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leveldb/db/db_impl.cc
leveldb Team 8f1861462b Sync MANIFEST before closing in db_impl when creating a new DB. 
Add logging with debugging information when failing to load a version set.

PiperOrigin-RevId: 351432332
2021-01-12 21:58:08 +00:00

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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "db/db_impl.h"
#include <algorithm>
#include <atomic>
#include <cstdint>
#include <cstdio>
#include <set>
#include <string>
#include <vector>
#include "db/builder.h"
#include "db/db_iter.h"
#include "db/dbformat.h"
#include "db/filename.h"
#include "db/log_reader.h"
#include "db/log_writer.h"
#include "db/memtable.h"
#include "db/table_cache.h"
#include "db/version_set.h"
#include "db/write_batch_internal.h"
#include "leveldb/db.h"
#include "leveldb/env.h"
#include "leveldb/status.h"
#include "leveldb/table.h"
#include "leveldb/table_builder.h"
#include "port/port.h"
#include "table/block.h"
#include "table/merger.h"
#include "table/two_level_iterator.h"
#include "util/coding.h"
#include "util/logging.h"
#include "util/mutexlock.h"
namespace leveldb {
const int kNumNonTableCacheFiles = 10;
// Information kept for every waiting writer
struct DBImpl::Writer {
explicit Writer(port::Mutex* mu)
: batch(nullptr), sync(false), done(false), cv(mu) {}
Status status;
WriteBatch* batch;
bool sync;
bool done;
port::CondVar cv;
};
struct DBImpl::CompactionState {
// Files produced by compaction
struct Output {
uint64_t number;
uint64_t file_size;
InternalKey smallest, largest;
};
Output* current_output() { return &outputs[outputs.size() - 1]; }
explicit CompactionState(Compaction* c)
: compaction(c),
smallest_snapshot(0),
outfile(nullptr),
builder(nullptr),
total_bytes(0) {}
Compaction* const compaction;
// Sequence numbers < smallest_snapshot are not significant since we
// will never have to service a snapshot below smallest_snapshot.
// Therefore if we have seen a sequence number S <= smallest_snapshot,
// we can drop all entries for the same key with sequence numbers < S.
SequenceNumber smallest_snapshot;
std::vector<Output> outputs;
// State kept for output being generated
WritableFile* outfile;
TableBuilder* builder;
uint64_t total_bytes;
};
// Fix user-supplied options to be reasonable
template <class T, class V>
static void ClipToRange(T* ptr, V minvalue, V maxvalue) {
if (static_cast<V>(*ptr) > maxvalue) *ptr = maxvalue;
if (static_cast<V>(*ptr) < minvalue) *ptr = minvalue;
}
Options SanitizeOptions(const std::string& dbname,
const InternalKeyComparator* icmp,
const InternalFilterPolicy* ipolicy,
const Options& src) {
Options result = src;
result.comparator = icmp;
result.filter_policy = (src.filter_policy != nullptr) ? ipolicy : nullptr;
ClipToRange(&result.max_open_files, 64 + kNumNonTableCacheFiles, 50000);
ClipToRange(&result.write_buffer_size, 64 << 10, 1 << 30);
ClipToRange(&result.max_file_size, 1 << 20, 1 << 30);
ClipToRange(&result.block_size, 1 << 10, 4 << 20);
if (result.info_log == nullptr) {
// Open a log file in the same directory as the db
src.env->CreateDir(dbname); // In case it does not exist
src.env->RenameFile(InfoLogFileName(dbname), OldInfoLogFileName(dbname));
Status s = src.env->NewLogger(InfoLogFileName(dbname), &result.info_log);
if (!s.ok()) {
// No place suitable for logging
result.info_log = nullptr;
}
}
if (result.block_cache == nullptr) {
result.block_cache = NewLRUCache(8 << 20);
}
return result;
}
static int TableCacheSize(const Options& sanitized_options) {
// Reserve ten files or so for other uses and give the rest to TableCache.
return sanitized_options.max_open_files - kNumNonTableCacheFiles;
}
DBImpl::DBImpl(const Options& raw_options, const std::string& dbname)
: env_(raw_options.env),
internal_comparator_(raw_options.comparator),
internal_filter_policy_(raw_options.filter_policy),
options_(SanitizeOptions(dbname, &internal_comparator_,
&internal_filter_policy_, raw_options)),
owns_info_log_(options_.info_log != raw_options.info_log),
owns_cache_(options_.block_cache != raw_options.block_cache),
dbname_(dbname),
table_cache_(new TableCache(dbname_, options_, TableCacheSize(options_))),
db_lock_(nullptr),
shutting_down_(false),
background_work_finished_signal_(&mutex_),
mem_(nullptr),
imm_(nullptr),
has_imm_(false),
logfile_(nullptr),
logfile_number_(0),
log_(nullptr),
seed_(0),
tmp_batch_(new WriteBatch),
background_compaction_scheduled_(false),
manual_compaction_(nullptr),
versions_(new VersionSet(dbname_, &options_, table_cache_,
&internal_comparator_)) {}
DBImpl::~DBImpl() {
// Wait for background work to finish.
mutex_.Lock();
shutting_down_.store(true, std::memory_order_release);
while (background_compaction_scheduled_) {
background_work_finished_signal_.Wait();
}
mutex_.Unlock();
if (db_lock_ != nullptr) {
env_->UnlockFile(db_lock_);
}
delete versions_;
if (mem_ != nullptr) mem_->Unref();
if (imm_ != nullptr) imm_->Unref();
delete tmp_batch_;
delete log_;
delete logfile_;
delete table_cache_;
if (owns_info_log_) {
delete options_.info_log;
}
if (owns_cache_) {
delete options_.block_cache;
}
}
Status DBImpl::NewDB() {
VersionEdit new_db;
new_db.SetComparatorName(user_comparator()->Name());
new_db.SetLogNumber(0);
new_db.SetNextFile(2);
new_db.SetLastSequence(0);
const std::string manifest = DescriptorFileName(dbname_, 1);
WritableFile* file;
Status s = env_->NewWritableFile(manifest, &file);
if (!s.ok()) {
return s;
}
{
log::Writer log(file);
std::string record;
new_db.EncodeTo(&record);
s = log.AddRecord(record);
if (s.ok()) {
s = file->Sync();
}
if (s.ok()) {
s = file->Close();
}
}
delete file;
if (s.ok()) {
// Make "CURRENT" file that points to the new manifest file.
