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dragonfly/src/server/transaction.cc
Vladislav 08d2fa52e1
fix: fixes for v1.14.0 (#2473) 
* fix: fixes for v1.14.0

Stop writing to the replication ring_buffer
Stop allocating in TopKeys
Tighter CHECKs around tx execution.

---------

Signed-off-by: Vladislav Oleshko <vlad@dragonflydb.io>
2024-01-25 11:23:14 +00:00

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// Copyright 2022, DragonflyDB authors. All rights reserved.
// See LICENSE for licensing terms.
//
#include "server/transaction.h"
#include <absl/strings/match.h>
#include "base/logging.h"
#include "server/blocking_controller.h"
#include "server/command_registry.h"
#include "server/db_slice.h"
#include "server/engine_shard_set.h"
#include "server/journal/journal.h"
#include "server/server_state.h"
ABSL_FLAG(uint32_t, tx_queue_warning_len, 96,
"Length threshold for warning about long transaction queue");
namespace dfly {
using namespace std;
using namespace util;
using absl::StrCat;
thread_local Transaction::TLTmpSpace Transaction::tmp_space;
namespace {
atomic_uint64_t op_seq{1};
constexpr size_t kTransSize [[maybe_unused]] = sizeof(Transaction);
void AnalyzeTxQueue(const EngineShard* shard, const TxQueue* txq) {
unsigned q_limit = absl::GetFlag(FLAGS_tx_queue_warning_len);
if (txq->size() > q_limit) {
static thread_local time_t last_log_time = 0;
// TODO: glog provides LOG_EVERY_T, which uses precise clock.
// We should introduce inside helio LOG_PERIOD_ATLEAST macro that takes seconds and
// uses low precision clock.
time_t now = time(nullptr);
if (now >= last_log_time + 10) {
last_log_time = now;
EngineShard::TxQueueInfo info = shard->AnalyzeTxQueue();
string msg =
StrCat("TxQueue is too long. Tx count:", info.tx_total, ", armed:", info.tx_armed,
", runnable:", info.tx_runnable, ", total locks: ", info.total_locks,
", contended locks: ", info.contended_locks, "\n");
absl::StrAppend(&msg, "max contention score: ", info.max_contention_score,
", lock: ", info.max_contention_lock_name,
", poll_executions:", shard->stats().poll_execution_total);
const Transaction* cont_tx = shard->GetContTx();
if (cont_tx) {
absl::StrAppend(&msg, " continuation_tx: ", cont_tx->DebugId(), " ",
cont_tx->IsArmedInShard(shard->shard_id()) ? " armed" : "");
}
LOG(WARNING) << msg;
}
}
}
void RecordTxScheduleStats(const Transaction* tx) {
auto* ss = ServerState::tlocal();
DCHECK(ss);
ss->stats.tx_width_freq_arr[tx->GetUniqueShardCnt() - 1]++;
if (tx->IsGlobal()) {
ss->stats.tx_type_cnt[ServerState::GLOBAL]++;
} else {
ss->stats.tx_type_cnt[ServerState::NORMAL]++;
}
}
} // namespace
IntentLock::Mode Transaction::LockMode() const {
return cid_->IsReadOnly() ? IntentLock::SHARED : IntentLock::EXCLUSIVE;
}
/**
* @brief Construct a new Transaction:: Transaction object
*
* @param cid
* @param ess
* @param cs
*/
Transaction::Transaction(const CommandId* cid) : cid_{cid} {
string_view cmd_name(cid_->name());
if (cmd_name == "EXEC" || cmd_name == "EVAL" || cmd_name == "EVALSHA") {
multi_.reset(new MultiData);
multi_->shard_journal_write.resize(shard_set->size(), false);
multi_->mode = NOT_DETERMINED;
multi_->role = DEFAULT;
}
}
Transaction::Transaction(const Transaction* parent, ShardId shard_id, std::optional<SlotId> slot_id)
: multi_{make_unique<MultiData>()},
txid_{parent->txid()},
unique_shard_cnt_{1},
unique_shard_id_{shard_id} {
if (parent->multi_) {
multi_->mode = parent->multi_->mode;
} else {
// Use squashing mechanism for inline execution of single-shard EVAL
multi_->mode = LOCK_AHEAD;
}
