Conditional S3 Requests

VAST Cluster supports the following types of S3 conditional requests:

Conditional Reads

VAST Cluster's support for S3 conditional reads includes GetObject and HeadObject requests that contain the If-Match HTTP header. The request succeeds only if the object's ETag matches the ETag provided in the request. Otherwise, a error 412 Precondition Failed is returned.

For example, to GET an object with an ETag of 6705f2cfc46c0f04559738bb039d59ae:

GET /myobject HTTP/1.1
If-Match: "6705f2cfc46c0f04559738bb039d59ae"

Conditional Writes

With S3 conditional writes, if a PutObject or CompleteMultipartUpload request contains the If-None-Match header and the value is '*', the object is uploaded only if there is no existing object with the same key name in the bucket.

Conditional writes are not supported for versioned buckets.

For example, to PUT an object only on condition that no such object exists in the bucket:

PUT /myobject HTTP/1.1
If-None-Match: *

Conditional Deletes

With S3 conditional deletes, conditions in DeleteObject or DeleteObjects requests let you check, prior to the deletion, if the intended object still exists or if it has been overwritten.

Conditional deletes are also supported for versioned objects. If an object in a versioned bucket has a delete marker, a simple DELETE request (the one that does not specify a particular version) against such an object is handled as though the object does not exist.

To check if the object still exists:.

For DeleteObject : Include the HTTP If-Match header with a value of *, for example:
```
DELETE /myobject HTTP/1.1
If-Match: *
```
For a versioned bucket:
```
DELETE /myobject?versionId=5 HTTP/1.1
If-Match: *
```

For DeleteObjects : Set the object's ETag element in the XML request body to *, for example:

POST /?delete HTTP/1.1
<?xml version="1.0" encoding="UTF-8"?>
<Delete xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
   <Object>
      <Key>myobject</Key>
      <ETag>*</ETag>
   </Object>
</Delete>

For a versioned bucket:

POST /?delete HTTP/1.1
<?xml version="1.0" encoding="UTF-8"?>
<Delete xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
   <Object>
      <Key>myobject1</Key>
      <ETag>*</ETag>
      <VersionId>5</VersionId>
   </Object>
   <Object>
      <Key>myobject2</Key>
      <ETag>*</ETag>
      <VersionId>5</VersionId>
   </Object>
</Delete>

This operation requires s3:DeleteObject permissions.

If the object exists, the operation succeeds and the object gets deleted. Otherwise, error code 404 is returned.

To check if the object has been overwritten:

For DeleteObject : Include the the HTTP If-Match header with a value that represents the ETag of the object to be deleted. For example:
```
DELETE /myobject HTTP/1.1
If-Match: "7f138a09169b250e9dcb378140907378"
```
For a versioned bucket:
```
DELETE /myobject?versionId=5 HTTP/1.1
If-Match: "7f138a09169b250e9dcb378140907378"
```

For DeleteObjects: Set the object's ETag element in the XML request body to the ETag of the object to be deleted. For example:

POST /?delete HTTP/1.1
<?xml version="1.0" encoding="UTF-8"?>
<Delete xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
   <Object>
      <Key>myobject1</Key>
      <ETag>"9b2cf535f27731c974343645a3985328"</ETag>
   </Object>
   <Object>
      <Key>myobject2</Key>
      <ETag>"5d41402abc4b2a76b9719d911017c592"</ETag>
   </Object>
</Delete>

For a versioned bucket:

POST /?delete HTTP/1.1
<?xml version="1.0" encoding="UTF-8"?>
<Delete xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
   <Object>
      <Key>myobject1</Key>
      <ETag>"9b2cf535f27731c974343645a3985328"</ETag>
      <VersionId>5</VersionId>
   </Object>
   <Object>
      <Key>myobject2</Key>
      <ETag>"5d41402abc4b2a76b9719d911017c592"</ETag>
      <VersionId>5</VersionId>
   </Object>
</Delete>

This operation requires s3:DeleteObject and s3:GetObject permissions.

If the object's ETag matches the ETag in the delete request, the operation succeeds and the object gets deleted. Otherwise, error code 412 is returned.

Controlling Conditional Deletes with a Bucket Policy

You can configure a bucket policy to only accept a DeleteObject or DeleteObjects request when the request is conditional and includes an eTag, which can be a specific eTag value or the asterisk wildcard (*) for any value. This forces clients to use the If-Match HTTP header in their delete requests.

Documentation Index

Conditional S3 Requests

Conditional Reads

Conditional Writes

Conditional Deletes

Controlling Conditional Deletes with a Bucket Policy