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minio/rate-limit-handler.go

63 lines
1.9 KiB

/*
* Minio Cloud Storage, (C) 2016 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package main
import (
"net/http"
"sync"
)
// rateLimit - represents datatype of the functionality implemented to
// limit the number of concurrent http requests.
type rateLimit struct {
handler http.Handler
rqueue chan struct{}
releaseOnce sync.Once
}
// acquire and release implement a way to send and receive from the
// channel this is in-turn used to rate limit incoming connections in
// ServeHTTP() http.Handler method.
func (c *rateLimit) acquire() { c.rqueue <- struct{}{} }
func (c *rateLimit) release() { <-c.rqueue }
// ServeHTTP is an http.Handler ServeHTTP method, implemented to rate
// limit incoming HTTP requests.
func (c *rateLimit) ServeHTTP(w http.ResponseWriter, r *http.Request) {
// Acquire the connection if queue is not full, otherwise
// code path waits here until the previous case is true.
c.acquire()
// Serves the request.
c.handler.ServeHTTP(w, r)
// Release by draining the channel once.
c.releaseOnce.Do(c.release)
}
// setRateLimitHandler limits the number of concurrent http requests based on MINIO_MAXCONN.
func setRateLimitHandler(handler http.Handler) http.Handler {
if globalMaxConn == 0 {
return handler
} // else proceed to rate limiting.
// For max connection limit of > '0' we initialize rate limit handler.
return &rateLimit{
handler: handler,
rqueue: make(chan struct{}, globalMaxConn),
}
}