C# lambda function can't find json files in the project

Question

My lambda function uses a json credentials file (./credentials/myfile.json). Everything is working well on my computer or on lambdar test environment, but when I deploy it to AWS, it is enable to find the file, no matter its location.

Right now my files tree is:

myFunction

• Credentials
  • backupuser_OAuth2_Credentials.json
  • origin_GDrive_Credentials.json
• Utilities
  • GoogleDriveUtilities.cs
• Function.cs
• myFunction.csproj

And I am trying to access the credentials this way:

In Function.cs:

string originCredentialPath = "./Credentials/origin_GDrive_Credentials.json";

GoogleDriveUtilities origin_gdu = new GoogleDriveUtilities(originCredentialPath, "Origin account", 0); 

In my Utility class:

        string[] scopes = new string[]
        {
            //GDrive access
            DriveService.Scope.Drive,
        };

        GoogleCredential credential;

        try
        {
            using (var stream = new FileStream(credentialPath, FileMode.Open, FileAccess.Read))
            {
                credential = GoogleCredential.FromStream(stream)
                    .CreateScoped(DriveService.Scope.Drive);
            }

            driveService = new DriveService(new BaseClientService.Initializer()
            {
                HttpClientInitializer = credential,
                ApplicationName = applicationName,
            });

            Console.WriteLine("Google Drive service created: " + this.serviceName + ".");
            return driveService;
        }
        catch (Exception e)
        {
            Console.WriteLine("Error when creating Google Drive service:\n >>" + e);
        }
        return null;

On execution, I have the following error in cloudwatch logs:

System.IO.DirectoryNotFoundException: Could not find a part of the path '/var/task/Credentials/origin_GDrive_Credentials.json'.

Any clues?

Thank you!

Answer 1

Finally I fixed the issue by using AWS Secrets, in place of using files.

As I was not able to find a way to give my lambda access to local files, I stored the json (credential informations) in AWS Secrets.

I get the json data as below:

string secretName = secretId;
string region = "eu-west-3";

IAmazonSecretsManager client = new AmazonSecretsManagerClient(RegionEndpoint.GetBySystemName(region));

GetSecretValueRequest request = new GetSecretValueRequest
{
      SecretId = secretName,
      VersionStage = "AWSCURRENT",
};

GetSecretValueResponse response;

try
{
      response = await client.GetSecretValueAsync(request);
}
catch (Exception e)
{
      throw e;
}

var originCredentialJson = response.SecretString;

I then accessed these data programmatically and updated my connection method as below:

public DriveService initDriveServiceAccount(string json)
        {
            string[] scopes = new string[]
            {
                //GDrive access
                DriveService.Scope.Drive,
            };

            GoogleCredential credential;

            try
            {
                credential = GoogleCredential.FromJson(json).CreateScoped(DriveService.Scope.Drive);

                driveService = new DriveService(new BaseClientService.Initializer()
                {
                    HttpClientInitializer = credential,
                    ApplicationName = applicationName,
                });

                context.Logger.LogInformation("Google Drive service created: " + this.serviceName + ".");
                return driveService;
            }
            catch (Exception e)
            {
                context.Logger.LogInformation("Error when creating Google Drive service:\n >>" + e);
            }
            return null;
        }