Add an API to Pause and Resume background offlining requests.

components/offline_pages/background/request_queue_store_sql.cc

Index: components/offline_pages/background/request_queue_store_sql.cc
diff --git a/components/offline_pages/background/request_queue_store_sql.cc b/components/offline_pages/background/request_queue_store_sql.cc
index 264b2acb42734ee9db93c9ceefd8bde8a97f26b6..bdc91a7ba411667b5b3cf43792364f1710cd7b93 100644
--- a/components/offline_pages/background/request_queue_store_sql.cc
+++ b/components/offline_pages/background/request_queue_store_sql.cc
@@ -77,6 +77,28 @@ bool DeleteRequestByClientId(sql::Connection* db, const ClientId& client_id) {
   return statement.Run();
 }
 
+bool PauseRequest(sql::Connection* db, const int64_t request_id) {
+  const char kSql[] = "UPDATE " REQUEST_QUEUE_TABLE_NAME
+                      " SET state=?"
+                      " WHERE request_id=?";
+  sql::Statement statement(db->GetCachedStatement(SQL_FROM_HERE, kSql));
+  statement.BindInt64(
+      0, static_cast<long>(SavePageRequest::RequestState::PAUSED));
+  statement.BindInt64(1, request_id);
+  return statement.Run();
+}
+
+bool ResumeRequest(sql::Connection* db, const int64_t request_id) {
+  const char kSql[] = "UPDATE " REQUEST_QUEUE_TABLE_NAME
+                      " SET state=?"
+                      " WHERE request_id=?";
+  sql::Statement statement(db->GetCachedStatement(SQL_FROM_HERE, kSql));
+  statement.BindInt64(
+      0, static_cast<long>(SavePageRequest::RequestState::AVAILABLE));
+  statement.BindInt64(1, request_id);
+  return statement.Run();
+}
+
 bool DeleteRequestsByIds(sql::Connection* db,
                          const std::vector<int64_t>& request_ids,
                          int* count) {
@@ -123,6 +145,43 @@ bool DeleteRequestsByClientIds(sql::Connection* db,
   return true;
 }
 
+RequestQueueStore::UpdateStatus PauseRequests(
+    sql::Connection* db, const std::vector<int64_t>& request_ids) {
+  // If you create a transaction but don't Commit() it is automatically
+  // rolled back by its destructor when it falls out of scope.
+  sql::Transaction transaction(db);
+  if (!transaction.Begin())
+    return RequestQueueStore::UpdateStatus::FAILED;
+  for (const auto& request_id : request_ids) {
+    if (!PauseRequest(db, request_id))
+      return RequestQueueStore::UpdateStatus::FAILED;
+  }
+
+  if (!transaction.Commit())
+    return RequestQueueStore::UpdateStatus::FAILED;
+
+  return RequestQueueStore::UpdateStatus::UPDATED;
+}
+
+RequestQueueStore::UpdateStatus ResumeRequests(
+    sql::Connection* db, const std::vector<int64_t>& request_ids) {
+  // If you create a transaction but don't Commit() it is automatically
+  // rolled back by its destructor when it falls out of scope.
+  sql::Transaction transaction(db);
+  if (!transaction.Begin())
+    return RequestQueueStore::UpdateStatus::FAILED;
+
+  for (const auto& request_id : request_ids) {
+    if (!ResumeRequest(db, request_id))
+      return RequestQueueStore::UpdateStatus::FAILED;
+  }
+
+  if (!transaction.Commit())
+    return RequestQueueStore::UpdateStatus::FAILED;
+
+  return RequestQueueStore::UpdateStatus::UPDATED;
+}
+
 // Create a save page request from a SQL result.  Expects complete rows with
 // all columns present.  Columns are in order they are defined in select query
 // in |RequestQueueStore::RequestSync| method.
@@ -290,6 +349,30 @@ void RequestQueueStoreSQL::RemoveRequestsByClientIdSync(
 }
 
