kubernetes · thockin · May 27, 2015 · May 22, 2015
diff --git a/docs/design/expansion.md b/docs/design/expansion.md
@@ -207,9 +207,8 @@ The necessary changes to implement this functionality are:
 2.  Introduce `third_party/golang/expansion` package that provides:
     1.  An `Expand(string, func(string) string) string` function
     2.  A `MappingFuncFor(ObjectEventRecorder, ...map[string]string) string` function 
-3.  Add a new EnvVarSource for expansions and associated tests
-4.  Make the kubelet expand environment correctly
-5.  Make the kubelet expand command correctly
+3.  Make the kubelet expand environment correctly
+4.  Make the kubelet expand command correctly
 
 #### Event Recording
 
@@ -277,31 +276,17 @@ func Expand(input string, mapping func(string) string) string {
 }
 ```
 
-#### Expansion `EnvVarSource`
-
-In order to avoid changing the existing behavior of the `EnvVar.Value` field, there should be a new
-`EnvVarSource` that represents a variable expansion that an env var's value should come from:
-
-```go
-// EnvVarSource represents a source for the value of an EnvVar.
-type EnvVarSource struct {
-	// Other fields omitted
-
-	Expansion *EnvVarExpansion
-}
-
-type EnvVarExpansion struct {
-	// The input string to be expanded
-	Expand string
-}
-```
-
 #### Kubelet changes
 
-The Kubelet should change to:
+The Kubelet should be made to correctly expand variables references in a container's environment, 
+command, and args.  Changes will need to be made to:
 
-1.  Correctly expand environment variables with `Expansion` sources
-2.  Correctly expand references in the Command and Args
+1.  The `makeEnvironmentVariables` function in the kubelet; this is used by
+    `GenerateRunContainerOptions`, which is used by both the docker and rkt container runtimes
+2.  The docker manager `setEntrypointAndCommand` func has to be changed to perform variable
+    expansion
+3.  The rkt runtime should be made to support expansion in command and args when support for it is
+    implemented
 
 ### Examples
 

diff --git a/pkg/api/types.go b/pkg/api/types.go
@@ -541,7 +541,13 @@ type EnvVar struct {
 	// Required: This must be a C_IDENTIFIER.
 	Name string `json:"name"`
 	// Optional: no more than one of the following may be specified.
-	// Optional: Defaults to "".
+	// Optional: Defaults to ""; variable references $(VAR_NAME) are expanded
+	// using the previous defined environment variables in the container and
+	// any service environment variables.  If a variable cannot be resolved,
+	// the reference in the input string will be unchanged.  The $(VAR_NAME)
+	// syntax can be escaped with a double $$, ie: $$(VAR_NAME).  Escaped
+	// references will never be expanded, regardless of whether the variable
+	// exists or not.
 	Value string `json:"value,omitempty"`
 	// Optional: Specifies a source the value of this var should come from.
 	ValueFrom *EnvVarSource `json:"valueFrom,omitempty"`
@@ -640,8 +646,16 @@ type Container struct {
 	// Required.
 	Image string `json:"image"`
 	// Optional: The docker image's entrypoint is used if this is not provided; cannot be updated.
+	// Variable references $(VAR_NAME) are expanded using the container's environment.  If a variable
+	// cannot be resolved, the reference in the input string will be unchanged.  The $(VAR_NAME) syntax
+	// can be escaped with a double $$, ie: $$(VAR_NAME).  Escaped references will never be expanded,
+	// regardless of whether the variable exists or not.
 	Command []string `json:"command,omitempty"`
 	// Optional: The docker image's cmd is used if this is not provided; cannot be updated.
+	// Variable references $(VAR_NAME) are expanded using the container's environment.  If a variable
+	// cannot be resolved, the reference in the input string will be unchanged.  The $(VAR_NAME) syntax
+	// can be escaped with a double $$, ie: $$(VAR_NAME).  Escaped references will never be expanded,
+	// regardless of whether the variable exists or not.
 	Args []string `json:"args,omitempty"`
 	// Optional: Defaults to Docker's default.