multi_->role = SQUASHED_STUB;
time_now_ms_ = parent->time_now_ms_;
if (slot_id.has_value()) {
unique_slot_checker_.Add(*slot_id);
}
}
Transaction::~Transaction() {
DVLOG(3) << "Transaction " << StrCat(Name(), "@", txid_, "/", unique_shard_cnt_, ")")
<< " destroyed";
}
void Transaction::InitBase(DbIndex dbid, CmdArgList args) {
global_ = false;
db_index_ = dbid;
full_args_ = args;
local_result_ = OpStatus::OK;
}
void Transaction::InitGlobal() {
DCHECK(!multi_ || (multi_->mode == GLOBAL || multi_->mode == NON_ATOMIC));
global_ = true;
EnableAllShards();
}
void Transaction::BuildShardIndex(const KeyIndex& key_index, bool rev_mapping,
std::vector<PerShardCache>* out) {
auto args = full_args_;
auto& shard_index = *out;
auto add = [this, rev_mapping, &shard_index](uint32_t sid, uint32_t i) {
string_view val = ArgS(full_args_, i);
shard_index[sid].args.push_back(val);
if (rev_mapping)
shard_index[sid].original_index.push_back(i);
};
if (key_index.bonus) {
DCHECK(key_index.step == 1);
string_view key = ArgS(args, *key_index.bonus);
unique_slot_checker_.Add(key);
uint32_t sid = Shard(key, shard_data_.size());
add(sid, *key_index.bonus);
}
for (unsigned i = key_index.start; i < key_index.end; ++i) {
string_view key = ArgS(args, i);
unique_slot_checker_.Add(key);
uint32_t sid = Shard(key, shard_data_.size());
add(sid, i);
DCHECK_LE(key_index.step, 2u);
if (key_index.step == 2) { // Handle value associated with preceding key.
add(sid, ++i);
}
}
}
void Transaction::InitShardData(absl::Span<const PerShardCache> shard_index, size_t num_args,
bool rev_mapping) {
args_.reserve(num_args);
if (rev_mapping)
reverse_index_.reserve(num_args);
// Store the concatenated per-shard arguments from the shard index inside args_
// and make each shard data point to its own sub-span inside args_.
for (size_t i = 0; i < shard_data_.size(); ++i) {
auto& sd = shard_data_[i];
auto& si = shard_index[i];
sd.arg_count = si.args.size();
sd.arg_start = args_.size();
// Multi transactions can re-initialize on different shards, so clear ACTIVE flag.
DCHECK_EQ(sd.local_mask & ACTIVE, 0);
if (sd.arg_count == 0)
continue;
sd.local_mask |= ACTIVE;
unique_shard_cnt_++;
unique_shard_id_ = i;
for (size_t j = 0; j < si.args.size(); ++j) {
args_.push_back(si.args[j]);
if (rev_mapping)
reverse_index_.push_back(si.original_index[j]);
}
}
CHECK_EQ(args_.size(), num_args);
}
void Transaction::RecordMultiLocks(const KeyIndex& key_index) {
DCHECK(multi_);
DCHECK(!multi_->lock_mode);
if (multi_->mode == NON_ATOMIC)
return;
auto lock_key = [this](string_view key) { multi_->locks.emplace(KeyLockArgs::GetLockKey(key)); };
multi_->lock_mode.emplace(LockMode());
for (size_t i = key_index.start; i < key_index.end; i += key_index.step)
lock_key(ArgS(full_args_, i));
if (key_index.bonus)
lock_key(ArgS(full_args_, *key_index.bonus));
DCHECK(IsAtomicMulti());
DCHECK(multi_->mode == GLOBAL || !multi_->locks.empty());
}
void Transaction::StoreKeysInArgs(KeyIndex key_index, bool rev_mapping) {
DCHECK(!key_index.bonus);
DCHECK(key_index.step == 1u || key_index.step == 2u);
// even for a single key we may have multiple arguments per key (MSET).
for (unsigned j = key_index.start; j < key_index.end; j++) {
args_.push_back(ArgS(full_args_, j));
if (key_index.step == 2)
args_.push_back(ArgS(full_args_, ++j));
}
if (rev_mapping) {
reverse_index_.resize(args_.size());
for (unsigned j = 0; j < reverse_index_.size(); ++j) {
reverse_index_[j] = j + key_index.start;
}
}
}
/**
*
* There are 4 options that we consider here:
* a. T spans a single shard and it's not multi.
