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;

  DBRecoverContext() : flush_reason(FlushReason::kErrorRecovery) {}

  DBRecoverContext(FlushReason reason) : flush_reason(reason) {}
};

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),
         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 !bg_error_.ok() &&
            bg_error_.severity() >= Status::Severity::kHardError;
    }

    bool IsBGWorkStopped() {
      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_;

    // 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