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Diffstat (limited to 'src/leveldb/db/db_impl.cc')
| -rw-r--r-- | src/leveldb/db/db_impl.cc | 1467 |
1 files changed, 1467 insertions, 0 deletions
diff --git a/src/leveldb/db/db_impl.cc b/src/leveldb/db/db_impl.cc new file mode 100644 index 000000000..c9de169f2 --- /dev/null +++ b/src/leveldb/db/db_impl.cc @@ -0,0 +1,1467 @@ +// 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 <set> +#include <string> +#include <stdint.h> +#include <stdio.h> +#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 { + +// Information kept for every waiting writer +struct DBImpl::Writer { + Status status; + WriteBatch* batch; + bool sync; + bool done; + port::CondVar cv; + + explicit Writer(port::Mutex* mu) : cv(mu) { } +}; + +struct DBImpl::CompactionState { + 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; + + // Files produced by compaction + struct Output { + uint64_t number; + uint64_t file_size; + InternalKey smallest, largest; + }; + std::vector<Output> outputs; + + // State kept for output being generated + WritableFile* outfile; + TableBuilder* builder; + + uint64_t total_bytes; + + Output* current_output() { return &outputs[outputs.size()-1]; } + + explicit CompactionState(Compaction* c) + : compaction(c), + outfile(NULL), + builder(NULL), + total_bytes(0) { + } +}; + +// 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 != NULL) ? ipolicy : NULL; + ClipToRange(&result.max_open_files, 20, 50000); + ClipToRange(&result.write_buffer_size, 64<<10, 1<<30); + ClipToRange(&result.block_size, 1<<10, 4<<20); + if (result.info_log == NULL) { + // 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 = NULL; + } + } + if (result.block_cache == NULL) { + result.block_cache = NewLRUCache(8 << 20); + } + return result; +} + +DBImpl::DBImpl(const Options& options, const std::string& dbname) + : env_(options.env), + internal_comparator_(options.comparator), + internal_filter_policy_(options.filter_policy), + options_(SanitizeOptions( + dbname, &internal_comparator_, &internal_filter_policy_, options)), + owns_info_log_(options_.info_log != options.info_log), + owns_cache_(options_.block_cache != options.block_cache), + dbname_(dbname), + db_lock_(NULL), + shutting_down_(NULL), + bg_cv_(&mutex_), + mem_(new MemTable(internal_comparator_)), + imm_(NULL), + logfile_(NULL), + logfile_number_(0), + log_(NULL), + tmp_batch_(new WriteBatch), + bg_compaction_scheduled_(false), + manual_compaction_(NULL) { + mem_->Ref(); + has_imm_.Release_Store(NULL); + + // Reserve ten files or so for other uses and give the rest to TableCache. + const int table_cache_size = options.max_open_files - 10; + table_cache_ = new TableCache(dbname_, &options_, table_cache_size); + + versions_ = new VersionSet(dbname_, &options_, table_cache_, + &internal_comparator_); +} + +DBImpl::~DBImpl() { + // Wait for background work to finish + mutex_.Lock(); + shutting_down_.Release_Store(this); // Any non-NULL value is ok + while (bg_compaction_scheduled_) { + bg_cv_.Wait(); + } + mutex_.Unlock(); + + if (db_lock_ != NULL) { + env_->UnlockFile(db_lock_); + } + + delete versions_; + if (mem_ != NULL) mem_->Unref(); + if (imm_ != NULL) 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->Close(); + } + } + delete file; + if (s.ok()) { + // Make "CURRENT" file that points to the new manifest file. + s = SetCurrentFile(env_, dbname_, 1); + } else { + env_->DeleteFile(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::DeleteObsoleteFiles() { + // 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; + for (size_t i = 0; i < filenames.size(); i++) { + if (ParseFileName(filenames[i], &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) { + if (type == kTableFile) { + table_cache_->Evict(number); + } + Log(options_.info_log, "Delete type=%d #%lld\n", + int(type), + static_cast<unsigned long long>(number)); + env_->DeleteFile(dbname_ + "/" + filenames[i]); + } + } + } +} + +Status DBImpl::Recover(VersionEdit* edit) { + 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_ == NULL); + Status s = env_->LockFile(LockFileName(dbname_), &db_lock_); + if (!s.ok()) { + return s; + } + + if (!env_->FileExists(CurrentFileName(dbname_))) { + if (options_.create_if_missing) { + 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(); + if (s.ok()) { + 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; + } + 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) + && type == kLogFile + && ((number >= min_log) || (number == prev_log))) { + logs.push_back(number); + } + } + + // 