How to get blob as Stream when using blob-triggered Isolated Azure Function?

Question

Right now, my function looks like this:

[Function(nameof(Functions.ProcessUpload))]
public void ProcessUpload([BlobTrigger("integration/{name}")] object blob, string name)
{           
}

When triggered, parameter blob is an instance of System.ReadOnlyMemory<byte> type - meaning, all contents of the blog are provided in memory. All the examples I saw online have the parameter as a string. Neither System.ReadOnlyMemory<byte>, nor string are applicable in my case, since I need to be able to work with potentially 1GB+ big blobs.

With in-process functions, the blob parameter was of type Stream and everything worked. How can I process newly created blobs as streams with Isolated functions?

according to the documentation tih is not possible for the moment: learn.microsoft.com/en-us/azure/azure-functions/… — Thomas
– Thomas, Commented Aug 14, 2022 at 4:44
Thank you - yes, it looks like it is indeed a case. There are also multiple issues in azure-functions github related to this, all with the same answer, that this is not currently supported. I will probably just use in-processes model for a time being and hope that Streams will be at some point introduced to isolated model. Feel free to write your comment as an answer and I will accept it. — Route Rider
– Route Rider, Commented Aug 14, 2022 at 9:14

Thomas · Accepted Answer · 2022-08-14 09:52:24Z

6

As per August 2022, this is not supported:

Azure Blob storage trigger for Azure Functions

Looking at the Guide for running C# Azure Functions in an isolated process, there are some interesting notes:

Because .NET isolated projects run in a separate worker process, bindings can't take advantage of rich binding classes, such as ICollector<T>, IAsyncCollector<T>, and CloudBlockBlob. There's also no direct support for types inherited from underlying service SDKs, such as DocumentClient and BrokeredMessage. Instead, bindings rely on strings, arrays, and serializable types, such as plain old class objects (POCOs).

answered Aug 14, 2022 at 9:52

Thomas

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