terraform: create before destroy

terraform/context_test.go

@@ -3369,7 +3369,6 @@ func TestContext2Apply_provisionerFail(t *testing.T) {
 	}
 }
 
-/*
 func TestContext2Apply_provisionerFail_createBeforeDestroy(t *testing.T) {
 	m := testModule(t, "apply-provisioner-fail-create-before")
 	p := testProvider("aws")

terraform/eval_state.go

@@ -126,3 +126,99 @@ func (n *EvalWriteState) Eval(
 func (n *EvalWriteState) Type() EvalType {
 	return EvalTypeNull
 }
+
+// EvalDeposeState is an EvalNode implementation that reads the
+// InstanceState for a specific resource out of the state.
+type EvalDeposeState struct {
+	Name string
+}
+
+func (n *EvalDeposeState) Args() ([]EvalNode, []EvalType) {
+	return nil, nil
+}
+
+// TODO: test
+func (n *EvalDeposeState) Eval(
+	ctx EvalContext, args []interface{}) (interface{}, error) {
+	state, lock := ctx.State()
+
+	// Get a read lock so we can access this instance
+	lock.RLock()
+	defer lock.RUnlock()
+
+	// Look for the module state. If we don't have one, then it doesn't matter.
+	mod := state.ModuleByPath(ctx.Path())
+	if mod == nil {
+		return nil, nil
+	}
+
+	// Look for the resource state. If we don't have one, then it is okay.
+	rs := mod.Resources[n.Name]
+	if rs == nil {
+		return nil, nil
+	}
+
+	// If we don't have a primary, we have nothing to depose
+	if rs.Primary == nil {
+		return nil, nil
+	}
+
+	// Depose to the tainted
+	rs.Tainted = append(rs.Tainted, rs.Primary)
+	rs.Primary = nil
+
+	return nil, nil
+}
+
+func (n *EvalDeposeState) Type() EvalType {
+	return EvalTypeNull
+}
+
+// EvalUndeposeState is an EvalNode implementation that reads the
+// InstanceState for a specific resource out of the state.
+type EvalUndeposeState struct {
+	Name string
+}
+
+func (n *EvalUndeposeState) Args() ([]EvalNode, []EvalType) {
+	return nil, nil
+}
+
+// TODO: test
+func (n *EvalUndeposeState) Eval(
+	ctx EvalContext, args []interface{}) (interface{}, error) {
+	state, lock := ctx.State()
+
+	// Get a read lock so we can access this instance
+	lock.RLock()
+	defer lock.RUnlock()
+
+	// Look for the module state. If we don't have one, then it doesn't matter.
+	mod := state.ModuleByPath(ctx.Path())
+	if mod == nil {
+		return nil, nil
+	}
+
+	// Look for the resource state. If we don't have one, then it is okay.
+	rs := mod.Resources[n.Name]
+	if rs == nil {
+		return nil, nil
+	}
+
+	// If we don't have any tainted, then we don't have anything to do
+	if len(rs.Tainted) == 0 {
+		return nil, nil
+	}
+
+	// Undepose to the tainted
+	idx := len(rs.Tainted) - 1
+	rs.Primary = rs.Tainted[idx]
+	rs.Tainted[idx] = nil
+	rs.Tainted = rs.Tainted[:idx]
+
+	return nil, nil
+}
+
+func (n *EvalUndeposeState) Type() EvalType {
+	return EvalTypeNull
+}

terraform/graph_builder.go

@@ -81,7 +81,6 @@ func (b *BuiltinGraphBuilder) Steps() []GraphTransformer {
 		// Create all our resources from the configuration and state
 		&ConfigTransformer{Module: b.Root},
 		&OrphanTransformer{State: b.State, Module: b.Root},
-		&TaintedTransformer{State: b.State},
 
 		// Provider-related transformations
 		&MissingProviderTransformer{Providers: b.Providers},
@@ -105,6 +104,7 @@ func (b *BuiltinGraphBuilder) Steps() []GraphTransformer {
 
 		// Create the destruction nodes
 		&DestroyTransformer{},
+		&CreateBeforeDestroyTransformer{},
 		&PruneDestroyTransformer{Diff: b.Diff},
 
 		// Make sure we create one root

terraform/graph_config_node.go

@@ -177,7 +177,7 @@ type GraphNodeConfigResource struct {
 	// that logically this node is where it would happen.
 	Destroy bool
 
