BackupableDB delete backups with newer seq number

Summary: We now delete backups with newer sequence number, so the clients don't have to handle confusing situations when they restore from backup.

Test Plan: added a unit test

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14547

include/utilities/backupable_db.h

@@ -78,6 +78,9 @@ class BackupableDB : public StackableDB {
  public:
   // BackupableDBOptions have to be the same as the ones used in a previous
   // incarnation of the DB
+  //
+  // BackupableDB ownes the pointer `DB* db` now. You should not delete it or
+  // use it after the invocation of BackupableDB
   BackupableDB(DB* db, const BackupableDBOptions& options);
   virtual ~BackupableDB();
 
@@ -106,10 +109,12 @@ class RestoreBackupableDB {
 
    // restore from backup with backup_id
    // IMPORTANT -- if you restore from some backup that is not the latest,
-   // you HAVE to delete all the newer backups immediately, before creating
-   // new backup on the restored database. Otherwise, your new backups
-   // will be corrupted.
-   // TODO should we enforce this somehow?
+   // and you start creating new backups from the new DB, all the backups
+   // that were newer than the backup you restored from will be deleted
+   //
+   // Example: Let's say you have backups 1, 2, 3, 4, 5 and you restore 3.
+   // If you try creating a new backup now, old backups 4 and 5 will be deleted
+   // and new backup with ID 4 will be created.
    Status RestoreDBFromBackup(BackupID backup_id, const std::string& db_dir,
                               const std::string& wal_dir);
 

utilities/backupable/backupable_db.cc

@@ -40,6 +40,8 @@ class BackupEngine {
     return RestoreDBFromBackup(latest_backup_id_, db_dir, wal_dir);
   }
 
+  void DeleteBackupsNewerThan(uint64_t sequence_number);
+
  private:
   class BackupMeta {
    public:
@@ -59,6 +61,12 @@ class BackupEngine {
     uint64_t GetSize() const {
       return size_;
     }
+    void SetSequenceNumber(uint64_t sequence_number) {
+      sequence_number_ = sequence_number;
+    }
+    uint64_t GetSequenceNumber() {
+      return sequence_number_;
+    }
 
     void AddFile(const std::string& filename, uint64_t size);
     void Delete();
@@ -76,6 +84,9 @@ class BackupEngine {
 
    private:
     int64_t timestamp_;
+    // sequence number is only approximate, should not be used
+    // by clients
+    uint64_t sequence_number_;
     uint64_t size_;
     std::string const meta_filename_;
     // files with relative paths (without "/" prefix!!)
@@ -232,11 +243,31 @@ BackupEngine::~BackupEngine() {
   LogFlush(options_.info_log);
 }
 
+void BackupEngine::DeleteBackupsNewerThan(uint64_t sequence_number) {
+  for (auto backup : backups_) {
+    if (backup.second.GetSequenceNumber() > sequence_number) {
+      Log(options_.info_log,
+          "Deleting backup %u because sequence number (%lu) is newer than %lu",
+          backup.first, backup.second.GetSequenceNumber(), sequence_number);
+      backup.second.Delete();
+      obsolete_backups_.push_back(backup.first);
+    }
+  }
+  for (auto ob : obsolete_backups_) {
+    backups_.erase(backups_.find(ob));
+  }
+  auto itr = backups_.end();
+  latest_backup_id_ = (itr == backups_.begin()) ? 0 : (--itr)->first;
+  PutLatestBackupFileContents(latest_backup_id_); // Ignore errors
+  GarbageCollection(false);
+}
+
 Status BackupEngine::CreateNewBackup(DB* db, bool flush_before_backup) {
   Status s;
   std::vector<std::string> live_files;
   VectorLogPtr live_wal_files;
   uint64_t manifest_file_size = 0;
+  uint64_t sequence_number = db->GetLatestSequenceNumber();
 
   s = db->DisableFileDeletions();
   if (s.ok()) {
@@ -261,6 +292,7 @@ Status BackupEngine::CreateNewBackup(DB* db, bool flush_before_backup) {
   assert(ret.second == true);
   auto& new_backup = ret.first->second;
   new_backup.RecordTimestamp();
+  new_backup.SetSequenceNumber(sequence_number);
 
   Log(options_.info_log, "Started the backup process -- creating backup %u",
       new_backup_id);
@@ -603,8 +635,8 @@ void BackupEngine::GarbageCollection(bool full_scan) {
       Log(options_.info_log, "Deleting private dir %s -- %s",
           private_dir.c_str(), s.ToString().c_str());
     }
-    obsolete_backups_.clear();
   }
+  obsolete_backups_.clear();
 
   if (full_scan) {
     Log(options_.info_log, "Starting full scan garbage collection");
@@ -684,6 +716,7 @@ void BackupEngine::BackupMeta::Delete() {
 
