rocksdb/db/compaction/compaction_picker_level.cc
Levi Tamasi 3e1bf771a3 Make it possible to force the garbage collection of the oldest blob files (#8994)
Summary:
The current BlobDB garbage collection logic works by relocating the valid
blobs from the oldest blob files as they are encountered during compaction,
and cleaning up blob files once they contain nothing but garbage. However,
with sufficiently skewed workloads, it is theoretically possible to end up in a
situation when few or no compactions get scheduled for the SST files that contain
references to the oldest blob files, which can lead to increased space amp due
to the lack of GC.

In order to efficiently handle such workloads, the patch adds a new BlobDB
configuration option called `blob_garbage_collection_force_threshold`,
which signals to BlobDB to schedule targeted compactions for the SST files
that keep alive the oldest batch of blob files if the overall ratio of garbage in
the given blob files meets the threshold *and* all the given blob files are
eligible for GC based on `blob_garbage_collection_age_cutoff`. (For example,
if the new option is set to 0.9, targeted compactions will get scheduled if the
sum of garbage bytes meets or exceeds 90% of the sum of total bytes in the
oldest blob files, assuming all affected blob files are below the age-based cutoff.)
The net result of these targeted compactions is that the valid blobs in the oldest
blob files are relocated and the oldest blob files themselves cleaned up (since
*all* SST files that rely on them get compacted away).

These targeted compactions are similar to periodic compactions in the sense
that they force certain SST files that otherwise would not get picked up to undergo
compaction and also in the sense that instead of merging files from multiple levels,
they target a single file. (Note: such compactions might still include neighboring files
from the same level due to the need of having a "clean cut" boundary but they never
include any files from any other level.)

This functionality is currently only supported with the leveled compaction style
and is inactive by default (since the default value is set to 1.0, i.e. 100%).

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8994

Test Plan: Ran `make check` and tested using `db_bench` and the stress/crash tests.

Reviewed By: riversand963

Differential Revision: D31489850

Pulled By: ltamasi

fbshipit-source-id: 44057d511726a0e2a03c5d9313d7511b3f0c4eab
2021-10-11 18:03:01 -07:00

