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Copy pathgraph.go
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317 lines (264 loc) · 8.51 KB
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package terraform
import (
"fmt"
"log"
"strings"
"sync"
"github.com/hashicorp/terraform/dag"
)
// RootModuleName is the name given to the root module implicitly.
const RootModuleName = "root"
// RootModulePath is the path for the root module.
var RootModulePath = []string{RootModuleName}
// Graph represents the graph that Terraform uses to represent resources
// and their dependencies. Each graph represents only one module, but it
// can contain further modules, which themselves have their own graph.
type Graph struct {
// Graph is the actual DAG. This is embedded so you can call the DAG
// methods directly.
dag.AcyclicGraph
// Path is the path in the module tree that this Graph represents.
// The root is represented by a single element list containing
// RootModuleName
Path []string
// annotations are the annotations that are added to vertices. Annotations
// are arbitrary metadata taht is used for various logic. Annotations
// should have unique keys that are referenced via constants.
annotations map[dag.Vertex]map[string]interface{}
// dependableMap is a lookaside table for fast lookups for connecting
// dependencies by their GraphNodeDependable value to avoid O(n^3)-like
// situations and turn them into O(1) with respect to the number of new
// edges.
dependableMap map[string]dag.Vertex
once sync.Once
}
// Annotations returns the annotations that are configured for the
// given vertex. The map is guaranteed to be non-nil but may be empty.
//
// The returned map may be modified to modify the annotations of the
// vertex.
func (g *Graph) Annotations(v dag.Vertex) map[string]interface{} {
g.once.Do(g.init)
// If this vertex isn't in the graph, then just return an empty map
if !g.HasVertex(v) {
return map[string]interface{}{}
}
// Get the map, if it doesn't exist yet then initialize it
m, ok := g.annotations[v]
if !ok {
m = make(map[string]interface{})
g.annotations[v] = m
}
return m
}
// Add is the same as dag.Graph.Add.
func (g *Graph) Add(v dag.Vertex) dag.Vertex {
g.once.Do(g.init)
// Call upwards to add it to the actual graph
g.Graph.Add(v)
// If this is a depend-able node, then store the lookaside info
if dv, ok := v.(GraphNodeDependable); ok {
for _, n := range dv.DependableName() {
g.dependableMap[n] = v
}
}
// If this initializes annotations, then do that
if av, ok := v.(GraphNodeAnnotationInit); ok {
as := g.Annotations(v)
for k, v := range av.AnnotationInit() {
as[k] = v
}
}
return v
}
// Remove is the same as dag.Graph.Remove
func (g *Graph) Remove(v dag.Vertex) dag.Vertex {
g.once.Do(g.init)
// If this is a depend-able node, then remove the lookaside info
if dv, ok := v.(GraphNodeDependable); ok {
for _, n := range dv.DependableName() {
delete(g.dependableMap, n)
}
}
// Remove the annotations
delete(g.annotations, v)
// Call upwards to remove it from the actual graph
return g.Graph.Remove(v)
}
// Replace is the same as dag.Graph.Replace
func (g *Graph) Replace(o, n dag.Vertex) bool {
g.once.Do(g.init)
// Go through and update our lookaside to point to the new vertex
for k, v := range g.dependableMap {
if v == o {
if _, ok := n.(GraphNodeDependable); ok {
g.dependableMap[k] = n
} else {
delete(g.dependableMap, k)
}
}
}
// Move the annotation if it exists
if m, ok := g.annotations[o]; ok {
g.annotations[n] = m
delete(g.annotations, o)
}
return g.Graph.Replace(o, n)
}
// ConnectDependent connects a GraphNodeDependent to all of its
// GraphNodeDependables. It returns the list of dependents it was
// unable to connect to.
func (g *Graph) ConnectDependent(raw dag.Vertex) []string {
v, ok := raw.(GraphNodeDependent)
if !ok {
return nil
}
return g.ConnectTo(v, v.DependentOn())
}
// ConnectDependents goes through the graph, connecting all the
// GraphNodeDependents to GraphNodeDependables. This is safe to call
// multiple times.
