Service Topology implementation

* Implement Service Topology for ipvs and iptables proxier
* Add test files
* API validation

pkg/proxy/topology.go

@@ -0,0 +1,80 @@
+/*
+Copyright 2019 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package proxy
+
+import (
+	v1 "k8s.io/api/core/v1"
+)
+
+// FilterTopologyEndpoint returns the appropriate endpoints based on the cluster
+// topology.
+// This uses the current node's labels, which contain topology information, and
+// the required topologyKeys to find appropriate endpoints. If both the endpoint's
+// topology and the current node have matching values for topologyKeys[0], the
+// endpoint will be chosen.  If no endpoints are chosen, toplogyKeys[1] will be
+// considered, and so on.  If either the node or the endpoint do not have values
+// for a key, it is considered to not match.
+//
+// If topologyKeys is specified, but no endpoints are chosen for any key, the
+// the service has no viable endpoints for clients on this node, and connections
+// should fail.
+//
+// The special key "*" may be used as the last entry in topologyKeys to indicate
+// "any endpoint" is acceptable.
+//
+// If topologyKeys is not specified or empty, no topology constraints will be
+// applied and this will return all endpoints.
+func FilterTopologyEndpoint(nodeLabels map[string]string, topologyKeys []string, endpoints []Endpoint) []Endpoint {
+	// Do not filter endpoints if service has no topology keys.
+	if len(topologyKeys) == 0 {
+		return endpoints
+	}
+
+	filteredEndpoint := []Endpoint{}
+
+	if len(nodeLabels) == 0 {
+		if topologyKeys[len(topologyKeys)-1] == v1.TopologyKeyAny {
+			// edge case: include all endpoints if topology key "Any" specified
+			// when we cannot determine current node's topology.
+			return endpoints
+		}
+		// edge case: do not include any endpoints if topology key "Any" is
+		// not specified when we cannot determine current node's topology.
+		return filteredEndpoint
+	}
+
+	for _, key := range topologyKeys {
+		if key == v1.TopologyKeyAny {
+			return endpoints
+		}
+		topologyValue, found := nodeLabels[key]
+		if !found {
+			continue
+		}
+
+		for _, ep := range endpoints {
+			topology := ep.GetTopology()
+			if value, found := topology[key]; found && value == topologyValue {
+				filteredEndpoint = append(filteredEndpoint, ep)
+			}
+		}
+		if len(filteredEndpoint) > 0 {
+			return filteredEndpoint
+		}
+	}
+	return filteredEndpoint
+}