swarm id: Handle compatibility.

Containers created with Swarm<0.3.0 or directly on the host without
going through Swarm don't have a Swarm ID. We are going to fake it by
using the Container ID.

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

api/handlers.go

@@ -198,6 +198,11 @@ func getContainersJSON(c *context, w http.ResponseWriter, r *http.Request) {
 			tmp.Status = "Pending"
 		}
 
+		// Overwrite labels with the ones we have in the config.
+		// This ensures that we can freely manipulate them in the codebase and
+		// they will be properly exported back (for instance Swarm IDs).
+		tmp.Labels = container.Config.Labels
+
 		// TODO remove the Node Name in the name when we have a good solution
 		tmp.Names = make([]string, len(container.Names))
 		for i, name := range container.Names {
@@ -251,6 +256,32 @@ func getContainerJSON(c *context, w http.ResponseWriter, r *http.Request) {
 		httpError(w, err.Error(), http.StatusInternalServerError)
 		return
 	}
+	// Compatibility: Inject the Swarm ID label if not available.
+	// This **must** be done before inserting the `Node` field since it too has
+	// a `Label` field.
+	if !bytes.Contains(data, []byte("\"com.docker.swarm.id\":")) {
+		label := fmt.Sprintf("%q:%q", "com.docker.swarm.id", container.Config.SwarmID())
+		switch {
+		// No `Labels` section at all
+		case !bytes.Contains(data, []byte("\"Labels\":")):
+			data = bytes.Replace(data,
+				[]byte("\"Image\":"),
+				[]byte("\"Labels\":{"+label+"},\"Image\":"),
+				1)
+		// Empty `Labels` section
+		case bytes.Contains(data, []byte("\"Labels\":{}")):
+			data = bytes.Replace(data,
+				[]byte("\"Labels\":{}"),
+				[]byte("\"Labels\":{"+label+"}"),
+				1)
+		// `Labels` section with labels in it
+		case bytes.Contains(data, []byte("\"Labels\":{")):
+			data = bytes.Replace(data,
+				[]byte("\"Labels\":{"),
+				[]byte("\"Labels\":{"+label+","),
+				1)
+		}
+	}
 
 	// insert Node field
 	data = bytes.Replace(data, []byte("\"Name\":\"/"), []byte(fmt.Sprintf("\"Node\":%s,\"Name\":\"/", n)), -1)

cluster/engine.go

@@ -252,6 +252,13 @@ func (e *Engine) updateContainer(c dockerclient.Container, containers map[string
 		container.Config = BuildContainerConfig(*info.Config)
 		container.Config.CpuShares = container.Config.CpuShares * 1024.0 / e.Cpus
 
+		// Compatibility: Containers created with Swarm<0.3.0 or directly on
+		// the host without going through Swarm don't have a Swarm ID. We are
+		// going to fake it by using the Container ID.
+		if container.Config.SwarmID() == "" {
+			container.Config.SetSwarmID(c.Id)
+		}
+
 		// Save the entire inspect back into the container.
 		container.Info = *info
 	}

test/integration/swarm_id.bats

@@ -8,7 +8,7 @@ function teardown() {
 }
 
 @test "swarm id generation" {
-	start_docker_with_busybox 2
+	start_docker_with_busybox 1
 	swarm_manage
 
 	# Create a dummy container just so we interfere with the tests.
@@ -29,3 +29,27 @@ function teardown() {
 	# `docker ps` should be able to filter by Swarm ID using the label.
 	[[ $(docker_swarm ps -a -q --no-trunc --filter="label=com.docker.swarm.id=$swarm_id") == "$id" ]]
 }
+
+@test "swarm id compatbility" {
+	start_docker_with_busybox 1
+	swarm_manage
+
+	# Create a dummy container just so we interfere with the tests.
+	# This one won't be used.
+	docker -H "${HOSTS[0]}" run -d busybox true
+
+	# Create a container directly on the node.
+	id=$(docker -H "${HOSTS[0]}" run -d busybox true)
+
+	# Wait a few seconds for Swarm to detect the container.
+	retry 10 0.5 docker_swarm inspect "$id"
+
+	# Fetch its Swarm ID
+	swarm_id=$(docker_swarm inspect -f '{{ index .Config.Labels "com.docker.swarm.id" }}' "$id")
+
+	# Make sure it's the same as the Container ID.
+	[[ "$id" == "$swarm_id" ]]
+
+	# `docker ps` should be able to filter by Swarm ID using the label.
+	[[ $(docker_swarm ps -a -q --no-trunc --filter="label=com.docker.swarm.id=$swarm_id") == "$id" ]]
+}