aws: add rate_limiter_capacity to configure client-side rate limits

Issuing many S3 uploads in quick succession causes the following
error:

operation error S3: PutObject, failed to get rate limit token, retry quota exceeded, 0 available, 5 requested

By default, this rate limit is disabled to restore the same behavior
as SDK v1. If `rate_limiter_capacity` is set, then client-side rate
limits will take effect.

Closes google#3496

aws/aws.go

@@ -22,6 +22,9 @@ import (
 	"strconv"
 
 	awsv2 "github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/aws/ratelimit"
+	"github.com/aws/aws-sdk-go-v2/aws/retry"
+	"github.com/aws/aws-sdk-go-v2/config"
 	awsv2cfg "github.com/aws/aws-sdk-go-v2/config"
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/client"
@@ -197,9 +200,13 @@ func NewDefaultV2Config(ctx context.Context) (awsv2.Config, error) {
 //   - hostname_immutable: Make the hostname immutable, only works if endpoint is also set.
 //   - dualstack: A value of "true" enables dual stack (IPv4 and IPv6) endpoints.
 //   - fips: A value of "true" enables the use of FIPS endpoints.
+//   - rate_limiter_capacity: A integer value configures the capacity of a token bucket used
+//     in client-side rate limits. If no value is set, the client-side rate limiting is disabled.
+//     See https://aws.github.io/aws-sdk-go-v2/docs/configuring-sdk/retries-timeouts/#client-side-rate-limiting.
 func V2ConfigFromURLParams(ctx context.Context, q url.Values) (awsv2.Config, error) {
 	var endpoint string
 	var hostnameImmutable bool
+	var rateLimitCapacity int64
 	var opts []func(*awsv2cfg.LoadOptions) error
 	for param, values := range q {
 		value := values[0]
@@ -232,6 +239,12 @@ func V2ConfigFromURLParams(ctx context.Context, q url.Values) (awsv2.Config, err
 			if fips {
 				opts = append(opts, awsv2cfg.WithUseFIPSEndpoint(awsv2.FIPSEndpointStateEnabled))
 			}
+		case "rate_limiter_capacity":
+			var err error
+			rateLimitCapacity, err = strconv.ParseInt(value, 10, 32)
+			if err != nil {
+				return awsv2.Config{}, fmt.Errorf("invalid value for capacity: %w", err)
+			}
 		case "awssdk":
 			// ignore, should be handled before this
 		default:
@@ -251,5 +264,19 @@ func V2ConfigFromURLParams(ctx context.Context, q url.Values) (awsv2.Config, err
 		opts = append(opts, awsv2cfg.WithEndpointResolverWithOptions(customResolver))
 	}
 
+	// SDK v2 adds client-side rate limiting: https://aws.github.io/aws-sdk-go-v2/docs/configuring-sdk/retries-timeouts/#client-side-rate-limiting
+	// This can cause "failed to get rate limit token" errors. Disable this to restore
+	// the behavior of SDK v1.
+	var rateLimiter retry.RateLimiter
+	rateLimiter = ratelimit.None
+	if rateLimitCapacity > 0 {
+		rateLimiter = ratelimit.NewTokenRateLimit(uint(rateLimitCapacity))
+	}
+	opts = append(opts, config.WithRetryer(func() awsv2.Retryer {
+		return retry.NewStandard(func(so *retry.StandardOptions) {
+			so.RateLimiter = rateLimiter
+		})
+	}))
+
 	return awsv2cfg.LoadDefaultConfig(ctx, opts...)
 }

aws/aws_test.go

@@ -21,6 +21,7 @@ import (
 	"testing"
 
 	awsv2 "github.com/aws/aws-sdk-go-v2/aws"
+	awsv2retry "github.com/aws/aws-sdk-go-v2/aws/retry"
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/google/go-cmp/cmp"
 	gcaws "gocloud.dev/aws"
@@ -198,6 +199,10 @@ func TestV2ConfigFromURLParams(t *testing.T) {
 			name:  "FIPS and dual stack",
 			query: url.Values{"fips": {"true"}, "dualstack": {"true"}},
 		},
+		{
+			name:  "Rate limit capacity",
+			query: url.Values{"rate_limiter_capacity": {"500"}},
+		},
 		// Can't test "profile", since AWS validates that the profile exists.
 	}
 
@@ -227,6 +232,12 @@ func TestV2ConfigFromURLParams(t *testing.T) {
 					t.Errorf("got endpoint %+v, want %+v", gotE, *test.wantEndpoint)
 				}
 			}
+
+			// Unfortunately, we can't look at the options set for the rate limiter.
+			r, ok := got.Retryer().(*awsv2retry.Standard)
+			if !ok {
+				t.Errorf("expected a standard retryer, got %v, expected awsv2retry.Standard", r)
+			}
 		})
 	}
 }