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arangodb/arangod/RocksDBEngine/RocksDBCounterManager.cpp

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////////////////////////////////////////////////////////////////////////////////
/// DISCLAIMER
///
/// Copyright 2014-2017 ArangoDB GmbH, Cologne, Germany
/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
/// http://www.apache.org/licenses/LICENSE-2.0
///
/// Unless required by applicable law or agreed to in writing, software
/// distributed under the License is distributed on an "AS IS" BASIS,
/// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
/// See the License for the specific language governing permissions and
/// limitations under the License.
///
/// Copyright holder is ArangoDB GmbH, Cologne, Germany
///
/// @author Simon Grätzer
////////////////////////////////////////////////////////////////////////////////
#include "RocksDBCounterManager.h"
#include "Basics/ReadLocker.h"
#include "Basics/StringUtils.h"
#include "Basics/VelocyPackHelper.h"
#include "Basics/WriteLocker.h"
#include "Logger/Logger.h"
#include "RocksDBEngine/RocksDBCommon.h"
#include "RocksDBEngine/RocksDBKey.h"
#include "RocksDBEngine/RocksDBKeyBounds.h"
#include "RocksDBEngine/RocksDBValue.h"
#include "VocBase/ticks.h"
#include <rocksdb/utilities/transaction_db.h>
#include <rocksdb/utilities/write_batch_with_index.h>
#include <rocksdb/write_batch.h>
#include <velocypack/Iterator.h>
#include <velocypack/Parser.h>
#include <velocypack/Slice.h>
#include <velocypack/velocypack-aliases.h>
using namespace arangodb;
RocksDBCounterManager::CMValue::CMValue(VPackSlice const& slice)
: _sequenceNum(0), _count(0), _revisionId(0) {
if (!slice.isArray()) {
// got a somewhat invalid slice. probably old data from before the key
// structure changes
return;
}
velocypack::ArrayIterator array(slice);
if (array.valid()) {
this->_sequenceNum = (*array).getUInt();
this->_count = (*(++array)).getUInt();
this->_revisionId = (*(++array)).getUInt();
}
}
void RocksDBCounterManager::CMValue::serialize(VPackBuilder& b) const {
b.openArray();
b.add(VPackValue(this->_sequenceNum));
b.add(VPackValue(this->_count));
b.add(VPackValue(this->_revisionId));
b.close();
}
/// Constructor needs to be called synchrunously,
/// will load counts from the db and scan the WAL
RocksDBCounterManager::RocksDBCounterManager(rocksdb::DB* db)
: _syncing(false), _db(db) {
readSettings();
readCounterValues();
if (!_counters.empty()) {
if (parseRocksWAL()) {
sync(false);
}
}
}
RocksDBCounterManager::CounterAdjustment RocksDBCounterManager::loadCounter(
uint64_t objectId) const {
TRI_ASSERT(objectId != 0); // TODO fix this
READ_LOCKER(guard, _rwLock);
auto const& it = _counters.find(objectId);
if (it != _counters.end()) {
return CounterAdjustment(it->second._sequenceNum, it->second._count, 0,
it->second._revisionId);
}
return CounterAdjustment(); // do not create
}
/// collections / views / indexes can call this method to update
/// their total counts. Thread-Safe needs the snapshot so we know
/// the sequence number used
void RocksDBCounterManager::updateCounter(uint64_t objectId,
CounterAdjustment const& update) {
// From write_batch.cc in rocksdb: first 64 bits in the internal rep_
// buffer are the sequence number
/*TRI_ASSERT(trx->GetState() == rocksdb::Transaction::COMMITED);
rocksdb::WriteBatchWithIndex *batch = trx->GetWriteBatch();
rocksdb::SequenceNumber seq =
DecodeFixed64(batch->GetWriteBatch()->Data().data());*/
bool needsSync = false;
{
WRITE_LOCKER(guard, _rwLock);
auto it = _counters.find(objectId);
if (it != _counters.end()) {
it->second._count += update.added();
