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Revision 1f32dc7d2b6721a1fe13eb515d52e5cd6f110f59 authored by Andrew Kryczka on 14 June 2018, 00:28:31 UTC, committed by Facebook Github Bot on 14 June 2018, 00:32:04 UTC 
Check with PosixEnv before opening LOCK file (#3993)
 
Summary:
Rebased and resubmitting #1831 on behalf of stevelittle.

The problem is when a single process attempts to open the same DB twice, the second attempt fails due to LOCK file held. If the second attempt had opened the LOCK file, it'll now need to close it, and closing causes the file to be unlocked. Then, any subsequent attempt to open the DB will succeed, which is the wrong behavior.

The solution was to track which files a process has locked in PosixEnv, and check those before opening a LOCK file.

Fixes #1780.
Closes https://github.com/facebook/rocksdb/pull/3993

Differential Revision: D8398984

Pulled By: ajkr

fbshipit-source-id: 2755fe66950a0c9de63075f932f9e15768041918
1 parent 7497f99
Raw File
snapshot_checker.h 
// Copyright (c) 2011-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 "rocksdb/types.h"

namespace rocksdb {

// Callback class that control GC of duplicate keys in flush/compaction
class SnapshotChecker {
 public:
  virtual ~SnapshotChecker() {}
  virtual bool IsInSnapshot(SequenceNumber sequence,
                            SequenceNumber snapshot_sequence) const = 0;
};

class DisableGCSnapshotChecker : public SnapshotChecker {
 public:
  virtual ~DisableGCSnapshotChecker() {}
  virtual bool IsInSnapshot(SequenceNumber /*sequence*/,
                            SequenceNumber /*snapshot_sequence*/) const {
    // By returning false, we prevent all the values from being GCed
    return false;
  }
  static DisableGCSnapshotChecker* Instance() { return &instance_; }

 protected:
  static DisableGCSnapshotChecker instance_;
  explicit DisableGCSnapshotChecker() {}
};

class WritePreparedTxnDB;

// Callback class created by WritePreparedTxnDB to check if a key
// is visible by a snapshot.
class WritePreparedSnapshotChecker : public SnapshotChecker {
 public:
  explicit WritePreparedSnapshotChecker(WritePreparedTxnDB* txn_db);
  virtual ~WritePreparedSnapshotChecker() {}

  virtual bool IsInSnapshot(SequenceNumber sequence,
                            SequenceNumber snapshot_sequence) const override;

 private:
#ifndef ROCKSDB_LITE
  const WritePreparedTxnDB* const txn_db_;
#endif  // !ROCKSDB_LITE
};

}  // namespace rocksdb
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