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rocksdb/db/logs_with_prep_tracker.cc

68 lines
2.2 KiB

Skip deleted WALs during recovery Summary: This patch record min log number to keep to the manifest while flushing SST files to ignore them and any WAL older than them during recovery. This is to avoid scenarios when we have a gap between the WAL files are fed to the recovery procedure. The gap could happen by for example out-of-order WAL deletion. Such gap could cause problems in 2PC recovery where the prepared and commit entry are placed into two separate WAL and gap in the WALs could result into not processing the WAL with the commit entry and hence breaking the 2PC recovery logic. Before the commit, for 2PC case, we determined which log number to keep in FindObsoleteFiles(). We looked at the earliest logs with outstanding prepare entries, or prepare entries whose respective commit or abort are in memtable. With the commit, the same calculation is done while we apply the SST flush. Just before installing the flush file, we precompute the earliest log file to keep after the flush finishes using the same logic (but skipping the memtables just flushed), record this information to the manifest entry for this new flushed SST file. This pre-computed value is also remembered in memory, and will later be used to determine whether a log file can be deleted. This value is unlikely to change until next flush because the commit entry will stay in memtable. (In WritePrepared, we could have removed the older log files as soon as all prepared entries are committed. It's not yet done anyway. Even if we do it, the only thing we loss with this new approach is earlier log deletion between two flushes, which does not guarantee to happen anyway because the obsolete file clean-up function is only executed after flush or compaction) This min log number to keep is stored in the manifest using the safely-ignore customized field of AddFile entry, in order to guarantee that the DB generated using newer release can be opened by previous releases no older than 4.2. Closes https://github.com/facebook/rocksdb/pull/3765 Differential Revision: D7747618 Pulled By: siying fbshipit-source-id: d00c92105b4f83852e9754a1b70d6b64cb590729
7 years ago
// 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