59 lines
2.2 KiB
Go
59 lines
2.2 KiB
Go
// Copyright 2018 The etcd Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package balancer
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import "google.golang.org/grpc/connectivity"
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// connectivityStateEvaluator gets updated by addrConns when their
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// states transition, based on which it evaluates the state of
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// ClientConn.
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type connectivityStateEvaluator struct {
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numReady uint64 // Number of addrConns in ready state.
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numConnecting uint64 // Number of addrConns in connecting state.
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numTransientFailure uint64 // Number of addrConns in transientFailure.
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}
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// recordTransition records state change happening in every subConn and based on
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// that it evaluates what aggregated state should be.
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// It can only transition between Ready, Connecting and TransientFailure. Other states,
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// Idle and Shutdown are transitioned into by ClientConn; in the beginning of the connection
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// before any subConn is created ClientConn is in idle state. In the end when ClientConn
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// closes it is in Shutdown state.
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//
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// recordTransition should only be called synchronously from the same goroutine.
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func (cse *connectivityStateEvaluator) recordTransition(oldState, newState connectivity.State) connectivity.State {
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// Update counters.
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for idx, state := range []connectivity.State{oldState, newState} {
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updateVal := 2*uint64(idx) - 1 // -1 for oldState and +1 for new.
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switch state {
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case connectivity.Ready:
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cse.numReady += updateVal
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case connectivity.Connecting:
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cse.numConnecting += updateVal
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case connectivity.TransientFailure:
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cse.numTransientFailure += updateVal
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}
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}
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// Evaluate.
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if cse.numReady > 0 {
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return connectivity.Ready
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}
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if cse.numConnecting > 0 {
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return connectivity.Connecting
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}
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return connectivity.TransientFailure
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}
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