Administrator’s Command Line Guide

Chapter 3. Accessing Storage Clusters via S3 Protocol
3.1.5 Operations on Objects
This section familiarizes you with operations S3 storage processes: operations requests; create, read, and
delete operations.
3.1.5.1 Operation Requests
To create, delete, read an object or alter its data, S3 object storage must first request one if these operations
and then perform it. The overall process of requesting and performing an operation consists of the following:
1. Requesting user authentication data. It will be stored on a name server in a specific format (see Service
Buckets). To receive data (identifier, e-mail, access keys), a request with a lookup operation code is sent
to an appropriate name server.
2. Authenticating the user.
3. Requesting bucket’s and object’s metadata. To receive it, another request with a lookup operation code
is sent to the name server that stores names of objects and buckets.
4. Checking user’s access permissions to buckets and objects.
5. Performing the requested object operation: creating, editing or reading data or deleting the object.
3.1.5.2 Create Operation
To create an object, gateway sends the following requests:
1. Request with a guard operation code to a name server. It creates a guard with a timer which will check
after a fixed time period if an object with the data was indeed created. If it was not, the create
operation will fail and the guard will request the object server to delete the object’s data if some were
written. After that the guard is deleted.
2. Request with a create operation code to an object server followed by fixed-size messages containing
the object’s data. The last message includes an end-of-data flag.
3. Another request with a create operation code to the name server. The server checks if the
corresponding guard exists and, if it does not, the operation fails. Otherwise, the server creates a name
and sends a confirmation of successful creation to the gateway.
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