s = SetCurrentFile(env_, dbname_, 1);
} else {
env_->RemoveFile(manifest);
}
return s;
}
void DBImpl::MaybeIgnoreError(Status* s) const {
if (s->ok() || options_.paranoid_checks) {
// No change needed
} else {
Log(options_.info_log, "Ignoring error %s", s->ToString().c_str());
*s = Status::OK();
}
}
void DBImpl::RemoveObsoleteFiles() {
mutex_.AssertHeld();
if (!bg_error_.ok()) {
// After a background error, we don't know whether a new version may
// or may not have been committed, so we cannot safely garbage collect.
return;
}
// Make a set of all of the live files
std::set<uint64_t> live = pending_outputs_;
versions_->AddLiveFiles(&live);
std::vector<std::string> filenames;
env_->GetChildren(dbname_, &filenames); // Ignoring errors on purpose
uint64_t number;
FileType type;
std::vector<std::string> files_to_delete;
for (std::string& filename : filenames) {
if (ParseFileName(filename, &number, &type)) {
bool keep = true;
switch (type) {
case kLogFile:
keep = ((number >= versions_->LogNumber()) ||
(number == versions_->PrevLogNumber()));
break;
case kDescriptorFile:
// Keep my manifest file, and any newer incarnations'
// (in case there is a race that allows other incarnations)
keep = (number >= versions_->ManifestFileNumber());
break;
case kTableFile:
keep = (live.find(number) != live.end());
break;
case kTempFile:
// Any temp files that are currently being written to must
// be recorded in pending_outputs_, which is inserted into "live"
keep = (live.find(number) != live.end());
break;
case kCurrentFile:
case kDBLockFile:
case kInfoLogFile:
keep = true;
break;
}
if (!keep) {
files_to_delete.push_back(std::move(filename));
if (type == kTableFile) {
table_cache_->Evict(number);
}
Log(options_.info_log, "Delete type=%d #%lld\n", static_cast<int>(type),
static_cast<unsigned long long>(number));
}
}
}
// While deleting all files unblock other threads. All files being deleted
// have unique names which will not collide with newly created files and
// are therefore safe to delete while allowing other threads to proceed.
mutex_.Unlock();
for (const std::string& filename : files_to_delete) {
env_->RemoveFile(dbname_ + "/" + filename);
}
mutex_.Lock();
}
Status DBImpl::Recover(VersionEdit* edit, bool* save_manifest) {
mutex_.AssertHeld();
// Ignore error from CreateDir since the creation of the DB is
// committed only when the descriptor is created, and this directory
// may already exist from a previous failed creation attempt.
env_->CreateDir(dbname_);
assert(db_lock_ == nullptr);
Status s = env_->LockFile(LockFileName(dbname_), &db_lock_);
if (!s.ok()) {
return s;
}
if (!env_->FileExists(CurrentFileName(dbname_))) {
if (options_.create_if_missing) {
Log(options_.info_log, "Creating DB %s since it was missing.",
dbname_.c_str());
s = NewDB();
if (!s.ok()) {
return s;
}
} else {
return Status::InvalidArgument(
dbname_, "does not exist (create_if_missing is false)");
}
} else {
if (options_.error_if_exists) {
return Status::InvalidArgument(dbname_,
"exists (error_if_exists is true)");
}
}
s = versions_->Recover(save_manifest);
if (!s.ok()) {
return s;
}
SequenceNumber max_sequence(0);
// Recover from all newer log files than the ones named in the
// descriptor (new log files may have been added by the previous
// incarnation without registering them in the descriptor).
//
// Note that PrevLogNumber() is no longer used, but we pay
// attention to it in case we are recovering a database
// produced by an older version of leveldb.
const uint64_t min_log = versions_->LogNumber();
const uint64_t prev_log = versions_->PrevLogNumber();
std::vector<std::string> filenames;
s = env_->GetChildren(dbname_, &filenames);
if (!s.ok()) {
return s;
}
std::set<uint64_t> expected;
versions_->AddLiveFiles(&expected);
uint64_t number;
FileType type;
std::vector<uint64_t> logs;
for (size_t i = 0; i < filenames.size(); i++) {
if (ParseFileName(filenames[i], &number, &type)) {
expected.erase(number);
if (type == kLogFile && ((number >= min_log) || (number == prev_log)))
logs.push_back(number);
}
}
if (!expected.empty()) {
char buf[50];
std::snprintf(buf, sizeof(buf), "%d missing files; e.g.",
static_cast<int>(expected.size()));
return Status::Corruption(buf, TableFileName(dbname_, *(expected.begin())));
}
// Recover in the order in which the logs were generated
std::sort(logs.begin(), logs.end());
for (size_t i = 0; i < logs.size(); i++) {
s = RecoverLogFile(logs[i], (i == logs.size() - 1), save_manifest, edit,
&max_sequence);
if (!s.ok()) {
return s;
}
// The previous incarnation may not have written any MANIFEST
// records after allocating this log number. So we manually
// update the file number allocation counter in VersionSet.
versions_->MarkFileNumberUsed(logs[i]);
}
if (versions_->LastSequence() < max_sequence) {
versions_->SetLastSequence(max_sequence);
}
return Status::OK();
}
Status DBImpl::RecoverLogFile(uint64_t log_number, bool last_log,
bool* save_manifest, VersionEdit* edit,
SequenceNumber* max_sequence) {
struct LogReporter : public log::Reader::Reporter {
Env* env;
Logger* info_log;
const char* fname;
Status* status; // null if options_.paranoid_checks==false
void Corruption(size_t bytes, const Status& s) override {
Log(info_log, "%s%s: dropping %d bytes; %s",
(this->status == nullptr ? "(ignoring error) " : ""), fname,
static_cast<int>(bytes), s.ToString().c_str());
if (this->status != nullptr && this->status->ok()) *this->status = s;
}
};
mutex_.AssertHeld();
// Open the log file
std::string fname = LogFileName(dbname_, log_number);
SequentialFile* file;
Status status = env_->NewSequentialFile(fname, &file);
if (!status.ok()) {
MaybeIgnoreError(&status);
return status;
}
// Create the log reader.
