1 /*
2 *
3 * Copyright 2022 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 balancer
20 21 import "google.golang.org/grpc/connectivity"
22 23 // ConnectivityStateEvaluator takes the connectivity states of multiple SubConns
24 // and returns one aggregated connectivity state.
25 //
26 // It's not thread safe.
27 type ConnectivityStateEvaluator struct {
28 numReady uint64 // Number of addrConns in ready state.
29 numConnecting uint64 // Number of addrConns in connecting state.
30 numTransientFailure uint64 // Number of addrConns in transient failure state.
31 numIdle uint64 // Number of addrConns in idle state.
32 }
33 34 // RecordTransition records state change happening in subConn and based on that
35 // it evaluates what aggregated state should be.
36 //
37 // - If at least one SubConn in Ready, the aggregated state is Ready;
38 // - Else if at least one SubConn in Connecting, the aggregated state is Connecting;
39 // - Else if at least one SubConn is Idle, the aggregated state is Idle;
40 // - Else if at least one SubConn is TransientFailure (or there are no SubConns), the aggregated state is Transient Failure.
41 //
42 // Shutdown is not considered.
43 func (cse *ConnectivityStateEvaluator) RecordTransition(oldState, newState connectivity.State) connectivity.State {
44 // Update counters.
45 for idx, state := range []connectivity.State{oldState, newState} {
46 updateVal := 2*uint64(idx) - 1 // -1 for oldState and +1 for new.
47 switch state {
48 case connectivity.Ready:
49 cse.numReady += updateVal
50 case connectivity.Connecting:
51 cse.numConnecting += updateVal
52 case connectivity.TransientFailure:
53 cse.numTransientFailure += updateVal
54 case connectivity.Idle:
55 cse.numIdle += updateVal
56 }
57 }
58 return cse.CurrentState()
59 }
60 61 // CurrentState returns the current aggregate conn state by evaluating the counters
62 func (cse *ConnectivityStateEvaluator) CurrentState() connectivity.State {
63 // Evaluate.
64 if cse.numReady > 0 {
65 return connectivity.Ready
66 }
67 if cse.numConnecting > 0 {
68 return connectivity.Connecting
69 }
70 if cse.numIdle > 0 {
71 return connectivity.Idle
72 }
73 return connectivity.TransientFailure
74 }
75