// FindOverlappingHPAs scans the graph in search of HorizontalPodAutoscalers that are attempting to scale the same set of pods.
// This can occur in two ways:
// - 1. label selectors for two ReplicationControllers/DeploymentConfigs/etc overlap
// - 2. multiple HorizontalPodAutoscalers are attempting to scale the same ReplicationController/DeploymentConfig/etc
// Case 1 is handled by deconflicting the area of influence of ReplicationControllers/DeploymentConfigs/etc, and therefore we
// can assume that it will be handled before this step. Therefore, we are only concerned with finding HPAs that are trying to
// scale the same resources.
//
// The algorithm that is used to implement this check is described as follows:
// - create a sub-graph containing only HPA nodes and other nodes that can be scaled, as well as any scaling edges or other
// edges used to connect between objects that can be scaled
// - for every resulting edge in the new sub-graph, create an edge in the reverse direction
// - find the shortest paths between all HPA nodes in the graph
// - shortest paths connecting two horizontal pod autoscalers are used to create markers for the graph
func FindOverlappingHPAs(graph osgraph.Graph, namer osgraph.Namer) []osgraph.Marker {
markers := []osgraph.Marker{}
nodeFilter := osgraph.NodesOfKind(
kubenodes.HorizontalPodAutoscalerNodeKind,
kubenodes.ReplicationControllerNodeKind,
deploynodes.DeploymentConfigNodeKind,
)
edgeFilter := osgraph.EdgesOfKind(
kubegraph.ScalingEdgeKind,
deploygraph.DeploymentEdgeKind,
kubeedges.ManagedByControllerEdgeKind,
)
hpaSubGraph := graph.Subgraph(nodeFilter, edgeFilter)
for _, edge := range hpaSubGraph.Edges() {
osgraph.AddReversedEdge(hpaSubGraph, edge.From(), edge.To(), sets.NewString())
}
hpaNodes := hpaSubGraph.NodesByKind(kubenodes.HorizontalPodAutoscalerNodeKind)
for _, firstHPA := range hpaNodes {
// we can use Dijkstra's algorithm as we know we do not have any negative edge weights
shortestPaths := path.DijkstraFrom(firstHPA, hpaSubGraph)
for _, secondHPA := range hpaNodes {
if firstHPA == secondHPA {
continue
}
shortestPath, _ := shortestPaths.To(secondHPA)
if shortestPath == nil {
// if two HPAs have no path between them, no error exists
continue
}
markers = append(markers, osgraph.Marker{
Node: firstHPA,
Severity: osgraph.WarningSeverity,
RelatedNodes: shortestPath[1:],
Key: HPAOverlappingScaleRefWarning,
Message: fmt.Sprintf("%s and %s overlap because they both attempt to scale %s",
namer.ResourceName(firstHPA), namer.ResourceName(secondHPA), nameList(shortestPath[1:len(shortestPath)-1], namer)),
})
}
}
return markers
}
func TestDijkstraFrom(t *testing.T) {
for _, test := range shortestPathTests {
g := test.g()
for _, e := range test.edges {
g.SetEdge(e, e.Cost)
}
var (
pt path.Shortest
panicked bool
)
func() {
defer func() {
panicked = recover() != nil
}()
pt = path.DijkstraFrom(test.query.From(), g.(graph.Graph))
}()
if panicked || test.negative {
if !test.negative {
t.Errorf("%q: unexpected panic", test.name)
}
if !panicked {
t.Errorf("%q: expected panic for negative edge weight", test.name)
}
continue
}
if pt.From().ID() != test.query.From().ID() {
t.Fatalf("%q: unexpected from node ID: got:%d want:%d", pt.From().ID(), test.query.From().ID())
}
p, weight := pt.To(test.query.To())
if weight != test.weight {
t.Errorf("%q: unexpected weight from Between: got:%f want:%f",
test.name, weight, test.weight)
}
if weight := pt.WeightTo(test.query.To()); weight != test.weight {
t.Errorf("%q: unexpected weight from Weight: got:%f want:%f",
test.name, weight, test.weight)
}
var got []int
for _, n := range p {
got = append(got, n.ID())
}
ok := len(got) == 0 && len(test.want) == 0
for _, sp := range test.want {
if reflect.DeepEqual(got, sp) {
ok = true
break
}
}
if !ok {
t.Errorf("%q: unexpected shortest path:\ngot: %v\nwant from:%v",
test.name, p, test.want)
}
np, weight := pt.To(test.none.To())
if pt.From().ID() == test.none.From().ID() && (np != nil || !math.IsInf(weight, 1)) {
t.Errorf("%q: unexpected path:\ngot: path=%v weight=%f\nwant:path=<nil> weight=+Inf",
test.name, np, weight)
}
}
}