 // each backup meta file is of the format:
 // <timestamp>
+// <seq number>
 // <number of files>
 // <file1>
 // <file2>
@@ -711,14 +744,24 @@ Status BackupEngine::BackupMeta::LoadFromFile(const std::string& backup_dir) {
   int bytes_read = 0;
   sscanf(data.data(), "%ld%n", &timestamp_, &bytes_read);
   data.remove_prefix(bytes_read + 1); // +1 for '\n'
+  sscanf(data.data(), "%lu%n", &sequence_number_, &bytes_read);
+  data.remove_prefix(bytes_read + 1); // +1 for '\n'
   sscanf(data.data(), "%u%n", &num_files, &bytes_read);
   data.remove_prefix(bytes_read + 1); // +1 for '\n'
 
+  std::vector<std::pair<std::string, uint64_t>> files;
+
   for (uint32_t i = 0; s.ok() && i < num_files; ++i) {
     std::string filename = GetSliceUntil(&data, '\n').ToString();
     uint64_t size;
     s = env_->GetFileSize(backup_dir + "/" + filename, &size);
-    AddFile(filename, size);
+    files.push_back(std::make_pair(filename, size));
+  }
+
+  if (s.ok()) {
+    for (auto file : files) {
+      AddFile(file.first, file.second);
+    }
   }
 
   return s;
@@ -738,6 +781,8 @@ Status BackupEngine::BackupMeta::StoreToFile(bool sync) {
   unique_ptr<char[]> buf(new char[max_backup_meta_file_size_]);
   int len = 0, buf_size = max_backup_meta_file_size_;
   len += snprintf(buf.get(), buf_size, "%" PRId64 "\n", timestamp_);
+  len += snprintf(buf.get() + len, buf_size - len, "%" PRIu64 "\n",
+                  sequence_number_);
   len += snprintf(buf.get() + len, buf_size - len, "%zu\n", files_.size());
   for (size_t i = 0; i < files_.size(); ++i) {
     len += snprintf(buf.get() + len, buf_size - len, "%s\n", files_[i].c_str());
@@ -758,9 +803,10 @@ Status BackupEngine::BackupMeta::StoreToFile(bool sync) {
 
 // --- BackupableDB methods --------
 
-BackupableDB::BackupableDB(DB* db, const BackupableDBOptions& options) :
-  StackableDB(db),
-  backup_engine_(new BackupEngine(db->GetEnv(), options)) {}
+BackupableDB::BackupableDB(DB* db, const BackupableDBOptions& options)
+    : StackableDB(db), backup_engine_(new BackupEngine(db->GetEnv(), options)) {
+  backup_engine_->DeleteBackupsNewerThan(GetLatestSequenceNumber());
+}
 
 BackupableDB::~BackupableDB() {
   delete backup_engine_;

utilities/backupable/backupable_db_test.cc

@@ -7,6 +7,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file. See the AUTHORS file for names of contributors.
 
+#include "rocksdb/types.h"
 #include "rocksdb/transaction_log.h"
 #include "utilities/utility_db.h"
 #include "utilities/backupable_db.h"
@@ -29,7 +30,11 @@ class DummyDB : public StackableDB {
   /* implicit */
   DummyDB(const Options& options, const std::string& dbname)
      : StackableDB(nullptr), options_(options), dbname_(dbname),
-       deletions_enabled_(true) {}
+       deletions_enabled_(true), sequence_number_(0) {}
+
+  virtual SequenceNumber GetLatestSequenceNumber() const {
+    return ++sequence_number_;
+  }
 
   virtual const std::string& GetName() const override {
     return dbname_;
@@ -117,6 +122,7 @@ class DummyDB : public StackableDB {
   Options options_;
   std::string dbname_;
   bool deletions_enabled_;
+  mutable SequenceNumber sequence_number_;
 }; // DummyDB
 
 class TestEnv : public EnvWrapper {
@@ -292,7 +298,7 @@ class BackupableDBTest {
     // set up db options
     options_.create_if_missing = true;
     options_.paranoid_checks = true;
-    options_.write_buffer_size = 1 << 19; // 512KB
+    options_.write_buffer_size = 1 << 17; // 128KB
     options_.env = test_db_env_.get();
     options_.wal_dir = dbname_;
     // set up backup db options
@@ -305,6 +311,12 @@ class BackupableDBTest {
     DestroyDB(dbname_, Options());
   }
 