* unique_shard_id_ is predefined before the schedule() is called.
* In that case only a single thread will be scheduled and it will use shard_data[0] just because
* shard_data.size() = 1. Coordinator thread can access any data because there is a
* schedule barrier between InitByArgs and RunInShard/IsArmedInShard functions.
* b. T spans multiple shards and its not multi
* In that case multiple threads will be scheduled. Similarly they have a schedule barrier,
* and IsArmedInShard can read any variable from shard_data[x].
* c. Trans spans a single shard and it's multi. shard_data has size of ess_.size.
* IsArmedInShard will check shard_data[x].
* d. Trans spans multiple shards and it's multi. Similarly shard_data[x] will be checked.
* unique_shard_cnt_ and unique_shard_id_ are not accessed until shard_data[x] is armed, hence
* we have a barrier between coordinator and engine-threads. Therefore there should not be
* data races.
*
**/
void Transaction::InitByKeys(const KeyIndex& key_index) {
if (key_index.start == full_args_.size()) { // eval with 0 keys.
CHECK(absl::StartsWith(cid_->name(), "EVAL")) << cid_->name();
return;
}
DCHECK_LT(key_index.start, full_args_.size());
bool needs_reverse_mapping = cid_->opt_mask() & CO::REVERSE_MAPPING;
// Stub transactions always operate only on single shard.
bool is_stub = multi_ && multi_->role == SQUASHED_STUB;
if ((key_index.HasSingleKey() && !IsAtomicMulti()) || is_stub) {
DCHECK(!IsActiveMulti() || multi_->mode == NON_ATOMIC);
// We don't have to split the arguments by shards, so we can copy them directly.
StoreKeysInArgs(key_index, needs_reverse_mapping);
unique_shard_cnt_ = 1;
if (is_stub) // stub transactions don't migrate
DCHECK_EQ(unique_shard_id_, Shard(args_.front(), shard_set->size()));
else
unique_shard_id_ = Shard(args_.front(), shard_set->size());
// Multi transactions that execute commands on their own (not stubs) can't shrink the backing
// array, as it still might be read by leftover callbacks.
shard_data_.resize(IsActiveMulti() ? shard_set->size() : 1);
shard_data_[SidToId(unique_shard_id_)].local_mask |= ACTIVE;
return;
}
shard_data_.resize(shard_set->size()); // shard_data isn't sparse, so we must allocate for all :(
DCHECK(key_index.step == 1 || key_index.step == 2);
DCHECK(key_index.step != 2 || (full_args_.size() % 2) == 0);
// Safe, because flow below is not preemptive.
auto& shard_index = tmp_space.GetShardIndex(shard_data_.size());
// Distribute all the arguments by shards.
BuildShardIndex(key_index, needs_reverse_mapping, &shard_index);
// Initialize shard data based on distributed arguments.
InitShardData(shard_index, key_index.num_args(), needs_reverse_mapping);
if (multi_ && !multi_->lock_mode)
RecordMultiLocks(key_index);
DVLOG(1) << "InitByArgs " << DebugId() << " " << args_.front();
// Compress shard data, if we occupy only one shard.
if (unique_shard_cnt_ == 1) {
PerShardData* sd;
if (IsActiveMulti()) {
sd = &shard_data_[SidToId(unique_shard_id_)];
DCHECK(sd->local_mask & ACTIVE);
} else {
shard_data_.resize(1);
sd = &shard_data_.front();
sd->local_mask |= ACTIVE;
}
sd->arg_count = -1;
sd->arg_start = -1;
}
// Validation. Check reverse mapping was built correctly.
if (needs_reverse_mapping) {
for (size_t i = 0; i < args_.size(); ++i) {
DCHECK_EQ(args_[i], ArgS(full_args_, reverse_index_[i])) << full_args_;
}
}
// Validation.
for (const auto& sd : shard_data_) {
// sd.local_mask may be non-zero for multi transactions with instant locking.
// Specifically EVALs may maintain state between calls.