 	WorkingDir string          `json:"workingDir,omitempty"`

diff --git a/pkg/api/v1/types.go b/pkg/api/v1/types.go
@@ -550,9 +550,15 @@ type VolumeMount struct {
 type EnvVar struct {
 	// Required: This must be a C_IDENTIFIER.
 	Name string `json:"name" description:"name of the environment variable; must be a C_IDENTIFIER"`
-	// Optional: No more than one of the following may be set.
-	// Optional: Defaults to ""
-	Value string `json:"value,omitempty" description:"value of the environment variable; defaults to empty string"`
+	// Optional: no more than one of the following may be specified.
+	// Optional: Defaults to ""; variable references $(VAR_NAME) are expanded
+	// using the previous defined environment variables in the container and
+	// any service environment variables.  If a variable cannot be resolved,
+	// the reference in the input string will be unchanged.  The $(VAR_NAME)
+	// syntax can be escaped with a double $$, ie: $$(VAR_NAME).  Escaped
+	// references will never be expanded, regardless of whether the variable
+	// exists or not.
+	Value string `json:"value,omitempty" description:"value of the environment variable; defaults to empty string; variable references $(VAR_NAME) are expanded using the previously defined environment varibles in the container and any service environment variables; if a variable cannot be resolved, the reference in the input string will be unchanged; the $(VAR_NAME) syntax can be escaped with a double $$, ie: $$(VAR_NAME) ; escaped references will never be expanded, regardless of whether the variable exists or not"`
 	// Optional: Specifies a source the value of this var should come from.
 	ValueFrom *EnvVarSource `json:"valueFrom,omitempty" description:"source for the environment variable's value; cannot be used if value is not empty"`
 }
@@ -653,9 +659,17 @@ type Container struct {
 	// Required.
 	Image string `json:"image" description:"Docker image name"`
 	// Optional: The docker image's entrypoint is used if this is not provided; cannot be updated.
-	Command []string `json:"command,omitempty" description:"entrypoint array; not executed within a shell; the docker image's entrypoint is used if this is not provided; cannot be updated"`
+	// Variable references $(VAR_NAME) are expanded using the container's environment.  If a variable
+	// cannot be resolved, the reference in the input string will be unchanged.  The $(VAR_NAME) syntax
+	// can be escaped with a double $$, ie: $$(VAR_NAME).  Escaped references will never be expanded,
+	// regardless of whether the variable exists or not.
+	Command []string `json:"command,omitempty" description:"entrypoint array; not executed within a shell; the docker image's entrypoint is used if this is not provided; cannot be updated; variable references $(VAR_NAME) are expanded using the container's environment variables; if a variable cannot be resolved, the reference in the input string will be unchanged; the $(VAR_NAME) syntax can be escaped with a double $$, ie: $$(VAR_NAME) ; escaped references will never be expanded, regardless of whether the variable exists or not"`
 	// Optional: The docker image's cmd is used if this is not provided; cannot be updated.
-	Args []string `json:"args,omitempty" description:"command array; the docker image's cmd is used if this is not provided; arguments to the entrypoint; cannot be updated"`
+	// Variable references $(VAR_NAME) are expanded using the container's environment.  If a variable
+	// cannot be resolved, the reference in the input string will be unchanged.  The $(VAR_NAME) syntax
+	// can be escaped with a double $$, ie: $$(VAR_NAME).  Escaped references will never be expanded,
+	// regardless of whether the variable exists or not.
+	Args []string `json:"args,omitempty" description:"command array; the docker image's cmd is used if this is not provided; arguments to the entrypoint; cannot be updated; variable references $(VAR_NAME) are expanded using the container's environment variables; if a variable cannot be resolved, the reference in the input string will be unchanged; the $(VAR_NAME) syntax can be escaped with a double $$, ie: $$(VAR_NAME) ; escaped references will never be expanded, regardless of whether the variable exists or not"`
 	// Optional: Defaults to Docker's default.
 	WorkingDir     string               `json:"workingDir,omitempty" description:"container's working directory; defaults to image's default; cannot be updated"`
 	Ports          []ContainerPort      `json:"ports,omitempty" description:"list of ports to expose from the container; cannot be updated" patchStrategy:"merge" patchMergeKey:"containerPort"`

diff --git a/pkg/api/v1beta1/types.go b/pkg/api/v1beta1/types.go
@@ -439,9 +439,15 @@ type EnvVar struct {
 	// DEPRECATED: EnvVar.Key will be removed in a future version of the API.
