91 lines
3.4 KiB
Go
91 lines
3.4 KiB
Go
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/*
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*
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* Copyright 2016 gRPC 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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*
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*/
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package grpc
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import (
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"google.golang.org/grpc/balancer"
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"google.golang.org/grpc/resolver"
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)
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// The parent ClientConn should re-resolve when grpclb loses connection to the
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// remote balancer. When the ClientConn inside grpclb gets a TransientFailure,
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// it calls lbManualResolver.ResolveNow(), which calls parent ClientConn's
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// ResolveNow, and eventually results in re-resolve happening in parent
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// ClientConn's resolver (DNS for example).
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//
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// parent
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// ClientConn
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// +-----------------------------------------------------------------+
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// | parent +---------------------------------+ |
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// | DNS ClientConn | grpclb | |
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// | resolver balancerWrapper | | |
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// | + + | grpclb grpclb | |
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// | | | | ManualResolver ClientConn | |
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// | | | | + + | |
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// | | | | | | Transient | |
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// | | | | | | Failure | |
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// | | | | | <--------- | | |
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// | | | <--------------- | ResolveNow | | |
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// | | <--------- | ResolveNow | | | | |
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// | | ResolveNow | | | | | |
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// | | | | | | | |
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// | + + | + + | |
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// | +---------------------------------+ |
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// +-----------------------------------------------------------------+
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// lbManualResolver is used by the ClientConn inside grpclb. It's a manual
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// resolver with a special ResolveNow() function.
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//
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// When ResolveNow() is called, it calls ResolveNow() on the parent ClientConn,
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// so when grpclb client lose contact with remote balancers, the parent
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// ClientConn's resolver will re-resolve.
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type lbManualResolver struct {
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scheme string
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ccr resolver.ClientConn
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ccb balancer.ClientConn
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}
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func (r *lbManualResolver) Build(_ resolver.Target, cc resolver.ClientConn, _ resolver.BuildOption) (resolver.Resolver, error) {
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r.ccr = cc
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return r, nil
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}
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func (r *lbManualResolver) Scheme() string {
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return r.scheme
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}
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// ResolveNow calls resolveNow on the parent ClientConn.
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func (r *lbManualResolver) ResolveNow(o resolver.ResolveNowOption) {
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r.ccb.ResolveNow(o)
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}
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// Close is a noop for Resolver.
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func (*lbManualResolver) Close() {}
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// NewAddress calls cc.NewAddress.
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func (r *lbManualResolver) NewAddress(addrs []resolver.Address) {
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r.ccr.NewAddress(addrs)
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}
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// NewServiceConfig calls cc.NewServiceConfig.
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func (r *lbManualResolver) NewServiceConfig(sc string) {
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r.ccr.NewServiceConfig(sc)
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}
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