forked from hashicorp/terraform
/
transform_reference.go
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/
transform_reference.go
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package terraform
import (
"fmt"
"log"
"strings"
"github.com/hashicorp/terraform/config"
"github.com/hashicorp/terraform/dag"
)
// GraphNodeReferenceable must be implemented by any node that represents
// a Terraform thing that can be referenced (resource, module, etc.).
//
// Even if the thing has no name, this should return an empty list. By
// implementing this and returning a non-nil result, you say that this CAN
// be referenced and other methods of referencing may still be possible (such
// as by path!)
type GraphNodeReferenceable interface {
// ReferenceableName is the name by which this can be referenced.
// This can be either just the type, or include the field. Example:
// "aws_instance.bar" or "aws_instance.bar.id".
ReferenceableName() []string
}
// GraphNodeReferencer must be implemented by nodes that reference other
// Terraform items and therefore depend on them.
type GraphNodeReferencer interface {
// References are the list of things that this node references. This
// can include fields or just the type, just like GraphNodeReferenceable
// above.
References() []string
}
// GraphNodeReferenceGlobal is an interface that can optionally be
// implemented. If ReferenceGlobal returns true, then the References()
// and ReferenceableName() must be _fully qualified_ with "module.foo.bar"
// etc.
//
// This allows a node to reference and be referenced by a specific name
// that may cross module boundaries. This can be very dangerous so use
// this wisely.
//
// The primary use case for this is module boundaries (variables coming in).
type GraphNodeReferenceGlobal interface {
// Set to true to signal that references and name are fully
// qualified. See the above docs for more information.
ReferenceGlobal() bool
}
// ReferenceTransformer is a GraphTransformer that connects all the
// nodes that reference each other in order to form the proper ordering.
type ReferenceTransformer struct{}
func (t *ReferenceTransformer) Transform(g *Graph) error {
// Build a reference map so we can efficiently look up the references
vs := g.Vertices()
m := NewReferenceMap(vs)
// Find the things that reference things and connect them
for _, v := range vs {
parents, _ := m.References(v)
parentsDbg := make([]string, len(parents))
for i, v := range parents {
parentsDbg[i] = dag.VertexName(v)
}
log.Printf(
"[DEBUG] ReferenceTransformer: %q references: %v",
dag.VertexName(v), parentsDbg)
for _, parent := range parents {
g.Connect(dag.BasicEdge(v, parent))
}
}
return nil
}
// DestroyReferenceTransformer is a GraphTransformer that reverses the edges
// for locals and outputs that depend on other nodes which will be
// removed during destroy. If a destroy node is evaluated before the local or
// output value, it will be removed from the state, and the later interpolation
// will fail.
type DestroyValueReferenceTransformer struct{}
func (t *DestroyValueReferenceTransformer) Transform(g *Graph) error {
vs := g.Vertices()
for _, v := range vs {
switch v.(type) {
case *NodeApplyableOutput, *NodeLocal:
// OK
default:
continue
}
// reverse any outgoing edges so that the value is evaluated first.
for _, e := range g.EdgesFrom(v) {
target := e.Target()
// only destroy nodes will be evaluated in reverse
if _, ok := target.(GraphNodeDestroyer); !ok {
continue
}
log.Printf("[TRACE] output dep: %s", dag.VertexName(target))
g.RemoveEdge(e)
g.Connect(&DestroyEdge{S: target, T: v})
}
}
return nil
}
// PruneUnusedValuesTransformer is s GraphTransformer that removes local and
// output values which are not referenced in the graph. Since outputs and
// locals always need to be evaluated, if they reference a resource that is not
// available in the state the interpolation could fail.
type PruneUnusedValuesTransformer struct{}
func (t *PruneUnusedValuesTransformer) Transform(g *Graph) error {
// this might need multiple runs in order to ensure that pruning a value
// doesn't effect a previously checked value.
for removed := 0; ; removed = 0 {
for _, v := range g.Vertices() {
switch v.(type) {
case *NodeApplyableOutput, *NodeLocal:
// OK
default:
continue
}
dependants := g.UpEdges(v)
switch dependants.Len() {
case 0:
// nothing at all depends on this
g.Remove(v)
removed++
case 1:
// because an output's destroy node always depends on the output,
// we need to check for the case of a single destroy node.
d := dependants.List()[0]
if _, ok := d.(*NodeDestroyableOutput); ok {
g.Remove(v)
removed++
}
}
}
if removed == 0 {
break
}
}
return nil
}
// ReferenceMap is a structure that can be used to efficiently check
// for references on a graph.
type ReferenceMap struct {
// m is the mapping of referenceable name to list of verticies that
// implement that name. This is built on initialization.
references map[string][]dag.Vertex
referencedBy map[string][]dag.Vertex
}
// References returns the list of vertices that this vertex
// references along with any missing references.
func (m *ReferenceMap) References(v dag.Vertex) ([]dag.Vertex, []string) {
rn, ok := v.(GraphNodeReferencer)
if !ok {
return nil, nil
}
var matches []dag.Vertex
var missing []string
prefix := m.prefix(v)
for _, ns := range rn.References() {
found := false
for _, n := range strings.Split(ns, "/") {
n = prefix + n
parents, ok := m.references[n]
if !ok {
continue
}
// Mark that we found a match
found = true
for _, p := range parents {
// don't include self-references
if p == v {
continue
}
matches = append(matches, p)
}
break
}
if !found {
missing = append(missing, ns)
}
}
return matches, missing
}
// ReferencedBy returns the list of vertices that reference the
// vertex passed in.
