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5b92e7793d
Graph logic moves into depgraph package and makes internal fields inaccessible. Completes feedback from @LucasRoesler from previous PR where the dependency graph was added for 0.9.1 Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>
107 lines
2.2 KiB
Go
107 lines
2.2 KiB
Go
package depgraph
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import "log"
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// Node represents a node in a Graph with
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// 0 to many edges
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type Node struct {
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Name string
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Edges []*Node
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}
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// Graph is a collection of nodes
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type Graph struct {
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nodes []*Node
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}
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func NewDepgraph() *Graph {
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return &Graph{
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nodes: []*Node{},
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}
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}
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// Nodes returns the nodes within the graph
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func (g *Graph) Nodes() []*Node {
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return g.nodes
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}
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// Contains returns true if the target Node is found
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// in its list
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func (g *Graph) Contains(target *Node) bool {
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for _, g := range g.nodes {
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if g.Name == target.Name {
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return true
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}
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}
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return false
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}
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// Add places a Node into the current Graph
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func (g *Graph) Add(target *Node) {
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g.nodes = append(g.nodes, target)
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}
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// Remove deletes a target Node reference from the
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// list of nodes in the graph
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func (g *Graph) Remove(target *Node) {
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var found *int
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for i, n := range g.nodes {
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if n == target {
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found = &i
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break
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}
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}
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if found != nil {
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g.nodes = append(g.nodes[:*found], g.nodes[*found+1:]...)
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}
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}
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// Resolve retruns a list of node names in order of their dependencies.
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// A use case may be for determining the correct order to install
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// software packages, or to start services.
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// Based upon the algorithm described by Ferry Boender in the following article
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// https://www.electricmonk.nl/log/2008/08/07/dependency-resolving-algorithm/
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func (g *Graph) Resolve() []string {
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resolved := &Graph{}
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unresolved := &Graph{}
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for _, node := range g.nodes {
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resolve(node, resolved, unresolved)
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}
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order := []string{}
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for _, node := range resolved.Nodes() {
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order = append(order, node.Name)
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}
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return order
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}
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// resolve mutates the resolved graph for a given starting
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// node. The unresolved graph is used to detect a circular graph
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// error and will throw a panic. This can be caught with a resolve
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// in a go routine.
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func resolve(node *Node, resolved, unresolved *Graph) {
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unresolved.Add(node)
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for _, edge := range node.Edges {
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if !resolved.Contains(edge) && unresolved.Contains(edge) {
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log.Panicf("edge: %s may be a circular dependency", edge.Name)
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}
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resolve(edge, resolved, unresolved)
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}
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for _, r := range resolved.nodes {
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if r.Name == node.Name {
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return
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}
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}
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resolved.Add(node)
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unresolved.Remove(node)
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}
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