-	destroyNode dag.Vertex
+	destroyNode GraphNodeDestroy
 }
 
 func (n *GraphNodeConfigResource) DependableName() []string {
@@ -248,6 +248,11 @@ func (n *GraphNodeConfigResource) DynamicExpand(ctx EvalContext) (*Graph, error)
 			State: state,
 			View:  n.Resource.Id(),
 		})
+
+		steps = append(steps, &TaintedTransformer{
+			State: state,
+			View:  n.Resource.Id(),
+		})
 	}
 
 	// Always end with the root being added
@@ -288,7 +293,7 @@ func (n *GraphNodeConfigResource) ProvisionedBy() []string {
 }
 
 // GraphNodeDestroyable
-func (n *GraphNodeConfigResource) DestroyNode() dag.Vertex {
+func (n *GraphNodeConfigResource) DestroyNode() GraphNodeDestroy {
 	// If we're already a destroy node, then don't do anything
 	if n.Destroy {
 		return nil
@@ -300,13 +305,36 @@ func (n *GraphNodeConfigResource) DestroyNode() dag.Vertex {
 	}
 
 	// Just make a copy that is set to destroy
-	result := *n
+	result := &graphNodeResourceDestroy{
+		GraphNodeConfigResource: *n,
+		Original:                n,
+	}
 	result.Destroy = true
-	n.destroyNode = &result
+	n.destroyNode = result
 
 	return n.destroyNode
 }
 
+// graphNodeResourceDestroy represents the logical destruction of a
+// resource. This node doesn't mean it will be destroyed for sure, but
+// instead that if a destroy were to happen, it must happen at this point.
+type graphNodeResourceDestroy struct {
+	GraphNodeConfigResource
+	Original *GraphNodeConfigResource
+}
+
+func (n *graphNodeResourceDestroy) CreateBeforeDestroy() bool {
+	return n.Original.Resource.Lifecycle.CreateBeforeDestroy
+}
+
+func (n *graphNodeResourceDestroy) CreateNode() dag.Vertex {
+	return n.Original
+}
+
+func (n *graphNodeResourceDestroy) DiffId() string {
+	return ""
+}
+
 // graphNodeModuleExpanded represents a module where the graph has
 // been expanded. It stores the graph of the module as well as a reference
 // to the map of variables.

terraform/graph_old.go

@@ -663,7 +663,7 @@ func graphAddDiff(g *depgraph.Graph, gDiff *Diff, d *ModuleDiff) error {
 				}
 
 				// Set the ReplacePrimary flag on the new instance so that
-				// it will become the new primary, and Diposed flag on the
+				// it will become the new primary, and Deposed flag on the
 				// existing instance so that it will step down
 				rn.Resource.Flags |= FlagReplacePrimary
 				newNode.Resource.Flags |= FlagDeposed

terraform/test-fixtures/transform-create-before-destroy-basic/main.tf

@@ -0,0 +1,9 @@
+resource "aws_instance" "web" {
+    lifecycle {
+        create_before_destroy = true
+    }
+}
+
+resource "aws_load_balancer" "lb" {
+    member = "${aws_instance.web.id}"
+}

terraform/transform_destroy.go

@@ -14,14 +14,24 @@ type GraphNodeDestroyable interface {
 	// DestroyNode returns the node used for the destroy. This should
 	// return the same node every time so that it can be used later for
 	// lookups as well.
-	DestroyNode() dag.Vertex
+	DestroyNode() GraphNodeDestroy
 }
 
-// GraphNodeDestroyer is the interface that must implemented by
+// GraphNodeDestroy is the interface that must implemented by
 // nodes that destroy.
-type GraphNodeDestroyer interface {
+type GraphNodeDestroy interface {
 	dag.Vertex
 
+	// CreateBeforeDestroy is called to check whether this node
+	// should be created before it is destroyed. The CreateBeforeDestroy
+	// transformer uses this information to setup the graph.
+	CreateBeforeDestroy() bool
+
+	// CreateNode returns the node used for the create side of this
+	// destroy. This must already exist within the graph.
+	CreateNode() dag.Vertex
+
+	// Not used right now
 	DiffId() string
 }
 
@@ -94,6 +104,52 @@ func (t *DestroyTransformer) Transform(g *Graph) error {
 	return nil
 }
 