 	Name string `json:"name" description:"name of the environment variable; must be a C_IDENTIFIER"`
 	Key  string `json:"key,omitempty" description:"name of the environment variable; must be a C_IDENTIFIER; deprecated - use name instead"`
-	// Optional: No more than one of the following may be set.
-	// Optional: Defaults to ""
-	Value string `json:"value,omitempty" description:"value of the environment variable; defaults to empty string"`
+	// Optional: no more than one of the following may be specified.
+	// Optional: Defaults to ""; variable references $(VAR_NAME) are expanded
+	// using the previous defined environment variables in the container and
+	// any service environment variables.  If a variable cannot be resolved,
+	// the reference in the input string will be unchanged.  The $(VAR_NAME)
+	// syntax can be escaped with a double $$, ie: $$(VAR_NAME).  Escaped
+	// references will never be expanded, regardless of whether the variable
+	// exists or not.
+	Value string `json:"value,omitempty" description:"value of the environment variable; defaults to empty string; variable references $(VAR_NAME) are expanded using the previously defined environment varibles in the container and any service environment variables; if a variable cannot be resolved, the reference in the input string will be unchanged; the $(VAR_NAME) syntax can be escaped with a double $$, ie: $$(VAR_NAME) ; escaped references will never be expanded, regardless of whether the variable exists or not"`
 	// Optional: Specifies a source the value of this var should come from.
 	ValueFrom *EnvVarSource `json:"valueFrom,omitempty" description:"source for the environment variable's value; cannot be used if value is not empty"`
 }
@@ -542,9 +548,17 @@ type Container struct {
 	// Required.
 	Image string `json:"image" description:"Docker image name"`
 	// Optional: The image's entrypoint is used if this is not provided; cannot be updated.
-	Entrypoint []string `json:"entrypoint,omitempty" description:"entrypoint array; not executed within a shell; the image's entrypoint is used if this is not provided; cannot be updated"`
+	// Variable references $(VAR_NAME) are expanded using the container's environment.  If a variable
+	// cannot be resolved, the reference in the input string will be unchanged.  The $(VAR_NAME) syntax
+	// can be escaped with a double $$, ie: $$(VAR_NAME).  Escaped references will never be expanded,
+	// regardless of whether the variable exists or not.
+	Entrypoint []string `json:"entrypoint,omitempty" description:"entrypoint array; not executed within a shell; the image's entrypoint is used if this is not provided; cannot be updated; variable references $(VAR_NAME) are expanded using the container's environment variables; if a variable cannot be resolved, the reference in the input string will be unchanged; the $(VAR_NAME) syntax can be escaped with a double $$, ie: $$(VAR_NAME) ; escaped references will never be expanded, regardless of whether the variable exists or not"`
 	// Optional: The image's cmd is used if this is not provided; cannot be updated.
-	Command []string `json:"command,omitempty" description:"command argv array; not executed within a shell; the image's cmd is used if this is not provided; cannot be updated"`
+	// Variable references $(VAR_NAME) are expanded using the container's environment.  If a variable
+	// cannot be resolved, the reference in the input string will be unchanged.  The $(VAR_NAME) syntax
+	// can be escaped with a double $$, ie: $$(VAR_NAME).  Escaped references will never be expanded,
+	// regardless of whether the variable exists or not.
+	Command []string `json:"command,omitempty" description:"command argv array; not executed within a shell; the image's cmd is used if this is not provided; cannot be updated; variable references $(VAR_NAME) are expanded using the container's environment variables; if a variable cannot be resolved, the reference in the input string will be unchanged; the $(VAR_NAME) syntax can be escaped with a double $$, ie: $$(VAR_NAME) ; escaped references will never be expanded, regardless of whether the variable exists or not"`
 	// Optional: Docker's default is used if this is not provided.