func (m *ReferenceMap) ReferencedBy(v dag.Vertex) []dag.Vertex {
rn, ok := v.(GraphNodeReferenceable)
if !ok {
return nil
}
var matches []dag.Vertex
prefix := m.prefix(v)
for _, n := range rn.ReferenceableName() {
n = prefix + n
children, ok := m.referencedBy[n]
if !ok {
continue
}
// Make sure this isn't a self reference, which isn't included
selfRef := false
for _, p := range children {
if p == v {
selfRef = true
break
}
}
if selfRef {
continue
}
matches = append(matches, children...)
}
return matches
}
func (m *ReferenceMap) prefix(v dag.Vertex) string {
// If the node is stating it is already fully qualified then
// we don't have to create the prefix!
if gn, ok := v.(GraphNodeReferenceGlobal); ok && gn.ReferenceGlobal() {
return ""
}
// Create the prefix based on the path
var prefix string
if pn, ok := v.(GraphNodeSubPath); ok {
if path := normalizeModulePath(pn.Path()); len(path) > 1 {
prefix = modulePrefixStr(path) + "."
}
}
return prefix
}
// NewReferenceMap is used to create a new reference map for the
// given set of vertices.
func NewReferenceMap(vs []dag.Vertex) *ReferenceMap {
var m ReferenceMap
// Build the lookup table
refMap := make(map[string][]dag.Vertex)
for _, v := range vs {
// We're only looking for referenceable nodes
rn, ok := v.(GraphNodeReferenceable)
if !ok {
continue
}
// Go through and cache them
prefix := m.prefix(v)
for _, n := range rn.ReferenceableName() {
n = prefix + n
refMap[n] = append(refMap[n], v)
}
// If there is a path, it is always referenceable by that. For
// example, if this is a referenceable thing at path []string{"foo"},
// then it can be referenced at "module.foo"
if pn, ok := v.(GraphNodeSubPath); ok {
for _, p := range ReferenceModulePath(pn.Path()) {
refMap[p] = append(refMap[p], v)
}
}
}
// Build the lookup table for referenced by
refByMap := make(map[string][]dag.Vertex)
for _, v := range vs {
// We're only looking for referenceable nodes
rn, ok := v.(GraphNodeReferencer)
if !ok {
continue
}
// Go through and cache them
prefix := m.prefix(v)
for _, n := range rn.References() {
n = prefix + n
refByMap[n] = append(refByMap[n], v)
}
}
m.references = refMap
m.referencedBy = refByMap
return &m
}
// Returns the reference name for a module path. The path "foo" would return
// "module.foo". If this is a deeply nested module, it will be every parent
// as well. For example: ["foo", "bar"] would return both "module.foo" and
// "module.foo.module.bar"
func ReferenceModulePath(p []string) []string {
p = normalizeModulePath(p)
if len(p) == 1 {
// Root, no name
return nil
}
result := make([]string, 0, len(p)-1)
for i := len(p); i > 1; i-- {
result = append(result, modulePrefixStr(p[:i]))
}
return result
}
// ReferencesFromConfig returns the references that a configuration has
// based on the interpolated variables in a configuration.
func ReferencesFromConfig(c *config.RawConfig) []string {
var result []string
for _, v := range c.Variables {
if r := ReferenceFromInterpolatedVar(v); len(r) > 0 {
result = append(result, r...)
}
}
return result
}
// ReferenceFromInterpolatedVar returns the reference from this variable,
// or an empty string if there is no reference.
func ReferenceFromInterpolatedVar(v config.InterpolatedVariable) []string {
switch v := v.(type) {
case *config.ModuleVariable:
return []string{fmt.Sprintf("module.%s.output.%s", v.Name, v.Field)}
case *config.ResourceVariable:
id := v.ResourceId()
// If we have a multi-reference (splat), then we depend on ALL
// resources with this type/name.
if v.Multi && v.Index == -1 {
return []string{fmt.Sprintf("%s.*", id)}
}
// Otherwise, we depend on a specific index.
idx := v.Index
if !v.Multi || v.Index == -1 {
idx = 0
}
// Depend on the index, as well as "N" which represents the
// un-expanded set of resources.
return []string{fmt.Sprintf("%s.%d/%s.N", id, idx, id)}
case *config.UserVariable:
return []string{fmt.Sprintf("var.%s", v.Name)}
case *config.LocalVariable:
return []string{fmt.Sprintf("local.%s", v.Name)}
default:
return nil
}
}
func modulePrefixStr(p []string) string {
// strip "root"
if len(p) > 0 && p[0] == rootModulePath[0] {
p = p[1:]
}
parts := make([]string, 0, len(p)*2)
for _, p := range p {
parts = append(parts, "module", p)
}
return strings.Join(parts, ".")
}
func modulePrefixList(result []string, prefix string) []string {
if prefix != "" {
for i, v := range result {
result[i] = fmt.Sprintf("%s.%s", prefix, v)
}
}
return result
}