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package terraform
import (
"log"
"github.com/hashicorp/terraform/addrs"
"github.com/hashicorp/terraform/states"
"github.com/hashicorp/terraform/configs"
"github.com/hashicorp/terraform/dag"
)
// GraphNodeDestroyer must be implemented by nodes that destroy resources.
type GraphNodeDestroyer interface {
dag.Vertex
// DestroyAddr is the address of the resource that is being
// destroyed by this node. If this returns nil, then this node
// is not destroying anything.
DestroyAddr() *addrs.AbsResourceInstance
}
// GraphNodeCreator must be implemented by nodes that create OR update resources.
type GraphNodeCreator interface {
// CreateAddr is the address of the resource being created or updated
CreateAddr() *addrs.AbsResourceInstance
}
// DestroyEdgeTransformer is a GraphTransformer that creates the proper
// references for destroy resources. Destroy resources are more complex
// in that they must be depend on the destruction of resources that
// in turn depend on the CREATION of the node being destroy.
//
// That is complicated. Visually:
//
// B_d -> A_d -> A -> B
//
// Notice that A destroy depends on B destroy, while B create depends on
// A create. They're inverted. This must be done for example because often
// dependent resources will block parent resources from deleting. Concrete
// example: VPC with subnets, the VPC can't be deleted while there are
// still subnets.
type DestroyEdgeTransformer struct {
// These are needed to properly build the graph of dependencies
// to determine what a destroy node depends on. Any of these can be nil.
Config *configs.Config
State *states.State
// If configuration is present then Schemas is required in order to
// obtain schema information from providers and provisioners in order
// to properly resolve implicit dependencies.
Schemas *Schemas
}
func (t *DestroyEdgeTransformer) Transform(g *Graph) error {
// Build a map of what is being destroyed (by address string) to
// the list of destroyers. Usually there will be at most one destroyer
// per node, but we allow multiple if present for completeness.
destroyers := make(map[string][]GraphNodeDestroyer)
destroyerAddrs := make(map[string]addrs.AbsResourceInstance)
for _, v := range g.Vertices() {
dn, ok := v.(GraphNodeDestroyer)
if !ok {
continue
}
addrP := dn.DestroyAddr()
if addrP == nil {
continue
}
addr := *addrP
key := addr.String()
log.Printf("[TRACE] DestroyEdgeTransformer: %q (%T) destroys %s", dag.VertexName(dn), v, key)
destroyers[key] = append(destroyers[key], dn)
destroyerAddrs[key] = addr
}
// If we aren't destroying anything, there will be no edges to make
// so just exit early and avoid future work.
if len(destroyers) == 0 {
return nil
}
// Go through and connect creators to destroyers. Going along with
// our example, this makes: A_d => A
for _, v := range g.Vertices() {
cn, ok := v.(GraphNodeCreator)
if !ok {
continue
}
addr := cn.CreateAddr()
if addr == nil {
continue
}
key := addr.String()
ds := destroyers[key]
if len(ds) == 0 {
continue
}
for _, d := range ds {
// For illustrating our example
a_d := d.(dag.Vertex)
a := v
log.Printf(
"[TRACE] DestroyEdgeTransformer: connecting creator %q with destroyer %q",
dag.VertexName(a), dag.VertexName(a_d))
g.Connect(&DestroyEdge{S: a, T: a_d})
// Attach the destroy node to the creator
// There really shouldn't be more than one destroyer, but even if
// there are, any of them will represent the correct
// CreateBeforeDestroy status.
if n, ok := cn.(GraphNodeAttachDestroyer); ok {
if d, ok := d.(GraphNodeDestroyerCBD); ok {
n.AttachDestroyNode(d)
}
}
}
}
// This is strange but is the easiest way to get the dependencies
// of a node that is being destroyed. We use another graph to make sure
// the resource is in the graph and ask for references. We have to do this
// because the node that is being destroyed may NOT be in the graph.
//
// Example: resource A is force new, then destroy A AND create A are
// in the graph. BUT if resource A is just pure destroy, then only
// destroy A is in the graph, and create A is not.
providerFn := func(a *NodeAbstractProvider) dag.Vertex {
return &NodeApplyableProvider{NodeAbstractProvider: a}
}
steps := []GraphTransformer{
// Add the local values
&LocalTransformer{Config: t.Config},
// Add outputs and metadata
&OutputTransformer{Config: t.Config},
&AttachResourceConfigTransformer{Config: t.Config},
&AttachStateTransformer{State: t.State},
// Add all the variables. We can depend on resources through
// variables due to module parameters, and we need to properly
// determine that.