LogReporter reporter;
reporter.env = env_;
reporter.info_log = options_.info_log;
reporter.fname = fname.c_str();
reporter.status = (options_.paranoid_checks ? &status : nullptr);
// We intentionally make log::Reader do checksumming even if
// paranoid_checks==false so that corruptions cause entire commits
// to be skipped instead of propagating bad information (like overly
// large sequence numbers).
log::Reader reader(file, &reporter, true /*checksum*/, 0 /*initial_offset*/);
Log(options_.info_log, "Recovering log #%llu",
(unsigned long long)log_number);
// Read all the records and add to a memtable
std::string scratch;
Slice record;
WriteBatch batch;
int compactions = 0;
MemTable* mem = nullptr;
while (reader.ReadRecord(&record, &scratch) && status.ok()) {
if (record.size() < 12) {
reporter.Corruption(record.size(),
Status::Corruption("log record too small"));
continue;
}
WriteBatchInternal::SetContents(&batch, record);
if (mem == nullptr) {
mem = new MemTable(internal_comparator_);
mem->Ref();
}
status = WriteBatchInternal::InsertInto(&batch, mem);
MaybeIgnoreError(&status);
if (!status.ok()) {
break;
}
const SequenceNumber last_seq = WriteBatchInternal::Sequence(&batch) +
WriteBatchInternal::Count(&batch) - 1;
if (last_seq > *max_sequence) {
*max_sequence = last_seq;
}
if (mem->ApproximateMemoryUsage() > options_.write_buffer_size) {
compactions++;
*save_manifest = true;
status = WriteLevel0Table(mem, edit, nullptr);
mem->Unref();
mem = nullptr;
if (!status.ok()) {
// Reflect errors immediately so that conditions like full
// file-systems cause the DB::Open() to fail.
break;
}
}
}
delete file;
// See if we should keep reusing the last log file.
if (status.ok() && options_.reuse_logs && last_log && compactions == 0) {
assert(logfile_ == nullptr);
assert(log_ == nullptr);
assert(mem_ == nullptr);
uint64_t lfile_size;
if (env_->GetFileSize(fname, &lfile_size).ok() &&
env_->NewAppendableFile(fname, &logfile_).ok()) {
Log(options_.info_log, "Reusing old log %s \n", fname.c_str());
log_ = new log::Writer(logfile_, lfile_size);
logfile_number_ = log_number;
if (mem != nullptr) {
mem_ = mem;
mem = nullptr;
} else {
// mem can be nullptr if lognum exists but was empty.
mem_ = new MemTable(internal_comparator_);
mem_->Ref();
}
}
}
if (mem != nullptr) {
// mem did not get reused; compact it.
if (status.ok()) {
*save_manifest = true;
status = WriteLevel0Table(mem, edit, nullptr);
}
mem->Unref();
}
return status;
}
Status DBImpl::WriteLevel0Table(MemTable* mem, VersionEdit* edit,
Version* base) {
mutex_.AssertHeld();
const uint64_t start_micros = env_->NowMicros();
FileMetaData meta;
meta.number = versions_->NewFileNumber();
pending_outputs_.insert(meta.number);
Iterator* iter = mem->NewIterator();
Log(options_.info_log, "Level-0 table #%llu: started",
(unsigned long long)meta.number);
Status s;
{
mutex_.Unlock();
s = BuildTable(dbname_, env_, options_, table_cache_, iter, &meta);
mutex_.Lock();
}
Log(options_.info_log, "Level-0 table #%llu: %lld bytes %s",
(unsigned long long)meta.number, (unsigned long long)meta.file_size,
s.ToString().c_str());
delete iter;
pending_outputs_.erase(meta.number);
// Note that if file_size is zero, the file has been deleted and
// should not be added to the manifest.
int level = 0;
if (s.ok() && meta.file_size > 0) {
const Slice min_user_key = meta.smallest.user_key();
const Slice max_user_key = meta.largest.user_key();
if (base != nullptr) {
level = base->PickLevelForMemTableOutput(min_user_key, max_user_key);
}
edit->AddFile(level, meta.number, meta.file_size, meta.smallest,
meta.largest);
}
CompactionStats stats;
stats.micros = env_->NowMicros() - start_micros;
stats.bytes_written = meta.file_size;
stats_[level].Add(stats);
return s;
}
void DBImpl::CompactMemTable() {
mutex_.AssertHeld();
assert(imm_ != nullptr);
// Save the contents of the memtable as a new Table
VersionEdit edit;
Version* base = versions_->current();
base->Ref();
Status s = WriteLevel0Table(imm_, &edit, base);
base->Unref();
if (s.ok() && shutting_down_.load(std::memory_order_acquire)) {
s = Status::IOError("Deleting DB during memtable compaction");
}
// Replace immutable memtable with the generated Table
if (s.ok()) {
edit.SetPrevLogNumber(0);
edit.SetLogNumber(logfile_number_); // Earlier logs no longer needed
s = versions_->LogAndApply(&edit, &mutex_);
}
if (s.ok()) {
// Commit to the new state
imm_->Unref();
imm_ = nullptr;
has_imm_.store(false, std::memory_order_release);
RemoveObsoleteFiles();
} else {
RecordBackgroundError(s);
}
}
void DBImpl::CompactRange(const Slice* begin, const Slice* end) {
int max_level_with_files = 1;
{
MutexLock l(&mutex_);
Version* base = versions_->current();
for (int level = 1; level < config::kNumLevels; level++) {
if (base->OverlapInLevel(level, begin, end)) {
max_level_with_files = level;
}
}
}
TEST_CompactMemTable(); // TODO(sanjay): Skip if memtable does not overlap
for (int level = 0; level < max_level_with_files; level++) {
TEST_CompactRange(level, begin, end);
}
}
void DBImpl::TEST_CompactRange(int level, const Slice* begin,
const Slice* end) {
assert(level >= 0);
assert(level + 1 < config::kNumLevels);
InternalKey begin_storage, end_storage;
ManualCompaction manual;
manual.level = level;
manual.done = false;
if (begin == nullptr) {
manual.begin = nullptr;
} else {
begin_storage = InternalKey(*begin, kMaxSequenceNumber, kValueTypeForSeek);
manual.begin = &begin_storage;
}
if (end == nullptr) {
manual.end = nullptr;
} else {
end_storage = InternalKey(*end, 0, static_cast<ValueType>(0));
manual.end = &end_storage;
}
MutexLock l(&mutex_);
while (!manual.done && !shutting_down_.load(std::memory_order_acquire) &&
bg_error_.ok()) {
if (manual_compaction_ == nullptr) { // Idle
manual_compaction_ = &manual;
MaybeScheduleCompaction();
} else { // Running either my compaction or another compaction.
