This tutorial shows you how to download large amounts of data from Azure storage. To complete this tutorial, you must have completed the previous Storage tutorial: Upload large amounts of random data in parallel to Azure storage. To create a remote desktop session with the virtual machine, use the following command on your local machine.
When prompted, enter the credentials used when creating the virtual machine. In the previous tutorial, you only uploaded files to the storage account. Replace the Main method with the following sample. This example comments out the upload task and uncomments the download task and the task to delete the content in the storage account when complete.
After the application has been updated, you need to build the application again. Rebuild the application by running dotnet build as seen in the following example:. Now that the application has been rebuilt it is time to run the application with the updated code.
The application reads the containers located in the storage account specified in the storageconnectionstring. It iterates through the blobs using the GetBlobs method and downloads them to the local machine using the DownloadToAsync method.
It iterates through the blobs 10 at a time using the ListBlobsSegmentedAsync method in the containers and downloads them to the local machine using the DownloadToFileAsync method. The following table shows the BlobRequestOptions defined for each blob as it is downloaded. I appreciate this is a couple of years old now - but I'm coming up against this issue when downloading multiple files and zipping them. I provide SAS Urls for single file downloads - works great, but when a user wants to download, say image files, I don't want to provide SAS URls to the browser to download, I want to consolidate them in to a zip file.
I want to do this without completely freezing my server but am yet to find a front end framework that supports zipping blob files using the clients resources. Any guidance will be greatly appreciated — George Harnwell.
How can we modify the above snippet if we have to preview the file in browser without downloading the actual file to user's local storage — Chaitanya Sairam. DownloadToStream memStream ; Response. ContentType; Response. AddHeader "Content-Length", blob. ToString ; Response. BinaryWrite memStream. So, by doing this, you do realize that the entire contents of the blob will route through your server, right? I can't give my end users access to the entire storage, so an Azure storage explorer wouldn't work.
I posted an alternative answer. I found this was slow as the first byte wont go to the browser until the last byte has come from blob storage. Use Andy's two line answer instead for less memory overhead and a 10ms latency! OpenReadAsync ; return File stream, blob. ContentType, option ;. Andrew Chaa Andrew Chaa 5, 2 2 gold badges 38 38 silver badges 29 29 bronze badges.
This is the best solution if you don't want to risk your SAS tokens getting stolen, they are just in the query string after all so are not encrypted even with https. Also if you are streaming secure videos set EnableRangeProcessing on the File object before returning it and it will let the browser skip through the video without downloading the whole file! DanielBailey I disagree, this will make the whole blob be unnecessarily downloaded to your application, thus consuming bandwidth of your servers, also making the process slower.
You can set expiry date on SAS tokens like David's answer, also you can't just stole a token and read anything, the token appended to the Uri is for that blob only, that means anyone with that Uri could do exactly the same with a Uri from your application that would execute Andy's code above.
It is a bit magical but the whole blob is not downloaded, only the range, it is like the blob storage knows you only want a part of the file and streams only that part to the host, then the host forwards it on with only a tiny buffer. You would need a pretty small expiry date on the SAS tokens to prevent anyone who is doing basic logging of what goes through an access point from not immediately downloading whatever it is, and you cant have it too short as the browser needs time to do the round trip and make the request back out direct to blob storage.
At least if you do a POST under https they will need to decrypt the message to get at the necessary keys to get at the blob, much safer I think but I am no expert on SAS token protection. On a mac machine, use the Homebrew to install python 3,. Next you will need the azure python sdk for blob storage access. Use pip to install the azure python sdk,. The following python program uses Azure python SDK for storage to download all blobs in a storage container to a specified local folder.
The program will create local folders for blobs which use virtual folder names name containing slashes. Next, we are going get access keys for access blob storage which we have created. From this screen, we are going to copy the Connection string key 1.
Adding DemoController and injecting IConfiguration for accessing method We are going to add a controller with name DemoController after adding we are going to add a constructor to it. Mvc; using Microsoft.
Configuration; namespace WebBlobDemo. FileName; await cloudBlobContainer. After selecting the file to upload, click on submit button to upload file to azure blob storage. Implementing UploadFromStreamAsync method to upload file In this method, we are going to upload a file using UploadFromStreamAsync method this method Initiates an asynchronous operation to upload a stream to a block blob.
After selecting the file click on submit to upload file to azure blob storage. After uploading files to blob storage next, we are going get all files from blob storage. See All Blob files In this part, we are going get all blobs which we have uploaded to the Azure blob storage container.
ListBlobsSegmentedAsync string. Empty, true, BlobListingDetails. Round blob. Parse blob. Result; return File blobStream, blockBlob. ContentType, blockBlob. Next, we are going to delete the file from azure blob storage. GetBlobReference blobName ; await blob. Core Extensions.
0コメント