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], edit, &max_sequence); + + // 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 (s.ok()) { + if (versions_->LastSequence() < max_sequence) { + versions_->SetLastSequence(max_sequence); + } + } + } + + return s; +} + +Status DBImpl::RecoverLogFile(uint64_t log_number, + 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 + virtual void Corruption(size_t bytes, const Status& s) { + Log(info_log, "%s%s: dropping %d bytes; %s", + (this->status == NULL ? "(ignoring error) " : ""), + fname, static_cast<int>(bytes), s.ToString().c_str()); + if (this->status != NULL && 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 : NULL); + // We intentially 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; + MemTable* mem = NULL; + 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 == NULL) { + 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) { + status = WriteLevel0Table(mem, edit, NULL); + if (!status.ok()) { + // Reflect errors immediately so that conditions like full + // file-systems cause the DB::Open() to fail. + break; + } + mem->Unref(); + mem = NULL; + } + } + + if (status.ok() && mem != NULL) { + status = WriteLevel0Table(mem, edit, NULL); + // Reflect errors immediately so that conditions like full + // file-systems cause the DB::Open() to fail. + } + + if (mem != NULL) mem->Unref(); + delete file; + 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 != NULL) { + 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; +} + +Status DBImpl::CompactMemTable() { + mutex_.AssertHeld(); + assert(imm_ != NULL); + + // 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_.Acquire_Load()) { + 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_ = NULL; + has_imm_.Release_Store(NULL); + DeleteObsoleteFiles(); + } + + return 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 == NULL) { + manual.begin = NULL; + } else { + begin_storage = InternalKey(*begin, kMaxSequenceNumber, kValueTypeForSeek); + manual.begin = &begin_storage; + } + if (end == NULL) { + manual.end = NULL; + } else { + end_storage = InternalKey(*end, 0, static_cast<ValueType>(0)); + manual.end = &end_storage; + } + + MutexLock l(&mutex_); + while (!manual.done) { + while (manual_compaction_ != NULL) { + bg_cv_.Wait(); + } + manual_compaction_ = &manual; + MaybeScheduleCompaction(); + while (manual_compaction_ == &manual) { + bg_cv_.Wait(); + } + } +} + +Status DBImpl::TEST_CompactMemTable() { + // NULL batch means just wait for earlier writes to be done + Status s = Write(WriteOptions(), NULL); + if (s.ok()) { + // Wait until the compaction completes + MutexLock l(&mutex_); + while (imm_ != NULL && bg_error_.ok()) { + bg_cv_.Wait(); + } + if (imm_ != NULL) { + s = bg_error_; + } + } + return s; +} + +void DBImpl::MaybeScheduleCompaction() { + mutex_.AssertHeld(); + if (bg_compaction_scheduled_) { + // Already scheduled + } else if (shutting_down_.Acquire_Load()) { + // DB is being deleted; no more background compactions + } else if (imm_ == NULL && + manual_compaction_ == NULL && + !versions_->NeedsCompaction()) { + // No work to be done + } else { + bg_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(bg_compaction_scheduled_); + if (!shutting_down_.Acquire_Load()) { + Status s = BackgroundCompaction(); + if (s.ok()) { + // Success + } else if (shutting_down_.Acquire_Load()) { + // Error most likely due to shutdown; do not wait + } else { + // Wait a little bit before retrying background compaction in + // case this is an environmental problem and we do not want to + // chew up resources for failed compactions for the duration of + // the problem. + bg_cv_.SignalAll(); // In case a waiter can proceed despite the error + Log(options_.info_log, "Waiting after background compaction error: %s", + s.ToString().c_str()); + mutex_.Unlock(); + env_->SleepForMicroseconds(1000000); + mutex_.Lock(); + } + } + + bg_compaction_scheduled_ = false; + + // Previous compaction may have produced too many files in a level, + // so reschedule another compaction if needed. + MaybeScheduleCompaction(); + bg_cv_.SignalAll(); +} + +Status DBImpl::BackgroundCompaction() { + mutex_.AssertHeld(); + + if (imm_ != NULL) { + return CompactMemTable(); + } + + Compaction* c; + bool is_manual = (manual_compaction_ != NULL); + InternalKey manual_end; + if (is_manual) { + ManualCompaction* m = manual_compaction_; + c = versions_->CompactRange(m->level, m->begin, m->end); + m->done = (c == NULL); + if (c != NULL) { + 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 == NULL) { + // 