Do SAS URIs expire after successful file uploads in IoT Hub?

Question

I am running a script that collects data from a device and uploads it to a storage account at regular intervals. This process is leading to an error, as described in this issue (403 TooManyDevicesError after 10 Files).

I suspect that I might be hitting the file upload limit of 10 concurrent uploads, even though the files are already stored. According to the documentation, SAS URIs are valid for at least one hour (or one minute according to this document, but there seems to be no option to set them for less than one hour).

My questions are:

• While the SAS URIs are valid, is the upload still active?
• Are the URIs deleted once the file upload is completed?
• Is there a way to delete them manually, or is it simply a limitation that allows for only 10 uploads within an hour?

Thank you in advance.

Answer 1

1. While the SAS URIs are valid, is the upload still active?
   No, the SAS URI's validity indicates the time period during which the URI can be used to perform operations on the associated resource (e.g., upload, read, or delete a file). Once a file upload completes, the operation is finalized, but the SAS URI remains valid until its expiration time, allowing additional operations on the resource if permitted by the URI's configuration.
2. Are the URIs deleted once the file upload is completed?
   No, SAS URIs are not "deleted" upon file upload completion because they are essentially temporary tokens tied to the storage account. They remain valid until their expiry time unless the associated access key or policy is revoked.
3. Is there a way to delete them manually, or is it simply a limitation that allows for only 10 uploads within an hour?
   SAS URIs themselves cannot be "deleted," but you can revoke their validity by:
   • Regenerating the storage account key if the SAS was generated using an account key.
   • Deleting or updating the stored access policy if the SAS was created with one.

The 10 concurrent uploads limit you mentioned may be specific to the configuration of your storage account or the device. This is not directly tied to SAS URI limitations but rather to constraints on concurrent operations imposed by your application, device, or storage settings. You can explore strategies like queuing uploads, reducing concurrency, or leveraging Azure Storage batch operations to overcome the limitation.

To address your current issue, consider adjusting the script to upload files sequentially or limit the number of concurrent uploads to less than 10.

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hth

Marcin