feat: make grpc-gcp default enabled

[rahul2393]

This PR enables the gRPC-GCP channel pool extension by default for Cloud Spanner Java client.

What's Changing for Customers

Before this change

• gRPC-GCP extension was disabled by default
• Default number of channels: 4
• Channel pooling was handled by GAX

After this change

• gRPC-GCP extension is enabled by default
• Default number of channels: 8
• Channel pooling is handled by gRPC-GCP extension

Benefits of gRPC-GCP

• Improved resilience: When a network connection fails on a particular channel, operations can be automatically retried on a different gRPC channel
• Better channel management: gRPC-GCP provides more sophisticated channel affinity and load balancing

How to Disable gRPC-GCP (Switch Back to GAX Channel Pool)

If you need to disable gRPC-GCP and use the previous GAX channel pooling behavior, use the disableGrpcGcpExtension() method:

SpannerOptions options = SpannerOptions.newBuilder()
    .setProjectId("my-project")
    .disableGrpcGcpExtension()
    .build();

When disabled, the default number of channels reverts to 4 (the previous default).

When You Might Want to Disable gRPC-GCP

• Maintaining previous behavior: If you want to keep the exact same behavior as before this change (GAX channel pool with 4 default channels).
• Troubleshooting: If you experience any unexpected behavior, disabling gRPC-GCP can help isolate whether the issue is related to the channel pooling mechanism.

[gemini-code-assist]

Summary of Changes

Hello @rahul2393, 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 transitions the grpc-gcp extension in the Spanner client library to be enabled by default. This change simplifies the client's internal logic by removing a configuration flag and its conditional code paths, ensuring that all users benefit from the performance and reliability improvements offered by gRPC-GCP without requiring manual activation.

Highlights

• Default gRPC-GCP Enablement: The grpc-gcp extension is now enabled by default, removing the need for explicit configuration to activate it.
• Code Simplification: The grpcGcpExtensionEnabled boolean field and all associated conditional logic have been removed from SpannerOptions and GapicSpannerRpc, streamlining the codebase.
• Consistent Channel Management: Channel affinity and the number of channels are now consistently managed under the assumption that gRPC-GCP is always active, simplifying channel configuration.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request makes the grpc-gcp extension enabled by default, which is a good simplification. The changes correctly remove the feature flag and update the related logic. My review includes a few suggestions to improve API clarity and test naming following these changes:

• API Clarity: The methods enableGrpcGcpExtension and disableGrpcGcpExtension are now misleading or no-ops. I've suggested addressing this to avoid confusion.
• Test Naming: Some test method names have become outdated due to the changes. I've pointed these out with suggestions for new names that better reflect their current purpose.

[sakthivelmanii]

@rahul2393 as a first step, can you please enable it by default without removing the option? If needed, customer can disable it.

[olavloite]

This should probably be replaced with CreateSession. It works (for now), but once the session pool is removed, this will silently be ignored, as there are no calls to BatchCreateSessions.

[rahul2393]

Noted, I will update it in separate PR where we are removing session pool

[nimf]

Note, that, AFAIU, this will also enable grpc-gcp metrics by default (and these are many more metrics than session metrics), this can be an issue if it's shipped to the custom namespace.

[rahul2393]

Thanks @nimf for pointing since Opencensus is already marked deprecated, updated the PR to skip passing MetricRegistry(OpenCensus) to grpc-gcp