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/*
*
* Copyright 2020 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 serviceconfig contains utility functions to parse service config.
package serviceconfig
import (
"encoding/json"
"fmt"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/grpclog"
externalserviceconfig "google.golang.org/grpc/serviceconfig"
)
var logger = grpclog.Component("core")
// BalancerConfig wraps the name and config associated with one load balancing
// policy. It corresponds to a single entry of the loadBalancingConfig field
// from ServiceConfig.
//
// It implements the json.Unmarshaler interface.
//
// https://github.com/grpc/grpc-proto/blob/54713b1e8bc6ed2d4f25fb4dff527842150b91b2/grpc/service_config/service_config.proto#L247
type BalancerConfig struct {
Name string
Config externalserviceconfig.LoadBalancingConfig
}
type intermediateBalancerConfig []map[string]json.RawMessage
// UnmarshalJSON implements the json.Unmarshaler interface.
//
// ServiceConfig contains a list of loadBalancingConfigs, each with a name and
// config. This method iterates through that list in order, and stops at the
// first policy that is supported.
// - If the config for the first supported policy is invalid, the whole service
// config is invalid.
// - If the list doesn't contain any supported policy, the whole service config
// is invalid.
func (bc *BalancerConfig) UnmarshalJSON(b []byte) error {
var ir intermediateBalancerConfig
err := json.Unmarshal(b, &ir)
if err != nil {
return err
}
for i, lbcfg := range ir {
if len(lbcfg) != 1 {
return fmt.Errorf("invalid loadBalancingConfig: entry %v does not contain exactly 1 policy/config pair: %q", i, lbcfg)
}
var (
name string
jsonCfg json.RawMessage
)
// Get the key:value pair from the map. We have already made sure that
// the map contains a single entry.
for name, jsonCfg = range lbcfg {
}
builder := balancer.Get(name)
if builder == nil {
// If the balancer is not registered, move on to the next config.
// This is not an error.
continue
}
bc.Name = name
parser, ok := builder.(balancer.ConfigParser)
if !ok {
if string(jsonCfg) != "{}" {
logger.Warningf("non-empty balancer configuration %q, but balancer does not implement ParseConfig", string(jsonCfg))
}
// Stop at this, though the builder doesn't support parsing config.
return nil
}
cfg, err := parser.ParseConfig(jsonCfg)
if err != nil {
return fmt.Errorf("error parsing loadBalancingConfig for policy %q: %v", name, err)
}
bc.Config = cfg
return nil
}
// This is reached when the for loop iterates over all entries, but didn't
// return. This means we had a loadBalancingConfig slice but did not
// encounter a registered policy. The config is considered invalid in this
// case.
return fmt.Errorf("invalid loadBalancingConfig: no supported policies found")
}
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