X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/1535c8d141b07f246a501d288a0d3a903ce41a56..6fe8e52020d421797306e5c6536afbcee761510a:/sdk/go/httpserver/request_limiter.go

diff --git a/sdk/go/httpserver/request_limiter.go b/sdk/go/httpserver/request_limiter.go
index 178ffb90f4..e7192d5b4f 100644
--- a/sdk/go/httpserver/request_limiter.go
+++ b/sdk/go/httpserver/request_limiter.go
@@ -1,21 +1,49 @@
+// Copyright (C) The Arvados Authors. All rights reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+
 package httpserver
 
 import (
 	"net/http"
 )
 
+// RequestCounter is an http.Handler that tracks the number of
+// requests in progress.
+type RequestCounter interface {
+	http.Handler
+
+	// Current() returns the number of requests in progress.
+	Current() int
+
+	// Max() returns the maximum number of concurrent requests
+	// that will be accepted.
+	Max() int
+}
+
 type limiterHandler struct {
 	requests chan struct{}
 	handler  http.Handler
 }
 
-func NewRequestLimiter(maxRequests int, handler http.Handler) http.Handler {
+// NewRequestLimiter returns a RequestCounter that delegates up to
+// maxRequests at a time to the given handler, and responds 503 to all
+// incoming requests beyond that limit.
+func NewRequestLimiter(maxRequests int, handler http.Handler) RequestCounter {
 	return &limiterHandler{
 		requests: make(chan struct{}, maxRequests),
 		handler:  handler,
 	}
 }
 
+func (h *limiterHandler) Current() int {
+	return len(h.requests)
+}
+
+func (h *limiterHandler) Max() int {
+	return cap(h.requests)
+}
+
 func (h *limiterHandler) ServeHTTP(resp http.ResponseWriter, req *http.Request) {
 	select {
 	case h.requests <- struct{}{}: