[Offline Pages] Pick correct request when resuming.

components/offline_pages/core/background/pick_request_task.cc

 // Copyright 2016 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 "components/offline_pages/core/background/pick_request_task.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/time/time.h"
 #include "components/offline_pages/core/background/device_conditions.h"
@@ skipping 17 matching lines @@
 }  // namespace
 
 namespace offline_pages {
 
 PickRequestTask::PickRequestTask(RequestQueueStore* store,
                                  OfflinerPolicy* policy,
                                  RequestPickedCallback picked_callback,
                                  RequestNotPickedCallback not_picked_callback,
                                  RequestCountCallback request_count_callback,
                                  DeviceConditions& device_conditions,
-                                 const std::set<int64_t>& disabled_requests)
+                                 const std::set<int64_t>& disabled_requests,
+                                 std::list<int64_t>& priortized_requests)
     : store_(store),
       policy_(policy),
       picked_callback_(picked_callback),
       not_picked_callback_(not_picked_callback),
       request_count_callback_(request_count_callback),
       disabled_requests_(disabled_requests),
+      priortized_requests_(priortized_requests),
       weak_ptr_factory_(this) {
   device_conditions_.reset(new DeviceConditions(device_conditions));
 }
 
 PickRequestTask::~PickRequestTask() {}
 
 void PickRequestTask::Run() {
   GetRequests();
 }
 
@@ skipping 21 matching lines @@
 
   // Choose which comparison function to use based on policy.
   if (policy_->RetryCountIsMoreImportantThanRecency())
     comparator = &PickRequestTask::RetryCountFirstCompareFunction;
   else
     comparator = &PickRequestTask::RecencyFirstCompareFunction;
 
   // TODO(petewil): Consider replacing this bool with a better named enum.
   bool non_user_requested_tasks_remaining = false;
   bool cleanup_needed = false;
+  bool is_priortized_request_picked = false;

[Pete Williamson, 2017/03/06 18:30:57]

nit: was_prioritized_request_picked might be better

[romax, 2017/03/07 18:40:44]

Done.

 
   size_t available_request_count = 0;
 
-  // Iterate once through the requests, keeping track of best candidate.
+  // Search for the priortized requests before iterating all the requests.

[Pete Williamson, 2017/03/06 18:30:57]

There is an implicit assumption here that we should make explicit with a
comment.  Requests earlier in the list have higher priority than requests older
in the list.

[romax, 2017/03/07 18:40:44]

Done.

+  while (!picked_request && !priortized_requests_.empty()) {
+    int64_t id = priortized_requests_.front();
+    for (unsigned i = 0; i < requests.size(); ++i) {
+      if (requests[i]->request_id() == id) {
+        picked_request = requests[i].get();
+        is_priortized_request_picked = true;
+        break;
+      }
+    }
+    // Remove the priortized requests which are not in request queue.
+    priortized_requests_.pop_front();
+  }
+
+  // Iterate once through the requests, keeping track of best candidate if no
+  // priortized request has been chosen.

[fgorski, 2017/03/06 18:12:45]

if statement should probably happen outside of the for look to not make a check
multiple times. Unless there is a chance to get a better fit of course.

[Pete Williamson, 2017/03/06 18:30:57]

Agreed, if a prioritized request is found, we should probably not run this loop
at all.  

Today the loop does two things, it finds a better candidate if one exists, and
detects if there are non-user-requested tasks remaining.  We are going to be
removing the checks for non-user-requested tasks.  If we were keeping them, we
could pull them into a separate loop, instead, we could just ignore them, and
leave them in the loop for now until we properly remove the feature.

[romax, 2017/03/07 18:40:44]

Refactored a little bit. Not sure if it's necessary to have a list of filtered
requests, but otherwise I think there will be some duplicate code for checking
disabled etc. Please share your input :)

   for (unsigned i = 0; i < requests.size(); ++i) {
     // If the request is expired or has exceeded the retry count, skip it.
     if (OfflinerPolicyUtils::CheckRequestExpirationStatus(requests[i].get(),
                                                           policy_) !=
         OfflinerPolicyUtils::RequestExpirationStatus::VALID) {
       cleanup_needed = true;
       continue;
     }
 
-    // If the  request is on the disabled list, skip it.
+    // If the request is on the disabled list, skip it.
     auto search = disabled_requests_.find(requests[i]->request_id());
     if (search != disabled_requests_.end())

[fgorski, 2017/03/06 18:12:45]

Is there a chance that prioritized request is on the disabled list?

[romax, 2017/03/07 18:40:44]

yeah there might be. added a check

       continue;
 
     // If there are non-user-requested tasks remaining, we need to make sure
     // that they are scheduled after we run out of user requested tasks. Here we
     // detect if any exist. If we don't find any user-requested tasks, we will
     // inform the "not_picked_callback_" that it needs to schedule a task for
     // non-user-requested items, which have different network and power needs.
     if (!requests[i]->user_requested())
       non_user_requested_tasks_remaining = true;
     if (requests[i]->request_state() ==
         SavePageRequest::RequestState::AVAILABLE) {
       available_request_count++;
     }
-    if (!RequestConditionsSatisfied(requests[i].get()))
-      continue;
-    if (IsNewRequestBetter(picked_request, requests[i].get(), comparator))
-      picked_request = requests[i].get();
+
+    if (!is_priortized_request_picked) {
+      if (!RequestConditionsSatisfied(requests[i].get()))
+        continue;
+      if (IsNewRequestBetter(picked_request, requests[i].get(), comparator))
+        picked_request = requests[i].get();
+    }
   }
 
   // Report the request queue counts.
   request_count_callback_.Run(requests.size(), available_request_count);
 
   // If we have a best request to try next, get the request coodinator to
   // start it.  Otherwise return that we have no candidates.
   if (picked_request != nullptr) {
     picked_callback_.Run(*picked_request, cleanup_needed);
   } else {
@@ skipping 117 matching lines @@
   int result = signum(difference.InMilliseconds());
 
   // Flip the direction of comparison if policy prefers fewer retries.
   if (policy_->ShouldPreferEarlierRequests())
     result *= -1;
 
   return result;
 }
 
 }  // namespace offline_pages