rocksdb/db/db_impl_secondary.cc
Yanqin Jin 9358178edc Support for single-primary, multi-secondary instances (#4899)
Summary:
This PR allows RocksDB to run in single-primary, multi-secondary process mode.
The writer is a regular RocksDB (e.g. an `DBImpl`) instance playing the role of a primary.
Multiple `DBImplSecondary` processes (secondaries) share the same set of SST files, MANIFEST, WAL files with the primary. Secondaries tail the MANIFEST of the primary and apply updates to their own in-memory state of the file system, e.g. `VersionStorageInfo`.

This PR has several components:
1. (Originally in #4745). Add a `PathNotFound` subcode to `IOError` to denote the failure when a secondary tries to open a file which has been deleted by the primary.

2. (Similar to #4602). Add `FragmentBufferedReader` to handle partially-read, trailing record at the end of a log from where future read can continue.

3. (Originally in #4710 and #4820). Add implementation of the secondary, i.e. `DBImplSecondary`.
3.1 Tail the primary's MANIFEST during recovery.
3.2 Tail the primary's MANIFEST during normal processing by calling `ReadAndApply`.
3.3 Tailing WAL will be in a future PR.

4. Add an example in 'examples/multi_processes_example.cc' to demonstrate the usage of secondary RocksDB instance in a multi-process setting. Instructions to run the example can be found at the beginning of the source code.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4899

Differential Revision: D14510945

Pulled By: riversand963

fbshipit-source-id: 4ac1c5693e6012ad23f7b4b42d3c374fecbe8886
2019-03-26 16:45:31 -07:00

