Add control over container entrypoint

duda · Mar 31, 2015 · 7628b37 · 7628b37
1 parent 9ed8761
commit 7628b37
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diff --git a/contrib/for-tests/entrypoint-tester/Dockerfile b/contrib/for-tests/entrypoint-tester/Dockerfile
@@ -0,0 +1,20 @@
+# Copyright 2015 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+FROM scratch
+ADD ep ep
+ADD ep ep-2
+EXPOSE 8080
+ENTRYPOINT ["/ep"]
+CMD ["default", "arguments"]
diff --git a/contrib/for-tests/entrypoint-tester/Makefile b/contrib/for-tests/entrypoint-tester/Makefile
@@ -0,0 +1,15 @@
+all: push
+
+TAG = 0.1
+
+ep: ep.go
+	CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -ldflags '-w' ./ep.go
+
+image: ep
+	sudo docker build -t kubernetes/eptest:$(TAG) .
+
+push: image
+	sudo docker push kubernetes/eptest:$(TAG)
+
+clean:
+	rm -f ep
diff --git a/contrib/for-tests/entrypoint-tester/ep.go b/contrib/for-tests/entrypoint-tester/ep.go
@@ -0,0 +1,29 @@
+/*
+Copyright 2015 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+// This program prints the arguments it's passed and exits.
+func main() {
+	args := os.Args
+	fmt.Printf("%v\n", args)
+	os.Exit(0)
+}
diff --git a/docs/containers.md b/docs/containers.md
@@ -1,4 +1,46 @@
-# Container with Kubernetes
+# Containers with Kubernetes
+
+## Containers and commands
+
+So far the Pods we've seen have all used the `image` field to indicate what process Kubernetes
+should run in a container.  In this case, Kubernetes runs the image's default command.  If we want
+to run a particular command or override the image's defaults, there are two additional fields that
+we can use:
+
+1.  `Command`: Controls the actual command run by the image
+2.  `Args`: Controls the arguments passed to the command
+
+### How docker handles command and arguments
+
+Docker images have metadata associated with them that is used to store information about the image.
+The image author may use this to define defaults for the command and arguments to run a container
+when the user does not supply values.  Docker calls the fields for commands and arguments
+`Entrypoint` and `Cmd` respectively.  The full details for this feature are too complicated to 
+describe here, mostly due to the fact that the docker API allows users to specify both of these
+fields as either a string array or a string and there are subtle differences in how those cases are
+handled.  We encourage the curious to check out [docker's documentation]() for this feature.
+
+Kubernetes allows you to override both the image's default command (docker `Entrypoint`) and args
+(docker `Cmd`) with the `Command` and `Args` fields of `Container`.  The rules are:
+
+1.  If you do not supply a `Command` or `Args` for a container, the defaults defined by the image
+    will be used
+2.  If you supply a `Command` but no `Args` for a container, only the supplied `Command` will be
+    used; the image's default arguments are ignored
+3.  If you supply only `Args`, the image's default command will be used with the arguments you
+    supply
+4.  If you supply a `Command` **and** `Args`, the image's defaults will be ignored and the values
+    you supply will be used
+
+Here are examples for these rules in table format
+
+| Image `Entrypoint` |    Image `Cmd`   | Container `Command` |  Container `Args`  |    Command Run   |
+|--------------------|------------------|---------------------|--------------------|------------------|
+|     `[/ep-1]`      |   `[foo bar]`    |   &lt;not set&gt;   |   &lt;not set&gt;  | `[ep-1 foo bar]` | 
+|     `[/ep-1]`      |   `[foo bar]`    |      `[/ep-2]`      |   &lt;not set&gt;  |     `[ep-2]`     | 
+|     `[/ep-1]`      |   `[foo bar]`    |   &lt;not set&gt;   |     `[zoo boo]`    | `[ep-1 zoo boo]` | 
+|     `[/ep-1]`      |   `[foo bar]`    |      `[/ep-2]`      |     `[zoo boo]`    | `[ep-2 zoo boo]` | 
+
 
