3.4. S3 support in DIRAC

New in version v7r0p19.

DIRAC can be instrumented to work with S3 technology like AWS or CEPH. This technology relies on username/password authentication, so there are two ways of accessing files:

  • If the credentials are available, we perform a direct access
  • If not, we ask the DIRAC service S3Gateway for a presigned URL

Thus, in order to have a fully functionnal system, you need to configure your storage and install the S3Gateway.

Do not forget to add s3 to the appropriate lists of protocols (Multi Protocol)

Warning

S3 is not a third party capable protocol, so you should never add it there. If you try replicating a file from/to S3, DIRAC will make an intermediate local copy

3.4.1. Storage configuration

The S3 storage is configured like any other SE (see StorageElement), but needs 3 more parameters in the protocol section:

  • SecureConnection: if True, connect with https (default)
  • Aws_access_key_id: the access id
  • Aws_secret_access_key: the access password

If the Aws variables are not defined, a presigned URL will be requested to the S3Gateway. The recommended way to set up your storage is to define all it’s configuration in the central CS except the Aws parameters, and define just these specific parameters in the servers local dirac.cfg.

DIRAC expects that there is one bucket per SE, whose name corresponds to the Path parameter of its configuration.

3.4.2. S3Gateway

This installs like any service:

dirac-admin-sysadmin-cli -H diracserver034.institute.tld
> install service DataManagement S3Gateway

Upon starting, the gateway will check all the available S3 SEs defined and load the credentials. This means that one S3Gateway can serve presigned URL for all the S3 storages you may have, and that it can be duplicated at will.

Before returning the URL, the S3Gateway queries the FileCatalog to check permissions.

The URLs are normally valid for 1 hour, except when asking for a URL to be given to an external application (dirac-dms-lfn-accessURL usecase).