background_work_finished_signal_.Wait();
}
}
if (manual_compaction_ == &manual) {
// Cancel my manual compaction since we aborted early for some reason.
manual_compaction_ = nullptr;
}
}
Status DBImpl::TEST_CompactMemTable() {
// nullptr batch means just wait for earlier writes to be done
Status s = Write(WriteOptions(), nullptr);
if (s.ok()) {
// Wait until the compaction completes
MutexLock l(&mutex_);
while (imm_ != nullptr && bg_error_.ok()) {
background_work_finished_signal_.Wait();
}
if (imm_ != nullptr) {
s = bg_error_;
}
}
return s;
}
void DBImpl::RecordBackgroundError(const Status& s) {
mutex_.AssertHeld();
if (bg_error_.ok()) {
bg_error_ = s;
background_work_finished_signal_.SignalAll();
}
}
void DBImpl::MaybeScheduleCompaction() {
mutex_.AssertHeld();
if (background_compaction_scheduled_) {
// Already scheduled
} else if (shutting_down_.load(std::memory_order_acquire)) {
// DB is being deleted; no more background compactions
} else if (!bg_error_.ok()) {
// Already got an error; no more changes
} else if (imm_ == nullptr && manual_compaction_ == nullptr &&
!versions_->NeedsCompaction()) {
// No work to be done
} else {
background_compaction_scheduled_ = true;
env_->Schedule(&DBImpl::BGWork, this);
}
}
void DBImpl::BGWork(void* db) {
reinterpret_cast<DBImpl*>(db)->BackgroundCall();
}
void DBImpl::BackgroundCall() {
MutexLock l(&mutex_);
assert(background_compaction_scheduled_);
if (shutting_down_.load(std::memory_order_acquire)) {
// No more background work when shutting down.
} else if (!bg_error_.ok()) {
// No more background work after a background error.
} else {
BackgroundCompaction();
}
background_compaction_scheduled_ = false;
// Previous compaction may have produced too many files in a level,
// so reschedule another compaction if needed.
MaybeScheduleCompaction();
background_work_finished_signal_.SignalAll();
}
void DBImpl::BackgroundCompaction() {
mutex_.AssertHeld();
if (imm_ != nullptr) {
CompactMemTable();
return;
}
Compaction* c;
bool is_manual = (manual_compaction_ != nullptr);
InternalKey manual_end;
if (is_manual) {
ManualCompaction* m = manual_compaction_;
c = versions_->CompactRange(m->level, m->begin, m->end);
m->done = (c == nullptr);
if (c != nullptr) {
manual_end = c->input(0, c->num_input_files(0) - 1)->largest;
}
Log(options_.info_log,
"Manual compaction at level-%d from %s .. %s; will stop at %s\n",
m->level, (m->begin ? m->begin->DebugString().c_str() : "(begin)"),
(m->end ? m->end->DebugString().c_str() : "(end)"),
(m->done ? "(end)" : manual_end.DebugString().c_str()));
} else {
c = versions_->PickCompaction();
}
Status status;
if (c == nullptr) {
// Nothing to do
} else if (!is_manual && c->IsTrivialMove()) {
// Move file to next level
assert(c->num_input_files(0) == 1);
FileMetaData* f = c->input(0, 0);
c->edit()->RemoveFile(c->level(), f->number);
c->edit()->AddFile(c->level() + 1, f->number, f->file_size, f->smallest,
f->largest);
status = versions_->LogAndApply(c->edit(), &mutex_);
if (!status.ok()) {
RecordBackgroundError(status);
}
VersionSet::LevelSummaryStorage tmp;
Log(options_.info_log, "Moved #%lld to level-%d %lld bytes %s: %s\n",
static_cast<unsigned long long>(f->number), c->level() + 1,
static_cast<unsigned long long>(f->file_size),
status.ToString().c_str(), versions_->LevelSummary(&tmp));
} else {
CompactionState* compact = new CompactionState(c);
status = DoCompactionWork(compact);
if (!status.ok()) {
RecordBackgroundError(status);
}
CleanupCompaction(compact);
c->ReleaseInputs();
RemoveObsoleteFiles();
}
delete c;
if (status.ok()) {
// Done
} else if (shutting_down_.load(std::memory_order_acquire)) {
// Ignore compaction errors found during shutting down
} else {
Log(options_.info_log, "Compaction error: %s", status.ToString().c_str());
}
if (is_manual) {
ManualCompaction* m = manual_compaction_;
if (!status.ok()) {
m->done = true;
}
if (!m->done) {
// We only compacted part of the requested range. Update *m
// to the range that is left to be compacted.
