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