Update federation target to etcd/clientv3 (#6119)

With CoreDNS now supporting etcdv3 as the DNS backend, we
can update our federation target to etcdv3. Users will now be
able to use etcdv3 server as the federation backbone.

Minio will update bucket data to etcdv3 and CoreDNS can pick
that data up and serve it as bucket style DNS path.

vendor/google.golang.org/grpc/backoff.go

@@ -1,80 +1,38 @@
+/*
+ *
+ * Copyright 2017 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.
+ *
+ */
+
+// See internal/backoff package for the backoff implementation. This file is
+// kept for the exported types and API backward compatility.
+
 package grpc
 
 import (
-	"math/rand"
 	"time"
 )
 
 // DefaultBackoffConfig uses values specified for backoff in
 // https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
-var (
-	DefaultBackoffConfig = BackoffConfig{
-		MaxDelay:  120 * time.Second,
-		baseDelay: 1.0 * time.Second,
-		factor:    1.6,
-		jitter:    0.2,
-	}
-)
-
-// backoffStrategy defines the methodology for backing off after a grpc
-// connection failure.
-//
-// This is unexported until the gRPC project decides whether or not to allow
-// alternative backoff strategies. Once a decision is made, this type and its
-// method may be exported.
-type backoffStrategy interface {
-	// backoff returns the amount of time to wait before the next retry given
-	// the number of consecutive failures.
-	backoff(retries int) time.Duration
+var DefaultBackoffConfig = BackoffConfig{
+	MaxDelay: 120 * time.Second,
 }
 
 // BackoffConfig defines the parameters for the default gRPC backoff strategy.
 type BackoffConfig struct {
 	// MaxDelay is the upper bound of backoff delay.
 	MaxDelay time.Duration
-
-	// TODO(stevvooe): The following fields are not exported, as allowing
-	// changes would violate the current gRPC specification for backoff. If
-	// gRPC decides to allow more interesting backoff strategies, these fields
-	// may be opened up in the future.
-
-	// baseDelay is the amount of time to wait before retrying after the first
-	// failure.
-	baseDelay time.Duration
-
-	// factor is applied to the backoff after each retry.
-	factor float64
-
-	// jitter provides a range to randomize backoff delays.
-	jitter float64
-}
-
-func setDefaults(bc *BackoffConfig) {
-	md := bc.MaxDelay
-	*bc = DefaultBackoffConfig
-
-	if md > 0 {
-		bc.MaxDelay = md
-	}
-}
-
-func (bc BackoffConfig) backoff(retries int) time.Duration {
-	if retries == 0 {
-		return bc.baseDelay
-	}
-	backoff, max := float64(bc.baseDelay), float64(bc.MaxDelay)
-	for backoff < max && retries > 0 {
-		backoff *= bc.factor
-		retries--
-	}
-	if backoff > max {
-		backoff = max
-	}
-	// Randomize backoff delays so that if a cluster of requests start at
-	// the same time, they won't operate in lockstep.
-	backoff *= 1 + bc.jitter*(rand.Float64()*2-1)
-	if backoff < 0 {
-		return 0
-	}
-	return time.Duration(backoff)
 }