1/*
 2 *
 3 * Copyright 2020 gRPC authors.
 4 *
 5 * Licensed under the Apache License, Version 2.0 (the "License");
 6 * you may not use this file except in compliance with the License.
 7 * You may obtain a copy of the License at
 8 *
 9 *     http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 */
18
19// Package state declares grpclb types to be set by resolvers wishing to pass
20// information to grpclb via resolver.State Attributes.
21package state
22
23import (
24	"google.golang.org/grpc/resolver"
25)
26
27// keyType is the key to use for storing State in Attributes.
28type keyType string
29
30const key = keyType("grpc.grpclb.state")
31
32// State contains gRPCLB-relevant data passed from the name resolver.
33type State struct {
34	// BalancerAddresses contains the remote load balancer address(es).  If
35	// set, overrides any resolver-provided addresses with Type of GRPCLB.
36	BalancerAddresses []resolver.Address
37}
38
39// Set returns a copy of the provided state with attributes containing s.  s's
40// data should not be mutated after calling Set.
41func Set(state resolver.State, s *State) resolver.State {
42	state.Attributes = state.Attributes.WithValue(key, s)
43	return state
44}
45
46// Get returns the grpclb State in the resolver.State, or nil if not present.
47// The returned data should not be mutated.
48func Get(state resolver.State) *State {
49	s, _ := state.Attributes.Value(key).(*State)
50	return s
51}