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engine: Rewrite the core algorithm

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The engine core had some unfortunate bugs that were the result of some
early design errors when I wasn't as familiar with channels. I've
finally rewritten most of the bad parts, and I think it's much more
logical and stable now.

This also simplifies the resource API, since more of the work is done
completely in the engine, and hidden from view.

Lastly, this adds a few new metaparameters and associated code.

There are still some open problems left to solve, but hopefully this
brings us one step closer.
This commit is contained in:
James Shubin
2019-02-13 15:40:08 -05:00
parent 4860d833c7
commit 253ed78cc6
42 changed files with 891 additions and 1080 deletions
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44
pgraph/graphsync.go
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@@ -40,10 +40,10 @@ func strEdgeCmpFn(e1, e2 Edge) (bool, error) {
// GraphSync updates the Graph so that it matches the newGraph. It leaves
// identical elements alone so that they don't need to be refreshed.
// It tries to mutate existing elements into new ones, if they support this.
// This updates the Graph on success only.
// This updates the Graph on success only. If it fails, then the graph won't
// have been modified.
// FIXME: should we do this with copies of the vertex resources?
func (obj *Graph) GraphSync(newGraph *Graph, vertexCmpFn func(Vertex, Vertex) (bool, error), vertexAddFn func(Vertex) error, vertexRemoveFn func(Vertex) error, edgeCmpFn func(Edge, Edge) (bool, error)) error {
oldGraph := obj.Copy() // work on a copy of the old graph
if oldGraph == nil {
var err error
@@ -69,8 +69,11 @@ func (obj *Graph) GraphSync(newGraph *Graph, vertexCmpFn func(Vertex, Vertex) (b
var lookup = make(map[Vertex]Vertex)
var vertexKeep []Vertex // list of vertices which are the same in new graph
var edgeKeep []Edge // list of vertices which are the same in new graph
var vertexDels []Vertex // list of vertices which are to be removed
var vertexAdds []Vertex // list of vertices which are to be added
var edgeKeep []Edge // list of edges which are the same in new graph
// XXX: run this as a topological sort or reverse topological sort?
for v := range newGraph.Adjacency() { // loop through the vertices (resources)
var vertex Vertex
// step one, direct compare with res.Cmp
@@ -92,27 +95,44 @@ func (obj *Graph) GraphSync(newGraph *Graph, vertexCmpFn func(Vertex, Vertex) (b
// vertex = oldGraph.MutateMatch(res)
//}
// run the removes BEFORE the adds, so don't do the add here...
if vertex == nil { // no match found yet
if err := vertexAddFn(v); err != nil {
return errwrap.Wrapf(err, "vertexAddFn failed")
}
vertexAdds = append(vertexAdds, v) // append
vertex = v
oldGraph.AddVertex(vertex) // call standalone in case not part of an edge
}
lookup[v] = vertex // used for constructing edges
vertexKeep = append(vertexKeep, vertex) // append
}
// get rid of any vertices we shouldn't keep (that aren't in new graph)
for v := range oldGraph.Adjacency() {
if !VertexContains(v, vertexKeep) {
if err := vertexRemoveFn(v); err != nil {
return errwrap.Wrapf(err, "vertexRemoveFn failed")
}
oldGraph.DeleteVertex(v)
vertexDels = append(vertexDels, v) // append
}
}
// see if any of the add/remove functions actually fail first
// XXX: run this as a reverse topological sort or topological sort?
for _, vertex := range vertexDels {
if err := vertexRemoveFn(vertex); err != nil {
return errwrap.Wrapf(err, "vertexRemoveFn failed")
}
}
for _, vertex := range vertexAdds {
if err := vertexAddFn(vertex); err != nil {
return errwrap.Wrapf(err, "vertexAddFn failed")
}
}
// no add/remove functions failed, so we can actually modify the graph!
for _, vertex := range vertexDels {
oldGraph.DeleteVertex(vertex)
}
for _, vertex := range vertexAdds {
oldGraph.AddVertex(vertex) // call standalone in case not part of an edge
}
// XXX: fixup this part so the CmpFn stuff fails early, and THEN we edit
// the graph at the end, if no errors happened...
// compare edges
for v1 := range newGraph.Adjacency() { // loop through the vertices (resources)
for v2, e := range newGraph.Adjacency()[v1] {