305 lines
9.1 KiB
Go
305 lines
9.1 KiB
Go
package terraform
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import (
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"log"
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"sort"
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"github.com/hashicorp/terraform/addrs"
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"github.com/hashicorp/terraform/states"
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"github.com/hashicorp/terraform/configs"
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"github.com/hashicorp/terraform/dag"
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)
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// GraphNodeDestroyer must be implemented by nodes that destroy resources.
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type GraphNodeDestroyer interface {
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dag.Vertex
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// DestroyAddr is the address of the resource that is being
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// destroyed by this node. If this returns nil, then this node
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// is not destroying anything.
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DestroyAddr() *addrs.AbsResourceInstance
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}
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// GraphNodeCreator must be implemented by nodes that create OR update resources.
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type GraphNodeCreator interface {
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// CreateAddr is the address of the resource being created or updated
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CreateAddr() *addrs.AbsResourceInstance
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}
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// DestroyEdgeTransformer is a GraphTransformer that creates the proper
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// references for destroy resources. Destroy resources are more complex
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// in that they must be depend on the destruction of resources that
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// in turn depend on the CREATION of the node being destroy.
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//
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// That is complicated. Visually:
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//
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// B_d -> A_d -> A -> B
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//
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// Notice that A destroy depends on B destroy, while B create depends on
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// A create. They're inverted. This must be done for example because often
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// dependent resources will block parent resources from deleting. Concrete
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// example: VPC with subnets, the VPC can't be deleted while there are
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// still subnets.
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type DestroyEdgeTransformer struct {
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// These are needed to properly build the graph of dependencies
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// to determine what a destroy node depends on. Any of these can be nil.
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Config *configs.Config
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State *states.State
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// If configuration is present then Schemas is required in order to
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// obtain schema information from providers and provisioners in order
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// to properly resolve implicit dependencies.
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Schemas *Schemas
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}
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func (t *DestroyEdgeTransformer) Transform(g *Graph) error {
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// Build a map of what is being destroyed (by address string) to
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// the list of destroyers.
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destroyers := make(map[string][]GraphNodeDestroyer)
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// Record the creators, which will need to depend on the destroyers if they
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// are only being updated.
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creators := make(map[string]GraphNodeCreator)
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// destroyersByResource records each destroyer by the ConfigResource
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// address. We use this because dependencies are only referenced as
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// resources and have no index or module instance information, but we will
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// want to connect all the individual instances for correct ordering.
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destroyersByResource := make(map[string][]GraphNodeDestroyer)
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for _, v := range g.Vertices() {
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switch n := v.(type) {
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case GraphNodeDestroyer:
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addrP := n.DestroyAddr()
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if addrP == nil {
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log.Printf("[WARN] DestroyEdgeTransformer: %q (%T) has no destroy address", dag.VertexName(n), v)
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continue
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}
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addr := *addrP
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key := addr.String()
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log.Printf("[TRACE] DestroyEdgeTransformer: %q (%T) destroys %s", dag.VertexName(n), v, key)
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destroyers[key] = append(destroyers[key], n)
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resAddr := addr.ContainingResource().Config().String()
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destroyersByResource[resAddr] = append(destroyersByResource[resAddr], n)
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case GraphNodeCreator:
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addr := n.CreateAddr()
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creators[addr.String()] = n
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}
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}
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// If we aren't destroying anything, there will be no edges to make
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// so just exit early and avoid future work.
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if len(destroyers) == 0 {
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return nil
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}
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// Connect destroy despendencies as stored in the state
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for _, ds := range destroyers {
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for _, des := range ds {
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ri, ok := des.(GraphNodeResourceInstance)
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if !ok {
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continue
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}
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for _, resAddr := range ri.StateDependencies() {
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for _, desDep := range destroyersByResource[resAddr.String()] {
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log.Printf("[TRACE] DestroyEdgeTransformer: %s has stored dependency of %s\n", dag.VertexName(desDep), dag.VertexName(des))
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g.Connect(dag.BasicEdge(desDep, des))
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}
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}
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}
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}
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// connect creators to any destroyers on which they may depend
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for _, c := range creators {
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ri, ok := c.(GraphNodeResourceInstance)
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if !ok {
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continue
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}
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for _, resAddr := range ri.StateDependencies() {
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for _, desDep := range destroyersByResource[resAddr.String()] {
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log.Printf("[TRACE] DestroyEdgeTransformer: %s has stored dependency of %s\n", dag.VertexName(c), dag.VertexName(desDep))
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g.Connect(dag.BasicEdge(c, desDep))
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}
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}
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}
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// Go through and connect creators to destroyers. Going along with
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// our example, this makes: A_d => A
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for _, v := range g.Vertices() {
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cn, ok := v.(GraphNodeCreator)
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if !ok {
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continue
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}
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addr := cn.CreateAddr()
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if addr == nil {
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continue
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}
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for _, d := range destroyers[addr.String()] {
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// For illustrating our example
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a_d := d.(dag.Vertex)
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a := v
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log.Printf(
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"[TRACE] DestroyEdgeTransformer: connecting creator %q with destroyer %q",
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dag.VertexName(a), dag.VertexName(a_d))
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g.Connect(dag.BasicEdge(a, a_d))
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// Attach the destroy node to the creator
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// There really shouldn't be more than one destroyer, but even if
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// there are, any of them will represent the correct
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// CreateBeforeDestroy status.