//
// To get details on whether dependencies could be found/made, the more
// specific ConnectDependent should be used.
func (g *Graph) ConnectDependents() {
for _, v := range g.Vertices() {
if dv, ok := v.(GraphNodeDependent); ok {
g.ConnectDependent(dv)
}
}
}
// ConnectFrom creates an edge by finding the source from a DependableName
// and connecting it to the specific vertex.
func (g *Graph) ConnectFrom(source string, target dag.Vertex) {
g.once.Do(g.init)
if source := g.dependableMap[source]; source != nil {
g.Connect(dag.BasicEdge(source, target))
}
}
// ConnectTo connects a vertex to a raw string of targets that are the
// result of DependableName, and returns the list of targets that are missing.
func (g *Graph) ConnectTo(v dag.Vertex, targets []string) []string {
g.once.Do(g.init)
var missing []string
for _, t := range targets {
if dest := g.dependableMap[t]; dest != nil {
g.Connect(dag.BasicEdge(v, dest))
} else {
missing = append(missing, t)
}
}
return missing
}
// Dependable finds the vertices in the graph that have the given dependable
// names and returns them.
func (g *Graph) Dependable(n string) dag.Vertex {
// TODO: do we need this?
return nil
}
// Walk walks the graph with the given walker for callbacks. The graph
// will be walked with full parallelism, so the walker should expect
// to be called in concurrently.
func (g *Graph) Walk(walker GraphWalker) error {
return g.walk(walker)
}
func (g *Graph) init() {
if g.annotations == nil {
g.annotations = make(map[dag.Vertex]map[string]interface{})
}
if g.dependableMap == nil {
g.dependableMap = make(map[string]dag.Vertex)
}
}
func (g *Graph) walk(walker GraphWalker) error {
// The callbacks for enter/exiting a graph
ctx := walker.EnterPath(g.Path)
defer walker.ExitPath(g.Path)
// Get the path for logs
path := strings.Join(ctx.Path(), ".")
// Walk the graph.
var walkFn dag.WalkFunc
walkFn = func(v dag.Vertex) (rerr error) {
log.Printf("[DEBUG] vertex '%s.%s': walking", path, dag.VertexName(v))
walker.EnterVertex(v)
defer func() { walker.ExitVertex(v, rerr) }()
// vertexCtx is the context that we use when evaluating. This
// is normally the context of our graph but can be overridden
// with a GraphNodeSubPath impl.
vertexCtx := ctx
if pn, ok := v.(GraphNodeSubPath); ok && len(pn.Path()) > 0 {
vertexCtx = walker.EnterPath(normalizeModulePath(pn.Path()))
defer walker.ExitPath(pn.Path())
}
// If the node is eval-able, then evaluate it.
if ev, ok := v.(GraphNodeEvalable); ok {
tree := ev.EvalTree()
if tree == nil {
panic(fmt.Sprintf(
"%s.%s (%T): nil eval tree", path, dag.VertexName(v), v))
}
// Allow the walker to change our tree if needed. Eval,
// then callback with the output.
log.Printf("[DEBUG] vertex '%s.%s': evaluating", path, dag.VertexName(v))
tree = walker.EnterEvalTree(v, tree)
output, err := Eval(tree, vertexCtx)
if rerr = walker.ExitEvalTree(v, output, err); rerr != nil {
return
}
}
// If the node is dynamically expanded, then expand it
if ev, ok := v.(GraphNodeDynamicExpandable); ok {
log.Printf(
"[DEBUG] vertex '%s.%s': expanding/walking dynamic subgraph",
path,
dag.VertexName(v))
g, err := ev.DynamicExpand(vertexCtx)
if err != nil {
rerr = err
return
}
if g != nil {
// Walk the subgraph
if rerr = g.walk(walker); rerr != nil {
return
}
}
}
// If the node has a subgraph, then walk the subgraph
if sn, ok := v.(GraphNodeSubgraph); ok {
log.Printf(
"[DEBUG] vertex '%s.%s': walking subgraph",
path,
dag.VertexName(v))
if rerr = sn.Subgraph().walk(walker); rerr != nil {
return
}
}
return nil
}
return g.AcyclicGraph.Walk(walkFn)
}
// GraphNodeAnnotationInit is an interface that allows a node to
// initialize it's annotations.
//
// AnnotationInit will be called _once_ when the node is added to a
// graph for the first time and is expected to return it's initial
// annotations.
type GraphNodeAnnotationInit interface {
AnnotationInit() map[string]interface{}
}
// GraphNodeDependable is an interface which says that a node can be
// depended on (an edge can be placed between this node and another) according
// to the well-known name returned by DependableName.
//
// DependableName can return multiple names it is known by.
type GraphNodeDependable interface {
DependableName() []string
}
// GraphNodeDependent is an interface which says that a node depends
// on another GraphNodeDependable by some name. By implementing this
// interface, Graph.ConnectDependents() can be called multiple times
// safely and efficiently.
type GraphNodeDependent interface {
DependentOn() []string
}