Add a Restore() method to ValueStore and make StorageAPI use it

chrome/browser/value_store/leveldb_value_store_unittest.cc

Index: chrome/browser/value_store/leveldb_value_store_unittest.cc
diff --git a/chrome/browser/value_store/leveldb_value_store_unittest.cc b/chrome/browser/value_store/leveldb_value_store_unittest.cc
index 7a7e82ffd3474316e53ffa3eab9757e3f08abe82..67fc3821cffcc69676497c7f360672d6241fde6a 100644
--- a/chrome/browser/value_store/leveldb_value_store_unittest.cc
+++ b/chrome/browser/value_store/leveldb_value_store_unittest.cc
@@ -4,8 +4,17 @@
 
 #include "chrome/browser/value_store/value_store_unittest.h"
 
+#include "base/file_util.h"
+#include "base/files/file_enumerator.h"
+#include "base/files/scoped_temp_dir.h"
 #include "base/memory/ref_counted.h"
+#include "base/message_loop/message_loop.h"
+#include "base/values.h"
 #include "chrome/browser/value_store/leveldb_value_store.h"
+#include "content/public/test/test_browser_thread_bundle.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/leveldatabase/src/include/leveldb/db.h"
+#include "third_party/leveldatabase/src/include/leveldb/write_batch.h"
 
