14287: Add ensure_unique_name param to untrash options.

[arvados.git] / sdk / go / httpserver / request_limiter.go

diff --git a/sdk/go/httpserver/request_limiter.go b/sdk/go/httpserver/request_limiter.go
index 178ffb90f4facbebdfd6809bb1448e84904bc82f..e7192d5b4f407560d1545ac02264c1f11c70684d 100644 (file)
--- 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{}{}: