grpc/grpc-go · error

xds_wrr_locality: config generated

Error message

xds_wrr_locality: config generated %v is invalid: %v

What it means

Returned when the weighted-target child balancer's ConfigParser rejects the config that wrr_locality generated from locality weights and the configured child policy. The generated weighted target JSON is logged so you can see exactly what was rejected.

Solutions

1. Read the nested child-parser error (the second %v) to identify which childPolicy failed.
2. Ensure the named child balancer is registered: import the balancer package (e.g. _ "google.golang.org/grpc/balancer/weightedroundrobin") or use a built-in like round_robin.
3. Correct the childPolicy entry in the xDS/LB config to a registered, correctly-shaped policy.
4. Upgrade grpc-go if the policy is supported only in a newer version.

Example fix

// before: childPolicy references an unregistered balancer
{"childPolicy":[{"wrr":{}}]}

// after: use a registered balancer
{"childPolicy":[{"round_robin":{}}]}

// Confirm the childPolicy names a registered balancer before publishing config.
func childPolicyRegistered(name string) bool {
    return balancer.Get(name) != nil
}

// The nested child-parser error is wrapped; inspect it.
if err := b.UpdateClientConnState(s); err != nil {
    if strings.Contains(err.Error(), "config generated") {
        // pull the nested cause and fix the childPolicy block.
    }
}

When it happens

Trigger: Triggered at balancer.go:182 when b.childParser.ParseConfig(wtCfgJSON) (the weighted_target parser) returns an error. Root cause is usually an invalid or unregistered childPolicy inside the wrr_locality LBConfig.

Common situations: The childPolicy named in the wrr_locality config is not a registered balancer (typo, e.g. 'wrr' instead of 'weighted_round_robin'); the child policy requires config fields that were not supplied; grpc-go version that does not register the requested policy.

Related errors

• xds_wrr_locality: invalid LBConfig
• failed to push new configuration
• LB policy name found in Children field ( ) is not found in…
• LB policy name found in Priorities field ( ) is not found…
• xds_wrr_locality: error marshalling prepared config

AI-assisted analysis of grpc/grpc-go@0c51461d27 (2026-08-11). Data as JSON: /api/errors/50525c786926ac6f. Report an issue: GitHub.

Appendix: source

Thrown at internal/xds/balancer/wrrlocality/balancer.go:182

		// shouldn't happen though (this attribute that is set actually gets
		// used to build localities in the first place), and thus don't error
		// out, and just build a weighted target with undefined behavior.
		locality := xdsinternal.LocalityString(xdsinternal.LocalityIDFromEndpoint(ep))
		ai, ok := getAddrInfo(ep)
		if !ok {
			return fmt.Errorf("xds_wrr_locality: missing locality weight information in endpoint %q", ep)
		}
		weightedTargets[locality] = weightedtarget.Target{Weight: ai.LocalityWeight, ChildPolicy: lbCfg.ChildPolicy}
	}
	wtCfg := &weightedtarget.LBConfig{Targets: weightedTargets}
	wtCfgJSON, err := json.Marshal(wtCfg)
	if err != nil {
		// Shouldn't happen.
		return fmt.Errorf("xds_wrr_locality: error marshalling prepared config: %v", wtCfg)
	}
	var sc serviceconfig.LoadBalancingConfig
	if sc, err = b.childParser.ParseConfig(wtCfgJSON); err != nil {
		return fmt.Errorf("xds_wrr_locality: config generated %v is invalid: %v", wtCfgJSON, err)
	}

	return b.child.UpdateClientConnState(balancer.ClientConnState{
		ResolverState:  s.ResolverState,
		BalancerConfig: sc,
	})
}

func (b *wrrLocalityBalancer) ResolverError(err error) {
	b.child.ResolverError(err)
}

func (b *wrrLocalityBalancer) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) {
	b.logger.Errorf("UpdateSubConnState(%v, %+v) called unexpectedly", sc, state)
}

func (b *wrrLocalityBalancer) Close() {
	b.child.Close()

View on GitHub (pinned to 0c51461d27)