spec: add ExitPolicy type in pod manifest.

The optional `ExitPolicy` type defines the behavior of the pod when
the apps within it exit.

This PR adds 3 valid policies:

- untilAll: The pod exits only when all the apps exit (no matter they
are successful or not).

- onAny: The pod exits when any of the apps exit (no matter they are
successful or not).

- onAnyFailure: The pod exits when any of the apps exit unsuccessfully.

Author: Yifan Gu

examples/pod_runtime.json

@@ -102,5 +102,6 @@
             "name": "ip-address",
             "value": "10.1.2.3"
         }
-    ]
+    ],
+    "exitPolicy": "onAnyFailure"
 }

schema/pod.go

@@ -32,6 +32,7 @@ type PodManifest struct {
 	Isolators   []types.Isolator    `json:"isolators"`
 	Annotations types.Annotations   `json:"annotations"`
 	Ports       []types.ExposedPort `json:"ports"`
+	ExitPolicy  types.ExitPolicy    `json:"exitPolicy"`
 }
 
 // podManifest is a model to facilitate extra validation during the

schema/types/exitpolicy.go

@@ -0,0 +1,57 @@
+// Copyright 2015 The appc Authors
+//
+// 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 types
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+type ExitPolicy string
+
+var validPolicies = map[ExitPolicy]struct{}{
+	"untilAll":     struct{}{},
+	"onAny":        struct{}{},
+	"onAnyFailure": struct{}{},
+}
+
+type exitPolicy ExitPolicy
+
+func (e *ExitPolicy) UnmarshalJSON(data []byte) error {
+	var ep exitPolicy
+	if err := json.Unmarshal(data, &ep); err != nil {
+		return err
+	}
+	ee := ExitPolicy(ep)
+	if err := ee.assertValid(); err != nil {
+		return err
+	}
+	*e = ee
+	return nil
+}
+
+func (e ExitPolicy) MarshalJSON() ([]byte, error) {
+	if err := e.assertValid(); err != nil {
+		return nil, err
+	}
+	return json.Marshal(exitPolicy(e))
+}
+
+func (e ExitPolicy) assertValid() error {
+	if _, ok := validPolicies[e]; !ok {
+		return fmt.Errorf("invalid exit policy %q", string(e))
+	}
+	return nil
+}

schema/types/exitpolicy_test.go

@@ -0,0 +1,34 @@
+// Copyright 2015 The appc Authors
+//
+// 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 types
+
+import (
+	"testing"
+)
+
+func TestGoodExitPolicy(t *testing.T) {
+	for e := range validPolicies {
+		if err := e.assertValid(); err != nil {
+			t.Errorf("good exit policy failed: %v", err)
+		}
+	}
+}
+
+func TestBadExitPolicy(t *testing.T) {
+	e := ExitPolicy("bad")
+	if err := e.assertValid(); err == nil {
+		t.Errorf("bad exit policy valid: %v", err)
+	}
+}

spec/pods.md

@@ -150,7 +150,8 @@ JSON Schema for the Pod Manifest, conforming to [RFC4627](https://tools.ietf.org
             "name": "ftp",
             "hostPort": 2121
         }
-    ]
+    ],
+    "exitPolicy": "onAnyFailure"
 }
 ```
 
@@ -179,3 +180,7 @@ JSON Schema for the Pod Manifest, conforming to [RFC4627](https://tools.ietf.org
 * **ports** (list of objects, optional) list of ports that SHOULD be exposed on the host.
     * **name** (string, required, restricted to the [AC Name](#ac-name-type) formatting) name of the port to be exposed on the host. This field is a key referencing by name ports specified in the Image Manifest(s) of the app(s) within this Pod Manifest; consequently, port names MUST be unique among apps within a pod.
     * **hostPort** (integer, required) port number on the host that will be mapped to the application port.
+* **exitPolicy** (string, optional) a string that specify the exit policy of the pod, if left empty, then it's up to ACE to choose the default behavior. Valid values are:
+    * **untilAll** - the pod exits only when all the apps exit, no matter they are successful or not.
+    * **onAny** - the pod exits when any of the apps exits either successfully or unsuccessfully.
+    * **onAnyFailure** -the pod exits when any of the pod exits unsuccessfully, also the pod exits when there is no app running.