m->tmp_storage = manual_end;
m->begin = &m->tmp_storage;
}
manual_compaction_ = nullptr;
}
}
void DBImpl::CleanupCompaction(CompactionState* compact) {
mutex_.AssertHeld();
if (compact->builder != nullptr) {
// May happen if we get a shutdown call in the middle of compaction
compact->builder->Abandon();
delete compact->builder;
} else {
assert(compact->outfile == nullptr);
}
delete compact->outfile;
for (size_t i = 0; i < compact->outputs.size(); i++) {
const CompactionState::Output& out = compact->outputs[i];
pending_outputs_.erase(out.number);
}
delete compact;
}
Status DBImpl::OpenCompactionOutputFile(CompactionState* compact) {
assert(compact != nullptr);
assert(compact->builder == nullptr);
uint64_t file_number;
{
mutex_.Lock();
file_number = versions_->NewFileNumber();
pending_outputs_.insert(file_number);
CompactionState::Output out;
out.number = file_number;
out.smallest.Clear();
out.largest.Clear();
compact->outputs.push_back(out);
mutex_.Unlock();
}
// Make the output file
std::string fname = TableFileName(dbname_, file_number);
Status s = env_->NewWritableFile(fname, &compact->outfile);
if (s.ok()) {
compact->builder = new TableBuilder(options_, compact->outfile);
}
return s;
}
Status DBImpl::FinishCompactionOutputFile(CompactionState* compact,
Iterator* input) {
assert(compact != nullptr);
assert(compact->outfile != nullptr);
assert(compact->builder != nullptr);
const uint64_t output_number = compact->current_output()->number;
assert(output_number != 0);
// Check for iterator errors
Status s = input->status();
const uint64_t current_entries = compact->builder->NumEntries();
if (s.ok()) {
s = compact->builder->Finish();
} else {
compact->builder->Abandon();
}
const uint64_t current_bytes = compact->builder->FileSize();
compact->current_output()->file_size = current_bytes;
compact->total_bytes += current_bytes;
delete compact->builder;
compact->builder = nullptr;
// Finish and check for file errors
if (s.ok()) {
s = compact->outfile->Sync();
}
if (s.ok()) {
s = compact->outfile->Close();
}
delete compact->outfile;
compact->outfile = nullptr;
if (s.ok() && current_entries > 0) {
// Verify that the table is usable
Iterator* iter =
table_cache_->NewIterator(ReadOptions(), output_number, current_bytes);
s = iter->status();
delete iter;
if (s.ok()) {
Log(options_.info_log, "Generated table #%llu@%d: %lld keys, %lld bytes",
(unsigned long long)output_number, compact->compaction->level(),
(unsigned long long)current_entries,
(unsigned long long)current_bytes);
}
}
return s;
}
Status DBImpl::InstallCompactionResults(CompactionState* compact) {
mutex_.AssertHeld();
Log(options_.info_log, "Compacted %d@%d + %d@%d files => %lld bytes",
compact->compaction->num_input_files(0), compact->compaction->level(),
compact->compaction->num_input_files(1), compact->compaction->level() + 1,
static_cast<long long>(compact->total_bytes));
// Add compaction outputs
compact->compaction->AddInputDeletions(compact->compaction->edit());
const int level = compact->compaction->level();
for (size_t i = 0; i < compact->outputs.size(); i++) {
const CompactionState::Output& out = compact->outputs[i];
compact->compaction->edit()->AddFile(level + 1, out.number, out.file_size,
out.smallest, out.largest);
}
return versions_->LogAndApply(compact->compaction->edit(), &mutex_);
}
Status DBImpl::DoCompactionWork(CompactionState* compact) {
const uint64_t start_micros = env_->NowMicros();
int64_t imm_micros = 0; // Micros spent doing imm_ compactions
Log(options_.info_log, "Compacting %d@%d + %d@%d files",
compact->compaction->num_input_files(0), compact->compaction->level(),
compact->compaction->num_input_files(1),
compact->compaction->level() + 1);
assert(versions_->NumLevelFiles(compact->compaction->level()) > 0);
assert(compact->builder == nullptr);
assert(compact->outfile == nullptr);
if (snapshots_.empty()) {
compact->smallest_snapshot = versions_->LastSequence();
} else {
compact->smallest_snapshot = snapshots_.oldest()->sequence_number();
}
Iterator* input = versions_->MakeInputIterator(compact->compaction);
// Release mutex while we're actually doing the compaction work
mutex_.Unlock();
input->SeekToFirst();
Status status;
ParsedInternalKey ikey;
std::string current_user_key;
bool has_current_user_key = false;
SequenceNumber last_sequence_for_key = kMaxSequenceNumber;
while (input->Valid() && !shutting_down_.load(std::memory_order_acquire)) {
// Prioritize immutable compaction work
if (has_imm_.load(std::memory_order_relaxed)) {
const uint64_t imm_start = env_->NowMicros();
mutex_.Lock();
if (imm_ != nullptr) {
CompactMemTable();
// Wake up MakeRoomForWrite() if necessary.
background_work_finished_signal_.SignalAll();
}
mutex_.Unlock();
imm_micros += (env_->NowMicros() - imm_start);
}
Slice key = input->key();
if (compact->compaction->ShouldStopBefore(key) &&
compact->builder != nullptr) {
status = FinishCompactionOutputFile(compact, input);
if (!status.ok()) {
break;
}
}
// Handle key/value, add to state, etc.
bool drop = false;
if (!ParseInternalKey(key, &ikey)) {
// Do not hide error keys
current_user_key.clear();
has_current_user_key = false;
last_sequence_for_key = kMaxSequenceNumber;
} else {
if (!has_current_user_key ||
user_comparator()->Compare(ikey.user_key, Slice(current_user_key)) !=
0) {
// First occurrence of this user key
current_user_key.assign(ikey.user_key.data(), ikey.user_key.size());
has_current_user_key = true;
last_sequence_for_key = kMaxSequenceNumber;
}
if (last_sequence_for_key <= compact->smallest_snapshot) {
// Hidden by an newer entry for same user key
drop = true; // (A)
} else if (ikey.type == kTypeDeletion &&
ikey.sequence <= compact->smallest_snapshot &&
compact->compaction->IsBaseLevelForKey(ikey.user_key)) {
// For this user key:
// (1) there is no data in higher levels
// (2) data in lower levels will have larger sequence numbers
// (3) data in layers that are being compacted here and have
// smaller sequence numbers will be dropped in the next
// few iterations of this loop (by rule (A) above).