 // static
+void RequestQueueStoreSQL::PauseRequestsSync(
+    sql::Connection* db,
+    scoped_refptr<base::SingleThreadTaskRunner> runner,
+    const std::vector<int64_t>& request_ids,
+    const UpdateCallback& callback) {
+  // TODO(fgorski): add UMA metrics here.
+  RequestQueueStore::UpdateStatus status =
+      offline_pages::PauseRequests(db, request_ids);
+  runner->PostTask(FROM_HERE, base::Bind(callback, status));
+}
+
+// static
+void RequestQueueStoreSQL::ResumeRequestsSync(
+    sql::Connection* db,
+    scoped_refptr<base::SingleThreadTaskRunner> runner,
+    const std::vector<int64_t>& request_ids,
+    const UpdateCallback& callback) {
+  // TODO(fgorski): add UMA metrics here.
+  RequestQueueStore::UpdateStatus status =
+      offline_pages::ResumeRequests(db, request_ids);
+  runner->PostTask(FROM_HERE, base::Bind(callback, status));
+}
+
+// static
 void RequestQueueStoreSQL::ResetSync(
     sql::Connection* db,
     const base::FilePath& db_file_path,
@@ -335,10 +418,6 @@ void RequestQueueStoreSQL::AddOrUpdateRequest(const SavePageRequest& request,
                  base::ThreadTaskRunnerHandle::Get(), request, callback));
 }
 
-// TODO(petewil): This is unused, since request_coordinator doesn't keep
-// request_ids, and neither do clients.  Plan is to remove this API in a future
-// changelist.  If we do discover a need to keep it, name it
-// RemoveRequestsByRequestId to be more parallell with RemoveRequestsByClientId.
 void RequestQueueStoreSQL::RemoveRequests(
     const std::vector<int64_t>& request_ids,
     const RemoveCallback& callback) {
@@ -375,6 +454,44 @@ void RequestQueueStoreSQL::RemoveRequestsByClientId(
                  base::ThreadTaskRunnerHandle::Get(), client_ids, callback));
 }
 
+
+void RequestQueueStoreSQL::PauseRequests(
+    const std::vector<int64_t>& request_ids,
+    const UpdateCallback& callback) {
+  DCHECK(db_.get());
+  if (!db_.get()) {

[Dmitry Titov, 2016/08/09 21:01:43]

Could you pull all these identical blocks into something like 

if (!checkDb(callback))
  return;

with checkDb having the code to post task etc? and change to it in whole file.

[Pete Williamson, 2016/08/09 22:53:24]

Done.  Unfortunately, the callbacks have different types and take different
parameter sets, so we ended up with 4 CheckDb functions instead of one.

I skipped RemoveRequestByClientId since it is being deleted in a different
changelist (to reduce merge problems later).

+    // Nothing to do, but post a callback instead of calling directly
+    // to preserve the async style behavior to prevent bugs.
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::Bind(callback, UpdateStatus::FAILED));
+    return;
+  }
+
+  background_task_runner_->PostTask(

[Dmitry Titov, 2016/08/09 21:01:43]

Is there a reason we don't use PostTaskAndReply in all these methods?

[Pete Williamson, 2016/08/09 22:53:24]

I'm following the model in the rest of the file.  I can convert the whole file
in another changelist if you like.

+      FROM_HERE,
+      base::Bind(&RequestQueueStoreSQL::PauseRequestsSync, db_.get(),
+                 base::ThreadTaskRunnerHandle::Get(), request_ids, callback));
+}
+
+void RequestQueueStoreSQL::ResumeRequests(
+    const std::vector<int64_t>& request_ids,
+    const UpdateCallback& callback) {
+  DCHECK(db_.get());
+  if (!db_.get()) {
+    // Nothing to do, but post a callback instead of calling directly
+    // to preserve the async style behavior to prevent bugs.
+    base::ThreadTaskRunnerHandle::Get()->PostTask(
+        FROM_HERE, base::Bind(callback, UpdateStatus::FAILED));
+    return;
+  }
+
+  background_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&RequestQueueStoreSQL::ResumeRequestsSync, db_.get(),
+                 base::ThreadTaskRunnerHandle::Get(), request_ids, callback));
+}
+
+
 void RequestQueueStoreSQL::Reset(const ResetCallback& callback) {
   DCHECK(db_.get());
   if (!db_.get()) {