Implement URLRequestBackoffManager for managing Backoff headers

net/url_request/url_request_backoff_manager.cc

Index: net/url_request/url_request_backoff_manager.cc
diff --git a/net/url_request/url_request_backoff_manager.cc b/net/url_request/url_request_backoff_manager.cc
new file mode 100644
index 0000000000000000000000000000000000000000..51560e32981c90d13273e93db0476bb2901bde03
--- /dev/null
+++ b/net/url_request/url_request_backoff_manager.cc
@@ -0,0 +1,144 @@
+// Copyright 2015 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.
+
+#include "net/url_request/url_request_backoff_manager.h"
+
+#include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+#include "net/http/http_response_headers.h"
+
+namespace net {
+
+const uint16 URLRequestBackoffManager::kMinimumBackoffInSeconds = 1;
+const uint16 URLRequestBackoffManager::kMaximumBackoffInSeconds = 50000;
+const uint16 URLRequestBackoffManager::kNewEntriesBetweenCollecting = 200;
+
+URLRequestBackoffManager::URLRequestBackoffManager()
+    : new_entries_since_last_gc_(0) {
+  url_id_replacements_.ClearPassword();
+  url_id_replacements_.ClearUsername();
+  url_id_replacements_.ClearQuery();
+  url_id_replacements_.ClearRef();
+
+  NetworkChangeNotifier::AddIPAddressObserver(this);
+  NetworkChangeNotifier::AddConnectionTypeObserver(this);
+}
+
+URLRequestBackoffManager::~URLRequestBackoffManager() {
+  NetworkChangeNotifier::RemoveIPAddressObserver(this);
+  NetworkChangeNotifier::RemoveConnectionTypeObserver(this);
+  for (UrlEntryMap::iterator it = url_entries_.begin();
+       it != url_entries_.end(); ++it) {
+    delete it->second;
+  }
+  url_entries_.clear();
+}
+
+void URLRequestBackoffManager::UpdateWithResponse(
+    const GURL& url,
+    HttpResponseHeaders* headers,
+    const base::Time& response_time) {
+  CalledOnValidThread();
+  base::TimeDelta result;
+  if (GetBackoffTime(headers, &result)) {
+    new_entries_since_last_gc_++;
+    std::string url_id = GetIdFromUrl(url);
+    url_entries_[url_id] =
+        new Entry(response_time + result, response_time + result * 1.1);
+    GarbageCollectEntriesIfNecessary();
+  }
+}
+
+bool URLRequestBackoffManager::ShouldRejectRequest(
+    const GURL& url,
+    const base::Time& request_time) {
+  CalledOnValidThread();
+  std::string url_id = GetIdFromUrl(url);
+  UrlEntryMap::iterator it = url_entries_.find(url_id);
+  if (it == url_entries_.end())
+    return false;
+  Entry* entry = it->second;
+  if (request_time < entry->throttled_time)
+    return true;
+  // Allow one request between throttled_time and release_time.

[Deprecated (see juliatuttle), 2015/07/13 20:30:41]

I'd like a comment (here or elsewhere) noting that this does not implement the
uniform distribution part of the "retry between time and 1.1 * time from now"
requirement.

Also, have you considered how a caller might implement that? Right now, the
caller would have to re-parse the backoff header and manually calculate a good
time.

[xunjieli, 2015/07/13 20:53:37]

Done.
I imagine I'd implement a GetReleaseTime in the backoff manager for the consumer
to get the release time(s) for a particular URL.

+  if (request_time >= entry->throttled_time &&
+      request_time < entry->release_time) {
+    if (entry->used)
+      return true;
+    entry->used = true;
+  }
+  return false;
+}
+
+void URLRequestBackoffManager::OnIPAddressChanged() {
+  OnNetworkChange();
+}
+
+void URLRequestBackoffManager::OnConnectionTypeChanged(
+    NetworkChangeNotifier::ConnectionType type) {
+  OnNetworkChange();
+}
+
+int URLRequestBackoffManager::GetNumberOfEntriesForTests() const {
+  return url_entries_.size();
+}
+
+void URLRequestBackoffManager::GarbageCollectEntriesIfNecessary() {
+  CalledOnValidThread();
+  if (new_entries_since_last_gc_ < kNewEntriesBetweenCollecting)
+    return;
+
+  new_entries_since_last_gc_ = 0;
+  UrlEntryMap::iterator it = url_entries_.begin();
+  while (it != url_entries_.end()) {
+    Entry* entry = it->second;
+    if (entry->IsOutDated()) {
+      url_entries_.erase(it++);
+      delete entry;
+    } else {
+      ++it;
+    }
+  }
+}
+
+bool URLRequestBackoffManager::GetBackoffTime(HttpResponseHeaders* headers,
+                                              base::TimeDelta* result) const {
+  base::StringPiece name("Backoff");
+  std::string value;
+  void* iter = NULL;
+  while (headers->EnumerateHeader(&iter, name, &value)) {
+    int64 seconds;
+    base::StringToInt64(value, &seconds);
+    if (seconds >= kMinimumBackoffInSeconds &&
+        seconds <= kMaximumBackoffInSeconds) {
+      *result = base::TimeDelta::FromSeconds(seconds);
+      return true;
+    }
+  }
+  return false;
+}
+
+std::string URLRequestBackoffManager::GetIdFromUrl(const GURL& url) const {
+  if (!url.is_valid())
+    return url.possibly_invalid_spec();
+
+  GURL id = url.ReplaceComponents(url_id_replacements_);
+  return base::StringToLowerASCII(id.spec()).c_str();
+}
+
+void URLRequestBackoffManager::OnNetworkChange() {
+  CalledOnValidThread();
+
+  new_entries_since_last_gc_ = 0;
+  // Remove all entries.
+  for (UrlEntryMap::iterator it = url_entries_.begin();
+       it != url_entries_.end(); ++it) {
+    delete it->second;
+  }
+  url_entries_.clear();
+}
+
+}  // namespace net