This page discusses the metadata fields that are stored along with buckets in Cloud Storage.
Buckets created in Cloud Storage have metadata associated with them. Metadata identifies properties of the bucket and specifies how the bucket should be handled when it's accessed.
Some metadata exists as
key: value pairs. For example, the name of a bucket is
represented by the metadata entry
name: my-bucket-name for the JSON API. The
XML API presents such metadata as
<elements></elements>, such as
<LocationConstraint>US</LocationConstraint> for the bucket location.
Other metadata can have an array of data associated with the key. For example, the lifecycle management metadata can contain a set of rules that apply to current and future objects in a bucket.
The mutability of metadata varies:
Some you can only view.
Some you can only set when the bucket is first created, and cannot edit or remove.
Some you can add and edit, but not remove.
Some you can add, edit, and remove at any time.
The following metadata is set during bucket creation, and cannot be edited or removed:
The project the bucket is a part of
- A bucket's metageneration number uniquely identifies the metadata state of
the bucket. The metageneration number is
1at the time of bucket creation and increases each time you modify the bucket's metadata.
- A bucket's metageneration number uniquely identifies the metadata state of the bucket. The metageneration number is
Editable bucket metadata is metadata whose values you can typically modify at any time. In some cases, such as the bucket being subject to an organization policy constraint, there are restrictions on modifying certain metadata values.
1 This metadata cannot be viewed or managed using the XML API.
2 You can use the XML API to set this metadata during bucket creation, but not to view or manage this metadata.
Bucket labels allow you to create arbitrary key:value pairs that are stored
as part of the bucket's metadata. You can use labels to organize your buckets
along with other Google Cloud resources such as virtual machine instances
and persistent disks. For example, say you want a key named
has the values
delta, which you will use to indicate
which team is associated with certain Google Cloud resources. You can
apply the labels
team:delta to the
desired resources to achieve this.
Keep in mind the following when working with bucket labels:
- Keys and values cannot be longer than 63 characters each.
- Keys and values can only contain lowercase letters, numeric characters, underscores, and dashes. International characters are allowed.
- Label keys must start with a lowercase letter and international characters are allowed.
- Label keys cannot be empty.
- Each bucket can have a maximum of 64 labels actively applied to it.
- As is generally the case for bucket metadata, bucket labels are not associated with individual objects or object metadata.
For a general example of using labels to organize your resources in billing, see Billing Export to BigQuery Query Examples.