 ## Capabilities
 

diff --git a/pkg/api/types.go b/pkg/api/types.go
@@ -505,8 +505,10 @@ type Container struct {
 	Name string `json:"name"`
 	// Required.
 	Image string `json:"image"`
-	// Optional: Defaults to whatever is defined in the image.
+	// Optional: The docker image's entrypoint is used if this is not provided; cannot be updated.
 	Command []string `json:"command,omitempty"`
+	// Optional: The docker image's cmd is used if this is not provided; cannot be updated.
+	Args []string `json:"args,omitempty"`
 	// Optional: Defaults to Docker's default.
 	WorkingDir string          `json:"workingDir,omitempty"`
 	Ports      []ContainerPort `json:"ports,omitempty"`

diff --git a/pkg/api/v1beta1/conversion.go b/pkg/api/v1beta1/conversion.go
@@ -532,7 +532,10 @@ func init() {
 			if err := s.Convert(&in.Image, &out.Image, 0); err != nil {
 				return err
 			}
-			if err := s.Convert(&in.Command, &out.Command, 0); err != nil {
+			if err := s.Convert(&in.Command, &out.Entrypoint, 0); err != nil {
+				return err
+			}
+			if err := s.Convert(&in.Args, &out.Command, 0); err != nil {
 				return err
 			}
 			if err := s.Convert(&in.WorkingDir, &out.WorkingDir, 0); err != nil {
@@ -615,7 +618,10 @@ func init() {
 			if err := s.Convert(&in.Image, &out.Image, 0); err != nil {
 				return err
 			}
-			if err := s.Convert(&in.Command, &out.Command, 0); err != nil {
+			if err := s.Convert(&in.Command, &out.Args, 0); err != nil {
+				return err
+			}
+			if err := s.Convert(&in.Entrypoint, &out.Command, 0); err != nil {
 				return err
 			}
 			if err := s.Convert(&in.WorkingDir, &out.WorkingDir, 0); err != nil {

diff --git a/pkg/api/v1beta1/types.go b/pkg/api/v1beta1/types.go
@@ -411,9 +411,11 @@ type Container struct {
 	Name string `json:"name" description:"name of the container; must be a DNS_LABEL and unique within the pod; cannot be updated"`
 	// Required.
 	Image string `json:"image" description:"Docker image name"`
-	// Optional: Defaults to whatever is defined in the image.
-	Command []string `json:"command,omitempty" description:"command argv array; not executed within a shell; defaults to entrypoint or command in the image; cannot be updated"`
-	// Optional: Defaults to Docker's default.
+	// 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"`
+	// 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"`
+	// 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"`
 	Env        []EnvVar             `json:"env,omitempty" description:"list of environment variables to set in the container; cannot be updated"`

diff --git a/pkg/api/v1beta2/conversion.go b/pkg/api/v1beta2/conversion.go
@@ -317,13 +317,15 @@ func init() {
 			if err := s.Convert(&in.Image, &out.Image, 0); err != nil {
 				return err
 			}
-			if err := s.Convert(&in.Command, &out.Command, 0); err != nil {
+			if err := s.Convert(&in.Command, &out.Entrypoint, 0); err != nil {
+				return err
+			}
+			if err := s.Convert(&in.Args, &out.Command, 0); err != nil {
 				return err
 			}
 			if err := s.Convert(&in.WorkingDir, &out.WorkingDir, 0); err != nil {
 				return err
 			}
-
 			if err := s.Convert(&in.Ports, &out.Ports, 0); err != nil {
 				return err
 			}
@@ -403,7 +405,10 @@ func init() {
 			if err := s.Convert(&in.Image, &out.Image, 0); err != nil {
 				return err
 			}
-			if err := s.Convert(&in.Command, &out.Command, 0); err != nil {
+			if err := s.Convert(&in.Command, &out.Args, 0); err != nil {
+				return err
+			}
+			if err := s.Convert(&in.Entrypoint, &out.Command, 0); err != nil {
 				return err
 			}
 			if err := s.Convert(&in.WorkingDir, &out.WorkingDir, 0); err != nil {

diff --git a/pkg/api/v1beta2/types.go b/pkg/api/v1beta2/types.go
@@ -393,9 +393,11 @@ type Container struct {
 	Name string `json:"name" description:"name of the container; must be a DNS_LABEL and unique within the pod; cannot be updated"`
 	// Required.
 	Image string `json:"image" description:"Docker image name"`
-	// Optional: Defaults to whatever is defined in the image.
-	Command []string `json:"command,omitempty" description:"command argv array; not executed within a shell; defaults to entrypoint or command in the image; cannot be updated"`
-	// Optional: Defaults to Docker's default.
+	// 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"`
+	// 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"`
+	// 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"`
 	Env        []EnvVar             `json:"env,omitempty" description:"list of environment variables to set in the container; cannot be updated"`

