xds RDS weighted_cluster totalWeight default 100

[alpha-baby]

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before submitting your issue.

What version of gRPC are you using?

latest version

https://github.com/grpc/grpc-go/blob/master/xds/internal/client/xds.go#L525

What version of Go are you using (go version)?

1.16

What operating system (Linux, Windows, …) and version?

macOS

What did you do?

What did you expect to see?

not return NACK

xds weighted_cluster DOC:

https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/route/v3/route_components.proto.html?highlight=weighted_clusters#config-route-v3-weightedcluster

What did you see instead?

WARNING: 2021/05/13 14:57:03 [xds] [xds-client 0xc0002a6d00] Sending NACK for response type: RouteConfigResource, version: 2021-05-13T14:54:33+08:00/9, nonce: tR5YMAcCo6M=1b2e0689-8aa9-43af-9fa5-abdf340a0864, reason: error parsing "RDS" response: xxx... route:{weighted_clusters:{clusters:{name:"outbound|50002|aaaaaasssss|xxx" weight:{value:36}} clusters:{name:"outbound|50002|efwewef|xxx" weight:{value:13}} clusters:{name:"outbound|50002|efsegwsefwefwe|xxx" weight:{value:14}} clusters:{name:"outbound|50002|sdrgsfsefewf|xxx" weight:{value:31}} clusters:{name:"outbound|50002|dfefwewe|xxx" weight:{value:6}}} timeout:{} retry_policy:{retry_on:"connect-failure,refused-stream,unavailable,cancelled,retriable-status-codes" num_retries:{value:2} retry_host_predicate:{name:"envoy.retry_host_predicates.previous_hosts"} host_selection_retry_max_attempts:5 retriable_status_codes:503}} metadata:{filter_metadata:{key:"istio" value:{fields:{key:"config" value:{string_value:"/apis/networking.istio.io/v1alpha3/namespaces/jsfns/virtual-service/xxx"}}}}} decorator:{operation:"xxx/*"}, action &{WeightedClusters:clusters:{name:"outbound|50002|aaaaaasssss|xxx" weight:{value:36}} clusters:{name:"outbound|50002|efwewef|xxx" weight:{value:13}} clusters:{name:"outbound|50002|efsegwsefwefwe|xxx" weight:{value:14}} clusters:{name:"outbound|50002|sdrgsfsefewf|xxx" weight:{value:31}} clusters:{name:"outbound|50002|dfefwewe|xxx" weight:{value:6}}}, weights of clusters do not add up to total total weight, got: 0, want 100

If you also think this is a bug, I'm happy to commit a PR to fix it

[menghanl]

Yes, this looks like a bug. We should check for nil and use default value 100:

grpc-go/xds/internal/client/xds.go

Lines 525 to 527 in dc77d7f

	if totalWeight != wcs.GetTotalWeight().GetValue() {
	return nil, fmt.Errorf("route %+v, action %+v, weights of clusters do not add up to total total weight, got: %v, want %v", r, a, wcs.GetTotalWeight().GetValue(), totalWeight)
	}

I'll be great if you can send a PR (if you do, please also add a test). Thanks!