522 lines
19 KiB
C++

// 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).
//
// 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 <string>
#include <utility>
#include <vector>
#include "db/compaction/compaction_picker_level.h"
#include "logging/log_buffer.h"
#include "test_util/sync_point.h"
namespace ROCKSDB_NAMESPACE {
bool LevelCompactionPicker::NeedsCompaction(
const VersionStorageInfo* vstorage) const {
if (!vstorage->ExpiredTtlFiles().empty()) {
return true;
}
if (!vstorage->FilesMarkedForPeriodicCompaction().empty()) {
return true;
}
if (!vstorage->BottommostFilesMarkedForCompaction().empty()) {
return true;
}
if (!vstorage->FilesMarkedForCompaction().empty()) {
return true;
}
if (!vstorage->FilesMarkedForForcedBlobGC().empty()) {
return true;
}
for (int i = 0; i <= vstorage->MaxInputLevel(); i++) {
if (vstorage->CompactionScore(i) >= 1) {
return true;
}
}
return false;
}
namespace {
// A class to build a leveled compaction step-by-step.
class LevelCompactionBuilder {
public:
LevelCompactionBuilder(const std::string& cf_name,
VersionStorageInfo* vstorage,
SequenceNumber earliest_mem_seqno,
CompactionPicker* compaction_picker,
LogBuffer* log_buffer,
const MutableCFOptions& mutable_cf_options,
const ImmutableOptions& ioptions,
const MutableDBOptions& mutable_db_options)
: cf_name_(cf_name),
vstorage_(vstorage),
earliest_mem_seqno_(earliest_mem_seqno),
compaction_picker_(compaction_picker),
log_buffer_(log_buffer),
mutable_cf_options_(mutable_cf_options),
ioptions_(ioptions),
mutable_db_options_(mutable_db_options) {}
// Pick and return a compaction.
Compaction* PickCompaction();
// Pick the initial files to compact to the next level. (or together
// in Intra-L0 compactions)
void SetupInitialFiles();
// If the initial files are from L0 level, pick other L0
// files if needed.
bool SetupOtherL0FilesIfNeeded();
// Based on initial files, setup other files need to be compacted
// in this compaction, accordingly.
bool SetupOtherInputsIfNeeded();
Compaction* GetCompaction();
// For the specfied level, pick a file that we want to compact.
// Returns false if there is no file to compact.
// If it returns true, inputs->files.size() will be exactly one.
// If level is 0 and there is already a compaction on that level, this
// function will return false.
bool PickFileToCompact();
// For L0->L0, picks the longest span of files that aren't currently
// undergoing compaction for which work-per-deleted-file decreases. The span
// always starts from the newest L0 file.
//
// Intra-L0 compaction is independent of all other files, so it can be
// performed even when L0->base_level compactions are blocked.
//
// Returns true if `inputs` is populated with a span of files to be compacted;
// otherwise, returns false.
bool PickIntraL0Compaction();
// Picks a file from level_files to compact.
// level_files is a vector of (level, file metadata) in ascending order of
// level. If compact_to_next_level is true, compact the file to the next
// level, otherwise, compact to the same level as the input file.
void PickFileToCompact(
const autovector<std::pair<int, FileMetaData*>>& level_files,
bool compact_to_next_level);
const std::string& cf_name_;
VersionStorageInfo* vstorage_;
SequenceNumber earliest_mem_seqno_;
CompactionPicker* compaction_picker_;
LogBuffer* log_buffer_;
int start_level_ = -1;
int output_level_ = -1;
int parent_index_ = -1;
int base_index_ = -1;
double start_level_score_ = 0;
bool is_manual_ = false;
CompactionInputFiles start_level_inputs_;
std::vector<CompactionInputFiles> compaction_inputs_;
CompactionInputFiles output_level_inputs_;
std::vector<FileMetaData*> grandparents_;
CompactionReason compaction_reason_ = CompactionReason::kUnknown;
const MutableCFOptions& mutable_cf_options_;
const ImmutableOptions& ioptions_;
const MutableDBOptions& mutable_db_options_;
// Pick a path ID to place a newly generated file, with its level
static uint32_t GetPathId(const ImmutableCFOptions& ioptions,
const MutableCFOptions& mutable_cf_options,
int level);
static const int kMinFilesForIntraL0Compaction = 4;
};
void LevelCompactionBuilder::PickFileToCompact(
const autovector<std::pair<int, FileMetaData*>>& level_files,