it->second._count -= update.removed();
// just use the latest trx info
if (update.sequenceNumber() > it->second._sequenceNum) {
it->second._sequenceNum = update.sequenceNumber();
it->second._revisionId = update.revisionId();
}
} else {
// insert new counter
_counters.emplace(std::make_pair(
objectId,
CMValue(update.sequenceNumber(), update.added() - update.removed(),
update.revisionId())));
needsSync = true; // only count values from WAL if they are in the DB
}
}
if (needsSync) {
sync(true);
}
}
arangodb::Result RocksDBCounterManager::setAbsoluteCounter(uint64_t objectId, uint64_t value) {
arangodb::Result res;
WRITE_LOCKER(guard, _rwLock);
auto it = _counters.find(objectId);
if (it != _counters.end()) {
it->second._count = value;
} else {
// nothing to do as the counter has never been written it can not be set to
// a value that would require correction. but we use the return value to
// signal that no sync is rquired
res.reset(TRI_ERROR_INTERNAL, "counter value not found - no sync required");
}
return res;
}
void RocksDBCounterManager::removeCounter(uint64_t objectId) {
WRITE_LOCKER(guard, _rwLock);
auto const& it = _counters.find(objectId);
if (it != _counters.end()) {
RocksDBKey key = RocksDBKey::CounterValue(it->first);
rocksdb::WriteOptions options;
rocksdb::Status s = _db->Delete(options, key.string());
if (!s.ok()) {
LOG_TOPIC(ERR, Logger::ENGINES) << "deleting counter failed";
}
_counters.erase(it);
}
}
/// Thread-Safe force sync
Result RocksDBCounterManager::sync(bool force) {
if (force) {
while (true) {
bool expected = false;
bool res = _syncing.compare_exchange_strong(
expected, true, std::memory_order_acquire, std::memory_order_relaxed);
if (res) {
break;
}
usleep(10000);
}
} else {
bool expected = false;
if (!_syncing.compare_exchange_strong(expected, true,
std::memory_order_acquire,
std::memory_order_relaxed)) {
return Result();
}
}
TRI_DEFER(_syncing = false);
std::unordered_map<uint64_t, CMValue> copy;
{ // block all updates
WRITE_LOCKER(guard, _rwLock);
copy = _counters;
}
rocksdb::WriteOptions writeOptions;
rocksdb::TransactionDB* db = rocksutils::globalRocksDB();
std::unique_ptr<rocksdb::Transaction> rtrx(
db->BeginTransaction(writeOptions));
VPackBuilder b;
for (std::pair<uint64_t, CMValue> const& pair : copy) {
// Skip values which we did not change
auto const& it = _syncedSeqNums.find(pair.first);
if (it != _syncedSeqNums.end() && it->second == pair.second._sequenceNum) {
continue;
}
b.clear();
pair.second.serialize(b);
RocksDBKey key = RocksDBKey::CounterValue(pair.first);
rocksdb::Slice value((char*)b.start(), b.size());
rocksdb::Status s = rtrx->Put(key.string(), value);
if (!s.ok()) {
rtrx->Rollback();
LOG_TOPIC(WARN, Logger::ENGINES) << "writing counters failed";
return rocksutils::convertStatus(s);
}
}
// now write global settings
b.clear();
b.openObject();
b.add("tick", VPackValue(std::to_string(TRI_CurrentTickServer())));
b.add("hlc", VPackValue(std::to_string(TRI_HybridLogicalClock())));
b.close();
VPackSlice slice = b.slice();
LOG_TOPIC(TRACE, Logger::ENGINES) << "writing settings: " << slice.toJson();
RocksDBKey key = RocksDBKey::SettingsValue();
rocksdb::Slice value(slice.startAs<char>(), slice.byteSize());
rocksdb::Status s = rtrx->Put(key.string(), value);
if (!s.ok()) {
LOG_TOPIC(WARN, Logger::ENGINES) << "writing settings failed";
rtrx->Rollback();
return rocksutils::convertStatus(s);
}
// we have to commit all counters in one batch
s = rtrx->Commit();
if (s.ok()) {
for (std::pair<uint64_t, CMValue> const& pair : copy) {
_syncedSeqNums[pair.first] = pair.second._sequenceNum;
}
}
return rocksutils::convertStatus(s);