+// CreateBeforeDestroyTransformer is a GraphTransformer that modifies
+// the destroys of some nodes so that the creation happens before the
+// destroy.
+type CreateBeforeDestroyTransformer struct{}
+
+func (t *CreateBeforeDestroyTransformer) Transform(g *Graph) error {
+	for _, v := range g.Vertices() {
+		// We only care to use the destroy nodes
+		dn, ok := v.(GraphNodeDestroy)
+		if !ok {
+			continue
+		}
+
+		// If the node doesn't need to create before destroy, then continue
+		if !dn.CreateBeforeDestroy() {
+			continue
+		}
+
+		// Get the creation side of this node
+		cn := dn.CreateNode()
+
+		// Take all the things which depend on the web creation and
+		// make them dependencies on the destruction. Clarifying this
+		// with an example: if you have a web server and a load balancer
+		// and the load balancer depends on the web server, then when we
+		// do a create before destroy, we want to make sure the steps are:
+		//
+		// 1.) Create new web server
+		// 2.) Update load balancer
+		// 3.) Delete old web server
+		//
+		// This ensures that.
+		for _, sourceRaw := range g.UpEdges(cn).List() {
+			source := sourceRaw.(dag.Vertex)
+			g.Connect(dag.BasicEdge(dn, source))
+		}
+
+		// Swap the edge so that the destroy depends on the creation
+		// happening...
+		g.Connect(dag.BasicEdge(dn, cn))
+		g.RemoveEdge(dag.BasicEdge(cn, dn))
+	}
+
+	return nil
+}
+
 // PruneDestroyTransformer is a GraphTransformer that removes the destroy
 // nodes that aren't in the diff.
 type PruneDestroyTransformer struct {
@@ -108,7 +164,7 @@ func (t *PruneDestroyTransformer) Transform(g *Graph) error {
 
 	for _, v := range g.Vertices() {
 		// If it is not a destroyer, we don't care
-		dn, ok := v.(GraphNodeDestroyer)
+		dn, ok := v.(GraphNodeDestroy)
 		if !ok {
 			continue
 		}

terraform/transform_destroy_test.go

@@ -30,6 +30,38 @@ func TestDestroyTransformer(t *testing.T) {
 	}
 }
 
+func TestCreateBeforeDestroyTransformer(t *testing.T) {
+	mod := testModule(t, "transform-create-before-destroy-basic")
+
+	g := Graph{Path: RootModulePath}
+	{
+		tf := &ConfigTransformer{Module: mod}
+		if err := tf.Transform(&g); err != nil {
+			t.Fatalf("err: %s", err)
+		}
+	}
+
+	{
+		tf := &DestroyTransformer{}
+		if err := tf.Transform(&g); err != nil {
+			t.Fatalf("err: %s", err)
+		}
+	}
+
+	{
+		tf := &CreateBeforeDestroyTransformer{}
+		if err := tf.Transform(&g); err != nil {
+			t.Fatalf("err: %s", err)
+		}
+	}
+
+	actual := strings.TrimSpace(g.String())
+	expected := strings.TrimSpace(testTransformCreateBeforeDestroyBasicStr)
+	if actual != expected {
+		t.Fatalf("bad:\n\n%s", actual)
+	}
+}
+
 const testTransformDestroyBasicStr = `
 aws_instance.bar
   aws_instance.bar (destroy)
@@ -40,3 +72,15 @@ aws_instance.foo
 aws_instance.foo (destroy)
   aws_instance.bar (destroy)
 `
+
+const testTransformCreateBeforeDestroyBasicStr = `
+aws_instance.web
+aws_instance.web (destroy)
+  aws_instance.web
+  aws_load_balancer.lb
+  aws_load_balancer.lb (destroy)
+aws_load_balancer.lb
+  aws_instance.web
+  aws_load_balancer.lb (destroy)
+aws_load_balancer.lb (destroy)
+`

terraform/transform_resource.go

@@ -251,6 +251,15 @@ func (n *graphNodeExpandedResource) EvalTree() EvalNode {
 					Node: EvalNoop{},
 				},
 
