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// Copyright (c) 2011 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_URL_REQUEST_URL_REQUEST_THROTTLER_MANAGER_H_
#define NET_URL_REQUEST_URL_REQUEST_THROTTLER_MANAGER_H_
#pragma once
#include <map>
#include <set>
#include <string>
#include "base/basictypes.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/singleton.h"
#include "base/threading/non_thread_safe.h"
#include "googleurl/src/gurl.h"
#include "net/url_request/url_request_throttler_entry.h"
namespace net {
// Class that registers URL request throttler entries for URLs being accessed
// in order to supervise traffic. URL requests for HTTP contents should
// register their URLs in this manager on each request.
//
// URLRequestThrottlerManager maintains a map of URL IDs to URL request
// throttler entries. It creates URL request throttler entries when new URLs
// are registered, and does garbage collection from time to time in order to
// clean out outdated entries. URL ID consists of lowercased scheme, host, port
// and path. All URLs converted to the same ID will share the same entry.
//
// NOTE: All usage of this singleton object must be on the same thread,
// although to allow it to be used as a singleton, construction and destruction
// can occur on a separate thread.
class URLRequestThrottlerManager : public base::NonThreadSafe {
public:
static URLRequestThrottlerManager* GetInstance();
// Must be called for every request, returns the URL request throttler entry
// associated with the URL. The caller must inform this entry of some events.
// Please refer to url_request_throttler_entry_interface.h for further
// informations.
scoped_refptr<URLRequestThrottlerEntryInterface> RegisterRequestUrl(
const GURL& url);
// Adds the given host to a list of sites for which exponential back-off
// throttling will be disabled. Subdomains are not included, so they
// must be added separately.
void AddToOptOutList(const std::string& host);
// Registers a new entry in this service and overrides the existing entry (if
// any) for the URL. The service will hold a reference to the entry.
// It is only used by unit tests.
void OverrideEntryForTests(const GURL& url, URLRequestThrottlerEntry* entry);
// Explicitly erases an entry.
// This is useful to remove those entries which have got infinite lifetime and
// thus won't be garbage collected.
// It is only used by unit tests.
void EraseEntryForTests(const GURL& url);
// Turns threading model verification on or off. Any code that correctly
// uses the network stack should preferably call this function to enable
// verification of correct adherence to the network stack threading model.
void set_enable_thread_checks(bool enable);
bool enable_thread_checks() const;
// Whether throttling is enabled or not.
void set_enforce_throttling(bool enforce);
bool enforce_throttling();
protected:
URLRequestThrottlerManager();
~URLRequestThrottlerManager();
// Method that allows us to transform a URL into an ID that can be used in our
// map. Resulting IDs will be lowercase and consist of the scheme, host, port
// and path (without query string, fragment, etc.).
// If the URL is invalid, the invalid spec will be returned, without any
// transformation.
std::string GetIdFromUrl(const GURL& url) const;
// Method that ensures the map gets cleaned from time to time. The period at
// which garbage collecting happens is adjustable with the
// kRequestBetweenCollecting constant.
void GarbageCollectEntriesIfNecessary();
// Method that does the actual work of garbage collecting.
void GarbageCollectEntries();
// Used by tests.
int GetNumberOfEntriesForTests() const { return url_entries_.size(); }
private:
friend struct DefaultSingletonTraits<URLRequestThrottlerManager>;
// From each URL we generate an ID composed of the scheme, host, port and path
// that allows us to uniquely map an entry to it.
typedef std::map<std::string, scoped_refptr<URLRequestThrottlerEntry> >
UrlEntryMap;
// We maintain a set of hosts that have opted out of exponential
// back-off throttling.
typedef std::set<std::string> OptOutHosts;
// 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;
// Map that contains a list of URL ID and their matching
// URLRequestThrottlerEntry.
UrlEntryMap url_entries_;
// Set of hosts that have opted out.
OptOutHosts opt_out_hosts_;
// This keeps track of how many requests have been made. Used with
// GarbageCollectEntries.
unsigned int requests_since_last_gc_;
// Valid after construction.
GURL::Replacements url_id_replacements_;
// Whether we would like to reject outgoing HTTP requests during the back-off
// period.
bool enforce_throttling_;
// Certain tests do not obey the net component's threading policy, so we
// keep track of whether we're being used by tests, and turn off certain
// checks.
//
// TODO(joi): See if we can fix the offending unit tests and remove this
// workaround.
bool enable_thread_checks_;
DISALLOW_COPY_AND_ASSIGN(URLRequestThrottlerManager);
};
} // namespace net
#endif // NET_URL_REQUEST_URL_REQUEST_THROTTLER_MANAGER_H_
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