}
void RocksDBCounterManager::readSettings() {
RocksDBKey key = RocksDBKey::SettingsValue();
std::string result;
rocksdb::Status status =
_db->Get(rocksdb::ReadOptions(), key.string(), &result);
if (status.ok()) {
// key may not be there, so don't fail when not found
VPackSlice slice = VPackSlice(result.data());
TRI_ASSERT(slice.isObject());
LOG_TOPIC(TRACE, Logger::ENGINES) << "read initial settings: "
<< slice.toJson();
if (!result.empty()) {
try {
uint64_t lastTick =
basics::VelocyPackHelper::stringUInt64(slice.get("tick"));
LOG_TOPIC(TRACE, Logger::ENGINES) << "using last tick: " << lastTick;
TRI_UpdateTickServer(lastTick);
if (slice.hasKey("hlc")) {
uint64_t lastHlc =
basics::VelocyPackHelper::stringUInt64(slice.get("hlc"));
LOG_TOPIC(TRACE, Logger::ENGINES) << "using last hlc: " << lastHlc;
TRI_HybridLogicalClock(lastHlc);
}
} catch (...) {
LOG_TOPIC(WARN, Logger::ENGINES)
<< "unable to read initial settings: invalid data";
}
}
}
}
/// Parse counter values from rocksdb
void RocksDBCounterManager::readCounterValues() {
WRITE_LOCKER(guard, _rwLock);
RocksDBKeyBounds bounds = RocksDBKeyBounds::CounterValues();
rocksdb::Comparator const* cmp = _db->GetOptions().comparator;
rocksdb::ReadOptions readOptions;
std::unique_ptr<rocksdb::Iterator> iter(_db->NewIterator(readOptions));
iter->Seek(bounds.start());
while (iter->Valid() && cmp->Compare(iter->key(), bounds.end()) < 0) {
uint64_t objectId = RocksDBKey::counterObjectId(iter->key());
auto const& it =
_counters.emplace(objectId, CMValue(VPackSlice(iter->value().data())));
_syncedSeqNums[objectId] = it.first->second._sequenceNum;
iter->Next();
}
}
/// WAL parser, no locking required here, because we have been locked from the
/// outside
struct WBReader final : public rocksdb::WriteBatch::Handler {
// must be set by the counter manager
std::unordered_map<uint64_t, rocksdb::SequenceNumber> seqStart;
std::unordered_map<uint64_t, RocksDBCounterManager::CounterAdjustment> deltas;
rocksdb::SequenceNumber currentSeqNum;
uint64_t _maxTick = 0;
uint64_t _maxHLC = 0;
WBReader() : currentSeqNum(0) {}
~WBReader() {
// update ticks after parsing wal
LOG_TOPIC(TRACE, Logger::ENGINES) << "max tick found in WAL: " << _maxTick << ", last HLC value: " << _maxHLC;
TRI_UpdateTickServer(_maxTick);
TRI_HybridLogicalClock(_maxHLC);
}
bool prepKey(const rocksdb::Slice& key) {
if (RocksDBKey::type(key) == RocksDBEntryType::Document) {
uint64_t objectId = RocksDBKey::counterObjectId(key);
auto const& it = seqStart.find(objectId);
if (it != seqStart.end()) {
if (deltas.find(objectId) == deltas.end()) {
deltas.emplace(objectId, RocksDBCounterManager::CounterAdjustment());
}
return it->second <= currentSeqNum;
}
}
return false;
}
void storeMaxHLC(uint64_t hlc) {
if (hlc > _maxHLC) {
_maxHLC = hlc;
}
}
void storeMaxTick(uint64_t tick) {
if (tick > _maxTick) {
_maxTick = tick;
}
}
void updateMaxTick(const rocksdb::Slice& key, const rocksdb::Slice& value) {
// RETURN (side-effect): update _maxTick
//
// extract max tick from Markers and store them as side-effect in
// _maxTick member variable that can be used later (dtor) to call
// TRI_UpdateTickServer (ticks.h)
// Markers: - collections (id,objectid) as tick and max tick in indexes
// array
// - documents - _rev (revision as maxtick)
// - databases
auto const type = RocksDBKey::type(key);
if (type == RocksDBEntryType::Document) {
storeMaxHLC(RocksDBKey::revisionId(key));
} else if (type == RocksDBEntryType::PrimaryIndexValue) {
// document key
StringRef ref = RocksDBKey::primaryKey(key);
TRI_ASSERT(!ref.empty());
// check if the key is numeric
if (ref[0] >= '1' && ref[0] <= '9') {