DCHECK(!sd.is_armed.load(std::memory_order_relaxed));
if (!multi_) {
DCHECK_EQ(TxQueue::kEnd, sd.pq_pos);
}
}
}
OpStatus Transaction::InitByArgs(DbIndex index, CmdArgList args) {
InitBase(index, args);
if ((cid_->opt_mask() & CO::GLOBAL_TRANS) > 0) {
InitGlobal();
return OpStatus::OK;
}
if ((cid_->opt_mask() & CO::NO_KEY_TRANSACTIONAL) > 0) {
if ((cid_->opt_mask() & CO::NO_KEY_TX_SPAN_ALL) > 0)
EnableAllShards();
else
EnableShard(0);
return OpStatus::OK;
}
DCHECK_EQ(unique_shard_cnt_, 0u);
DCHECK(args_.empty());
OpResult<KeyIndex> key_index = DetermineKeys(cid_, args);
if (!key_index)
return key_index.status();
InitByKeys(*key_index);
return OpStatus::OK;
}
void Transaction::PrepareSquashedMultiHop(const CommandId* cid,
absl::FunctionRef<bool(ShardId)> enabled) {
CHECK(multi_->mode == GLOBAL || multi_->mode == LOCK_AHEAD);
MultiSwitchCmd(cid);
multi_->role = SQUASHER;
InitBase(db_index_, {});
// Because squashing already determines active shards by partitioning commands,
// we don't have to work with keys manually and can just mark active shards.
// The partitioned commands know it's keys and assume they have correct access.
DCHECK_EQ(shard_data_.size(), shard_set->size());
for (unsigned i = 0; i < shard_data_.size(); i++) {
if (enabled(i)) {
shard_data_[i].local_mask |= ACTIVE;
unique_shard_cnt_++;
unique_shard_id_ = i;
} else {
shard_data_[i].local_mask &= ~ACTIVE;
}
shard_data_[i].arg_start = 0;
shard_data_[i].arg_count = 0;
}
}
void Transaction::StartMultiGlobal(DbIndex dbid) {
CHECK(multi_);
CHECK(shard_data_.empty()); // Make sure default InitByArgs didn't run.
multi_->mode = GLOBAL;
InitBase(dbid, {});
InitGlobal();
multi_->lock_mode = IntentLock::EXCLUSIVE;
ScheduleInternal();
}
void Transaction::StartMultiLockedAhead(DbIndex dbid, CmdArgList keys) {
DVLOG(1) << "StartMultiLockedAhead on " << keys.size() << " keys";
DCHECK(multi_);
DCHECK(shard_data_.empty()); // Make sure default InitByArgs didn't run.
multi_->mode = LOCK_AHEAD;
InitBase(dbid, keys);
InitByKeys(KeyIndex::Range(0, keys.size()));
ScheduleInternal();
}
void Transaction::StartMultiNonAtomic() {
DCHECK(multi_);
multi_->mode = NON_ATOMIC;
}
void Transaction::MultiSwitchCmd(const CommandId* cid) {
DCHECK(multi_);
DCHECK(!cb_ptr_);
multi_->cmd_seq_num++;
if (multi_->role != SQUASHED_STUB) // stub transactions don't migrate between threads
unique_shard_id_ = 0;
unique_shard_cnt_ = 0;
args_.clear();
reverse_index_.clear();
cid_ = cid;
cb_ptr_ = nullptr;
for (auto& sd : shard_data_) {
sd.arg_count = sd.arg_start = 0;
if (multi_->mode == NON_ATOMIC) {
sd.local_mask = 0; // Non atomic transactions schedule each time, so remove all flags
DCHECK_EQ(sd.pq_pos, TxQueue::kEnd);
} else {
DCHECK(IsAtomicMulti()); // Every command determines it's own active shards
sd.local_mask &= ~ACTIVE; // so remove ACTIVE flags, but keep KEYLOCK_ACQUIRED
}
DCHECK(!sd.is_armed.load(memory_order_relaxed));
}
if (multi_->mode == NON_ATOMIC) {
coordinator_state_ = 0;
txid_ = 0;
} else if (multi_->role == SQUASHED_STUB) {
DCHECK_EQ(coordinator_state_, 0u);
}
if (multi_->role == SQUASHER)
multi_->role = DEFAULT;
}
string Transaction::DebugId() const {
DCHECK_GT(use_count_.load(memory_order_relaxed), 0u);
string res = StrCat(Name(), "@", txid_, "/", unique_shard_cnt_);
if (multi_) {
absl::StrAppend(&res, ":", multi_->cmd_seq_num);
}
absl::StrAppend(&res, " (", trans_id(this), ")");
return res;
}
void Transaction::PrepareMultiForScheduleSingleHop(ShardId sid, DbIndex db, CmdArgList args) {
multi_.reset();
InitBase(db, args);
EnableShard(sid);
OpResult<KeyIndex> key_index = DetermineKeys(cid_, args);
CHECK(key_index);
StoreKeysInArgs(*key_index, false);
}
// Runs in the dbslice thread. Returns true if the transaction continues running in the thread.
