limithandler: Return ResourceExhausted for rate limiterjc-change-backpressure-to-resource-exhausted

If a rate limiter idicates no more traffic is allowed, Gitaly should
return a non-retryable error. gRPC Unavailable indicates a retry is
possible, so gRPC ResourceExhausted is more appropriate to return to the
client.

Changelog: changed

2 files changed, 26 insertions, 4 deletions

diff --git a/internal/middleware/limithandler/middleware_test.go b/internal/middleware/limithandler/middleware_test.go
index 4ccdad848..852c490de 100644
--- a/internal/middleware/limithandler/middleware_test.go
+++ b/internal/middleware/limithandler/middleware_test.go
@@ -3,6 +3,7 @@ package limithandler_test
 import (
 	"bytes"
 	"context"
+	"errors"
 	"net"
 	"sync"
 	"testing"
@@ -19,8 +20,6 @@ import (
 	"gitlab.com/gitlab-org/gitaly/v14/internal/testhelper"
 	"gitlab.com/gitlab-org/gitaly/v14/proto/go/gitalypb"
 	"google.golang.org/grpc"
-	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/status"
 )
 
 func TestMain(m *testing.M) {
@@ -370,7 +369,18 @@ func testRateLimitHandler(t *testing.T, ctx context.Context) {
 			_, err := client.Unary(ctx, &pb.UnaryRequest{})
 
 			if featureflag.RateLimit.IsEnabled(ctx) {
-				testhelper.RequireGrpcError(t, status.Error(codes.Unavailable, "too many requests"), err)
+				testhelper.RequireGrpcError(
+					t,
+					limithandler.ErrWithDetails(
+						t,
+						helper.ErrResourceExhausted(errors.New("too many requests")),
+						&gitalypb.SystemResourceError{
+							ErrorMessage: "too many requests",
+							Retryable:    false,
+						},
+					),
+					err,
+				)
 			} else {
 				require.NoError(t, err)
 			}
diff --git a/internal/middleware/limithandler/rate_limiter.go b/internal/middleware/limithandler/rate_limiter.go
index f47bb5409..241546a68 100644
--- a/internal/middleware/limithandler/rate_limiter.go
+++ b/internal/middleware/limithandler/rate_limiter.go
@@ -10,6 +10,7 @@ import (
 	"gitlab.com/gitlab-org/gitaly/v14/internal/gitaly/config"
 	"gitlab.com/gitlab-org/gitaly/v14/internal/helper"
 	"gitlab.com/gitlab-org/gitaly/v14/internal/metadata/featureflag"
+	"gitlab.com/gitlab-org/gitaly/v14/proto/go/gitalypb"
 	"golang.org/x/time/rate"
 )
 
@@ -37,7 +38,18 @@ func (r *RateLimiter) Limit(ctx context.Context, lockKey string, f LimitedFunc)
 		// of traffic.
 		r.requestsDroppedMetric.Inc()
 		if featureflag.RateLimit.IsEnabled(ctx) {
-			return nil, helper.ErrUnavailable(errors.New("too many requests"))
+			detailedErr, err := helper.ErrWithDetails(
+				helper.ErrResourceExhausted(errors.New("too many requests")),
+				&gitalypb.SystemResourceError{
+					ErrorMessage: "too many requests",
+					Retryable:    false,
+				},
+			)
+			if err != nil {
+				return nil, helper.ErrInternalf("error details: %w", err)
+			}
+
+			return nil, detailedErr
 		}
 	}