chore(spanner): introduce commitRpcTimeout to connection properties

[sagnghos]

This explicitly sets an operation timeout bound for Spanner transactions so that severe network blockholes do not lead to an infinite connection timeout at the YCSB or application layer when proxy mechanisms (like PGAdapter) are routing via EKS Load Balancers.

[gemini-code-assist]

Code Review

This pull request introduces a new commitRpcTimeout configuration option to customize the RPC timeout specifically for commit operations in Spanner. The feedback highlights a few areas for improvement: correcting misplaced Javadoc comments in ConnectionOptions.java, ensuring consistent private final visibility and this reference usage for the new field in SpannerPoolKey, and adding a precondition check in SpannerOptions.Builder to prevent negative timeout values.

[gemini-code-assist]

The Javadoc comment for getGrpcKeepAliveTime() was accidentally moved above getCommitRpcTimeout(), resulting in duplicated Javadoc blocks for getCommitRpcTimeout() and leaving getGrpcKeepAliveTime() without any documentation. Please correct the placement of these Javadoc comments.

Suggested change

	/** The gRPC keepalive time for this connection. */
	/** The commit RPC timeout for this connection. */
	public Duration getCommitRpcTimeout() {
	return getInitialConnectionPropertyValue(COMMIT_RPC_TIMEOUT);
	}
	public Duration getGrpcKeepAliveTime() {
	return getInitialConnectionPropertyValue(GRPC_KEEPALIVE_TIME);
	}
	/** The commit RPC timeout for this connection. */
	public Duration getCommitRpcTimeout() {
	return getInitialConnectionPropertyValue(COMMIT_RPC_TIMEOUT);
	}
	/** The gRPC keepalive time for this connection. */
	public Duration getGrpcKeepAliveTime() {
	return getInitialConnectionPropertyValue(GRPC_KEEPALIVE_TIME);
	}

[gemini-code-assist]

The field commitRpcTimeout in SpannerPoolKey is declared with package-private visibility, whereas all other fields in this class are declared as private final. For consistency and proper encapsulation, please make it private final.

Suggested change

	final Duration commitRpcTimeout;
	private final Duration commitRpcTimeout;

[gemini-code-assist]

For consistency with the other fields referenced in this method, please use this.commitRpcTimeout instead of commitRpcTimeout.

Suggested change

	commitRpcTimeout,
	this.commitRpcTimeout,

[gemini-code-assist]

To prevent invalid configurations early, consider adding a check to ensure that commitRpcTimeout is not negative when it is non-null.

    public Builder setCommitRpcTimeout(Duration commitRpcTimeout) {
      if (commitRpcTimeout != null) {
        Preconditions.checkArgument(
            !commitRpcTimeout.isNegative(), "commitRpcTimeout cannot be negative");
      }
      this.commitRpcTimeout = commitRpcTimeout;
      return this;
    }