bool Transaction::RunInShard(EngineShard* shard, bool txq_ooo) {
DCHECK_GT(run_count_.load(memory_order_relaxed), 0u);
CHECK(cb_ptr_) << DebugId();
DCHECK_GT(txid_, 0u);
// Unlike with regular transactions we do not acquire locks upon scheduling
// because Scheduling is done before multi-exec batch is executed. Therefore we
// lock keys right before the execution of each statement.
unsigned idx = SidToId(shard->shard_id());
auto& sd = shard_data_[idx];
CHECK(sd.is_armed.exchange(false, memory_order_relaxed));
CHECK_GT(run_count_.load(memory_order_relaxed), 0u);
VLOG(2) << "RunInShard: " << DebugId() << " sid:" << shard->shard_id() << " " << sd.local_mask;
bool was_suspended = sd.local_mask & SUSPENDED_Q;
bool awaked_prerun = sd.local_mask & AWAKED_Q;
bool is_concluding = coordinator_state_ & COORD_CONCLUDING;
IntentLock::Mode mode = LockMode();
DCHECK(IsGlobal() || (sd.local_mask & KEYLOCK_ACQUIRED) || (multi_ && multi_->mode == GLOBAL));
DCHECK(!txq_ooo || (sd.local_mask & OUT_OF_ORDER));
/*************************************************************************/
// Actually running the callback.
// If you change the logic here, also please change the logic
RunnableResult result;
try {
// if a transaction is suspended, we still run it because of brpoplpush/blmove case
// that needs to run lpush on its suspended shard.
result = (*cb_ptr_)(this, shard);
if (unique_shard_cnt_ == 1) {
cb_ptr_ = nullptr; // We can do it because only a single thread runs the callback.
local_result_ = result;
} else {
if (result == OpStatus::OUT_OF_MEMORY) {
absl::base_internal::SpinLockHolder lk{&local_result_mu_};
CHECK(local_result_ == OpStatus::OK || local_result_ == OpStatus::OUT_OF_MEMORY);
local_result_ = result;
} else {
CHECK_EQ(OpStatus::OK, result);
}
}
} catch (std::bad_alloc&) {
LOG_FIRST_N(ERROR, 16) << " out of memory"; // TODO: to log at most once per sec.
absl::base_internal::SpinLockHolder lk{&local_result_mu_};
local_result_ = OpStatus::OUT_OF_MEMORY;
} catch (std::exception& e) {
LOG(FATAL) << "Unexpected exception " << e.what();
}
/*************************************************************************/
// at least the coordinator thread owns the reference.
DCHECK_GE(GetUseCount(), 1u);
shard->db_slice().OnCbFinish();
// Handle result flags to alter behaviour.
if (result.flags & RunnableResult::AVOID_CONCLUDING) {
// Multi shard callbacks should either all or none choose to conclude. Because they can't
// communicate, the must know their decision ahead, consequently there is no point in using this
// flag.
CHECK_EQ(unique_shard_cnt_, 1u);
DCHECK(is_concluding || multi_->concluding);
is_concluding = false;
}
// Log to jounrnal only once the command finished running
if (is_concluding || (multi_ && multi_->concluding))
LogAutoJournalOnShard(shard, result);
// If we're the head of tx queue (txq_ooo is false), we remove ourselves upon first invocation
// and successive hops are run by continuation_trans_ in engine shard.
