Implement exponential back-off mechanism and enforce it at the URLRequestHttpJob level.

chrome/service/cloud_print/cloud_print_url_fetcher.cc

 // 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.
 
 #include "chrome/service/cloud_print/cloud_print_url_fetcher.h"
 
 #include "base/string_util.h"
 #include "base/values.h"
 #include "chrome/common/net/http_return.h"
-#include "chrome/common/net/url_fetcher_protect.h"
 #include "chrome/service/cloud_print/cloud_print_consts.h"
 #include "chrome/service/cloud_print/cloud_print_helpers.h"
 #include "chrome/service/net/service_url_request_context.h"
 #include "googleurl/src/gurl.h"
+#include "net/url_request/request_throttler_manager.h"
 #include "net/url_request/url_request_status.h"
 
 CloudPrintURLFetcher::CloudPrintURLFetcher()
     : delegate_(NULL),
-      protect_entry_(NULL),
+      request_throttler_manager_(Singleton<RequestThrottlerManager>::get()),
       num_retries_(0) {
 }
 
 void CloudPrintURLFetcher::StartGetRequest(const GURL& url,
                                            Delegate* delegate,
                                            const std::string& auth_token,
-                                           const std::string& retry_policy) {
-  StartRequestHelper(url, URLFetcher::GET, delegate, auth_token, retry_policy,
+                                           int max_retries) {
+  StartRequestHelper(url, URLFetcher::GET, delegate, auth_token, max_retries,
                      std::string(), std::string());
 }
 
 void CloudPrintURLFetcher::StartPostRequest(
     const GURL& url,
     Delegate* delegate,
     const std::string& auth_token,
-    const std::string& retry_policy,
+    int max_retries,
     const std::string& post_data_mime_type,
     const std::string& post_data) {
-  StartRequestHelper(url, URLFetcher::POST, delegate, auth_token, retry_policy,
+  StartRequestHelper(url, URLFetcher::POST, delegate, auth_token, max_retries,
                      post_data_mime_type, post_data);
 }
 
   // URLFetcher::Delegate implementation.
 void CloudPrintURLFetcher::OnURLFetchComplete(
     const URLFetcher* source,
     const GURL& url,
     const URLRequestStatus& status,
     int response_code,
     const ResponseCookies& cookies,
@@ skipping 32 matching lines @@
         action = delegate_->HandleJSONData(source,
                                            url,
                                            response_dict,
                                            succeeded);
       else
         action = RETRY_REQUEST;
     }
   }
   // Retry the request if needed.
   if (action == RETRY_REQUEST) {
-    int64 back_off_time =
-        protect_entry_->UpdateBackoff(URLFetcherProtectEntry::FAILURE);
+    scoped_refptr<RequestThrottlerEntryInterface> entry =
+        request_throttler_manager_->RegisterRequestUrl(url);
+    // If the response code is greater than or equal to 500, then the back-off
+    // period has been increased at the network level; otherwise, explicitly
+    // call ReceivedContentWasMalformed() to count the current request as a
+    // failure and increase the back-off period.
+    if (response_code < 500)
+      entry->ReceivedContentWasMalformed();
+
     ++num_retries_;
-    int max_retries = protect_entry_->max_retries();
-    if ((-1 != max_retries) && (num_retries_ > max_retries)) {
+    if ((-1 != source->max_retries()) &&
+        (num_retries_ > source->max_retries())) {
       // Retry limit reached. Give up.
       delegate_->OnRequestGiveUp();
     } else {
       // Either no retry limit specified or retry limit has not yet been
       // reached. Try again.
       MessageLoop::current()->PostDelayedTask(
           FROM_HERE,
           NewRunnableMethod(this, &CloudPrintURLFetcher::StartRequestNow),
-          back_off_time);
+          entry->GetRecommendedDelayForNextRequest());

[Jói, 2010/11/17 16:39:18]

Same comment here on the sliding window - doesn't this add an entry to it, that
should have already been added when the request was initially sent?

[yzshen, 2010/11/19 23:51:36]

I realize that we don't even need to wait here, since the underlying URLFetcher
will handle it.
Thanks for pointing it out!

     }
-  } else {
-    protect_entry_->UpdateBackoff(URLFetcherProtectEntry::SUCCESS);
   }
 }
 
 void CloudPrintURLFetcher::StartRequestHelper(
     const GURL& url,
     URLFetcher::RequestType request_type,
     Delegate* delegate,
     const std::string& auth_token,
-    const std::string& retry_policy,
+    int max_retries,
     const std::string& post_data_mime_type,
     const std::string& post_data) {
   DCHECK(delegate);
   request_.reset(new URLFetcher(url, request_type, this));
   request_->set_request_context(GetRequestContextGetter());
   // Since we implement our own retry logic, disable the retry in URLFetcher.
   request_->set_automatically_retry_on_5xx(false);
+  request_->set_max_retries(max_retries);
   delegate_ = delegate;
   std::string headers = "Authorization: GoogleLogin auth=";
   headers += auth_token;
   headers += "\r\n";
   headers += kChromeCloudPrintProxyHeader;
   request_->set_extra_request_headers(headers);
   if (request_type == URLFetcher::POST) {
     request_->set_upload_data(post_data_mime_type, post_data);
   }
-  // Initialize the retry policy for this request.
-  protect_entry_ =
-      URLFetcherProtectManager::GetInstance()->Register(retry_policy);
+
+  scoped_refptr<RequestThrottlerEntryInterface> entry =
+      request_throttler_manager_->RegisterRequestUrl(url);
   MessageLoop::current()->PostDelayedTask(
       FROM_HERE,
       NewRunnableMethod(this, &CloudPrintURLFetcher::StartRequestNow),
-      protect_entry_->UpdateBackoff(URLFetcherProtectEntry::SEND));
+      entry->GetRecommendedDelayForNextRequest());
 }
 
 void CloudPrintURLFetcher::StartRequestNow() {
   request_->Start();
 }
 
 URLRequestContextGetter* CloudPrintURLFetcher::GetRequestContextGetter() {
   ServiceURLRequestContextGetter* getter =
       new ServiceURLRequestContextGetter();
   // Now set up the user agent for cloudprint.
   std::string user_agent = getter->user_agent();
   base::StringAppendF(&user_agent, " %s", kCloudPrintUserAgent);
   getter->set_user_agent(user_agent);
   return getter;
 }