg.IsTracingEnabled(mrdWrapper.config))
	}