bool compact_to_next_level) {
for (auto& level_file : level_files) {
// If it's being compacted it has nothing to do here.
// If this assert() fails that means that some function marked some
// files as being_compacted, but didn't call ComputeCompactionScore()
assert(!level_file.second->being_compacted);
start_level_ = level_file.first;
if ((compact_to_next_level &&
start_level_ == vstorage_->num_non_empty_levels() - 1) ||
(start_level_ == 0 &&
!compaction_picker_->level0_compactions_in_progress()->empty())) {
continue;
}
if (compact_to_next_level) {
output_level_ =
(start_level_ == 0) ? vstorage_->base_level() : start_level_ + 1;
} else {
output_level_ = start_level_;
}
start_level_inputs_.files = {level_file.second};
start_level_inputs_.level = start_level_;
if (compaction_picker_->ExpandInputsToCleanCut(cf_name_, vstorage_,
&start_level_inputs_)) {
return;
}
}
start_level_inputs_.files.clear();
}
void LevelCompactionBuilder::SetupInitialFiles() {
// Find the compactions by size on all levels.
bool skipped_l0_to_base = false;
for (int i = 0; i < compaction_picker_->NumberLevels() - 1; i++) {
start_level_score_ = vstorage_->CompactionScore(i);
start_level_ = vstorage_->CompactionScoreLevel(i);
assert(i == 0 || start_level_score_ <= vstorage_->CompactionScore(i - 1));
if (start_level_score_ >= 1) {
if (skipped_l0_to_base && start_level_ == vstorage_->base_level()) {
// If L0->base_level compaction is pending, don't schedule further
// compaction from base level. Otherwise L0->base_level compaction
// may starve.
continue;
}
output_level_ =
(start_level_ == 0) ? vstorage_->base_level() : start_level_ + 1;
if (PickFileToCompact()) {
// found the compaction!
if (start_level_ == 0) {
// L0 score = `num L0 files` / `level0_file_num_compaction_trigger`
compaction_reason_ = CompactionReason::kLevelL0FilesNum;
} else {
// L1+ score = `Level files size` / `MaxBytesForLevel`
compaction_reason_ = CompactionReason::kLevelMaxLevelSize;
}
break;
} else {
// didn't find the compaction, clear the inputs
start_level_inputs_.clear();
if (start_level_ == 0) {
skipped_l0_to_base = true;
// L0->base_level may be blocked due to ongoing L0->base_level
// compactions. It may also be blocked by an ongoing compaction from
// base_level downwards.
//
// In these cases, to reduce L0 file count and thus reduce likelihood
// of write stalls, we can attempt compacting a span of files within
// L0.
if (PickIntraL0Compaction()) {
output_level_ = 0;
compaction_reason_ = CompactionReason::kLevelL0FilesNum;
break;
}
}
}
} else {
// Compaction scores are sorted in descending order, no further scores
// will be >= 1.
break;
}
}
if (!start_level_inputs_.empty()) {
return;
}
// if we didn't find a compaction, check if there are any files marked for
// compaction
parent_index_ = base_index_ = -1;
compaction_picker_->PickFilesMarkedForCompaction(
cf_name_, vstorage_, &start_level_, &output_level_, &start_level_inputs_);
if (!start_level_inputs_.empty()) {
compaction_reason_ = CompactionReason::kFilesMarkedForCompaction;
return;
}
// Bottommost Files Compaction on deleting tombstones
PickFileToCompact(vstorage_->BottommostFilesMarkedForCompaction(), false);
if (!start_level_inputs_.empty()) {
compaction_reason_ = CompactionReason::kBottommostFiles;
return;
}
// TTL Compaction
PickFileToCompact(vstorage_->ExpiredTtlFiles(), true);
if (!start_level_inputs_.empty()) {
compaction_reason_ = CompactionReason::kTtl;
return;
}
// Periodic Compaction
PickFileToCompact(vstorage_->FilesMarkedForPeriodicCompaction(), false);
if (!start_level_inputs_.empty()) {
compaction_reason_ = CompactionReason::kPeriodicCompaction;
return;
}
// Forced blob garbage collection
PickFileToCompact(vstorage_->FilesMarkedForForcedBlobGC(), false);
if (!start_level_inputs_.empty()) {
compaction_reason_ = CompactionReason::kForcedBlobGC;
return;
}
}
bool LevelCompactionBuilder::SetupOtherL0FilesIfNeeded() {
if (start_level_ == 0 && output_level_ != 0) {
return compaction_picker_->GetOverlappingL0Files(
vstorage_, &start_level_inputs_, output_level_, &parent_index_);
}
return true;
}
bool LevelCompactionBuilder::SetupOtherInputsIfNeeded() {
