Add annotations and labels to the Spec.

Signed-off-by: Vishnu kannan <vishnuk@google.com>

config.go

@@ -18,6 +18,10 @@ type Spec struct {
 	Mounts []Mount `json:"mounts"`
 	// Hooks are the commands run at various lifecycle events of the container.
 	Hooks Hooks `json:"hooks"`
+	// Labels is a map of string keys and values that can be used to group containers.
+	Labels map[string]string `json:"labels,omitempty"`
+	// Annotations is an unstructured key value map that may be set by external tools to store and retrieve arbitrary metadata.
+	Annotations map[string]string `json:"annotations,omitempty"`
 }
 
 // Process contains information to start a specific application inside the container.

config.md

@@ -231,4 +231,79 @@ If a hook returns a non-zero exit code, then an error is logged and the remainin
 `args` and `env` are optional.
 The semantics are the same as `Path`, `Args` and `Env` in [golang Cmd](https://golang.org/pkg/os/exec/#Cmd).
 
+## Labels
+
+_Labels_ are key/value pairs that can be optionally attached to containers.
+Labels are intended to be used to specify identifying attributes of containers that are meaningful and relevant to users, but which do not directly imply semantics to the runtime.
+Labels can be used to select subsets of containers.
+Each Key must be unique for a container.
+
+```json
+"labels": {
+	"key1": "value1",
+	"key2": "value2"
+}
+```
+
+Since labels will be used to sorting and grouping in UIs, CLIs, etc., we don't want to pollute labels with non-identifying, especially large and/or structured, data.
+Non-identifying information should be recorded using Annotations.
+
+### Syntax and character set
+
+_Labels_ are key value pairs.
+Valid label keys have two segments: an optional prefix and name, separated by a slash (`/`).
+The name segment is required and must be 63 characters or less, beginning and ending with an alphanumeric character (`[a-z0-9A-Z]`) with dashes (`-`), underscores (`_`), dots (`.`), and alphanumerics between.
+The prefix is optional.
+If specified, the prefix must be a DNS subdomain: a series of DNS labels separated by dots (`.`), not longer than 253 characters in total, followed by a slash (`/`).
+If the prefix is omitted, the label key is presumed to be private to the user.
+
+Valid label values must be 63 characters or less and must be empty or begin and end with an alphanumeric character (`[a-z0-9A-Z]`) with dashes (`-`), underscores (`_`), dots (`.`), and alphanumerics between.
+
+### Label selectors
+
+Labels do not provide uniqueness.
+In general, we expect many containers to carry the same label(s).
+
+Via a _label selector_, the client/user can identify a set of containers. 
+
+A label selector can be made of multiple _requirements_ which are comma-separated.
+In the case of multiple requirements, all must be satisfied so the comma separator acts as an _AND_ logical operator.
+
+An empty label selector (that is, one with zero requirements) selects all containers.
+
+#### _Equality-based_ requirement
+
+_Equality-_ or _inequality-based_ requirements allow filtering by label keys and values.
+Matching containers must satisfy all of the specified label constraints, though they may have additional labels as well.
+Three kinds of operators are admitted `=`,`==`,`!=`.
+The first two represent _equality_ (and are simply synonyms), while the latter represents _inequality_. For example:
+
+```
+environment = production
+tier != frontend
+```
+
+The former selects all resources with key equal to `environment` and value equal to `production`.
+The latter selects all resources with key equal to `tier` and value distinct from `frontend`, and all resources with no labels with the `tier` key.
+One could filter for resources in `production` excluding `frontend` using the comma operator: `environment=production,tier!=frontend`
+
+### CLI Examples
+
+```console
+$ runtime list -l enviroment=production,tier=frontend
+```
+
+## Annotations
+
+Annotations are optional arbitrary non-identifying metadata that can be attached to containers.
+This information may be large, may be structured or unstructured, may include characters not permitted by labels.
+Annotations are key-value maps.
+
+```json
+"annotations": {
+	"key1" : "value1",
+	"key2" : "value2"
+}
+```
+
 [uts-namespace]: http://man7.org/linux/man-pages/man7/namespaces.7.html

state.go

@@ -13,4 +13,8 @@ type State struct {
 	Pid int `json:"pid"`
 	// BundlePath is the path to the container's bundle directory.
 	BundlePath string `json:"bundlePath"`
+	// Labels is a map of string keys and values that can be used to group containers.
+	Labels map[string]string `json:"labels,omitempty"`
+	// Annotations is an unstructured key value map that may be set by external tools to store and retrieve arbitrary metadata.
+	Annotations map[string]string `json:"annotations,omitempty"`
 }