Add support for templating Node.Hostname in docker executor

agent/exec/dockerapi/adapter.go

@@ -29,8 +29,8 @@ type containerAdapter struct {
 	secrets   exec.SecretGetter
 }
 
-func newContainerAdapter(client engineapi.APIClient, task *api.Task, secrets exec.SecretGetter) (*containerAdapter, error) {
-	ctnr, err := newContainerConfig(task)
+func newContainerAdapter(client engineapi.APIClient, nodeDescription *api.NodeDescription, task *api.Task, secrets exec.SecretGetter) (*containerAdapter, error) {
+	ctnr, err := newContainerConfig(nodeDescription, task)
 	if err != nil {
 		return nil, err
 	}

agent/exec/dockerapi/container.go

@@ -42,12 +42,12 @@ type containerConfig struct {
 
 // newContainerConfig returns a validated container config. No methods should
 // return an error if this function returns without error.
-func newContainerConfig(t *api.Task) (*containerConfig, error) {
+func newContainerConfig(n *api.NodeDescription, t *api.Task) (*containerConfig, error) {
 	var c containerConfig
-	return &c, c.setTask(t)
+	return &c, c.setTask(n, t)
 }
 
-func (c *containerConfig) setTask(t *api.Task) error {
+func (c *containerConfig) setTask(n *api.NodeDescription, t *api.Task) error {
 	container := t.Spec.GetContainer()
 	if container == nil {
 		return exec.ErrRuntimeUnsupported
@@ -64,7 +64,7 @@ func (c *containerConfig) setTask(t *api.Task) error {
 	}
 
 	c.task = t
-	preparedSpec, err := template.ExpandContainerSpec(t)
+	preparedSpec, err := template.ExpandContainerSpec(n, t)
 	if err != nil {
 		return err
 	}

agent/exec/dockerapi/controller.go

@@ -41,8 +41,8 @@ type controller struct {
 var _ exec.Controller = &controller{}
 
 // newController returns a docker exec controller for the provided task.
-func newController(client engineapi.APIClient, task *api.Task, secrets exec.SecretGetter) (exec.Controller, error) {
-	adapter, err := newContainerAdapter(client, task, secrets)
+func newController(client engineapi.APIClient, nodeDescription *api.NodeDescription, task *api.Task, secrets exec.SecretGetter) (exec.Controller, error) {
+	adapter, err := newContainerAdapter(client, nodeDescription, task, secrets)
 	if err != nil {
 		return nil, err
 	}

agent/exec/dockerapi/controller_integration_test.go

@@ -80,7 +80,7 @@ func TestControllerFlowIntegration(t *testing.T) {
 		return nil
 	})
 
-	ctlr, err := newController(client, task, nil)
+	ctlr, err := newController(client, nil, task, nil)
 	assert.NoError(t, err)
 	assert.NotNil(t, ctlr)
 	assert.NoError(t, ctlr.Prepare(ctx))

agent/exec/dockerapi/controller_test.go

@@ -411,11 +411,19 @@ func TestControllerRemove(t *testing.T) {
 }
 
 func genTestControllerEnv(t *testing.T, task *api.Task) (context.Context, *StubAPIClient, exec.Controller, *containerConfig, func()) {
+	testNodeDescription := &api.NodeDescription{
+		Hostname: "testHostname",
+		Platform: &api.Platform{
+			OS:           "linux",
+			Architecture: "x86_64",
+		},
+	}
+
 	client := NewStubAPIClient()
-	ctlr, err := newController(client, task, nil)
+	ctlr, err := newController(client, testNodeDescription, task, nil)
 	assert.NoError(t, err)
 
-	config, err := newContainerConfig(task)
+	config, err := newContainerConfig(testNodeDescription, task)
 	assert.NoError(t, err)
 	assert.NotNil(t, config)
 

agent/exec/dockerapi/executor.go

@@ -11,21 +11,25 @@ import (
 	"github.com/docker/swarmkit/api"
 	"github.com/docker/swarmkit/log"
 	"golang.org/x/net/context"
+	"sync"
 )
 
 type executor struct {
 	client           engineapi.APIClient
 	secrets          exec.SecretsManager
 	genericResources []*api.GenericResource
+	mutex            sync.Mutex // This mutex protects the following node field
+	node             *api.NodeDescription
 }
 