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if n, ok := cn.(GraphNodeAttachDestroyer); ok {
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if d, ok := d.(GraphNodeDestroyerCBD); ok {
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n.AttachDestroyNode(d)
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}
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}
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}
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}
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return nil
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}
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// Remove any nodes that aren't needed when destroying modules.
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// Variables, outputs, locals, and expanders may not be able to evaluate
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// correctly, so we can remove these if nothing depends on them. The module
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// closers also need to disable their use of expansion if the module itself is
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// no longer present.
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type pruneUnusedNodesTransformer struct {
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}
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func (t *pruneUnusedNodesTransformer) Transform(g *Graph) error {
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// We need a reverse depth first walk of modules, processing them in order
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// from the leaf modules to the root. This allows us to remove unneeded
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// dependencies from child modules, freeing up nodes in the parent module
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// to also be removed.
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// First collect the nodes into their respective modules based on
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// configuration path.
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moduleMap := make(map[string]pruneUnusedNodesMod)
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for _, v := range g.Vertices() {
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var path addrs.Module
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switch v := v.(type) {
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case GraphNodeModulePath:
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path = v.ModulePath()
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default:
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continue
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}
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m := moduleMap[path.String()]
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m.addr = path
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m.nodes = append(m.nodes, v)
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moduleMap[path.String()] = m
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}
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// now we need to restructure the modules so we can sort them
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var modules []pruneUnusedNodesMod
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for _, mod := range moduleMap {
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modules = append(modules, mod)
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}
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// Sort them by path length, longest first, so that we start with the
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// deepest modules. The order of modules at the same tree level doesn't
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// matter, we just need to ensure that child modules are processed before
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// parent modules.
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sort.Slice(modules, func(i, j int) bool {
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return len(modules[i].addr) > len(modules[j].addr)
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})
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for _, mod := range modules {
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mod.removeUnused(g)
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}
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return nil
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}
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// pruneUnusedNodesMod is a container to hold the nodes that belong to a
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// particular configuration module for the pruneUnusedNodesTransformer
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type pruneUnusedNodesMod struct {
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addr addrs.Module
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nodes []dag.Vertex
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}
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// Remove any unused locals, variables, outputs and expanders. Since module
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// closers can also lookup expansion info to detect orphaned instances, disable
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// them if their associated expander is removed.
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func (m *pruneUnusedNodesMod) removeUnused(g *Graph) {
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// We modify the nodes slice during processing here.
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// Make a copy so no one is surprised by this changing in the future.
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nodes := make([]dag.Vertex, len(m.nodes))
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copy(nodes, m.nodes)
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// since we have no defined structure within the module, just cycle through
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// the nodes in each module until there are no more removals
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removed := true
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for {
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if !removed {
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return
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}
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removed = false
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for i := 0; i < len(nodes); i++ {
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// run this in a closure, so we can return early rather than
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// dealing with complex looping and labels
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func() {
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n := nodes[i]
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switch n := n.(type) {
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case graphNodeTemporaryValue:
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// root module outputs indicate they are not temporary by
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// returning false here.
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if !n.temporaryValue() {
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return
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}
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// temporary values, which consist of variables, locals,
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// and outputs, must be kept if anything refers to them.
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for _, v := range g.UpEdges(n) {
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// keep any value which is connected through a
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// reference
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if _, ok := v.(GraphNodeReferencer); ok {
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return
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}
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}
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case graphNodeExpandsInstances:
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// Any nodes that expand instances are kept when their
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// instances may need to be evaluated.
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for _, v := range g.UpEdges(n) {
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switch v.(type) {
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case graphNodeExpandsInstances:
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// expanders can always depend on module expansion
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// themselves
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return
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case GraphNodeResourceInstance:
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// resource instances always depend on their
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// resource node, which is an expander
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return
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}
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}
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default:
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return
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}
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log.Printf("[DEBUG] pruneUnusedNodes: %s is no longer needed, removing", dag.VertexName(n))
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g.Remove(n)
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removed = true
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// remove the node from our iteration as well
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last := len(nodes) - 1
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nodes[i], nodes[last] = nodes[last], nodes[i]
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nodes = nodes[:last]
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}()
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}
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}
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}
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