upstream endpoints load balancer weights (#1830)

config/constants.go

@@ -3,19 +3,40 @@ package config
 import (
 	"errors"
 
+	"github.com/mitchellh/mapstructure"
+	"github.com/spf13/viper"
 	"google.golang.org/protobuf/encoding/protojson"
 )
 
 const (
-	policyKey    = "policy"
 	toKey        = "to"
 	envoyOptsKey = "_envoy_opts"
 )
 
 var (
-	errKeysMustBeStrings = errors.New("cannot convert nested map: all keys must be strings")
+	errKeysMustBeStrings          = errors.New("cannot convert nested map: all keys must be strings")
+	errZeroWeight                 = errors.New("zero load balancing weight not permitted")
+	errEndpointWeightsSpec        = errors.New("either no weights should be provided, or all endpoints must have non-zero weight specified")
+	errHostnameMustBeSpecified    = errors.New("endpoint hostname must be specified")
+	errSchemeMustBeSpecified      = errors.New("url scheme must be provided")
+	errEmptyUrls                  = errors.New("url list is empty")
+	errEitherToOrRedirectRequired = errors.New("policy should have either `to` or `redirect` defined")
 )
 
 var (
 	protoPartial = protojson.UnmarshalOptions{AllowPartial: true, DiscardUnknown: true}
 )
+
+var (
+
+	// viperPolicyHooks are used to decode options and policy coming from YAML and env vars
+	viperPolicyHooks = viper.DecodeHook(mapstructure.ComposeDecodeHookFunc(
+		mapstructure.StringToTimeDurationHookFunc(),
+		mapstructure.StringToSliceHookFunc(","),
+		// decode policy including all protobuf-native notations - i.e. duration as `1s`
+		// https://developers.google.com/protocol-buffers/docs/proto3#json
+		DecodePolicyHookFunc(),
+		// parse base-64 encoded POLICY that is bound to environment variable
+		DecodePolicyBase64Hook(),
+	))
+)