// Therefore this deletion marker is obsolete and can be dropped.
drop = true;
}
last_sequence_for_key = ikey.sequence;
}
#if 0
Log(options_.info_log,
" Compact: %s, seq %d, type: %d %d, drop: %d, is_base: %d, "
"%d smallest_snapshot: %d",
ikey.user_key.ToString().c_str(),
(int)ikey.sequence, ikey.type, kTypeValue, drop,
compact->compaction->IsBaseLevelForKey(ikey.user_key),
(int)last_sequence_for_key, (int)compact->smallest_snapshot);
#endif
if (!drop) {
// Open output file if necessary
if (compact->builder == nullptr) {
status = OpenCompactionOutputFile(compact);
if (!status.ok()) {
break;
}
}
if (compact->builder->NumEntries() == 0) {
compact->current_output()->smallest.DecodeFrom(key);
}
compact->current_output()->largest.DecodeFrom(key);
compact->builder->Add(key, input->value());
// Close output file if it is big enough
if (compact->builder->FileSize() >=
compact->compaction->MaxOutputFileSize()) {
status = FinishCompactionOutputFile(compact, input);
if (!status.ok()) {
break;
}
}
}
input->Next();
}
if (status.ok() && shutting_down_.load(std::memory_order_acquire)) {
status = Status::IOError("Deleting DB during compaction");
}
if (status.ok() && compact->builder != nullptr) {
status = FinishCompactionOutputFile(compact, input);
}
if (status.ok()) {
status = input->status();
}
delete input;
input = nullptr;
CompactionStats stats;
stats.micros = env_->NowMicros() - start_micros - imm_micros;
for (int which = 0; which < 2; which++) {
for (int i = 0; i < compact->compaction->num_input_files(which); i++) {
stats.bytes_read += compact->compaction->input(which, i)->file_size;
}
}
for (size_t i = 0; i < compact->outputs.size(); i++) {
stats.bytes_written += compact->outputs[i].file_size;
}
mutex_.Lock();
stats_[compact->compaction->level() + 1].Add(stats);
if (status.ok()) {
status = InstallCompactionResults(compact);
}
if (!status.ok()) {
RecordBackgroundError(status);
}
VersionSet::LevelSummaryStorage tmp;
Log(options_.info_log, "compacted to: %s", versions_->LevelSummary(&tmp));
return status;
}
namespace {
struct IterState {
port::Mutex* const mu;
Version* const version GUARDED_BY(mu);
MemTable* const mem GUARDED_BY(mu);
MemTable* const imm GUARDED_BY(mu);
IterState(port::Mutex* mutex, MemTable* mem, MemTable* imm, Version* version)
: mu(mutex), version(version), mem(mem), imm(imm) {}
};
static void CleanupIteratorState(void* arg1, void* arg2) {
IterState* state = reinterpret_cast<IterState*>(arg1);
state->mu->Lock();
state->mem->Unref();
if (state->imm != nullptr) state->imm->Unref();
state->version->Unref();
state->mu->Unlock();
delete state;
}
} // anonymous namespace
Iterator* DBImpl::NewInternalIterator(const ReadOptions& options,
SequenceNumber* latest_snapshot,
uint32_t* seed) {
mutex_.Lock();
*latest_snapshot = versions_->LastSequence();
// Collect together all needed child iterators
std::vector<Iterator*> list;
list.push_back(mem_->NewIterator());
mem_->Ref();
if (imm_ != nullptr) {
list.push_back(imm_->NewIterator());
imm_->Ref();
}
versions_->current()->AddIterators(options, &list);
Iterator* internal_iter =
NewMergingIterator(&internal_comparator_, &list[0], list.size());
versions_->current()->Ref();
IterState* cleanup = new IterState(&mutex_, mem_, imm_, versions_->current());
internal_iter->RegisterCleanup(CleanupIteratorState, cleanup, nullptr);
*seed = ++seed_;
mutex_.Unlock();
return internal_iter;
}
Iterator* DBImpl::TEST_NewInternalIterator() {
SequenceNumber ignored;
uint32_t ignored_seed;
return NewInternalIterator(ReadOptions(), &ignored, &ignored_seed);
}
int64_t DBImpl::TEST_MaxNextLevelOverlappingBytes() {
MutexLock l(&mutex_);
return versions_->MaxNextLevelOverlappingBytes();
}
Status DBImpl::Get(const ReadOptions& options, const Slice& key,
std::string* value) {
Status s;
MutexLock l(&mutex_);
SequenceNumber snapshot;
if (options.snapshot != nullptr) {
snapshot =
static_cast<const SnapshotImpl*>(options.snapshot)->sequence_number();
} else {
snapshot = versions_->LastSequence();
}
MemTable* mem = mem_;
MemTable* imm = imm_;
Version* current = versions_->current();
mem->Ref();
if (imm != nullptr) imm->Ref();
current->Ref();
bool have_stat_update = false;
Version::GetStats stats;
// Unlock while reading from files and memtables
{
mutex_.Unlock();
// First look in the memtable, then in the immutable memtable (if any).
LookupKey lkey(key, snapshot);
if (mem->Get(lkey, value, &s)) {
// Done
} else if (imm != nullptr && imm->Get(lkey, value, &s)) {
// Done
} else {
s = current->Get(options, lkey, value, &stats);
have_stat_update = true;
}
mutex_.Lock();
}
if (have_stat_update && current->UpdateStats(stats)) {
MaybeScheduleCompaction();
}
mem->Unref();
if (imm != nullptr) imm->Unref();
current->Unref();
return s;
}
Iterator* DBImpl::NewIterator(const ReadOptions& options) {
SequenceNumber latest_snapshot;
uint32_t seed;
Iterator* iter = NewInternalIterator(options, &latest_snapshot, &seed);
return NewDBIterator(this, user_comparator(), iter,
(options.snapshot != nullptr
? static_cast<const SnapshotImpl*>(options.snapshot)
->sequence_number()
: latest_snapshot),
seed);
}
void DBImpl::RecordReadSample(Slice key) {
MutexLock l(&mutex_);
if (versions_->current()->RecordReadSample(key)) {
MaybeScheduleCompaction();
}
}
const Snapshot* DBImpl::GetSnapshot() {
MutexLock l(&mutex_);
return snapshots_.New(versions_->LastSequence());
}
void DBImpl::ReleaseSnapshot(const Snapshot* snapshot) {
MutexLock l(&mutex_);
snapshots_.Delete(static_cast<const SnapshotImpl*>(snapshot));
}
// Convenience methods
Status DBImpl::Put(const WriteOptions& o, const Slice& key, const Slice& val) {
return DB::Put(o, key, val);
}
Status DBImpl::Delete(const WriteOptions& options, const Slice& key) {
return DB::Delete(options, key);
}
Status DBImpl::Write(const WriteOptions& options, WriteBatch* updates) {
Writer w(&mutex_);
w.batch = updates;
w.sync = options.sync;
w.done = false;
MutexLock l(&mutex_);
writers_.push_back(&w);
while (!w.done && &w != writers_.front()) {
w.cv.Wait();
}
if (w.done) {
return w.status;
}
// May temporarily unlock and wait.