 	WorkingDir string               `json:"workingDir,omitempty" description:"container's working directory; defaults to image's default; cannot be updated"`
 	Ports      []ContainerPort      `json:"ports,omitempty" description:"list of ports to expose from the container; cannot be updated"`

diff --git a/pkg/api/v1beta2/types.go b/pkg/api/v1beta2/types.go
@@ -413,9 +413,15 @@ type VolumeMount struct {
 type EnvVar struct {
 	// Required: This must be a C_IDENTIFIER.
 	Name string `json:"name" description:"name of the environment variable; must be a C_IDENTIFIER"`
-	// Optional: No more than one of the following may be set.
-	// Optional: Defaults to ""
-	Value string `json:"value,omitempty" description:"value of the environment variable; defaults to empty string"`
+	// Optional: no more than one of the following may be specified.
+	// Optional: Defaults to ""; variable references $(VAR_NAME) are expanded
+	// using the previous defined environment variables in the container and
+	// any service environment variables.  If a variable cannot be resolved,
+	// the reference in the input string will be unchanged.  The $(VAR_NAME)
+	// syntax can be escaped with a double $$, ie: $$(VAR_NAME).  Escaped
+	// references will never be expanded, regardless of whether the variable
+	// exists or not.
+	Value string `json:"value,omitempty" description:"value of the environment variable; defaults to empty string; variable references $(VAR_NAME) are expanded using the previously defined environment varibles in the container and any service environment variables; if a variable cannot be resolved, the reference in the input string will be unchanged; the $(VAR_NAME) syntax can be escaped with a double $$, ie: $$(VAR_NAME) ; escaped references will never be expanded, regardless of whether the variable exists or not"`
 	// Optional: Specifies a source the value of this var should come from.
 	ValueFrom *EnvVarSource `json:"valueFrom,omitempty" description:"source for the environment variable's value; cannot be used if value is not empty"`
 }
@@ -527,9 +533,17 @@ type Container struct {
 	// Required.
 	Image string `json:"image" description:"Docker image name"`
 	// Optional: The image's entrypoint is used if this is not provided; cannot be updated.
-	Entrypoint []string `json:"entrypoint,omitempty" description:"entrypoint array; not executed within a shell; the image's entrypoint is used if this is not provided; cannot be updated"`
+	// Variable references $(VAR_NAME) are expanded using the container's environment.  If a variable
+	// cannot be resolved, the reference in the input string will be unchanged.  The $(VAR_NAME) syntax
+	// can be escaped with a double $$, ie: $$(VAR_NAME).  Escaped references will never be expanded,
+	// regardless of whether the variable exists or not.
+	Entrypoint []string `json:"entrypoint,omitempty" description:"entrypoint array; not executed within a shell; the image's entrypoint is used if this is not provided; cannot be updated; variable references $(VAR_NAME) are expanded using the container's environment variables; if a variable cannot be resolved, the reference in the input string will be unchanged; the $(VAR_NAME) syntax can be escaped with a double $$, ie: $$(VAR_NAME) ; escaped references will never be expanded, regardless of whether the variable exists or not"`
 	// Optional: The image's cmd is used if this is not provided; cannot be updated.
-	Command []string `json:"command,omitempty" description:"command argv array; not executed within a shell; the image's cmd is used if this is not provided; cannot be updated"`
+	// Variable references $(VAR_NAME) are expanded using the container's environment.  If a variable
+	// cannot be resolved, the reference in the input string will be unchanged.  The $(VAR_NAME) syntax
+	// can be escaped with a double $$, ie: $$(VAR_NAME).  Escaped references will never be expanded,
+	// regardless of whether the variable exists or not.
+	Command []string `json:"command,omitempty" description:"command argv array; not executed within a shell; the image's cmd is used if this is not provided; cannot be updated; variable references $(VAR_NAME) are expanded using the container's environment variables; if a variable cannot be resolved, the reference in the input string will be unchanged; the $(VAR_NAME) syntax can be escaped with a double $$, ie: $$(VAR_NAME) ; escaped references will never be expanded, regardless of whether the variable exists or not"`
 	// Optional: Docker's default is used if this is not provided.
 	WorkingDir string               `json:"workingDir,omitempty" description:"container's working directory; defaults to image's default; cannot be updated"`
 	Ports      []ContainerPort      `json:"ports,omitempty" description:"list of ports to expose from the container; cannot be updated"`