 // NewExecutor returns an executor from the docker client.
 func NewExecutor(client engineapi.APIClient, genericResources []*api.GenericResource) exec.Executor {
-	return &executor{
+	var executor = &executor{
 		client:           client,
 		secrets:          secrets.NewManager(),
 		genericResources: genericResources,
 	}
+	return executor
 }
 
 // Describe returns the underlying node description from the docker client.
@@ -111,6 +115,11 @@ func (e *executor) Describe(ctx context.Context) (*api.NodeDescription, error) {
 		},
 	}
 
+	// Save the node information in the executor field
+	e.mutex.Lock()
+	e.node = description
+	e.mutex.Unlock()
+
 	return description, nil
 }
 
@@ -120,7 +129,11 @@ func (e *executor) Configure(ctx context.Context, node *api.Node) error {
 
 // Controller returns a docker container controller.
 func (e *executor) Controller(t *api.Task) (exec.Controller, error) {
-	ctlr, err := newController(e.client, t, secrets.Restrict(e.secrets, t))
+	// Get the node description from the executor field
+	e.mutex.Lock()
+	nodeDescription := e.node
+	e.mutex.Unlock()
+	ctlr, err := newController(e.client, nodeDescription, t, secrets.Restrict(e.secrets, t))
 	if err != nil {
 		return nil, err
 	}

manager/controlapi/service.go

@@ -128,7 +128,13 @@ func validateContainerSpec(taskSpec api.TaskSpec) error {
 	// Building a empty/dummy Task to validate the templating and
 	// the resulting container spec as well. This is a *best effort*
 	// validation.
-	container, err := template.ExpandContainerSpec(&api.Task{
+	container, err := template.ExpandContainerSpec(&api.NodeDescription{
+		Hostname: "nodeHostname",
+		Platform: &api.Platform{
+			OS:           "os",
+			Architecture: "architecture",
+		},
+	}, &api.Task{
 		Spec:      taskSpec,
 		ServiceID: "serviceid",
 		Slot:      1,

template/context.go

@@ -14,6 +14,12 @@ import (
 	"github.com/pkg/errors"
 )
 
+// Platform holds information about the underlying platform of the node
+type Platform struct {
+	Architecture string
+	OS           string
+}
+
 // Context defines the strict set of values that can be injected into a
 // template expression in SwarmKit data structure.
 // NOTE: Be very careful adding any fields to this structure with types
@@ -27,7 +33,9 @@ type Context struct {
 	}
 
 	Node struct {
-		ID string
+		ID       string
+		Hostname string
+		Platform Platform
 	}
 
 	Task struct {
@@ -41,16 +49,25 @@ type Context struct {
 	}
 }
 
-// NewContextFromTask returns a new template context from the data available in
-// task. The provided context can then be used to populate runtime values in a
+// NewContext returns a new template context from the data available in the
+// task and the node where it is scheduled to run.
+// The provided context can then be used to populate runtime values in a
 // ContainerSpec.
-func NewContextFromTask(t *api.Task) (ctx Context) {
+func NewContext(n *api.NodeDescription, t *api.Task) (ctx Context) {
 	ctx.Service.ID = t.ServiceID
 	ctx.Service.Name = t.ServiceAnnotations.Name
 	ctx.Service.Labels = t.ServiceAnnotations.Labels
 
 	ctx.Node.ID = t.NodeID
 
+	// Add node information to context only if we have them available
+	if n != nil {
+		ctx.Node.Hostname = n.Hostname
+		ctx.Node.Platform = Platform{
+			Architecture: n.Platform.Architecture,
+			OS:           n.Platform.OS,
+		}
+	}
 	ctx.Task.ID = t.ID
 	ctx.Task.Name = naming.Task(t)
 
