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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
logs_with_prep_tracker.cc 
//  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).
//
#include "db/logs_with_prep_tracker.h"

#include "port/likely.h"

namespace rocksdb {
void LogsWithPrepTracker::MarkLogAsHavingPrepSectionFlushed(uint64_t log) {
  assert(log != 0);
  std::lock_guard<std::mutex> lock(prepared_section_completed_mutex_);
  auto it = prepared_section_completed_.find(log);
  if (UNLIKELY(it == prepared_section_completed_.end())) {
    prepared_section_completed_[log] = 1;
  } else {
    it->second += 1;
  }
}

void LogsWithPrepTracker::MarkLogAsContainingPrepSection(uint64_t log) {
  assert(log != 0);
  std::lock_guard<std::mutex> lock(logs_with_prep_mutex_);

  auto rit = logs_with_prep_.rbegin();
  bool updated = false;
  // Most probably the last log is the one that is being marked for
  // having a prepare section; so search from the end.
  for (; rit != logs_with_prep_.rend() && rit->log >= log; ++rit) {
    if (rit->log == log) {
      rit->cnt++;
      updated = true;
      break;
    }
  }
  if (!updated) {
    // We are either at the start, or at a position with rit->log < log
    logs_with_prep_.insert(rit.base(), {log, 1});
  }
}

uint64_t LogsWithPrepTracker::FindMinLogContainingOutstandingPrep() {
  std::lock_guard<std::mutex> lock(logs_with_prep_mutex_);
  auto it = logs_with_prep_.begin();
  // start with the smallest log
  for (; it != logs_with_prep_.end();) {
    auto min_log = it->log;
    {
      std::lock_guard<std::mutex> lock2(prepared_section_completed_mutex_);
      auto completed_it = prepared_section_completed_.find(min_log);
      if (completed_it == prepared_section_completed_.end() ||
          completed_it->second < it->cnt) {
        return min_log;
      }
      assert(completed_it != prepared_section_completed_.end() &&
             completed_it->second == it->cnt);
      prepared_section_completed_.erase(completed_it);
    }
    // erase from beginning in vector is not efficient but this function is not
    // on the fast path.
    it = logs_with_prep_.erase(it);
  }
  // no such log found
  return 0;
}
}  // namespace rocksdb
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