// Otherwise we can remove ourselves only when we're concluding (so no more hops will follow).
if ((is_concluding || !txq_ooo) && sd.pq_pos != TxQueue::kEnd) {
VLOG(2) << "Remove from txq " << this->DebugId();
shard->txq()->Remove(sd.pq_pos);
sd.pq_pos = TxQueue::kEnd;
}
// For multi we unlock transaction (i.e. its keys) in UnlockMulti() call.
// If it's a final hop we should release the locks.
if (is_concluding) {
bool became_suspended = sd.local_mask & SUSPENDED_Q;
KeyLockArgs largs;
if (IsGlobal()) {
DCHECK(!awaked_prerun && !became_suspended); // Global transactions can not be blocking.
VLOG(2) << "Releasing shard lock";
shard->shard_lock()->Release(LockMode());
} else { // not global.
largs = GetLockArgs(idx);
DCHECK(sd.local_mask & KEYLOCK_ACQUIRED);
// If a transaction has been suspended, we keep the lock so that future transaction
// touching those keys will be ordered via TxQueue. It's necessary because we preserve
// the atomicity of awaked transactions by halting the TxQueue.
if (was_suspended || !became_suspended) {
shard->db_slice().Release(mode, largs);
sd.local_mask &= ~KEYLOCK_ACQUIRED;
}
sd.local_mask &= ~OUT_OF_ORDER;
}
// This is the last hop, so clear cont_trans if its held by the current tx
shard->RemoveContTx(this);
// It has 2 responsibilities.
// 1: to go over potential wakened keys, verify them and activate watch queues.
// 2: if this transaction was notified and finished running - to remove it from the head
// of the queue and notify the next one.
if (auto* bcontroller = shard->blocking_controller(); bcontroller) {
if (awaked_prerun || was_suspended) {
bcontroller->FinalizeWatched(largs, this);
}
// Wake only if no tx queue head is currently running
// Note: RemoveContTx might have no effect above if this tx had no continuations
if (shard->GetContTx() == nullptr) {
bcontroller->NotifyPending();
}
}
}
DecreaseRunCnt();
// From this point on we can not access 'this'.
return !is_concluding;
}
// TODO: For multi-transactions we should be able to deduce mode() at run-time based
// on the context. For regular multi-transactions we can actually inspect all commands.
// For eval-like transactions - we can decide based on the command flavor (EVAL/EVALRO) or
// auto-tune based on the static analysis (by identifying commands with hardcoded command names).
void Transaction::ScheduleInternal() {
DCHECK(!shard_data_.empty());
DCHECK_EQ(0u, txid_);
DCHECK_EQ(0, coordinator_state_ & COORD_SCHED);
DCHECK_GT(unique_shard_cnt_, 0u);
DVLOG(1) << "ScheduleInternal " << cid_->name() << " on " << unique_shard_cnt_ << " shards";
auto is_active = [this](uint32_t i) { return IsActive(i); };
// Loop until successfully scheduled in all shards.
while (true) {
txid_ = op_seq.fetch_add(1, memory_order_relaxed);
time_now_ms_ = GetCurrentTimeMs();
atomic_uint32_t schedule_fails = 0;
auto cb = [this, &schedule_fails](EngineShard* shard) {
if (!ScheduleInShard(shard)) {
schedule_fails.fetch_add(1, memory_order_relaxed);
}
};
shard_set->RunBriefInParallel(std::move(cb), is_active);
if (schedule_fails.load(memory_order_relaxed) == 0) {
coordinator_state_ |= COORD_SCHED;
RecordTxScheduleStats(this);
VLOG(2) << "Scheduled " << DebugId() << " num_shards: " << unique_shard_cnt_;
break;
}
VLOG(2) << "Cancelling " << DebugId();
ServerState::tlocal()->stats.tx_schedule_cancel_cnt += 1;
atomic_bool should_poll_execution{false};
auto cancel = [&](EngineShard* shard) {
bool res = CancelShardCb(shard);
if (res) {
should_poll_execution.store(true, memory_order_relaxed);
}
};
shard_set->RunBriefInParallel(std::move(cancel), is_active);
// We must follow up with PollExecution because in rare cases with multi-trans
// that follows this one, we may find the next transaction in the queue that is never
// trigerred. Which leads to deadlock. I could solve this by adding PollExecution to
// CancelShardCb above but then we would need to use the shard_set queue since PollExecution
// is blocking. I wanted to avoid the additional latency for the general case of running
// CancelShardCb because of the very rate case below. Therefore, I decided to just fetch the
// indication that we need to follow up with PollExecution and then send it to shard_set queue.