+  DB* OpenDB() {
+    DB* db;
+    ASSERT_OK(DB::Open(options_, dbname_, &db));
+    return db;
+  }
+
   void OpenBackupableDB(bool destroy_old_data = false, bool dummy = false) {
     // reset all the defaults
     test_backup_env_->SetLimitWrittenFiles(1000000);
@@ -354,12 +366,12 @@ class BackupableDBTest {
     } else {
       ASSERT_OK(restore_db_->RestoreDBFromLatestBackup(dbname_, dbname_));
     }
-    OpenBackupableDB();
-    AssertExists(db_.get(), start_exist, end_exist);
+    DB* db = OpenDB();
+    AssertExists(db, start_exist, end_exist);
     if (end != 0) {
-      AssertEmpty(db_.get(), end_exist, end);
+      AssertEmpty(db, end_exist, end);
     }
-    CloseBackupableDB();
+    delete db;
     if (opened_restore) {
       CloseRestoreDB();
     }
@@ -450,7 +462,7 @@ TEST(BackupableDBTest, NoDoubleCopy) {
 //      not be able to open that backup, but all other backups should be
 //      fine
 TEST(BackupableDBTest, CorruptionsTest) {
-  const int keys_iteration = 20000;
+  const int keys_iteration = 5000;
   Random rnd(6);
   Status s;
 
@@ -516,7 +528,7 @@ TEST(BackupableDBTest, CorruptionsTest) {
 // open DB, write, close DB, backup, restore, repeat
 TEST(BackupableDBTest, OfflineIntegrationTest) {
   // has to be a big number, so that it triggers the memtable flush
-  const int keys_iteration = 20000;
+  const int keys_iteration = 5000;
   const int max_key = keys_iteration * 4 + 10;
   // first iter -- flush before backup
   // second iter -- don't flush before backup
@@ -542,9 +554,9 @@ TEST(BackupableDBTest, OfflineIntegrationTest) {
       DestroyDB(dbname_, Options());
 
       // ---- make sure it's empty ----
-      OpenBackupableDB();
-      AssertEmpty(db_.get(), 0, fill_up_to);
-      CloseBackupableDB();
+      DB* db = OpenDB();
+      AssertEmpty(db, 0, fill_up_to);
+      delete db;
 
       // ---- restore the DB ----
       OpenRestoreDB();
@@ -563,7 +575,7 @@ TEST(BackupableDBTest, OfflineIntegrationTest) {
 // open DB, write, backup, write, backup, close, restore
 TEST(BackupableDBTest, OnlineIntegrationTest) {
   // has to be a big number, so that it triggers the memtable flush
-  const int keys_iteration = 20000;
+  const int keys_iteration = 5000;
   const int max_key = keys_iteration * 4 + 10;
   Random rnd(7);
   // delete old data
@@ -591,9 +603,9 @@ TEST(BackupableDBTest, OnlineIntegrationTest) {
   DestroyDB(dbname_, Options());
 
   // ---- make sure it's empty ----
-  OpenBackupableDB();
-  AssertEmpty(db_.get(), 0, max_key);
-  CloseBackupableDB();
+  DB* db = OpenDB();
+  AssertEmpty(db, 0, max_key);
+  delete db;
 
   // ---- restore every backup and verify all the data is there ----
   OpenRestoreDB();
@@ -624,6 +636,29 @@ TEST(BackupableDBTest, OnlineIntegrationTest) {
   CloseRestoreDB();
 }
 
+TEST(BackupableDBTest, DeleteNewerBackups) {
+  // create backups 1, 2, 3, 4, 5
+  OpenBackupableDB(true);
+  for (int i = 0; i < 5; ++i) {
+    FillDB(db_.get(), 100 * i, 100 * (i + 1));
+    ASSERT_OK(db_->CreateNewBackup(!!(i % 2)));
+  }
+  CloseBackupableDB();
+
+  // backup 3 is fine
+  AssertBackupConsistency(3, 0, 300, 500);
+  // this should delete backups 4 and 5
+  OpenBackupableDB();
+  CloseBackupableDB();
+  // backups 4 and 5 don't exist
+  OpenRestoreDB();
+  Status s = restore_db_->RestoreDBFromBackup(4, dbname_, dbname_);
+  ASSERT_TRUE(s.IsNotFound());
+  s = restore_db_->RestoreDBFromBackup(5, dbname_, dbname_);
+  ASSERT_TRUE(s.IsNotFound());
+  CloseRestoreDB();
+}
+
 } // anon namespace
 
 } //  namespace rocksdb