@@ -157,12 +174,13 @@ func (ctx PayloadContext) envGetter(variable string) (string, error) {
 }
 
 // NewPayloadContextFromTask returns a new template context from the data
-// available in the task. This context also provides access to the configs
+// available in the task and the node where it is scheduled to run.
+// This context also provides access to the configs
 // and secrets that the task has access to. The provided context can then
 // be used to populate runtime values in a templated config or secret.
-func NewPayloadContextFromTask(t *api.Task, dependencies exec.DependencyGetter) (ctx PayloadContext) {
+func NewPayloadContextFromTask(node *api.NodeDescription, t *api.Task, dependencies exec.DependencyGetter) (ctx PayloadContext) {
 	return PayloadContext{
-		Context:           NewContextFromTask(t),
+		Context:           NewContext(node, t),
 		t:                 t,
 		restrictedSecrets: secrets.Restrict(dependencies.Secrets(), t),
 		restrictedConfigs: configs.Restrict(dependencies.Configs(), t),

template/context_test.go

@@ -10,11 +10,12 @@ import (
 
 func TestTemplateContext(t *testing.T) {
 	for _, testcase := range []struct {
-		Test     string
-		Task     *api.Task
-		Context  Context
-		Expected *api.ContainerSpec
-		Err      error
+		Test            string
+		Task            *api.Task
+		Context         Context
+		Expected        *api.ContainerSpec
+		Err             error
+		NodeDescription *api.NodeDescription
 	}{
 		{
 			Test: "Identity",
@@ -35,6 +36,8 @@ func TestTemplateContext(t *testing.T) {
 					},
 				}
 			}),
+			NodeDescription: modifyNode(func(n *api.NodeDescription) {
+			}),
 			Expected: &api.ContainerSpec{
 				Env: []string{
 					"NOTOUCH=dont",
@@ -70,6 +73,8 @@ func TestTemplateContext(t *testing.T) {
 					},
 				}
 			}),
+			NodeDescription: modifyNode(func(n *api.NodeDescription) {
+			}),
 			Expected: &api.ContainerSpec{
 				Labels: map[string]string{
 					"ContainerLabel": "should-NOT-end-up-as-task",
@@ -106,6 +111,8 @@ func TestTemplateContext(t *testing.T) {
 					},
 				}
 			}),
+			NodeDescription: modifyNode(func(n *api.NodeDescription) {
+			}),
 			Expected: &api.ContainerSpec{
 				Mounts: []api.Mount{
 					{
@@ -130,13 +137,53 @@ func TestTemplateContext(t *testing.T) {
 					},
 				}
 			}),
+			NodeDescription: modifyNode(func(n *api.NodeDescription) {
+			}),
 			Expected: &api.ContainerSpec{
 				Hostname: "myhost-10",
 			},
 		},
+		{
+			Test: "Node hostname",
+			Task: modifyTask(func(t *api.Task) {
+				t.Spec = api.TaskSpec{
+					Runtime: &api.TaskSpec_Container{
+						Container: &api.ContainerSpec{
+							Hostname: "myservice-{{.Node.Hostname}}",
+						},
+					},
+				}
+			}),
+			NodeDescription: modifyNode(func(n *api.NodeDescription) {
+				n.Hostname = "mynode"
+			}),
+			Expected: &api.ContainerSpec{
+				Hostname: "myservice-mynode",
+			},
+		},
+		{
+			Test: "Node architecture",
+			Task: modifyTask(func(t *api.Task) {
+				t.Spec = api.TaskSpec{
+					Runtime: &api.TaskSpec_Container{
+						Container: &api.ContainerSpec{
+							Hostname: "{{.Node.Hostname}}-{{.Node.Platform.OS}}-{{.Node.Platform.Architecture}}",
+						},
+					},
+				}
+			}),
+			NodeDescription: modifyNode(func(n *api.NodeDescription) {
+				n.Hostname = "mynode"
+				n.Platform.Architecture = "myarchitecture"
+				n.Platform.OS = "myos"
+			}),
+			Expected: &api.ContainerSpec{
+				Hostname: "mynode-myos-myarchitecture",
+			},
+		},
 	} {
 		t.Run(testcase.Test, func(t *testing.T) {
-			spec, err := ExpandContainerSpec(testcase.Task)
+			spec, err := ExpandContainerSpec(testcase.NodeDescription, testcase.Task)
 			if err != nil {
 				if testcase.Err == nil {
 					t.Fatalf("unexpected error: %v", err)
@@ -194,6 +241,22 @@ func modifyTask(fn func(t *api.Task)) *api.Task {
 	return t
 }
 