&RootVariableTransformer{Config: t.Config},
&ModuleVariableTransformer{Config: t.Config},
TransformProviders(nil, providerFn, t.Config),
// Must attach schemas before ReferenceTransformer so that we can
// analyze the configuration to find references.
&AttachSchemaTransformer{Schemas: t.Schemas},
&ReferenceTransformer{},
}
// Go through all the nodes being destroyed and create a graph.
// The resulting graph is only of things being CREATED. For example,
// following our example, the resulting graph would be:
//
// A, B (with no edges)
//
var tempG Graph
var tempDestroyed []dag.Vertex
for d := range destroyers {
// d is the string key for the resource being destroyed. We actually
// want the address value, which we stashed earlier.
addr := destroyerAddrs[d]
// This part is a little bit weird but is the best way to
// find the dependencies we need to: build a graph and use the
// attach config and state transformers then ask for references.
abstract := NewNodeAbstractResourceInstance(addr)
tempG.Add(abstract)
tempDestroyed = append(tempDestroyed, abstract)
// We also add the destroy version here since the destroy can
// depend on things that the creation doesn't (destroy provisioners).
destroy := &NodeDestroyResourceInstance{NodeAbstractResourceInstance: abstract}
tempG.Add(destroy)
tempDestroyed = append(tempDestroyed, destroy)
}
// Run the graph transforms so we have the information we need to
// build references.
log.Printf("[TRACE] DestroyEdgeTransformer: constructing temporary graph for analysis of references, starting from:\n%s", tempG.StringWithNodeTypes())
for _, s := range steps {
log.Printf("[TRACE] DestroyEdgeTransformer: running %T on temporary graph", s)
if err := s.Transform(&tempG); err != nil {
log.Printf("[TRACE] DestroyEdgeTransformer: %T failed: %s", s, err)
return err
}
}
log.Printf("[TRACE] DestroyEdgeTransformer: temporary reference graph:\n%s", tempG.String())
// Go through all the nodes in the graph and determine what they
// depend on.
for _, v := range tempDestroyed {
// Find all ancestors of this to determine the edges we'll depend on
vs, err := tempG.Ancestors(v)
if err != nil {
return err
}
refs := make([]dag.Vertex, 0, vs.Len())
for _, raw := range vs.List() {
refs = append(refs, raw.(dag.Vertex))
}
refNames := make([]string, len(refs))
for i, ref := range refs {
refNames[i] = dag.VertexName(ref)
}
log.Printf(
"[TRACE] DestroyEdgeTransformer: creation node %q references %s",
dag.VertexName(v), refNames)
// If we have no references, then we won't need to do anything
if len(refs) == 0 {
continue
}
// Get the destroy node for this. In the example of our struct,
// we are currently at B and we're looking for B_d.
rn, ok := v.(GraphNodeResourceInstance)
if !ok {
log.Printf("[TRACE] DestroyEdgeTransformer: skipping %s, since it's not a resource", dag.VertexName(v))
continue
}
addr := rn.ResourceInstanceAddr()
dns := destroyers[addr.String()]
// We have dependencies, check if any are being destroyed
// to build the list of things that we must depend on!
//
// In the example of the struct, if we have:
//
// B_d => A_d => A => B
//
// Then at this point in the algorithm we started with B_d,
// we built B (to get dependencies), and we found A. We're now looking
// to see if A_d exists.
var depDestroyers []dag.Vertex
for _, v := range refs {
rn, ok := v.(GraphNodeResourceInstance)
if !ok {
continue
}
addr := rn.ResourceInstanceAddr()
key := addr.String()
if ds, ok := destroyers[key]; ok {
for _, d := range ds {
depDestroyers = append(depDestroyers, d.(dag.Vertex))
log.Printf(
"[TRACE] DestroyEdgeTransformer: destruction of %q depends on %s",
key, dag.VertexName(d))
}
}
}
// Go through and make the connections. Use the variable
// names "a_d" and "b_d" to reference our example.
for _, a_d := range dns {
for _, b_d := range depDestroyers {
if b_d != a_d {
log.Printf("[TRACE] DestroyEdgeTransformer: %q depends on %q", dag.VertexName(b_d), dag.VertexName(a_d))
g.Connect(dag.BasicEdge(b_d, a_d))
}
}
}
}
return nil
}
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