diff --git a/pkg/api/v1beta3/types.go b/pkg/api/v1beta3/types.go
@@ -520,8 +520,10 @@ type Container struct {
 	Name string `json:"name" description:"name of the container; must be a DNS_LABEL and unique within the pod; cannot be updated"`
 	// Required.
 	Image string `json:"image" description:"Docker image name"`
-	// Optional: Defaults to whatever is defined in the image.
-	Command []string `json:"command,omitempty" description:"command argv array; not executed within a shell; defaults to entrypoint or command in the image; cannot be updated"`
+	// 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"`
+	// 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"`
 	// 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"`

diff --git a/pkg/kubelet/container/container_reference_manager.go b/pkg/kubelet/container/container_reference_manager.go
@@ -17,7 +17,6 @@ limitations under the License.
 package container
 
 import (
-	"fmt"
 	"sync"
 
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
@@ -62,41 +61,3 @@ func (c *RefManager) GetRef(id string) (ref *api.ObjectReference, ok bool) {
 	ref, ok = c.containerIDToRef[id]
 	return ref, ok
 }
-
-// fieldPath returns a fieldPath locating container within pod.
-// Returns an error if the container isn't part of the pod.
-func fieldPath(pod *api.Pod, container *api.Container) (string, error) {
-	for i := range pod.Spec.Containers {
-		here := &pod.Spec.Containers[i]
-		if here.Name == container.Name {
-			if here.Name == "" {
-				return fmt.Sprintf("spec.containers[%d]", i), nil
-			} else {
-				return fmt.Sprintf("spec.containers{%s}", here.Name), nil
-			}
-		}
-	}
-	return "", fmt.Errorf("container %#v not found in pod %#v", container, pod)
-}
-
-// GenerateContainerRef returns an *api.ObjectReference which references the given container within the
-// given pod. Returns an error if the reference can't be constructed or the container doesn't
-// actually belong to the pod.
-// TODO: Pods that came to us by static config or over HTTP have no selfLink set, which makes
-// this fail and log an error. Figure out how we want to identify these pods to the rest of the
-// system.
-// TODO(yifan): Revisit this function later, for current case it does not need to use RefManager
-// as a receiver.
-func (c *RefManager) GenerateContainerRef(pod *api.Pod, container *api.Container) (*api.ObjectReference, error) {
-	fieldPath, err := fieldPath(pod, container)
-	if err != nil {
-		// TODO: figure out intelligent way to refer to containers that we implicitly
-		// start (like the pod infra container). This is not a good way, ugh.
-		fieldPath = "implicitly required container " + container.Name
-	}
-	ref, err := api.GetPartialReference(pod, fieldPath)
-	if err != nil {
-		return nil, err
-	}
-	return ref, nil
-}
diff --git a/pkg/kubelet/container/container_reference_manager_test.go b/pkg/kubelet/container/container_reference_manager_test.go
diff --git a/pkg/kubelet/container/ref.go b/pkg/kubelet/container/ref.go
@@ -0,0 +1,59 @@
+/*
+Copyright 2015 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package container
+
+import (
+	"fmt"
+
+	"github.com/GoogleCloudPlatform/kubernetes/pkg/api"
+)
+
+// GenerateContainerRef returns an *api.ObjectReference which references the given container
+// within the given pod. Returns an error if the reference can't be constructed or the
+// container doesn't actually belong to the pod.
+//
+// This function will return an error if the provided Pod does not have a selfLink,
+// but we expect selfLink to be populated at all call sites for the function.
+func GenerateContainerRef(pod *api.Pod, container *api.Container) (*api.ObjectReference, error) {
+	fieldPath, err := fieldPath(pod, container)
+	if err != nil {
+		// TODO: figure out intelligent way to refer to containers that we implicitly
+		// start (like the pod infra container). This is not a good way, ugh.
+		fieldPath = "implicitly required container " + container.Name
+	}
+	ref, err := api.GetPartialReference(pod, fieldPath)
+	if err != nil {
+		return nil, err
+	}
+	return ref, nil
+}
+
+// fieldPath returns a fieldPath locating container within pod.
+// Returns an error if the container isn't part of the pod.
+func fieldPath(pod *api.Pod, container *api.Container) (string, error) {
+	for i := range pod.Spec.Containers {
+		here := &pod.Spec.Containers[i]
+		if here.Name == container.Name {
+			if here.Name == "" {
+				return fmt.Sprintf("spec.containers[%d]", i), nil
+			} else {
+				return fmt.Sprintf("spec.containers{%s}", here.Name), nil
+			}
+		}
+	}
+	return "", fmt.Errorf("container %#v not found in pod %#v", container, pod)
+}