// Setup input files from output level. For output to L0, we only compact
// spans of files that do not interact with any pending compactions, so don't
// need to consider other levels.
if (output_level_ != 0) {
output_level_inputs_.level = output_level_;
if (!compaction_picker_->SetupOtherInputs(
cf_name_, mutable_cf_options_, vstorage_, &start_level_inputs_,
&output_level_inputs_, &parent_index_, base_index_)) {
return false;
}
compaction_inputs_.push_back(start_level_inputs_);
if (!output_level_inputs_.empty()) {
compaction_inputs_.push_back(output_level_inputs_);
}
// In some edge cases we could pick a compaction that will be compacting
// a key range that overlap with another running compaction, and both
// of them have the same output level. This could happen if
// (1) we are running a non-exclusive manual compaction
// (2) AddFile ingest a new file into the LSM tree
// We need to disallow this from happening.
if (compaction_picker_->FilesRangeOverlapWithCompaction(compaction_inputs_,
output_level_)) {
// This compaction output could potentially conflict with the output
// of a currently running compaction, we cannot run it.
return false;
}
compaction_picker_->GetGrandparents(vstorage_, start_level_inputs_,
output_level_inputs_, &grandparents_);
} else {
compaction_inputs_.push_back(start_level_inputs_);
}
return true;
}
Compaction* LevelCompactionBuilder::PickCompaction() {
// Pick up the first file to start compaction. It may have been extended
// to a clean cut.
SetupInitialFiles();
if (start_level_inputs_.empty()) {
return nullptr;
}
assert(start_level_ >= 0 && output_level_ >= 0);
// If it is a L0 -> base level compaction, we need to set up other L0
// files if needed.
if (!SetupOtherL0FilesIfNeeded()) {
return nullptr;
}
// Pick files in the output level and expand more files in the start level
// if needed.
if (!SetupOtherInputsIfNeeded()) {
return nullptr;
}
// Form a compaction object containing the files we picked.
Compaction* c = GetCompaction();
TEST_SYNC_POINT_CALLBACK("LevelCompactionPicker::PickCompaction:Return", c);
return c;
}
Compaction* LevelCompactionBuilder::GetCompaction() {
auto c = new Compaction(
vstorage_, ioptions_, mutable_cf_options_, mutable_db_options_,
std::move(compaction_inputs_), output_level_,
MaxFileSizeForLevel(mutable_cf_options_, output_level_,
ioptions_.compaction_style, vstorage_->base_level(),
ioptions_.level_compaction_dynamic_level_bytes),
mutable_cf_options_.max_compaction_bytes,
GetPathId(ioptions_, mutable_cf_options_, output_level_),
GetCompressionType(ioptions_, vstorage_, mutable_cf_options_,
output_level_, vstorage_->base_level()),
GetCompressionOptions(mutable_cf_options_, vstorage_, output_level_),
Temperature::kUnknown,
/* max_subcompactions */ 0, std::move(grandparents_), is_manual_,
start_level_score_, false /* deletion_compaction */, compaction_reason_);
// If it's level 0 compaction, make sure we don't execute any other level 0
// compactions in parallel
compaction_picker_->RegisterCompaction(c);
// Creating a compaction influences the compaction score because the score
// takes running compactions into account (by skipping files that are already
// being compacted). Since we just changed compaction score, we recalculate it
// here
vstorage_->ComputeCompactionScore(ioptions_, mutable_cf_options_);
return c;
}
/*
* Find the optimal path to place a file
* Given a level, finds the path where levels up to it will fit in levels
* up to and including this path
*/
uint32_t LevelCompactionBuilder::GetPathId(
const ImmutableCFOptions& ioptions,
const MutableCFOptions& mutable_cf_options, int level) {
uint32_t p = 0;
assert(!ioptions.cf_paths.empty());
// size remaining in the most recent path
uint64_t current_path_size = ioptions.cf_paths[0].target_size;
uint64_t level_size;
int cur_level = 0;
// max_bytes_for_level_base denotes L1 size.
// We estimate L0 size to be the same as L1.
level_size = mutable_cf_options.max_bytes_for_level_base;
// Last path is the fallback
while (p < ioptions.cf_paths.size() - 1) {
if (level_size <= current_path_size) {
if (cur_level == level) {
// Does desired level fit in this path?
return p;
} else {
current_path_size -= level_size;
