test(gax): add showcase harness for resumable uploads

[feywind]

Adds an end-to-end harness for the gapic-showcase ResumableUploadService, so the resumable upload client path can be exercised against a real server. It uses the resumable upload support from the google-gax PR in this series, so merge that one first.

• checked-in generated client for google.showcase.v1beta1.ResumableUploadService
• sample.js, which uploads a local file through a resumable session
• run.sh, which downloads gapic-showcase, compiles the client against the local google-gax checkout and runs the sample
• harness README plus a pointer from test/README.md, and a .gitignore entry for the generated protos

This is test tooling only; nothing in the published package changes.

Merge first: #9287
Related to: #9283

[gemini-code-assist]

Code Review

This pull request implements client-side support for the resumable upload protocol in google-gax, introducing the ResumableUploadSession state machine, file-backed seekable sources, and a showcase test harness. Feedback on the changes highlights an incorrect throughput constant (DEFAULT_UPLOAD_RATE_BYTES_PER_MS) that scales to gigabytes instead of megabytes per millisecond, as well as documentation examples in client-libraries.md that incorrectly reference uploadStream instead of uploadSource.

[gemini-code-assist]

The value of DEFAULT_UPLOAD_RATE_BYTES_PER_MS seems to be incorrect based on the accompanying comment. The comment suggests an assumed throughput of ~5 MB/s, but the constant is defined as 5 * 1024 * 1024.

If this value is in bytes per millisecond as the variable name suggests, it equates to ~5 GB/s, which is likely far too high and will result in unreasonably short deadlines for large uploads.

For an assumed rate of 5 MB/s, the value in bytes per millisecond should be closer to 5 * 1024 * 1024 / 1000, which is approximately 5243. A value of 5 * 1024 (5120) would be a reasonable approximation.

Suggested change

	const DEFAULT_UPLOAD_RATE_BYTES_PER_MS = 5 * 1024 * 1024;
	const DEFAULT_UPLOAD_RATE_BYTES_PER_MS = 5 * 1024;

[gemini-code-assist]

The example for starting a resumable upload appears to be incorrect. The start method expects an uploadSource parameter of type ResumableSource, but the example uses uploadStream. Additionally, the dataStream variable is not defined, which could be confusing.

Note: Since this is an auto-generated file, please do not edit it directly as these changes will be overwritten. Instead, apply this fix upstream in the generator or templates.

Suggested change

	const helper = await client.createResumableUpload(request);
	await helper.start({
	uploadStream: dataStream,
	chunkSize: 8 * 1024 * 1024, // 8MB chunks
	onProgress: status => {
	console.log(`Committed ${status.bytesUploaded} bytes to ${status.uploadUrl}`);
	},
	});
	const response = await helper.finished();
	const uploadSource = client.getResumableSource(filePath);
	const helper = await client.createResumableUpload(request);
	await helper.start({
	uploadSource,
	chunkSize: 8 * 1024 * 1024, // 8MB chunks
	onProgress: status => {
	console.log('Committed ' + status.bytesUploaded + ' bytes to ' + status.uploadUrl);
	},
	});
	const response = await helper.finished();

References

1. Do not manually edit auto-generated files to fix typos or make other changes, as these edits will be overwritten during the next regeneration. Instead, apply the fixes upstream in the generator or templates.

[gemini-code-assist]

Similar to the previous example, this code snippet for resuming an upload uses the incorrect uploadStream parameter. It should be uploadSource. When resuming, you still need to provide the same payload source.

Note: Since this is an auto-generated file, please do not edit it directly as these changes will be overwritten. Instead, apply this fix upstream in the generator or templates.

Suggested change

	const helper = await client.createResumableUpload();
	await helper.start({
	uploadStream: dataStream,
	resumeUrl: savedUploadUrl,
	});
	const response = await helper.finished();
	const uploadSource = client.getResumableSource(filePath);
	const helper = await client.createResumableUpload();
	await helper.start({
	uploadSource,
	resumeUrl: savedUploadUrl,
	});
	const response = await helper.finished();

References

1. Do not manually edit auto-generated files to fix typos or make other changes, as these edits will be overwritten during the next regeneration. Instead, apply the fixes upstream in the generator or templates.