+// modifyNode generates a node with interesting values then calls the function
+// with it. The caller can then modify the node and return the result.
+func modifyNode(fn func(n *api.NodeDescription)) *api.NodeDescription {
+	n := &api.NodeDescription{
+		Hostname: "nodeHostname",
+		Platform: &api.Platform{
+			Architecture: "x86_64",
+			OS:           "linux",
+		},
+	}
+
+	fn(n)
+
+	return n
+}
+
 // visitAllTemplatedFields does just that.
 // TODO(stevvooe): Might be best to make this the actual implementation.
 func visitAllTemplatedFields(spec *api.ContainerSpec, fn func(value string)) {

template/expand.go

@@ -10,18 +10,19 @@ import (
 )
 
 // ExpandContainerSpec expands templated fields in the runtime using the task
-// state. Templating is all evaluated on the agent-side, before execution.
+// state and the node where it is scheduled to run.
+// Templating is all evaluated on the agent-side, before execution.
 //
 // Note that these are projected only on runtime values, since active task
 // values are typically manipulated in the manager.
-func ExpandContainerSpec(t *api.Task) (*api.ContainerSpec, error) {
+func ExpandContainerSpec(n *api.NodeDescription, t *api.Task) (*api.ContainerSpec, error) {
 	container := t.Spec.GetContainer()
 	if container == nil {
 		return nil, errors.Errorf("task missing ContainerSpec to expand")
 	}
 
 	container = container.Copy()
-	ctx := NewContextFromTask(t)
+	ctx := NewContext(n, t)
 
 	var err error
 	container.Env, err = expandEnv(ctx, container.Env)
@@ -128,12 +129,12 @@ func expandPayload(ctx PayloadContext, payload []byte) ([]byte, error) {
 
 // ExpandSecretSpec expands the template inside the secret payload, if any.
 // Templating is evaluated on the agent-side.
-func ExpandSecretSpec(s *api.Secret, t *api.Task, dependencies exec.DependencyGetter) (*api.SecretSpec, error) {
+func ExpandSecretSpec(s *api.Secret, node *api.NodeDescription, t *api.Task, dependencies exec.DependencyGetter) (*api.SecretSpec, error) {
 	if s.Spec.Templating == nil {
 		return &s.Spec, nil
 	}
 	if s.Spec.Templating.Name == "golang" {
-		ctx := NewPayloadContextFromTask(t, dependencies)
+		ctx := NewPayloadContextFromTask(node, t, dependencies)
 		secretSpec := s.Spec.Copy()
 
 		var err error
@@ -145,12 +146,12 @@ func ExpandSecretSpec(s *api.Secret, t *api.Task, dependencies exec.DependencyGe
 
 // ExpandConfigSpec expands the template inside the config payload, if any.
 // Templating is evaluated on the agent-side.
-func ExpandConfigSpec(c *api.Config, t *api.Task, dependencies exec.DependencyGetter) (*api.ConfigSpec, error) {
+func ExpandConfigSpec(c *api.Config, node *api.NodeDescription, t *api.Task, dependencies exec.DependencyGetter) (*api.ConfigSpec, error) {
 	if c.Spec.Templating == nil {
 		return &c.Spec, nil
 	}
 	if c.Spec.Templating.Name == "golang" {
-		ctx := NewPayloadContextFromTask(t, dependencies)
+		ctx := NewPayloadContextFromTask(node, t, dependencies)
 		configSpec := c.Spec.Copy()
 
 		var err error