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I'm using Azure Storage to serve up static file blobs but I'd like to add a Cache-Control and Expires header to the files/blobs when served up to reduce bandwidth costs.

An application like CloudXplorer and Cerebrata's Cloud Storage Studio give options to set metadata properties on containers and blobs but get upset when trying to add Cache-Control.

Does anyone know if it's possible to set these headers for files?

1 Answer

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I had to run a batch job on about 600k blobs and found 2 things that really helped:

  1. Running the operation from a worker role in the same data center. The speed between Azure services is great as long as they are in the same affinity group. Plus there are no data transfer costs.
  2. Running the operation in parallel. The Task Parallel Library (TPL) in .net v4 makes this really easy. Here is the code to set the cache-control header for every blob in a container in parallel:

// get the info for every blob in the container

var blobInfos = cloudBlobContainer.ListBlobs(

    new BlobRequestOptions() { UseFlatBlobListing = true });

Parallel.ForEach(blobInfos, (blobInfo) =>

{

    // get the blob properties

    CloudBlob blob = container.GetBlobReference(blobInfo.Uri.ToString());

    blob.FetchAttributes();

    // set cache-control header if necessary

    if (blob.Properties.CacheControl != YOUR_CACHE_CONTROL_HEADER)

    {

        blob.Properties.CacheControl = YOUR_CACHE_CONTROL_HEADER;

        blob.SetProperties();

    }

});

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