Gcp Cloud Storage (Google)

Description

Google Cloud Storage can be used as the backing implementation for Flex file operations. Your application code should depend on IFlexFileStore, while Flex provides the provider bridge and wiring.

Important concepts

• IFlexFileStore is the contract: your code uploads/downloads through a shared abstraction.

• Streaming: uploads use a Stream; downloads return a Stream?.

• Credentials: prefer service accounts; keep credentials out of source control.

Configuration in DI

Add the provider in your DI composition root (commonly in EndPoints/...CommonConfigs/OtherApplicationServicesConfig.cs).

public static class OtherApplicationServicesConfig
{
	public static IServiceCollection AddOtherApplicationServices(
		this IServiceCollection services,
		IConfiguration configuration)
	{
		// Registers GCP Cloud Storage as the IFlexFileStore bridge.
		services.AddFlexGcpCloudStorageFileStore(configuration);
		return services;
	}
}

appsettings.json

Configuration is read from FlexBase:DataStores:File:GcpCloudStorage.

{
  "FlexBase": {
	"DataStores": {
	  "File": {
		"GcpCloudStorage": {
		  "ProjectId": "your-gcp-project-id",
		  "BucketName": "your-bucket-name",
		  "CredentialsJsonPath": "C:/secrets/gcp-service-account.json"
		}
	  }
	}
  }
}

Examples (template-based)

These examples mirror the generated Query and PostBusHandler templates. You do not register these types manually—Flex discovers and wires generated Queries/Handlers automatically.

Upload file (PostBusHandler)

using Microsoft.Extensions.Logging;
using Sumeru.Flex;
using System.IO;
using System.Threading.Tasks;

namespace {YourApplication}.Handlers.Files;

public partial class UploadFileHandler : IAmFlexCommandHandler<UploadFileCommand>
{
	protected string EventCondition = "";
	protected readonly ILogger<UploadFileHandler> _logger;
	protected readonly IFlexHost _flexHost;
	protected readonly IFlexFileStore _fileStore;

	public UploadFileHandler(ILogger<UploadFileHandler> logger, IFlexHost flexHost, IFlexFileStore fileStore)
	{
		_logger = logger;
		_flexHost = flexHost;
		_fileStore = fileStore;
	}

	public virtual async Task Execute(UploadFileCommand cmd, IFlexServiceBusContext serviceBusContext)
	{
		var appContext = cmd.Dto.GetAppContext(); // do not remove this line
		var model = _flexHost.GetDomainModel<FileModel>().Create(cmd);

		var fileId = await _fileStore.UploadAsync(cmd.Dto.Stream, cmd.Dto.FileName, cmd.Dto.ContentType, cmd.Dto.Metadata);
		await this.Fire(EventCondition, serviceBusContext);
	}
}

public class UploadFileCommand : FlexCommandBridge<UploadFileDto> { }
public class UploadFileDto : DtoBridge
{
	public Stream Stream { get; set; }
	public string FileName { get; set; }
	public string ContentType { get; set; }
	public IDictionary<string, string>? Metadata { get; set; }
}
public class FileModel : FlexDomainModelBridge { }

Download file (Query)

using Microsoft.Extensions.Logging;
using Sumeru.Flex;
using System.IO;
using System.Threading.Tasks;

namespace {YourApplication}.Queries.Files;

public class DownloadFileQuery : FlexiQueryBridgeAsync<FileDownloadOutput>
{
	protected readonly IFlexFileStore _fileStore;
	protected DownloadFileParams _params;

	public DownloadFileQuery(ILogger<DownloadFileQuery> logger, IFlexHost flexHost, IFlexFileStore fileStore)
		=> _fileStore = fileStore;

	public virtual DownloadFileQuery AssignParameters(DownloadFileParams @params)
	{
		_params = @params;
		return this;
	}

	public virtual async Task<FileDownloadOutput?> Fetch()
	{
		var appContext = _params.GetAppContext();
		var stream = await _fileStore.DownloadAsync(_params.FileId);
		if (stream == null) return default;
		return new FileDownloadOutput { FileId = _params.FileId, Stream = stream };
	}
}

public class DownloadFileParams : DtoBridge { public string FileId { get; set; } }
public class FileDownloadOutput : DtoBridge { public string FileId { get; set; } public Stream Stream { get; set; } }

Library-specific considerations

• Service account permissions: grant storage.objects.create, storage.objects.get, and storage.objects.list on the bucket.

• Credentials path: prefer mounting the JSON file at runtime (or use workload identity where available).