diff --git a/vendor/github.com/grpc-ecosystem/go-grpc-middleware/retry/backoff.go b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/retry/backoff.go
new file mode 100644
index 0000000..ad35f09
--- /dev/null
+++ b/vendor/github.com/grpc-ecosystem/go-grpc-middleware/retry/backoff.go
@@ -0,0 +1,44 @@
+// Copyright 2016 Michal Witkowski. All Rights Reserved.
+// See LICENSE for licensing terms.
+
+package grpc_retry
+
+import (
+	"time"
+
+	"github.com/grpc-ecosystem/go-grpc-middleware/util/backoffutils"
+)
+
+// BackoffLinear is very simple: it waits for a fixed period of time between calls.
+func BackoffLinear(waitBetween time.Duration) BackoffFunc {
+	return func(attempt uint) time.Duration {
+		return waitBetween
+	}
+}
+
+// BackoffLinearWithJitter waits a set period of time, allowing for jitter (fractional adjustment).
+//
+// For example waitBetween=1s and jitter=0.10 can generate waits between 900ms and 1100ms.
+func BackoffLinearWithJitter(waitBetween time.Duration, jitterFraction float64) BackoffFunc {
+	return func(attempt uint) time.Duration {
+		return backoffutils.JitterUp(waitBetween, jitterFraction)
+	}
+}
+
+// BackoffExponential produces increasing intervals for each attempt.
+//
+// The scalar is multiplied times 2 raised to the current attempt. So the first
+// retry with a scalar of 100ms is 100ms, while the 5th attempt would be 1.6s.
+func BackoffExponential(scalar time.Duration) BackoffFunc {
+	return func(attempt uint) time.Duration {
+		return scalar * time.Duration(backoffutils.ExponentBase2(attempt))
+	}
+}
+
+// BackoffExponentialWithJitter creates an exponential backoff like
+// BackoffExponential does, but adds jitter.
+func BackoffExponentialWithJitter(scalar time.Duration, jitterFraction float64) BackoffFunc {
+	return func(attempt uint) time.Duration {
+		return backoffutils.JitterUp(scalar*time.Duration(backoffutils.ExponentBase2(attempt)), jitterFraction)
+	}
+}