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()->DeleteFile(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_); + 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); + CleanupCompaction(compact); + c->ReleaseInputs(); + DeleteObsoleteFiles(); + } + delete c; + + if (status.ok()) { + // Done + } else if (shutting_down_.Acquire_Load()) { + // Ignore compaction errors found during shutting down + } else { + Log(options_.info_log, + "Compaction error: %s", status.ToString().c_str()); + if (options_.paranoid_checks && bg_error_.ok()) { + bg_error_ = status; + } + } + + 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_ = NULL; + } + return status; +} + +void DBImpl::CleanupCompaction(CompactionState* compact) { + mutex_.AssertHeld(); + if (compact->builder != NULL) { + // May happen if we get a shutdown call in the middle of compaction + compact->builder->Abandon(); + delete compact->builder; + } else { + assert(compact->outfile == NULL); + } + 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 != NULL); + assert(compact->builder == NULL); + 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 != NULL); + assert(compact->outfile != NULL); + assert(compact->builder != NULL); + + 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 = NULL; + + // 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 = NULL; + + 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: %lld keys, %lld bytes", + (unsigned long long) output_number, + (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 == NULL); + assert(compact->outfile == NULL); + if (snapshots_.empty()) { + compact->smallest_snapshot = versions_->LastSequence(); + } else { + compact->smallest_snapshot = snapshots_.oldest()->number_; + } + + // Release mutex while we're actually doing the compaction work + mutex_.Unlock(); + + Iterator* input = versions_->MakeInputIterator(compact->compaction); + input->SeekToFirst(); + Status status; + ParsedInternalKey ikey; + std::string current_user_key; + bool has_current_user_key = false; + SequenceNumber last_sequence_for_key = kMaxSequenceNumber; + for (; input->Valid() && !shutting_down_.Acquire_Load(); ) { + // Prioritize immutable compaction work + if (has_imm_.NoBarrier_Load() != NULL) { + const uint64_t imm_start = env_->NowMicros(); + mutex_.Lock(); + if (imm_ != NULL) { + CompactMemTable(); + bg_cv_.SignalAll(); // Wakeup MakeRoomForWrite() if necessary + } + mutex_.Unlock(); + imm_micros += (env_->NowMicros() - imm_start); + } + + Slice key = input->key(); + if (compact->compaction->ShouldStopBefore(key) && + compact->builder != NULL) { + 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 == NULL) { + 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_.Acquire_Load()) { + status = Status::IOError("Deleting DB during compaction"); + } + if (status.ok() && compact->builder != NULL) { + status = FinishCompactionOutputFile(compact, input); + } + if (status.ok()) { + status = input->status(); + } + delete input; + input = NULL; + + 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); + } + VersionSet::LevelSummaryStorage tmp; + Log(options_.info_log, + "compacted to: %s", versions_->LevelSummary(&tmp)); + return status; +} + +namespace { +struct IterState { + port::Mutex* mu; + Version* version; + MemTable* mem; + MemTable* imm; +}; + +static void CleanupIteratorState(void* arg1, void* arg2) { + IterState* state = reinterpret_cast<IterState*>(arg1); + state->mu->Lock(); + state->mem->Unref(); + if (state->imm != NULL) state->imm->Unref(); + state->version->Unref(); + state->mu->Unlock(); + delete state; +} +} // namespace + +Iterator* DBImpl::NewInternalIterator(const ReadOptions& options, + SequenceNumber* latest_snapshot) { + IterState* cleanup = new IterState; + 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_ != NULL) { + 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(); + + cleanup->mu = &mutex_; + cleanup->mem = mem_; + cleanup->imm = imm_; + cleanup->version = versions_->current(); + internal_iter->RegisterCleanup(CleanupIteratorState, cleanup, NULL); + + mutex_.Unlock(); + return internal_iter; +} + +Iterator* DBImpl::TEST_NewInternalIterator() { + SequenceNumber ignored; + return NewInternalIterator(ReadOptions(), &ignored); +} + +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 != NULL) { + snapshot = reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_; + } else { + snapshot = versions_->LastSequence(); + } + + MemTable* mem = mem_; + MemTable* imm = imm_; + Version* current = versions_->current(); + mem->Ref(); + if (imm != NULL) 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 != NULL && 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 != NULL) imm->Unref(); + current->Unref(); + return s; +} + +Iterator* DBImpl::NewIterator(const ReadOptions& options) { + SequenceNumber latest_snapshot; + Iterator* internal_iter = NewInternalIterator(options, &latest_snapshot); + return NewDBIterator( + &dbname_, env_, user_comparator(), internal_iter, + (options.snapshot != NULL + ? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_ + : latest_snapshot)); +} + +const Snapshot* DBImpl::GetSnapshot() { + MutexLock l(&mutex_); + return snapshots_.New(versions_->LastSequence()); +} + +void DBImpl::ReleaseSnapshot(const Snapshot* s) { + MutexLock l(&mutex_); + snapshots_.Delete(reinterpret_cast<const SnapshotImpl*>(s)); +} + +// 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* my_batch) { + Writer w(&mutex_); + w.batch = my_batch; + 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(my_batch == NULL); + uint64_t last_sequence = versions_->LastSequence(); + Writer* last_writer = &w; + if (status.ok() && my_batch != NULL) { // NULL batch is for compactions + WriteBatch* updates = BuildBatchGroup(&last_writer); + WriteBatchInternal::SetSequence(updates, last_sequence + 1); + last_sequence += WriteBatchInternal::Count(updates); + + // 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(updates)); + if (status.ok() && options.sync) { + status = logfile_->Sync(); + } + if (status.ok()) { + status = WriteBatchInternal::InsertInto(updates, mem_); + } + mutex_.Lock(); + } + if (updates == 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) { + assert(!writers_.empty()); + Writer* first = writers_.front(); + WriteBatch* result = first->batch; + assert(result != NULL); + + 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 != NULL) { + size += WriteBatchInternal::ByteSize(w->batch); + if (size > max_size) { + // Do not make batch too big + break; + } + + // Append to *reuslt + 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_ != NULL) { + // We have filled up the current memtable, but the previous + // one is still being compacted, so we wait. + bg_cv_.Wait(); + } else if (versions_->NumLevelFiles(0) >= config::kL0_StopWritesTrigger) { + // There are too many level-0 files. + Log(options_.info_log, "waiting...\n"); + bg_cv_.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 = NULL; + 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_.Release_Store(imm_); + 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]; + snprintf(buf, sizeof(buf), "%d", + versions_->NumLevelFiles(static_cast<int>(level))); + *value = buf; + return true; + } + } else if (in == "stats") { + char buf[200]; + 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) { + 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; + } + + return false; +} + +void DBImpl::GetApproximateSizes( + const Range* range, int n, + uint64_t* sizes) { + // TODO(opt): better implementation + Version* v; + { + MutexLock l(&mutex_); + versions_->current()->Ref(); + v = versions_->current(); + } + + 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); + } + + { + MutexLock l(&mutex_); + 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() { } + +Status DB::Open(const Options& options, const std::string& dbname, + DB** dbptr) { + *dbptr = NULL; + + DBImpl* impl = new DBImpl(options, dbname); + impl->mutex_.Lock(); + VersionEdit edit; + Status s = impl->Recover(&edit); // Handles create_if_missing, error_if_exists + if (s.ok()) { + 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); + s = impl->versions_->LogAndApply(&edit, &impl->mutex_); + } + if (s.ok()) { + impl->DeleteObsoleteFiles(); + impl->MaybeScheduleCompaction(); + } + } + impl->mutex_.Unlock(); + if (s.ok()) { + *dbptr = impl; + } else { + delete impl; + } + return s; +} + +Snapshot::~Snapshot() { +} + +Status DestroyDB(const std::string& dbname, const Options& options) { + Env* env = options.env; + std::vector<std::string> filenames; + // Ignore error in case directory does not exist + env->GetChildren(dbname, &filenames); + if (filenames.empty()) { + return Status::OK(); + } + + FileLock* lock; + const std::string lockname = LockFileName(dbname); + Status 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->DeleteFile(dbname + "/" + filenames[i]); + if (result.ok() && !del.ok()) { + result = del; + } + } + } + env->UnlockFile(lock); // Ignore error since state is already gone + env->DeleteFile(lockname); + env->DeleteDir(dbname); // Ignore error in case dir contains other files + } + return result; +} + +} // namespace leveldb |