Status status = MakeRoomForWrite(updates == nullptr);
uint64_t last_sequence = versions_->LastSequence();
Writer* last_writer = &w;
if (status.ok() && updates != nullptr) { // nullptr batch is for compactions
WriteBatch* write_batch = BuildBatchGroup(&last_writer);
WriteBatchInternal::SetSequence(write_batch, last_sequence + 1);
last_sequence += WriteBatchInternal::Count(write_batch);
// Add to log and apply to memtable. We can release the lock
// during this phase since &w is currently responsible for logging
// and protects against concurrent loggers and concurrent writes
// into mem_.
{
mutex_.Unlock();
status = log_->AddRecord(WriteBatchInternal::Contents(write_batch));
bool sync_error = false;
if (status.ok() && options.sync) {
status = logfile_->Sync();
if (!status.ok()) {
sync_error = true;
}
}
if (status.ok()) {
status = WriteBatchInternal::InsertInto(write_batch, mem_);
}
mutex_.Lock();
if (sync_error) {
// The state of the log file is indeterminate: the log record we
// just added may or may not show up when the DB is re-opened.
// So we force the DB into a mode where all future writes fail.
RecordBackgroundError(status);
}
}
if (write_batch == tmp_batch_) tmp_batch_->Clear();
versions_->SetLastSequence(last_sequence);
}
while (true) {
Writer* ready = writers_.front();
writers_.pop_front();
if (ready != &w) {
ready->status = status;
ready->done = true;
ready->cv.Signal();
}
if (ready == last_writer) break;
}
// Notify new head of write queue
if (!writers_.empty()) {
writers_.front()->cv.Signal();
}
return status;
}
// REQUIRES: Writer list must be non-empty
// REQUIRES: First writer must have a non-null batch
WriteBatch* DBImpl::BuildBatchGroup(Writer** last_writer) {
mutex_.AssertHeld();
assert(!writers_.empty());
Writer* first = writers_.front();
WriteBatch* result = first->batch;
assert(result != nullptr);
size_t size = WriteBatchInternal::ByteSize(first->batch);
// Allow the group to grow up to a maximum size, but if the
// original write is small, limit the growth so we do not slow
// down the small write too much.
size_t max_size = 1 << 20;
if (size <= (128 << 10)) {
max_size = size + (128 << 10);
}
*last_writer = first;
std::deque<Writer*>::iterator iter = writers_.begin();
++iter; // Advance past "first"
for (; iter != writers_.end(); ++iter) {
Writer* w = *iter;
if (w->sync && !first->sync) {
// Do not include a sync write into a batch handled by a non-sync write.
break;
}
if (w->batch != nullptr) {
size += WriteBatchInternal::ByteSize(w->batch);
if (size > max_size) {
// Do not make batch too big
break;
}
// Append to *result
if (result == first->batch) {
// Switch to temporary batch instead of disturbing caller's batch
result = tmp_batch_;
assert(WriteBatchInternal::Count(result) == 0);
WriteBatchInternal::Append(result, first->batch);
}
WriteBatchInternal::Append(result, w->batch);
}
*last_writer = w;
}
return result;
}
// REQUIRES: mutex_ is held
// REQUIRES: this thread is currently at the front of the writer queue
Status DBImpl::MakeRoomForWrite(bool force) {
mutex_.AssertHeld();
assert(!writers_.empty());
bool allow_delay = !force;
Status s;
while (true) {
if (!bg_error_.ok()) {
// Yield previous error
s = bg_error_;
break;
} else if (allow_delay && versions_->NumLevelFiles(0) >=
config::kL0_SlowdownWritesTrigger) {
// We are getting close to hitting a hard limit on the number of
// L0 files. Rather than delaying a single write by several
// seconds when we hit the hard limit, start delaying each
// individual write by 1ms to reduce latency variance. Also,
// this delay hands over some CPU to the compaction thread in
// case it is sharing the same core as the writer.
mutex_.Unlock();
env_->SleepForMicroseconds(1000);
allow_delay = false; // Do not delay a single write more than once
mutex_.Lock();
} else if (!force &&
(mem_->ApproximateMemoryUsage() <= options_.write_buffer_size)) {
// There is room in current memtable
break;
} else if (imm_ != nullptr) {
// We have filled up the current memtable, but the previous
// one is still being compacted, so we wait.
Log(options_.info_log, "Current memtable full; waiting...\n");
background_work_finished_signal_.Wait();
} else if (versions_->NumLevelFiles(0) >= config::kL0_StopWritesTrigger) {
// There are too many level-0 files.