 namespace {
 
@@ -19,3 +28,157 @@ INSTANTIATE_TEST_CASE_P(
     LeveldbValueStore,
     ValueStoreTest,
     testing::Values(&Param));
+
+class LeveldbValueStoreUnitTest : public testing::Test {
+ public:
+  LeveldbValueStoreUnitTest() {}
+  virtual ~LeveldbValueStoreUnitTest() {}
+
+ protected:
+  virtual void SetUp() OVERRIDE {
+    ASSERT_TRUE(database_dir_.CreateUniqueTempDir());
+    OpenStore();
+    ASSERT_FALSE(store_->Get()->HasError());
+  }
+
+  virtual void TearDown() OVERRIDE {
+    store_->Clear();
+    store_.reset();
+  }
+
+  void CloseStore() { store_.reset(); }
+
+  void OpenStore() { store_.reset(new LeveldbValueStore(database_path())); }
+
+  LeveldbValueStore* store() { return store_.get(); }
+  const base::FilePath& database_path() { return database_dir_.path(); }
+
+ private:
+  scoped_ptr<LeveldbValueStore> store_;
+  base::ScopedTempDir database_dir_;
+
+  content::TestBrowserThreadBundle thread_bundle_;
+};
+
+// Check that we can restore a single corrupted key in the LeveldbValueStore.
+TEST_F(LeveldbValueStoreUnitTest, RestoreKeyTest) {
+  const char kNotCorruptKey[] = "not-corrupt";
+  const char kValue[] = "value";
+
+  // Insert a valid pair.
+  scoped_ptr<base::Value> value(base::Value::CreateStringValue(kValue));
+  ASSERT_FALSE(
+      store()->Set(ValueStore::DEFAULTS, kNotCorruptKey, *value)->HasError());
+
+  // Insert a corrupt pair.
+  const char kCorruptKey[] = "corrupt";
+  leveldb::WriteBatch batch;
+  batch.Put(kCorruptKey, "[{(.*+\"\'\\");
+  ASSERT_TRUE(store()->WriteToDbForTest(&batch));
+
+  // Verify corruption.
+  ValueStore::ReadResult result = store()->Get(kCorruptKey);
+  ASSERT_TRUE(result->HasError());
+  ASSERT_EQ(ValueStore::CORRUPTION, result->error().code);
+
+  // Restore and verify.
+  ASSERT_TRUE(store()->RestoreKey(kCorruptKey));
+  result = store()->Get(kCorruptKey);
+  EXPECT_FALSE(result->HasError());
+  EXPECT_TRUE(result->settings().empty());
+
+  // Verify that the valid pair is still present.
+  result = store()->Get(kNotCorruptKey);
+  EXPECT_FALSE(result->HasError());
+  EXPECT_TRUE(result->settings().HasKey(kNotCorruptKey));
+  std::string value_string;
+  EXPECT_TRUE(result->settings().GetString(kNotCorruptKey, &value_string));
+  EXPECT_EQ(kValue, value_string);
+}
+
+// Test that the Restore() method does not just delete the entire database
+// (unless absolutely necessary), and instead only removes corrupted keys.
+TEST_F(LeveldbValueStoreUnitTest, RestoreDoesMinimumNecessary) {
+  const char* kNotCorruptKeys[] = {"a", "n", "z"};
+  const size_t kNotCorruptKeysSize = 3u;
+  const char kCorruptKey1[] = "f";
+  const char kCorruptKey2[] = "s";
+  const char kValue[] = "value";
+  const char kCorruptValue[] = "[{(.*+\"\'\\";
+
+  // Insert a collection of non-corrupted pairs.
+  scoped_ptr<base::Value> value(base::Value::CreateStringValue(kValue));
+  for (size_t i = 0; i < kNotCorruptKeysSize; ++i) {
+    ASSERT_FALSE(store()
+                     ->Set(ValueStore::DEFAULTS, kNotCorruptKeys[i], *value)
+                     ->HasError());
+  }
+
+  // Insert a few corrupted pairs.
+  leveldb::WriteBatch batch;
+  batch.Put(kCorruptKey1, kCorruptValue);
+  batch.Put(kCorruptKey2, kCorruptValue);
+  ASSERT_TRUE(store()->WriteToDbForTest(&batch));
+
+  // Verify that we broke it, and then fix it.
+  ValueStore::ReadResult result = store()->Get();
+  ASSERT_TRUE(result->HasError());
+  ASSERT_EQ(ValueStore::CORRUPTION, result->error().code);
+
+  ASSERT_TRUE(store()->Restore());
+
+  // We should still have all valid pairs present in the database.
+  std::string value_string;
+  for (size_t i = 0; i < kNotCorruptKeysSize; ++i) {
+    result = store()->Get(kNotCorruptKeys[i]);
+    EXPECT_FALSE(result->HasError());
+    EXPECT_TRUE(result->settings().HasKey(kNotCorruptKeys[i]));
+    EXPECT_TRUE(
+        result->settings().GetString(kNotCorruptKeys[i], &value_string));
+    EXPECT_EQ(kValue, value_string);
+  }
+}
+
+// Test that the LeveldbValueStore can recover in the case of a CATastrophic
+// failure and we have total corruption. In this case, the database is plagued
+// by LolCats.
+// Full corruption has been known to happen occasionally in strange edge cases,
+// such as after users use Windows Restore. We can't prevent it, but we need to
+// be able to handle it smoothly.
+TEST_F(LeveldbValueStoreUnitTest, RestoreFullDatabase) {
+  const std::string kLolCats("I can haz leveldb filez?");
+  const char* kNotCorruptKeys[] = {"a", "n", "z"};
+  const size_t kNotCorruptKeysSize = 3u;
+  const char kValue[] = "value";
+
+  // Generate a database.
+  scoped_ptr<base::Value> value(base::Value::CreateStringValue(kValue));
+  for (size_t i = 0; i < kNotCorruptKeysSize; ++i) {
+    ASSERT_FALSE(store()
+                     ->Set(ValueStore::DEFAULTS, kNotCorruptKeys[i], *value)
+                     ->HasError());
+  }
+
+  // Close it (so we remove the lock), and replace all files with LolCats.
+  CloseStore();
+  base::FileEnumerator enumerator(
+      database_path(), true /* recursive */, base::FileEnumerator::FILES);
+  for (base::FilePath file = enumerator.Next(); !file.empty();
+       file = enumerator.Next()) {
+    // WriteFile() failure is a result of -1.
+    ASSERT_NE(file_util::WriteFile(file, kLolCats.c_str(), kLolCats.length()),
+              -1);
+  }
+  OpenStore();
+
+  // We should definitely have an error.
+  ValueStore::ReadResult result = store()->Get();
+  ASSERT_TRUE(result->HasError());
+  ASSERT_EQ(ValueStore::CORRUPTION, result->error().code);
+
+  ASSERT_TRUE(store()->Restore());
+  result = store()->Get();
+  EXPECT_FALSE(result->HasError());
+  // We couldn't recover anything, but we should be in a sane state again.
+  EXPECT_EQ(0u, result->settings().size());
+}