+				&EvalIf{
+					If: func(ctx EvalContext) (bool, error) {
+						return n.Resource.Lifecycle.CreateBeforeDestroy, nil
+					},
+					Node: &EvalDeposeState{
+						Name: n.stateId(),
+					},
+				},
+
 				&EvalDiff{
 					Info:     info,
 					Config:   interpolateNode,
@@ -304,6 +313,15 @@ func (n *graphNodeExpandedResource) EvalTree() EvalNode {
 					Tainted:        &tainted,
 					Error:          &err,
 				},
+				&EvalIf{
+					If: func(ctx EvalContext) (bool, error) {
+						return n.Resource.Lifecycle.CreateBeforeDestroy &&
+							tainted, nil
+					},
+					Node: &EvalUndeposeState{
+						Name: n.stateId(),
+					},
+				},
 				&EvalWriteState{
 					Name:                n.stateId(),
 					ResourceType:        n.Resource.Type,
@@ -311,7 +329,7 @@ func (n *graphNodeExpandedResource) EvalTree() EvalNode {
 					State:               &state,
 					Tainted:             &tainted,
 					TaintedIndex:        -1,
-					TaintedClearPrimary: true,
+					TaintedClearPrimary: !n.Resource.Lifecycle.CreateBeforeDestroy,
 				},
 				&EvalApplyPost{
 					Info:  info,
@@ -391,6 +409,8 @@ func (n *graphNodeExpandedResourceDestroy) EvalTree() EvalNode {
 				&EvalReadState{
 					Name:         n.stateId(),
 					Output:       &state,
+					Tainted:      n.Resource.Lifecycle.CreateBeforeDestroy,
+					TaintedIndex: -1,
 				},
 				&EvalApply{
 					Info:     info,

terraform/transform_tainted.go

@@ -10,6 +10,10 @@ type TaintedTransformer struct {
 	// State is the global state. We'll automatically find the correct
 	// ModuleState based on the Graph.Path that is being transformed.
 	State *State
+
+	// View, if non-empty, is the ModuleState.View used around the state
+	// to find tainted resources.
+	View string
 }
 
 func (t *TaintedTransformer) Transform(g *Graph) error {
@@ -20,6 +24,11 @@ func (t *TaintedTransformer) Transform(g *Graph) error {
 		return nil
 	}
 
+	// If we have a view, apply it now
+	if t.View != "" {
+		state = state.View(t.View)
+	}
+
 	// Go through all the resources in our state to look for tainted resources
 	for k, rs := range state.Resources {
 		// If we have no tainted resources, then move on
@@ -31,16 +40,14 @@ func (t *TaintedTransformer) Transform(g *Graph) error {
 			// Add the graph node and make the connection from any untainted
 			// resources with this name to the tainted resource, so that
 			// the tainted resource gets destroyed first.
-			g.ConnectFrom(k, g.Add(&graphNodeTaintedResource{
+			g.Add(&graphNodeTaintedResource{
 				Index:        i,
 				ResourceName: k,
 				ResourceType: rs.Type,
-			}))
+			})
 		}
 	}
 
-	// TODO: Any other dependencies?
-
 	return nil
 }
 
@@ -51,10 +58,6 @@ type graphNodeTaintedResource struct {
 	ResourceType string
 }
 
-func (n *graphNodeTaintedResource) DependentOn() []string {
-	return []string{n.ResourceName}
-}
-
 func (n *graphNodeTaintedResource) Name() string {
 	return fmt.Sprintf("%s (tainted #%d)", n.ResourceName, n.Index+1)
 }
@@ -94,7 +97,6 @@ func (n *graphNodeTaintedResource) EvalTree() EvalNode {
 				&EvalWriteState{
 					Name:         n.ResourceName,
 					ResourceType: n.ResourceType,
-					Dependencies: n.DependentOn(),
 					State:        &state,
 					Tainted:      &tainted,
 					TaintedIndex: n.Index,
@@ -139,7 +141,6 @@ func (n *graphNodeTaintedResource) EvalTree() EvalNode {
 				&EvalWriteState{
 					Name:         n.ResourceName,
 					ResourceType: n.ResourceType,
-					Dependencies: n.DependentOn(),
 					State:        &state,
 					Tainted:      &tainted,
 					TaintedIndex: n.Index,

terraform/transform_tainted_test.go

@@ -61,5 +61,4 @@ func TestGraphNodeTaintedResource_ProvidedBy(t *testing.T) {
 const testTransformTaintedBasicStr = `
 aws_instance.web
 aws_instance.web (tainted #1)
-aws_instance.web (tainted #1)
 `