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// Copyright (c) 2013 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 "content/browser/indexed_db/indexed_db_transaction_coordinator.h"
#include "base/logging.h"
#include "content/browser/indexed_db/indexed_db_tracing.h"
#include "content/browser/indexed_db/indexed_db_transaction.h"
#include "third_party/WebKit/public/platform/modules/indexeddb/WebIDBTypes.h"
namespace content {
namespace {
// Only this many transactions can be active at any time before they are queued.
// Limited to prevent transaction trashing which can consume a ton of RAM. Ten
// is chosen to reduce performance regressions.
// TODO(dmurph): crbug.com/693260 Create better scheduling or limits.
static const size_t kMaxStartedTransactions = 10;
} // namespace
IndexedDBTransactionCoordinator::IndexedDBTransactionCoordinator() {}
IndexedDBTransactionCoordinator::~IndexedDBTransactionCoordinator() {
DCHECK(queued_transactions_.empty());
DCHECK(started_transactions_.empty());
}
void IndexedDBTransactionCoordinator::DidCreateTransaction(
IndexedDBTransaction* transaction) {
DCHECK(!queued_transactions_.count(transaction));
DCHECK(!started_transactions_.count(transaction));
DCHECK_EQ(IndexedDBTransaction::CREATED, transaction->state());
queued_transactions_.insert(transaction);
ProcessQueuedTransactions();
}
// Observer transactions jump to the front of the queue.
void IndexedDBTransactionCoordinator::DidCreateObserverTransaction(
IndexedDBTransaction* transaction) {
DCHECK(!queued_transactions_.count(transaction));
DCHECK(!started_transactions_.count(transaction));
DCHECK_EQ(IndexedDBTransaction::CREATED, transaction->state());
started_transactions_.insert_front(transaction);
ProcessQueuedTransactions();
}
void IndexedDBTransactionCoordinator::DidFinishTransaction(
IndexedDBTransaction* transaction) {
if (queued_transactions_.count(transaction)) {
DCHECK(!started_transactions_.count(transaction));
queued_transactions_.erase(transaction);
} else {
DCHECK(started_transactions_.count(transaction));
started_transactions_.erase(transaction);
}
ProcessQueuedTransactions();
}
bool IndexedDBTransactionCoordinator::IsRunningVersionChangeTransaction()
const {
return !started_transactions_.empty() &&
(*started_transactions_.begin())->mode() ==
blink::kWebIDBTransactionModeVersionChange;
}
#ifndef NDEBUG
// Verifies internal consistency while returning whether anything is found.
bool IndexedDBTransactionCoordinator::IsActive(
IndexedDBTransaction* transaction) {
bool found = false;
if (queued_transactions_.count(transaction))
found = true;
if (started_transactions_.count(transaction)) {
DCHECK(!found);
found = true;
}
return found;
}
#endif
std::vector<const IndexedDBTransaction*>
IndexedDBTransactionCoordinator::GetTransactions() const {
std::vector<const IndexedDBTransaction*> result;
result.reserve(started_transactions_.size() + queued_transactions_.size());
result.insert(result.end(), started_transactions_.begin(),
started_transactions_.end());
result.insert(result.end(), queued_transactions_.begin(),
queued_transactions_.end());
return result;
}
void IndexedDBTransactionCoordinator::RecordMetrics() const {
IDB_TRACE_COUNTER2("IndexedDBTransactionCoordinator", "StartedTransactions",
started_transactions_.size(), "QueuedTransactions",
queued_transactions_.size());
}
void IndexedDBTransactionCoordinator::ProcessQueuedTransactions() {
if (queued_transactions_.empty())
return;
DCHECK(!IsRunningVersionChangeTransaction());
// The locked_scope set accumulates the ids of object stores in the scope of
// running read/write transactions. Other read-write transactions with
// stores in this set may not be started. Read-only transactions may start,
// taking a snapshot of the database, which does not include uncommitted
// data. ("Version change" transactions are exclusive, but handled by the
// connection sequencing in IndexedDBDatabase.)
std::set<int64_t> locked_scope;
for (auto* transaction : started_transactions_) {
if (transaction->mode() == blink::kWebIDBTransactionModeReadWrite) {
// Started read/write transactions have exclusive access to the object
// stores within their scopes.
locked_scope.insert(transaction->scope().begin(),
transaction->scope().end());
}
}
auto it = queued_transactions_.begin();
while (it != queued_transactions_.end()) {
IndexedDBTransaction* transaction = *it;
++it;
if (CanStartTransaction(transaction, locked_scope)) {
DCHECK_EQ(IndexedDBTransaction::CREATED, transaction->state());
queued_transactions_.erase(transaction);
started_transactions_.insert(transaction);
transaction->Start();
DCHECK_EQ(IndexedDBTransaction::STARTED, transaction->state());
}
if (transaction->mode() == blink::kWebIDBTransactionModeReadWrite) {
// Either the transaction started, so it has exclusive access to the
// stores in its scope, or per the spec the transaction which was
// created first must get access first, so the stores are also locked.
locked_scope.insert(transaction->scope().begin(),
transaction->scope().end());
}
}
RecordMetrics();
}
template<typename T>
static bool DoSetsIntersect(const std::set<T>& set1,
const std::set<T>& set2) {
typename std::set<T>::const_iterator it1 = set1.begin();
typename std::set<T>::const_iterator it2 = set2.begin();
while (it1 != set1.end() && it2 != set2.end()) {
if (*it1 < *it2)
++it1;
else if (*it2 < *it1)
++it2;
else
return true;
}
return false;
}
bool IndexedDBTransactionCoordinator::CanStartTransaction(
IndexedDBTransaction* const transaction,
const std::set<int64_t>& locked_scope) const {
if (started_transactions_.size() >= kMaxStartedTransactions) {
return false;
}
DCHECK(queued_transactions_.count(transaction));
switch (transaction->mode()) {
case blink::kWebIDBTransactionModeVersionChange:
DCHECK_EQ(1u, queued_transactions_.size());
DCHECK(started_transactions_.empty());
DCHECK(locked_scope.empty());
return true;
case blink::kWebIDBTransactionModeReadOnly:
case blink::kWebIDBTransactionModeReadWrite:
return !DoSetsIntersect(transaction->scope(), locked_scope);
}
NOTREACHED();
return false;
}
} // namespace content
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