// numeric start byte. looks good
try {
// extract uint64_t value from key. this will throw if the key
// is non-numeric
uint64_t tick = basics::StringUtils::uint64_check(ref.data(), ref.size());
// if no previous _maxTick set or the numeric value found is
// "near" our previous _maxTick, then we update it
if (tick > _maxTick && (_maxTick == 0 || tick - _maxTick < 2048)) {
storeMaxTick(tick);
}
} catch (...) {
// non-numeric key. simply ignore it
}
}
} else if (type == RocksDBEntryType::Collection) {
storeMaxTick(RocksDBKey::collectionId(key));
auto slice = RocksDBValue::data(value);
storeMaxTick(basics::VelocyPackHelper::stringUInt64(slice, "objectId"));
VPackSlice indexes = slice.get("indexes");
for (VPackSlice const& idx : VPackArrayIterator(indexes)) {
storeMaxTick(
std::max(basics::VelocyPackHelper::stringUInt64(idx, "objectId"),
basics::VelocyPackHelper::stringUInt64(idx, "id")));
}
} else if (type == RocksDBEntryType::Database) {
storeMaxTick(RocksDBKey::databaseId(key));
} else if (type == RocksDBEntryType::View) {
LOG_TOPIC(ERR, Logger::STARTUP)
<< "tick update for views needs to be implemented";
}
}
void Put(const rocksdb::Slice& key, const rocksdb::Slice& value) override {
updateMaxTick(key, value);
if (prepKey(key)) {
uint64_t objectId = RocksDBKey::counterObjectId(key);
uint64_t revisionId = RocksDBKey::revisionId(key);
auto const& it = deltas.find(objectId);
if (it != deltas.end()) {
it->second._sequenceNum = currentSeqNum;
it->second._added++;
it->second._revisionId = revisionId;
}
}
}
void Delete(const rocksdb::Slice& key) override {
if (prepKey(key)) {
uint64_t objectId = RocksDBKey::counterObjectId(key);
uint64_t revisionId = RocksDBKey::revisionId(key);
auto const& it = deltas.find(objectId);
if (it != deltas.end()) {
it->second._sequenceNum = currentSeqNum;
it->second._removed++;
it->second._revisionId = revisionId;
}
}
}
void SingleDelete(const rocksdb::Slice& key) override { Delete(key); }
};
/// parse the WAL with the above handler parser class
bool RocksDBCounterManager::parseRocksWAL() {
WRITE_LOCKER(guard, _rwLock);
TRI_ASSERT(_counters.size() > 0);
rocksdb::SequenceNumber start = UINT64_MAX;
// Tell the WriteBatch reader the transaction markers to look for
auto handler = std::make_unique<WBReader>();
for (auto const& pair : _counters) {
handler->seqStart.emplace(pair.first, pair.second._sequenceNum);
start = std::min(start, pair.second._sequenceNum);
}
std::unique_ptr<rocksdb::TransactionLogIterator> iterator; // reader();
rocksdb::Status s = _db->GetUpdatesSince(start, &iterator);
if (!s.ok()) { // TODO do something?
return false;
}
while (iterator->Valid()) {
s = iterator->status();
if (s.ok()) {
rocksdb::BatchResult batch = iterator->GetBatch();
start = batch.sequence;
handler->currentSeqNum = start;
s = batch.writeBatchPtr->Iterate(handler.get());
}
if (!s.ok()) {
LOG_TOPIC(ERR, Logger::ENGINES) << "error during WAL scan";
break;
}
iterator->Next();
}
LOG_TOPIC(TRACE, Logger::ENGINES) << "finished WAL scan with "
<< handler->deltas.size();
for (std::pair<uint64_t, RocksDBCounterManager::CounterAdjustment> pair :
handler->deltas) {
auto const& it = _counters.find(pair.first);
if (it != _counters.end()) {
it->second._sequenceNum = start;
it->second._count += pair.second.added();
it->second._count -= pair.second.removed();
it->second._revisionId = pair.second._revisionId;
LOG_TOPIC(TRACE, Logger::ENGINES)
<< "WAL recovered " << pair.second.added() << " PUTs and "
<< pair.second.removed() << " DELETEs for a total of "
<< it->second._count;
}
}
return handler->deltas.size() > 0;
}
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