357 lines
13 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).
#include "db/db_impl_secondary.h"
#include "db/db_iter.h"
#include "db/merge_context.h"
#include "monitoring/perf_context_imp.h"
#include "util/auto_roll_logger.h"
namespace rocksdb {
#ifndef ROCKSDB_LITE
DBImplSecondary::DBImplSecondary(const DBOptions& db_options,
const std::string& dbname)
: DBImpl(db_options, dbname) {
ROCKS_LOG_INFO(immutable_db_options_.info_log,
"Opening the db in secondary mode");
LogFlush(immutable_db_options_.info_log);
}
DBImplSecondary::~DBImplSecondary() {}
Status DBImplSecondary::Recover(
const std::vector<ColumnFamilyDescriptor>& column_families,
bool /*readonly*/, bool /*error_if_log_file_exist*/,
bool /*error_if_data_exists_in_logs*/) {
mutex_.AssertHeld();
Status s;
s = static_cast<ReactiveVersionSet*>(versions_.get())
->Recover(column_families, &manifest_reader_, &manifest_reporter_,
&manifest_reader_status_);
if (!s.ok()) {
return s;
}
if (immutable_db_options_.paranoid_checks && s.ok()) {
s = CheckConsistency();
}
// Initial max_total_in_memory_state_ before recovery logs.
max_total_in_memory_state_ = 0;
for (auto cfd : *versions_->GetColumnFamilySet()) {
auto* mutable_cf_options = cfd->GetLatestMutableCFOptions();
max_total_in_memory_state_ += mutable_cf_options->write_buffer_size *
mutable_cf_options->max_write_buffer_number;
}
if (s.ok()) {
default_cf_handle_ = new ColumnFamilyHandleImpl(
versions_->GetColumnFamilySet()->GetDefault(), this, &mutex_);
default_cf_internal_stats_ = default_cf_handle_->cfd()->internal_stats();
single_column_family_mode_ =
versions_->GetColumnFamilySet()->NumberOfColumnFamilies() == 1;
}
// TODO: attempt to recover from WAL files.
return s;
}
// Implementation of the DB interface
Status DBImplSecondary::Get(const ReadOptions& read_options,
ColumnFamilyHandle* column_family, const Slice& key,
PinnableSlice* value) {
return GetImpl(read_options, column_family, key, value);
}
Status DBImplSecondary::GetImpl(const ReadOptions& read_options,
ColumnFamilyHandle* column_family,
const Slice& key, PinnableSlice* pinnable_val) {
assert(pinnable_val != nullptr);
PERF_CPU_TIMER_GUARD(get_cpu_nanos, env_);
StopWatch sw(env_, stats_, DB_GET);
PERF_TIMER_GUARD(get_snapshot_time);
auto cfh = static_cast<ColumnFamilyHandleImpl*>(column_family);
ColumnFamilyData* cfd = cfh->cfd();
if (tracer_) {
InstrumentedMutexLock lock(&trace_mutex_);
if (tracer_) {
tracer_->Get(column_family, key);
}
}
// Acquire SuperVersion
SuperVersion* super_version = GetAndRefSuperVersion(cfd);
SequenceNumber snapshot = versions_->LastSequence();
MergeContext merge_context;
SequenceNumber max_covering_tombstone_seq = 0;
Status s;
LookupKey lkey(key, snapshot);
PERF_TIMER_STOP(get_snapshot_time);
bool done = false;
if (super_version->mem->Get(lkey, pinnable_val->GetSelf(), &s, &merge_context,
&max_covering_tombstone_seq, read_options)) {
done = true;
pinnable_val->PinSelf();
RecordTick(stats_, MEMTABLE_HIT);
} else if ((s.ok() || s.IsMergeInProgress()) &&
super_version->imm->Get(
lkey, pinnable_val->GetSelf(), &s, &merge_context,
&max_covering_tombstone_seq, read_options)) {
done = true;
pinnable_val->PinSelf();
RecordTick(stats_, MEMTABLE_HIT);
}
if (!done && !s.ok() && !s.IsMergeInProgress()) {
ReturnAndCleanupSuperVersion(cfd, super_version);
return s;
}
if (!done) {
PERF_TIMER_GUARD(get_from_output_files_time);
super_version->current->Get(read_options, lkey, pinnable_val, &s,
&merge_context, &max_covering_tombstone_seq);
RecordTick(stats_, MEMTABLE_MISS);
}
{
PERF_TIMER_GUARD(get_post_process_time);
ReturnAndCleanupSuperVersion(cfd, super_version);
RecordTick(stats_, NUMBER_KEYS_READ);
size_t size = pinnable_val->size();
RecordTick(stats_, BYTES_READ, size);
RecordTimeToHistogram(stats_, BYTES_PER_READ, size);
PERF_COUNTER_ADD(get_read_bytes, size);
}
return s;
}
Iterator* DBImplSecondary::NewIterator(const ReadOptions& read_options,
ColumnFamilyHandle* column_family) {
if (read_options.managed) {
return NewErrorIterator(
Status::NotSupported("Managed iterator is not supported anymore."));
}
if (read_options.read_tier == kPersistedTier) {
return NewErrorIterator(Status::NotSupported(
"ReadTier::kPersistedData is not yet supported in iterators."));
}
Iterator* result = nullptr;
auto cfh = reinterpret_cast<ColumnFamilyHandleImpl*>(column_family);
auto cfd = cfh->cfd();
ReadCallback* read_callback = nullptr; // No read callback provided.
if (read_options.tailing) {
return NewErrorIterator(Status::NotSupported(
"tailing iterator not supported in secondary mode"));
} else if (read_options.snapshot != nullptr) {
// TODO (yanqin) support snapshot.
return NewErrorIterator(
Status::NotSupported("snapshot not supported in secondary mode"));
} else {
auto snapshot = versions_->LastSequence();
result = NewIteratorImpl(read_options, cfd, snapshot, read_callback);
}
return result;
}
ArenaWrappedDBIter* DBImplSecondary::NewIteratorImpl(
const ReadOptions& read_options, ColumnFamilyData* cfd,
SequenceNumber snapshot, ReadCallback* read_callback) {
assert(nullptr != cfd);
SuperVersion* super_version = cfd->GetReferencedSuperVersion(&mutex_);
auto db_iter = NewArenaWrappedDbIterator(
env_, read_options, *cfd->ioptions(), super_version->mutable_cf_options,
snapshot,
super_version->mutable_cf_options.max_sequential_skip_in_iterations,
super_version->version_number, read_callback);
auto internal_iter =
NewInternalIterator(read_options, cfd, super_version, db_iter->GetArena(),
db_iter->GetRangeDelAggregator(), snapshot);
db_iter->SetIterUnderDBIter(internal_iter);
return db_iter;
}
Status DBImplSecondary::NewIterators(
const ReadOptions& read_options,
const std::vector<ColumnFamilyHandle*>& column_families,
