rocksdb/db/error_handler.h

//  Copyright (c) 2018-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under both the GPLv2 (found in the
//  COPYING file in the root directory) and Apache 2.0 License
//  (found in the LICENSE.Apache file in the root directory).
#pragma once

#include "monitoring/instrumented_mutex.h"
#include "options/db_options.h"
#include "rocksdb/io_status.h"
#include "rocksdb/listener.h"
#include "rocksdb/status.h"

namespace ROCKSDB_NAMESPACE {

class DBImpl;

// This structure is used to store the DB recovery context. The context is
// the information that related to the recover actions. For example, it contains
// FlushReason, which tells the flush job why this flush is called.
struct DBRecoverContext {
  FlushReason flush_reason;
  bool flush_after_recovery;

  DBRecoverContext()
      : flush_reason(FlushReason::kErrorRecovery),
        flush_after_recovery(false) {}
  DBRecoverContext(FlushReason reason)
      : flush_reason(reason), flush_after_recovery(false) {}
};

class ErrorHandler {
 public:
  ErrorHandler(DBImpl* db, const ImmutableDBOptions& db_options,
               InstrumentedMutex* db_mutex)
      : db_(db),
        db_options_(db_options),
        cv_(db_mutex),
        end_recovery_(false),
        recovery_thread_(nullptr),
        db_mutex_(db_mutex),
        auto_recovery_(false),
        recovery_in_prog_(false),
        soft_error_no_bg_work_(false),
        is_db_stopped_(false),
        bg_error_stats_(db_options.statistics) {
    // Clear the checked flag for uninitialized errors
    bg_error_.PermitUncheckedError();
    recovery_error_.PermitUncheckedError();
    recovery_io_error_.PermitUncheckedError();
  }

  void EnableAutoRecovery() { auto_recovery_ = true; }

  Status::Severity GetErrorSeverity(BackgroundErrorReason reason,
                                    Status::Code code, Status::SubCode subcode);

  const Status& SetBGError(const Status& bg_err, BackgroundErrorReason reason);

  Status GetBGError() const { return bg_error_; }

  Status GetRecoveryError() const { return recovery_error_; }

  Status ClearBGError();

  bool IsDBStopped() { return is_db_stopped_.load(std::memory_order_acquire); }

  bool IsBGWorkStopped() {
    assert(db_mutex_);
    db_mutex_->AssertHeld();
    return !bg_error_.ok() &&
           (bg_error_.severity() >= Status::Severity::kHardError ||
            !auto_recovery_ || soft_error_no_bg_work_);
  }

  bool IsSoftErrorNoBGWork() { return soft_error_no_bg_work_; }

  bool IsRecoveryInProgress() { return recovery_in_prog_; }

  Status RecoverFromBGError(bool is_manual = false);
  void CancelErrorRecovery();

  void EndAutoRecovery();

 private:
  DBImpl* db_;
  const ImmutableDBOptions& db_options_;
  Status bg_error_;
  // A separate Status variable used to record any errors during the
  // recovery process from hard errors
  Status recovery_error_;
  // A separate IO Status variable used to record any IO errors during
  // the recovery process. At the same time, recovery_error_ is also set.
  IOStatus recovery_io_error_;
  // The condition variable used with db_mutex during auto resume for time
  // wait.
  InstrumentedCondVar cv_;
  bool end_recovery_;
  std::unique_ptr<port::Thread> recovery_thread_;

  InstrumentedMutex* db_mutex_;
  // A flag indicating whether automatic recovery from errors is enabled
  bool auto_recovery_;
  bool recovery_in_prog_;
  // A flag to indicate that for the soft error, we should not allow any
  // background work except the work is from recovery.
  bool soft_error_no_bg_work_;

  // Used to store the context for recover, such as flush reason.
  DBRecoverContext recover_context_;
  std::atomic<bool> is_db_stopped_;

  // The pointer of DB statistics.
  std::shared_ptr<Statistics> bg_error_stats_;

  const Status& HandleKnownErrors(const Status& bg_err,
                                  BackgroundErrorReason reason);
  Status OverrideNoSpaceError(const Status& bg_error, bool* auto_recovery);
  void RecoverFromNoSpace();
  const Status& StartRecoverFromRetryableBGIOError(const IOStatus& io_error);
  void RecoverFromRetryableBGIOError();
  // First, if it is in recovery and the recovery_error is ok. Set the
  // recovery_error_ to bg_err. Second, if the severity is higher than the
  // current bg_error_, overwrite it.
  void CheckAndSetRecoveryAndBGError(const Status& bg_err);
};

}  // namespace ROCKSDB_NAMESPACE