snapshot of https://github.com/livekit/livekit.git @ 08c5433449c106943231037d0b892895f6e92d3b (2026-09-15)

pkg/routing/selector/regionaware.go

@@ -0,0 +1,127 @@
+// Copyright 2023 LiveKit, Inc.
+//
+// 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 selector
+
+import (
+	"math"
+
+	"github.com/livekit/protocol/livekit"
+
+	"github.com/livekit/livekit-server/pkg/config"
+)
+
+// RegionAwareSelector prefers available nodes that are closest to the region of the current instance
+type RegionAwareSelector struct {
+	SystemLoadSelector
+	CurrentRegion   string
+	regionDistances map[string]float64
+	regions         []config.RegionConfig
+	SortBy          string
+	Algorithm       string
+}
+
+func NewRegionAwareSelector(currentRegion string, regions []config.RegionConfig, sortBy string, algorithm string) (*RegionAwareSelector, error) {
+	if currentRegion == "" {
+		return nil, ErrCurrentRegionNotSet
+	}
+	// build internal map of distances
+	s := &RegionAwareSelector{
+		CurrentRegion:   currentRegion,
+		regionDistances: make(map[string]float64),
+		regions:         regions,
+		SortBy:          sortBy,
+		Algorithm:       algorithm,
+	}
+
+	var currentRC *config.RegionConfig
+
+	for _, region := range regions {
+		if region.Name == currentRegion {
+			currentRC = &region
+			break
+		}
+	}
+
+	if currentRC == nil && len(regions) > 0 {
+		return nil, ErrCurrentRegionUnknownLatLon
+	}
+
+	if currentRC != nil {
+		for _, region := range regions {
+			s.regionDistances[region.Name] = distanceBetween(currentRC.Lat, currentRC.Lon, region.Lat, region.Lon)
+		}
+	}
+
+	return s, nil
+}
+
+func (s *RegionAwareSelector) SelectNode(nodes []*livekit.Node) (*livekit.Node, error) {
+	nodes, err := s.SystemLoadSelector.filterNodes(nodes)
+	if err != nil {
+		return nil, err
+	}
+
+	// find nodes nearest to current region
+	var nearestNodes []*livekit.Node
+	nearestRegion := ""
+	minDist := math.MaxFloat64
+	for _, node := range nodes {
+		if node.Region == nearestRegion {
+			nearestNodes = append(nearestNodes, node)
+			continue
+		}
+		if dist, ok := s.regionDistances[node.Region]; ok {
+			if dist < minDist {
+				minDist = dist
+				nearestRegion = node.Region
+				nearestNodes = nearestNodes[:0]
+				nearestNodes = append(nearestNodes, node)
+			}
+		}
+	}
+
+	if len(nearestNodes) > 0 {
+		nodes = nearestNodes
+	}
+
+	return SelectSortedNode(nodes, s.SortBy, s.Algorithm)
+}
+
+// haversine(θ) function
+func hsin(theta float64) float64 {
+	return math.Pow(math.Sin(theta/2), 2)
+}
+
+var piBy180 = math.Pi / 180
+
+// Haversine Distance Formula
+// http://en.wikipedia.org/wiki/Haversine_formula
+// from https://gist.github.com/cdipaolo/d3f8db3848278b49db68
+func distanceBetween(lat1, lon1, lat2, lon2 float64) float64 {
+	// convert to radians
+	// must cast radius as float to multiply later
+	var la1, lo1, la2, lo2, r float64
+	la1 = lat1 * piBy180
+	lo1 = lon1 * piBy180
+	la2 = lat2 * piBy180
+	lo2 = lon2 * piBy180
+
+	r = 6378100 // Earth radius in METERS
+
+	// calculate
+	h := hsin(la2-la1) + math.Cos(la1)*math.Cos(la2)*hsin(lo2-lo1)
+
+	return 2 * r * math.Asin(math.Sqrt(h))
+}