wfe: on rate limit error, serve 500 (#7796)

This affects NewAccount and NewOrder.

web/context.go

@@ -35,12 +35,7 @@ type RequestEvent struct {
 	Slug           string   `json:",omitempty"`
 	InternalErrors []string `json:",omitempty"`
 	Error          string   `json:",omitempty"`
-	// If there is an error checking the data store for our rate limits
-	// we ignore it, but attach the error to the log event for analysis.
-	// TODO(#7796): Treat errors from the rate limit system as normal
-	// errors and put them into InternalErrors.
-	IgnoredRateLimitError string `json:",omitempty"`
-	UserAgent             string `json:"ua,omitempty"`
+	UserAgent      string   `json:"ua,omitempty"`
 	// Origin is sent by the browser from XHR-based clients.
 	Origin string                 `json:",omitempty"`
 	Extra  map[string]interface{} `json:",omitempty"`

wfe2/wfe.go

@@ -798,7 +798,8 @@ func (wfe *WebFrontEndImpl) NewAccount(
 			wfe.sendError(response, logEvent, probs.RateLimited(err.Error()), err)
 			return
 		} else {
-			logEvent.IgnoredRateLimitError = err.Error()
+			wfe.sendError(response, logEvent, web.ProblemDetailsForError(err, "While checking rate limits"), err)
+			return
 		}
 	}
 
@@ -2401,14 +2402,13 @@ func (wfe *WebFrontEndImpl) NewOrder(
 	}
 
 	refundLimits, err := wfe.checkNewOrderLimits(ctx, acct.ID, names, isRenewal)
-	if err != nil {
+	if err != nil && features.Get().UseKvLimitsForNewOrder {
 		if errors.Is(err, berrors.RateLimit) {
-			if features.Get().UseKvLimitsForNewOrder {
-				wfe.sendError(response, logEvent, probs.RateLimited(err.Error()), err)
-				return
-			}
+			wfe.sendError(response, logEvent, probs.RateLimited(err.Error()), err)
+			return
 		} else {
-			logEvent.IgnoredRateLimitError = err.Error()
+			wfe.sendError(response, logEvent, web.ProblemDetailsForError(err, "While checking rate limits"), err)
+			return
 		}
 	}