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Re-add namespaces

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Tim Hockin 2014-09-11 11:04:54 -07:00
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docs/identifiers.md
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@ -36,18 +36,14 @@ Name
## General design
1. When an object is created via an api, a Name string (a DNS_SUBDOMAIN) must be provided.
1. must be non-empty and unique within the apiserver
2. enables idempotent and space-unique creation
1. generating random names will defeat idempotentcy
2. for situations where generating a name is impractical, some or all objects may support a param to auto-generate a name
3. parts of the system (e.g. replication controller) may join strings (e.g. a base name and a random suffix) to create a unique Name
Example: "guestbook.user"
Example: "backend-x4eb1"
1. When an object is created via an API, a Name string (a DNS_SUBDOMAIN) must be specified. Name must be non-empty and unique within the apiserver. This enables idempotent and space-unique creation operations. Parts of the system (e.g. replication controller) may join strings (e.g. a base name and a random suffix) to create a unique Name. For situations where generating a name is impractical, some or all objects may support a param to auto-generate a name. Generating random names will defeat idempotency.
* Examples: "guestbook.user", "backend-x4eb1"
2. Upon acceptance of an object via an api, the object is assigned a UID (a UUID).
1. must be non-empty and unique across space and time
Example: "01234567-89ab-cdef-0123-456789abcdef"
2. When an object is created via an api, a Namespace string (a DNS_SUBDOMAIN? format TBD via #1114) may be specified. Depending on the API receiver, namespaces might be validated (e.g. apiserver might ensure that the namespace actually exists). If a namespace is not specified, one will be assigned by the API receiver. This assignment policy might vary across API receivers (e.g. apiserver might have a default, kubelet might generate something semi-random).
* Example: "api.k8s.example.com"
3. Upon acceptance of an object via an API, the object is assigned a UID (a UUID). UID must be non-empty and unique across space and time.
* Example: "01234567-89ab-cdef-0123-456789abcdef"
## Case study: Scheduling a pod
@ -58,40 +54,37 @@ objectives.
### A pod scheduled by a user through the apiserver
1. A user submits a pod named "guestbook" to the apiserver.
1. A user submits a pod with Namespace="" and Name="guestbook" to the apiserver.
2. The apiserver validates the input.
1. The pod name must be space-unique within the apiserver.
2. Each container within the pod has a name which must be space-unique within the pod.
1. A default Namespace is assigned.
2. The pod name must be space-unique within the Namespace.
3. Each container within the pod has a name which must be space-unique within the pod.
3. The pod is accepted and a UID is assigned.
3. The pod is accepted.
1. A new UID is assigned.
4. The pod is bound to a node.
1. The kubelet on the node is passed the pod's UID and name.
1. The kubelet on the node is passed the pod's UID, Namespace, and Name.
5. Kubelet validates the input.
6. Kubelet further namespaces the pod name with information about the source of the pod.
1. E.g. Namespace="api.k8s.example.com"
7. Kubelet runs the pod.
6. Kubelet runs the pod.
1. Each container is started up with enough metadata to distinguish the pod from whence it came.
2. Each attempt to run a container is assigned a UID (a string) that is unique across time.
1. This may correspond to Docker's container ID.
* This may correspond to Docker's container ID.
### A pod placed by a config file on the node
1. A config file is stored on the node, containing a pod named "cadvisor" with no UID.
1. A config file is stored on the node, containing a pod with UID="", Namespace="", and Name="cadvisor".
2. Kubelet validates the input.
1. Since UID is not provided, kubelet generates one.
2. Since Namespace is not provided, kubelet generates one.
1. The generated namespace should be deterministic and cluster-unique for the source, such as a hash of the hostname and file path.
* E.g. Namespace="file-f4231812554558a718a01ca942782d81"
3. Kubelet further namespaces the pod name with information about the source of the pod.
1. The generated namespace should be deterministic and cluster-unique for the source.
1. E.g. a hash of the hostname and file path.
2. E.g. Namespace="file-f4231812554558a718a01ca942782d81"
4. Kubelet runs the pod.
3. Kubelet runs the pod.
1. Each container is started up with enough metadata to distinguish the pod from whence it came.
2. Each attempt to run a container is assigned a UID (a string) that is unique across time.
1. This may correspond to Docker's container ID.