Request Throttler : Exponential back-off

net/request_throttler/request_throttler_manager.h

+// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NET_REQUEST_THROTTLER_REQUEST_THROTTLER_MANAGER_H_
+#define NET_REQUEST_THROTTLER_REQUEST_THROTTLER_MANAGER_H_
+
+#include <map>
+#include <string>
+
+#include "base/lock.h"
+#include "base/non_thread_safe.h"
+#include "base/singleton.h"
+#include "base/scoped_ptr.h"
+#include "base/time.h"
+#include "googleurl/src/gurl.h"
+#include "net/request_throttler/request_throttler_entry.h"
+
+class MessageLoop;
+
+// Class that registers a request throttler entry for each URL being accessed in
+// order to supervise traffic. URL Http Request should register their URL in
+// this request throttler manager on each request.
+class RequestThrottlerManager  {
+ public:
+  // Must be called for every request, returns the request throttler entry
+  // associated with the URL. The caller must inform this entry of some events.
+  // Please refer to request_throttler_entry.h for further informations.
+  scoped_refptr<RequestThrottlerEntryInterface> RegisterRequestUrl(
+      const GURL& url);
+
+  // This method is used by higher level modules which can notify this class if
+  // the response they received was malformed. It is useful because
+  // in the case where the response header returned 200 response code but had
+  // a malformed content body we will categorize it as a success and so we
+  // defer this decision to the module that had requested the resource.
+  void NotifyRequestBodyWasMalformed(const GURL& url);
+
+ protected:
+  RequestThrottlerManager();
+  virtual ~RequestThrottlerManager();
+
+  // From each URL we generate an ID composed of the host and path
+  // that allows us to uniquely map an entry to it.
+  typedef std::map<std::string, scoped_refptr<RequestThrottlerEntry> >
+      UrlEntryMap;
+
+  friend struct DefaultSingletonTraits<RequestThrottlerManager>;
+
+  // Map that contains a list of URL ID and their matching
+  // RequestThrottlerEntry.
+  UrlEntryMap url_entries_;
+
+  // Method that allows us to transform an URL into an ID that is useful and
+  // can be used in our map. Resulting IDs will be lowercase and be missing both
+  // the query string and fragment.
+  std::string GetIdFromUrl(const GURL& url);
+
+  // Method that ensures the map gets cleaned from time to time. The period at
+  // which this GarbageCollection happens is adjustable with the
+  // kRequestBetweenCollecting constant.
+  void GarbageCollectEntries();
+
+ private:
+  MessageLoop* current_loop_;
+
+  // Maximum number of entries that we are willing to collect in our map.
+  static const unsigned int kMaximumNumberOfEntries;
+  // Number of requests that will be made between garbage collection.
+  static const unsigned int kRequestsBetweenCollecting;
+
+  // This keeps track of how many request have been made. Used with
+  // GarbageCollectEntries.
+  unsigned int requests_since_last_gc_;
+
+  DISALLOW_COPY_AND_ASSIGN(RequestThrottlerManager);
+};
+
+#endif  // NET_REQUEST_THROTTLER_REQUEST_THROTTLER_MANAGER_H_