std::vector<Iterator*>* iterators) {
if (read_options.managed) {
return Status::NotSupported("Managed iterator is not supported anymore.");
}
if (read_options.read_tier == kPersistedTier) {
return Status::NotSupported(
"ReadTier::kPersistedData is not yet supported in iterators.");
}
ReadCallback* read_callback = nullptr; // No read callback provided.
if (iterators == nullptr) {
return Status::InvalidArgument("iterators not allowed to be nullptr");
}
iterators->clear();
iterators->reserve(column_families.size());
if (read_options.tailing) {
return Status::NotSupported(
"tailing iterator not supported in secondary mode");
} else if (read_options.snapshot != nullptr) {
// TODO (yanqin) support snapshot.
return Status::NotSupported("snapshot not supported in secondary mode");
} else {
SequenceNumber read_seq = versions_->LastSequence();
for (auto cfh : column_families) {
ColumnFamilyData* cfd = static_cast<ColumnFamilyHandleImpl*>(cfh)->cfd();
iterators->push_back(
NewIteratorImpl(read_options, cfd, read_seq, read_callback));
}
}
return Status::OK();
}
Status DBImplSecondary::TryCatchUpWithPrimary() {
assert(versions_.get() != nullptr);
assert(manifest_reader_.get() != nullptr);
Status s;
std::unordered_set<ColumnFamilyData*> cfds_changed;
InstrumentedMutexLock lock_guard(&mutex_);
s = static_cast<ReactiveVersionSet*>(versions_.get())
->ReadAndApply(&mutex_, &manifest_reader_, &cfds_changed);
if (s.ok()) {
SuperVersionContext sv_context(true /* create_superversion */);
for (auto cfd : cfds_changed) {
sv_context.NewSuperVersion();
cfd->InstallSuperVersion(&sv_context, &mutex_);
}
sv_context.Clean();
}
return s;
}
Status DB::OpenAsSecondary(const Options& options, const std::string& dbname,
const std::string& secondary_path, DB** dbptr) {
*dbptr = nullptr;
DBOptions db_options(options);
ColumnFamilyOptions cf_options(options);
std::vector<ColumnFamilyDescriptor> column_families;
column_families.emplace_back(kDefaultColumnFamilyName, cf_options);
std::vector<ColumnFamilyHandle*> handles;
Status s = DB::OpenAsSecondary(db_options, dbname, secondary_path,
column_families, &handles, dbptr);
if (s.ok()) {
assert(handles.size() == 1);
delete handles[0];
}
return s;
}
Status DB::OpenAsSecondary(
const DBOptions& db_options, const std::string& dbname,
const std::string& secondary_path,
const std::vector<ColumnFamilyDescriptor>& column_families,
std::vector<ColumnFamilyHandle*>* handles, DB** dbptr) {
*dbptr = nullptr;
if (db_options.max_open_files != -1) {
// TODO (yanqin) maybe support max_open_files != -1 by creating hard links
// on SST files so that db secondary can still have access to old SSTs
// while primary instance may delete original.
return Status::InvalidArgument("require max_open_files to be -1");
}
DBOptions tmp_opts(db_options);
if (nullptr == tmp_opts.info_log) {
Env* env = tmp_opts.env;
assert(env != nullptr);
std::string secondary_abs_path;
env->GetAbsolutePath(secondary_path, &secondary_abs_path);
std::string fname = InfoLogFileName(secondary_path, secondary_abs_path,
tmp_opts.db_log_dir);
env->CreateDirIfMissing(secondary_path);
if (tmp_opts.log_file_time_to_roll > 0 || tmp_opts.max_log_file_size > 0) {
AutoRollLogger* result = new AutoRollLogger(
env, secondary_path, tmp_opts.db_log_dir, tmp_opts.max_log_file_size,
tmp_opts.log_file_time_to_roll, tmp_opts.info_log_level);
Status s = result->GetStatus();
if (!s.ok()) {
delete result;
} else {
tmp_opts.info_log.reset(result);
}
}
if (nullptr == tmp_opts.info_log) {
env->RenameFile(
fname, OldInfoLogFileName(secondary_path, env->NowMicros(),
secondary_abs_path, tmp_opts.db_log_dir));
Status s = env->NewLogger(fname, &(tmp_opts.info_log));
if (tmp_opts.info_log != nullptr) {
tmp_opts.info_log->SetInfoLogLevel(tmp_opts.info_log_level);
}
}
}
assert(tmp_opts.info_log != nullptr);
handles->clear();
DBImplSecondary* impl = new DBImplSecondary(tmp_opts, dbname);
impl->versions_.reset(new ReactiveVersionSet(
dbname, &impl->immutable_db_options_, impl->env_options_,
impl->table_cache_.get(), impl->write_buffer_manager_,
&impl->write_controller_));
impl->column_family_memtables_.reset(
new ColumnFamilyMemTablesImpl(impl->versions_->GetColumnFamilySet()));
impl->mutex_.Lock();
Status s = impl->Recover(column_families, true, false, false);
if (s.ok()) {
for (auto cf : column_families) {
auto cfd =
impl->versions_->GetColumnFamilySet()->GetColumnFamily(cf.name);
if (nullptr == cfd) {
s = Status::InvalidArgument("Column family not found: ", cf.name);
break;
}
handles->push_back(new ColumnFamilyHandleImpl(cfd, impl, &impl->mutex_));
}
}
SuperVersionContext sv_context(true /* create_superversion */);
if (s.ok()) {
for (auto cfd : *impl->versions_->GetColumnFamilySet()) {
sv_context.NewSuperVersion();
cfd->InstallSuperVersion(&sv_context, &impl->mutex_);
}
}
impl->mutex_.Unlock();
sv_context.Clean();
if (s.ok()) {
*dbptr = impl;
for (auto h : *handles) {
impl->NewThreadStatusCfInfo(
reinterpret_cast<ColumnFamilyHandleImpl*>(h)->cfd());
}
} else {
for (auto h : *handles) {
delete h;
}
handles->clear();
delete impl;
}
return s;
}
#else // !ROCKSDB_LITE
Status DB::OpenAsSecondary(const Options& /*options*/,
const std::string& /*name*/,
const std::string& /*secondary_path*/,
DB** /*dbptr*/) {
return Status::NotSupported("Not supported in ROCKSDB_LITE.");
}
Status DB::OpenAsSecondary(
const DBOptions& /*db_options*/, const std::string& /*dbname*/,
const std::string& /*secondary_path*/,
const std::vector<ColumnFamilyDescriptor>& /*column_families*/,
std::vector<ColumnFamilyHandle*>* /*handles*/, DB** /*dbptr*/) {
return Status::NotSupported("Not supported in ROCKSDB_LITE.");
}
#endif // !ROCKSDB_LITE
} // namespace rocksdb