Menu
At http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectPUT.html, I found the following:
Amazon S3 never adds partial objects; if you receive a success response, Amazon S3 added the entire object to the bucket.
But that's talking about me receiving a success response. Am I guaranteed that no other client will see the object when listing objects in the bucket -- until the entire object is uploaded?
I want to use S3 as a "spool" directory -- I'll upload files there, and another client will periodically list the files and then download them. I don't want it attempting to download a file that's not completely uploaded.
535
If you pass the same key to upload a file, it is replaced, unless versioning is on. S3 supports versioning. This means that when you upload to the same key twice, two versions of the file are stored. Note that if you upload the exact same file twice, you get to pay for two identical copies of the same file on S3.
Your answer Simply upload your new file on top of your old file to replace an old file in an S3 bucket. The existing file will be overwritten by your new file.
Multipart Upload allows you to upload a single object as a set of parts. After all parts of your object are uploaded, Amazon S3 then presents the data as a single object. With this feature you can create parallel uploads, pause and resume an object upload, and begin uploads before you know the total object size.
In AWS Explorer, expand the Amazon S3 node, and double-click a bucket or open the context (right-click) menu for the bucket and choose Browse. In the Browse view of your bucket, choose Upload File or Upload Folder. In the File-Open dialog box, navigate to the files to upload, choose them, and then choose Open.
When you upload a file to Amazon S3, it is stored as an S3 object. Objects consist of the file data and metadata that describes the object. You can have an unlimited number of objects in a bucket. Before you can upload files to an Amazon S3 bucket, you need write permissions for the bucket.
To upload a large file, run the cp command: Note: The file must be in the same directory that you're running the command from. When you run a high-level (aws s3) command such as aws s3 cp, Amazon S3 automatically performs a multipart upload for large objects.
To store your data in Amazon S3, you work with resources known as buckets and objects. A bucket is a container for objects. An object is a file and any metadata that describes that file.
You can upload any file type—images, backups, data, movies, etc.—into an S3 bucket. The maximum size of a file that you can upload by using the Amazon S3 console is 160 GB. To upload a file larger than 160 GB, use the AWS CLI, AWS SDK, or Amazon S3 REST API.
The answer is along the same line as this:
Amazon S3 never adds partial objects
Until an upload completes, the content that was being uploaded is not technically "in" the bucket.
S3, as you likely know, is not a hierarchical filesystem. It has at least two significant components, the backing store and the index which, unlike in a typical filesystem, are separate... so when you're writing an object, you're not really writing it "in place." Uploading an object saves the object to the backing store, and then adds it to the bucket's index, which is used by GET and other requests to fetch the stored data and metadata for retrieval.
With no entry in the index, the object is not accessible. So you're good. Downloading an object that hasn't finished uploading yet is impossible. The object, technically, doesn't yet exist.
Similarly, if an object already exists and you start overwriting it, anyone attempting to download it would get the "old" copy of the object at least until your upload has finished, and this is true even in a bucket without versioning enabled -- overwriting doesn't overwrite the actual object, it overwrites the index entry, and this only happens when the upload is complete. Note that this mechanism appears to be responsible for the eventual consistency model that applies to PUT requests that overwrite existing objects.
Note, with regard to data integrity: be sure that whatever you are using upload sets the Content-MD request header. This prevents a corrupted upload by giving S3 a mechanism to detect transmission errors and force a failure if the content being uploaded doesn't match.
73
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