if (cur_level > 0) {
if (ioptions.level_compaction_dynamic_level_bytes) {
// Currently, level_compaction_dynamic_level_bytes is ignored when
// multiple db paths are specified. https://github.com/facebook/
// rocksdb/blob/main/db/column_family.cc.
// Still, adding this check to avoid accidentally using
// max_bytes_for_level_multiplier_additional
level_size = static_cast<uint64_t>(
level_size * mutable_cf_options.max_bytes_for_level_multiplier);
} else {
level_size = static_cast<uint64_t>(
level_size * mutable_cf_options.max_bytes_for_level_multiplier *
mutable_cf_options.MaxBytesMultiplerAdditional(cur_level));
}
}
cur_level++;
continue;
}
}
p++;
current_path_size = ioptions.cf_paths[p].target_size;
}
return p;
}
bool LevelCompactionBuilder::PickFileToCompact() {
// level 0 files are overlapping. So we cannot pick more
// than one concurrent compactions at this level. This
// could be made better by looking at key-ranges that are
// being compacted at level 0.
if (start_level_ == 0 &&
!compaction_picker_->level0_compactions_in_progress()->empty()) {
TEST_SYNC_POINT("LevelCompactionPicker::PickCompactionBySize:0");
return false;
}
start_level_inputs_.clear();
assert(start_level_ >= 0);
// Pick the largest file in this level that is not already
// being compacted
const std::vector<int>& file_size =
vstorage_->FilesByCompactionPri(start_level_);
const std::vector<FileMetaData*>& level_files =
vstorage_->LevelFiles(start_level_);
unsigned int cmp_idx;
for (cmp_idx = vstorage_->NextCompactionIndex(start_level_);
cmp_idx < file_size.size(); cmp_idx++) {
int index = file_size[cmp_idx];
auto* f = level_files[index];
// do not pick a file to compact if it is being compacted
// from n-1 level.
if (f->being_compacted) {
continue;
}
start_level_inputs_.files.push_back(f);
start_level_inputs_.level = start_level_;
if (!compaction_picker_->ExpandInputsToCleanCut(cf_name_, vstorage_,
&start_level_inputs_) ||
compaction_picker_->FilesRangeOverlapWithCompaction(
{start_level_inputs_}, output_level_)) {
// A locked (pending compaction) input-level file was pulled in due to
// user-key overlap.
start_level_inputs_.clear();
continue;
}
// Now that input level is fully expanded, we check whether any output files
// are locked due to pending compaction.
//
// Note we rely on ExpandInputsToCleanCut() to tell us whether any output-
// level files are locked, not just the extra ones pulled in for user-key
// overlap.
InternalKey smallest, largest;
compaction_picker_->GetRange(start_level_inputs_, &smallest, &largest);
CompactionInputFiles output_level_inputs;
output_level_inputs.level = output_level_;
vstorage_->GetOverlappingInputs(output_level_, &smallest, &largest,
&output_level_inputs.files);
if (!output_level_inputs.empty() &&
!compaction_picker_->ExpandInputsToCleanCut(cf_name_, vstorage_,
&output_level_inputs)) {
start_level_inputs_.clear();
continue;
}
base_index_ = index;
break;
}
// store where to start the iteration in the next call to PickCompaction
vstorage_->SetNextCompactionIndex(start_level_, cmp_idx);
return start_level_inputs_.size() > 0;
}
bool LevelCompactionBuilder::PickIntraL0Compaction() {
start_level_inputs_.clear();
const std::vector<FileMetaData*>& level_files =
vstorage_->LevelFiles(0 /* level */);
if (level_files.size() <
static_cast<size_t>(
mutable_cf_options_.level0_file_num_compaction_trigger + 2) ||
level_files[0]->being_compacted) {
// If L0 isn't accumulating much files beyond the regular trigger, don't
// resort to L0->L0 compaction yet.
return false;
}
return FindIntraL0Compaction(level_files, kMinFilesForIntraL0Compaction,
port::kMaxUint64,
mutable_cf_options_.max_compaction_bytes,
&start_level_inputs_, earliest_mem_seqno_);
}
} // namespace
Compaction* LevelCompactionPicker::PickCompaction(
const std::string& cf_name, const MutableCFOptions& mutable_cf_options,
const MutableDBOptions& mutable_db_options, VersionStorageInfo* vstorage,
LogBuffer* log_buffer, SequenceNumber earliest_mem_seqno) {
LevelCompactionBuilder builder(cf_name, vstorage, earliest_mem_seqno, this,
log_buffer, mutable_cf_options, ioptions_,
mutable_db_options);
return builder.PickCompaction();
}
} // namespace ROCKSDB_NAMESPACE