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configbuilder_childname.go
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/
configbuilder_childname.go
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/*
*
* Copyright 2022 gRPC 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 clusterresolver
import (
"fmt"
"google.golang.org/grpc/xds/internal"
"google.golang.org/grpc/xds/internal/xdsclient/xdsresource"
)
// nameGenerator generates a child name for a list of priorities (each priority
// is a list of localities).
//
// The purpose of this generator is to reuse names between updates. So the
// struct keeps state between generate() calls, and a later generate() might
// return names returned by the previous call.
type nameGenerator struct {
existingNames map[internal.LocalityID]string
prefix uint64
nextID uint64
}
func newNameGenerator(prefix uint64) *nameGenerator {
return &nameGenerator{prefix: prefix}
}
// generate returns a list of names for the given list of priorities.
//
// Each priority is a list of localities. The name for the priority is picked as
// - for each locality in this priority, if it exists in the existing names,
// this priority will reuse the name
// - if no reusable name is found for this priority, a new name is generated
//
// For example:
// - update 1: [[L1], [L2], [L3]] --> ["0", "1", "2"]
// - update 2: [[L1], [L2], [L3]] --> ["0", "1", "2"]
// - update 3: [[L1, L2], [L3]] --> ["0", "2"] (Two priorities were merged)
// - update 4: [[L1], [L4]] --> ["0", "3",] (A priority was split, and a new priority was added)
func (ng *nameGenerator) generate(priorities [][]xdsresource.Locality) []string {
var ret []string
usedNames := make(map[string]bool)
newNames := make(map[internal.LocalityID]string)
for _, priority := range priorities {
var nameFound string
for _, locality := range priority {
if name, ok := ng.existingNames[locality.ID]; ok {
if !usedNames[name] {
nameFound = name
// Found a name to use. No need to process the remaining
// localities.
break
}
}
}
if nameFound == "" {
// No appropriate used name is found. Make a new name.
nameFound = fmt.Sprintf("priority-%d-%d", ng.prefix, ng.nextID)
ng.nextID++
}
ret = append(ret, nameFound)
// All localities in this priority share the same name. Add them all to
// the new map.
for _, l := range priority {
newNames[l.ID] = nameFound
}
usedNames[nameFound] = true
}
ng.existingNames = newNames
return ret
}