feat: initial tracing support (#1623)

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

@@ -0,0 +1,73 @@
+/*
+ *
+ * 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.
+ *
+ */
+
+// Package backoff implement the backoff strategy for gRPC.
+//
+// This is kept in internal until the gRPC project decides whether or not to
+// allow alternative backoff strategies.
+package backoff
+
+import (
+	"time"
+
+	grpcbackoff "google.golang.org/grpc/backoff"
+	"google.golang.org/grpc/internal/grpcrand"
+)
+
+// Strategy defines the methodology for backing off after a grpc connection
+// failure.
+type Strategy interface {
+	// Backoff returns the amount of time to wait before the next retry given
+	// the number of consecutive failures.
+	Backoff(retries int) time.Duration
+}
+
+// DefaultExponential is an exponential backoff implementation using the
+// default values for all the configurable knobs defined in
+// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
+var DefaultExponential = Exponential{Config: grpcbackoff.DefaultConfig}
+
+// Exponential implements exponential backoff algorithm as defined in
+// https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.
+type Exponential struct {
+	// Config contains all options to configure the backoff algorithm.
+	Config grpcbackoff.Config
+}
+
+// Backoff returns the amount of time to wait before the next retry given the
+// number of retries.
+func (bc Exponential) Backoff(retries int) time.Duration {
+	if retries == 0 {
+		return bc.Config.BaseDelay
+	}
+	backoff, max := float64(bc.Config.BaseDelay), float64(bc.Config.MaxDelay)
+	for backoff < max && retries > 0 {
+		backoff *= bc.Config.Multiplier
+		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.Config.Jitter*(grpcrand.Float64()*2-1)
+	if backoff < 0 {
+		return 0
+	}
+	return time.Duration(backoff)
+}