core/expiration: Add backoff jitter to the expiration retries (#10937)

vault/expiration.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"math/rand"
 	"os"
 	"path"
 	"strconv"
@@ -218,8 +219,7 @@ func (r *revocationJob) OnFailure(err error) {
 		return
 	}
 
-	// TODO vault 1.8 we added an exponential backoff library, check to see if it would be useful here
-	pending.timer.Reset((1 << pending.revokesAttempted) * revokeRetryBase)
+	pending.timer.Reset(revokeExponentialBackoff(pending.revokesAttempted))
 	r.m.pending.Store(r.leaseID, pending)
 }
 
@@ -248,6 +248,15 @@ func expireLeaseStrategyFairsharing(ctx context.Context, m *ExpirationManager, l
 	m.jobManager.AddJob(job, mountAccessor)
 }
 
+func revokeExponentialBackoff(attempt uint8) time.Duration {
+	exp := (1 << attempt) * revokeRetryBase
+	randomDelta := 0.5 * float64(exp)
+
+	// Allow backoff time to be a random value between exp +/- (0.5*exp)
+	backoffTime := (float64(exp) - randomDelta) + (rand.Float64() * (2 * randomDelta))
+	return time.Duration(backoffTime)
+}
+
 // revokeIDFunc is invoked when a given ID is expired
 func expireLeaseStrategyRevoke(ctx context.Context, m *ExpirationManager, leaseID string, ns *namespace.Namespace) {
 	for attempt := uint(0); attempt < maxRevokeAttempts; attempt++ {