Log(options_.info_log, "Too many L0 files; waiting...\n");
background_work_finished_signal_.Wait();
} else {
// Attempt to switch to a new memtable and trigger compaction of old
assert(versions_->PrevLogNumber() == 0);
uint64_t new_log_number = versions_->NewFileNumber();
WritableFile* lfile = nullptr;
s = env_->NewWritableFile(LogFileName(dbname_, new_log_number), &lfile);
if (!s.ok()) {
// Avoid chewing through file number space in a tight loop.
versions_->ReuseFileNumber(new_log_number);
break;
}
delete log_;
delete logfile_;
logfile_ = lfile;
logfile_number_ = new_log_number;
log_ = new log::Writer(lfile);
imm_ = mem_;
has_imm_.store(true, std::memory_order_release);
mem_ = new MemTable(internal_comparator_);
mem_->Ref();
force = false; // Do not force another compaction if have room
MaybeScheduleCompaction();
}
}
return s;
}
bool DBImpl::GetProperty(const Slice& property, std::string* value) {
value->clear();
MutexLock l(&mutex_);
Slice in = property;
Slice prefix("leveldb.");
if (!in.starts_with(prefix)) return false;
in.remove_prefix(prefix.size());
if (in.starts_with("num-files-at-level")) {
in.remove_prefix(strlen("num-files-at-level"));
uint64_t level;
bool ok = ConsumeDecimalNumber(&in, &level) && in.empty();
if (!ok || level >= config::kNumLevels) {
return false;
} else {
char buf[100];
std::snprintf(buf, sizeof(buf), "%d",
versions_->NumLevelFiles(static_cast<int>(level)));
*value = buf;
return true;
}
} else if (in == "stats") {
char buf[200];
std::snprintf(buf, sizeof(buf),
" Compactions\n"
"Level Files Size(MB) Time(sec) Read(MB) Write(MB)\n"
"--------------------------------------------------\n");
value->append(buf);
for (int level = 0; level < config::kNumLevels; level++) {
int files = versions_->NumLevelFiles(level);
if (stats_[level].micros > 0 || files > 0) {
std::snprintf(buf, sizeof(buf), "%3d %8d %8.0f %9.0f %8.0f %9.0f\n",
level, files, versions_->NumLevelBytes(level) / 1048576.0,
stats_[level].micros / 1e6,
stats_[level].bytes_read / 1048576.0,
stats_[level].bytes_written / 1048576.0);
value->append(buf);
}
}
return true;
} else if (in == "sstables") {
*value = versions_->current()->DebugString();
return true;
} else if (in == "approximate-memory-usage") {
size_t total_usage = options_.block_cache->TotalCharge();
if (mem_) {
total_usage += mem_->ApproximateMemoryUsage();
}
if (imm_) {
total_usage += imm_->ApproximateMemoryUsage();
}
char buf[50];
std::snprintf(buf, sizeof(buf), "%llu",
static_cast<unsigned long long>(total_usage));
value->append(buf);
return true;
}
return false;
}
void DBImpl::GetApproximateSizes(const Range* range, int n, uint64_t* sizes) {
// TODO(opt): better implementation
MutexLock l(&mutex_);
Version* v = versions_->current();
v->Ref();
for (int i = 0; i < n; i++) {
// Convert user_key into a corresponding internal key.
InternalKey k1(range[i].start, kMaxSequenceNumber, kValueTypeForSeek);
InternalKey k2(range[i].limit, kMaxSequenceNumber, kValueTypeForSeek);
uint64_t start = versions_->ApproximateOffsetOf(v, k1);
uint64_t limit = versions_->ApproximateOffsetOf(v, k2);
sizes[i] = (limit >= start ? limit - start : 0);
}
v->Unref();
}
// Default implementations of convenience methods that subclasses of DB
// can call if they wish
Status DB::Put(const WriteOptions& opt, const Slice& key, const Slice& value) {
WriteBatch batch;
batch.Put(key, value);
return Write(opt, &batch);
}
Status DB::Delete(const WriteOptions& opt, const Slice& key) {
WriteBatch batch;
batch.Delete(key);
return Write(opt, &batch);
}
DB::~DB() = default;
Status DB::Open(const Options& options, const std::string& dbname, DB** dbptr) {
*dbptr = nullptr;
DBImpl* impl = new DBImpl(options, dbname);
impl->mutex_.Lock();
VersionEdit edit;
// Recover handles create_if_missing, error_if_exists
bool save_manifest = false;
Status s = impl->Recover(&edit, &save_manifest);
if (s.ok() && impl->mem_ == nullptr) {
// Create new log and a corresponding memtable.
uint64_t new_log_number = impl->versions_->NewFileNumber();
WritableFile* lfile;
s = options.env->NewWritableFile(LogFileName(dbname, new_log_number),
&lfile);
if (s.ok()) {
edit.SetLogNumber(new_log_number);
impl->logfile_ = lfile;
impl->logfile_number_ = new_log_number;
impl->log_ = new log::Writer(lfile);
impl->mem_ = new MemTable(impl->internal_comparator_);
impl->mem_->Ref();
}
}
if (s.ok() && save_manifest) {
edit.SetPrevLogNumber(0); // No older logs needed after recovery.
edit.SetLogNumber(impl->logfile_number_);
s = impl->versions_->LogAndApply(&edit, &impl->mutex_);
}
if (s.ok()) {
impl->RemoveObsoleteFiles();
impl->MaybeScheduleCompaction();
}
impl->mutex_.Unlock();
if (s.ok()) {
assert(impl->mem_ != nullptr);
*dbptr = impl;
} else {
delete impl;
}
return s;
}
Snapshot::~Snapshot() = default;
Status DestroyDB(const std::string& dbname, const Options& options) {
Env* env = options.env;
std::vector<std::string> filenames;
Status result = env->GetChildren(dbname, &filenames);
if (!result.ok()) {
// Ignore error in case directory does not exist
return Status::OK();
}
FileLock* lock;
const std::string lockname = LockFileName(dbname);
result = env->LockFile(lockname, &lock);
if (result.ok()) {
uint64_t number;
FileType type;
for (size_t i = 0; i < filenames.size(); i++) {
if (ParseFileName(filenames[i], &number, &type) &&
type != kDBLockFile) { // Lock file will be deleted at end
Status del = env->RemoveFile(dbname + "/" + filenames[i]);
if (result.ok() && !del.ok()) {
result = del;
}
}
}
env->UnlockFile(lock); // Ignore error since state is already gone
env->RemoveFile(lockname);
env->RemoveDir(dbname); // Ignore error in case dir contains other files
}
return result;
}
} // namespace leveldb
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