feat(storage): Synchronous gRPC Interceptor

[v-pratap]

No description provided.

[gemini-code-assist]

Code Review

This pull request introduces a FeatureTracker to monitor and report client-side optimizations and configuration choices via the x-goog-storage-cpp-features header. The code reviewer identified that statically adding the tracker during stub creation in StorageMetadata is redundant and can lead to stale headers, recommending its removal along with the associated test. Additionally, to comply with the repository's style guide, the reviewer suggested factoring out duplicated logic for retrieving the tracker's header value into a centralized helper function, FeatureTrackerHeaderValue, to be used across both gRPC and REST paths.

[gemini-code-assist]

Adding the feature tracker header to fixed_metadata in StorageMetadata captures a static snapshot of the tracker's value at stub creation time. Since ApplyQueryParameters (for unary RPCs) and OpenObject::CreateRpc (for streaming RPCs) already dynamically add the up-to-date header value to the ClientContext for each request, having it in StorageMetadata is redundant and leads to duplicate x-goog-storage-cpp-features headers on the wire. Furthermore, the static value in StorageMetadata will not reflect any operation-driven features registered after stub creation, potentially sending stale/conflicting information. We should remove this block entirely.

  std::multimap<std::string, std::string> fixed_metadata;

[gemini-code-assist]

To adhere to the repository style guide regarding factoring out duplicated code (which appears 3 or more times in non-test files), we should introduce a helper function FeatureTrackerHeaderValue to centralize the logic of checking EnableFeatureReportsOption and retrieving the header value.

Options SetupFeatureTracker(Options opts);

std::string FeatureTrackerHeaderValue(Options const& opts);

References

1. prefers to factor out duplicated code if it appears 3 or more times in non-test files. ^(link)

[gemini-code-assist]

Implement the helper function FeatureTrackerHeaderValue to centralize the logic of checking if feature reporting is enabled and retrieving the header value from the tracker.

  return opts;
}

std::string FeatureTrackerHeaderValue(Options const& opts) {
  if (opts.has<EnableFeatureReportsOption>() &&
      !opts.get<EnableFeatureReportsOption>()) {
    return {};
  }
  if (!opts.has<FeatureTrackerOption>()) return {};
  auto const& tracker = opts.get<FeatureTrackerOption>();
  if (!tracker) return {};
  return tracker->HeaderValue();
}

[gemini-code-assist]

Use the centralized FeatureTrackerHeaderValue helper function to simplify the code and avoid duplication.

  auto const val = storage::internal::FeatureTrackerHeaderValue(options);
  if (!val.empty()) {
    ctx.AddMetadata(storage::internal::kFeatureTrackerHeaderName, val);
  }

References

1. prefers to factor out duplicated code if it appears 3 or more times in non-test files. ^(link)

[gemini-code-assist]

Use the centralized FeatureTrackerHeaderValue helper function to simplify the code and avoid duplication.

  auto const val = FeatureTrackerHeaderValue(options);
  if (!val.empty()) {
    builder.AddHeader(kFeatureTrackerHeaderName, val);
  }

References

1. prefers to factor out duplicated code if it appears 3 or more times in non-test files. ^(link)

[gemini-code-assist]

Since the feature tracker is no longer added to StorageMetadata (to avoid duplication and ensure dynamic tracking), this test is no longer applicable and should be removed.