CODEWITHSUNDEEP
azure-functions
Dan Friedman
Dan Friedman

Reputation: 5218

Conditionally output to blob storage with Azure Functions

I have a HTTP function that returns a status code, but I also want to bind output to a blob. But when the request is not valid, I don't want to create the output blob at all. I tried something like:

public async Task<IActionResult> Run(
    [HttpTrigger(AuthorizationLevel.Anonymous, "post", Route = "{userName}/messages")] HttpRequest req,
    string userName,
    [Blob("users/{userName}/{DateTime}.json", FileAccess.Write)] Stream outputStream)
{
    if (IsValid(req.Body))
    {
        await req.Body.CopyToAsync(outputStream);
        return new AcceptedResult();
    }
    else
    {
        return new BadRequestResult();
    }
}

But, unfortunately, the output blob is always created, even when the BadRequest is returned. (The file created is blank, but I don't want it created at all.)

I also tried settting outputStream = null right before the BadRequest is returned, but that didn't help.

Is there a way to conditioanl create the blob file?

Upvotes: 2

Views: 465

Answers (1)

Joey Cai
Joey Cai

Reputation: 20067

In blob function, when the {DateTime}.json is not exist in the container, it will create the blob automatically. So, if you were to set your output blob path to users/{userName}/{DateTime}.json the system will automatically generate a new datetime.json file for you so that the output blob is always created.

So, you could use the following code to conditional create the blob file.

public static async Task<IActionResult> Run(
    [HttpTrigger(AuthorizationLevel.Function,  "post", Route = "{userName}/messages")] HttpRequest req, 
    string userName,
    [Blob("users/{userName}", Connection = "StorageConnectionString")] CloudBlobContainer outputContainer)
    {
        if (IsValid(req.Body))
        {
            await outputContainer.CreateIfNotExistsAsync();
            var requestBody = await new StreamReader(req.Body).ReadToEndAsync();
            var blobName = DateTime.Now.ToString() + ".json";
            var cloudBlockBlob = outputContainer.GetBlockBlobReference(blobName);
            await cloudBlockBlob.UploadTextAsync(requestBody);
            return new AcceptedResult();
        }else{
            return new BadRequestObjectResult("bad request");
        }
    }

Upvotes: 1

Related Questions