grpclb: enter fallback if no balancer addresses are available #3119
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dfawley
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Oct 29, 2019
balancer/grpclb/grpclb.go
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| @@ -426,6 +426,8 @@ func (lb *lbBalancer) UpdateClientConnState(ccs balancer.ClientConnState) error | |||
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| addrs := ccs.ResolverState.Addresses | |||
| if len(addrs) == 0 { | |||
| // There's should be at least one address, either grpclb server or | |||
| PermitWithoutStream: true, | ||
| })) | ||
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| // DialContext using manualResolver.Scheme, which is a random scheme |
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This comment is no longer accurate (both parts).
balancer/grpclb/grpclb_test.go
Outdated
| return nil, nil, errors.New("received unexpected server name") | ||
| if authority != string(b) { | ||
| fmt.Printf("test-creds: got authority from ClientConn %q, expected by server %q\n", authority, string(b)) | ||
| return nil, nil, errors.New("received unexpected server nameq") |
menghanl
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dfawley
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Oct 30, 2019
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This is necessary because there's another way to select grpclb (by specifying grpclb in service config's balancing policy field). So it's possible that grpclb is picked, but resolver doesn't have any balancer addresses.
When an update without balancer address is received, grpclb closes the underlying ClientConn to remote balancer, and enters fallback mode.
Note that grpclb waits until the ClientConn and the RPC goroutines are actually closed to do the fallback work. This can avoid race caused by async close.
fixes #3064