[GitHub] chetanmeh commented on issue #3356: Add method to delete attachment to ArtifactStore

[GitBox <gi...@apache.org>]

chetanmeh commented on issue #3356: Add method to delete attachment to ArtifactStore
URL: https://github.com/apache/incubator-openwhisk/issues/3356#issuecomment-368923722
 
 
   Currently when any entity is deleted we do not have entity instance. So this would make it tricky to implement `deleteAttachment(docInfo, name)`. Instead we can have a method like
   
   ```
   protected[core] def deleteAttachments[T](doc: DocInfo)(
       implicit transid: TransactionId): Future[Boolean]
   ```
   Here the `ArtifactStore` implementation can remove all attachments related to the given docId. This requires that
   1. custom `AttachmentStore` (probably a new SPI for later) stores attachment with blob id set to "${doc.id.id}/$name"
   2. Delete operation can be implemented by removing all blobs with id starting with document id
   
   This may involve multiple calls depending on `AttachmentStore`  implementation. 
   
   ### S3
   
   S3 does not provide a direct call to [delete by prefix][1]. Instead we need to 
   
   1. first [list blobid][2] matching given prefix 
   2. Delete then via [multiple delete support][3]
   
   ### Azure Blob Storage
   
   It does not support performing multiple deletes in single call. Instead we would need to 
   
   1. [List Blobs][4] matching given prefix
   2. Delete then [one by one][5]
   
   [1]: https://stackoverflow.com/questions/3178685/how-to-delete-lot-of-objects-named-with-common-prefix-from-s3-bucket
   [2]: https://docs.aws.amazon.com/AmazonS3/latest/API/v2-RESTBucketGET.html
   [3]: https://docs.aws.amazon.com/AmazonS3/latest/API/multiobjectdeleteapi.html
   [4]: https://docs.microsoft.com/en-us/rest/api/storageservices/list-blobs
   [5]: https://docs.microsoft.com/en-us/rest/api/storageservices/delete-blob

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