// We do not need to wait for this callback to finish - just make sure it will eventually run.
// See https://github.com/dragonflydb/dragonfly/issues/150 for more info.
if (should_poll_execution.load(memory_order_relaxed)) {
for (uint32_t i = 0; i < shard_set->size(); ++i) {
if (!is_active(i))
continue;
shard_set->Add(i, [] { EngineShard::tlocal()->PollExecution("cancel_cleanup", nullptr); });
}
}
}
}
// Optimized "Schedule and execute" function for the most common use-case of a single hop
// transactions like set/mset/mget etc. Does not apply for more complicated cases like RENAME or
// BLPOP where a data must be read from multiple shards before performing another hop.
OpStatus Transaction::ScheduleSingleHop(RunnableType cb) {
if (multi_ && multi_->role == SQUASHED_STUB) {
return RunSquashedMultiCb(cb);
}
DCHECK(!cb_ptr_);
DCHECK(IsAtomicMulti() || (coordinator_state_ & COORD_SCHED) == 0); // Multi schedule in advance.
cb_ptr_ = &cb;
if (IsAtomicMulti()) {
multi_->concluding = true;
} else {
coordinator_state_ |= COORD_CONCLUDING; // Single hop means we conclude.
}
// If we run only on one shard and conclude, we can avoid scheduling at all
// and directly dispatch the task to its destination shard.
bool schedule_fast = (unique_shard_cnt_ == 1) && !IsGlobal() && !IsAtomicMulti();
bool was_ooo = false;
bool run_inline = false;
ServerState* ss = nullptr;
if (schedule_fast) {
DCHECK_NE(unique_shard_id_, kInvalidSid);
DCHECK(IsActive(unique_shard_id_));
DCHECK(shard_data_.size() == 1 || multi_->mode == NON_ATOMIC);
// IsArmedInShard() first checks run_count_ before shard_data, so use release ordering.
shard_data_[SidToId(unique_shard_id_)].is_armed.store(true, memory_order_relaxed);
run_count_.store(1, memory_order_release);
time_now_ms_ = GetCurrentTimeMs();
// NOTE: schedule_cb cannot update data on stack when run_fast is false.
// This is because ScheduleSingleHop can finish before the callback returns.
// This happens when ScheduleUniqueShard schedules into TxQueue (hence run_fast is false), and
// then calls PollExecute that in turn runs the callback which calls DecreaseRunCnt. As a result
// WaitForShardCallbacks below is unblocked before schedule_cb returns. However, if run_fast is
// true, then we may mutate stack variables, but only before DecreaseRunCnt is called.
auto schedule_cb = [this, &was_ooo] {
bool run_fast = ScheduleUniqueShard(EngineShard::tlocal());
if (run_fast) {
was_ooo = true;
// it's important to DecreaseRunCnt only for run_fast and after was_ooo is assigned.
// If DecreaseRunCnt were called before ScheduleUniqueShard finishes
// then WaitForShardCallbacks below could exit before schedule_cb assigns return value
// to was_ooo and cause stack corruption.
DecreaseRunCnt();
}
};
ss = ServerState::tlocal();
if (ss->thread_index() == unique_shard_id_ && ss->AllowInlineScheduling()) {
DVLOG(2) << "Inline scheduling a transaction";
schedule_cb();
run_inline = true;
} else {
shard_set->Add(unique_shard_id_, std::move(schedule_cb)); // serves as a barrier.
}
} else { // This transaction either spans multiple shards and/or is multi.
if (!IsAtomicMulti()) // Multi schedule in advance.
ScheduleInternal();
ExecuteAsync();
}
DVLOG(2) << "ScheduleSingleHop before Wait " << DebugId() << " " << run_count_.load();
WaitForShardCallbacks();
DVLOG(2) << "ScheduleSingleHop after Wait " << DebugId();
if (schedule_fast) {
CHECK(!cb_ptr_); // we should have reset it within the callback.
if (was_ooo) {
ss->stats.tx_type_cnt[run_inline ? ServerState::INLINE : ServerState::QUICK]++;
} else {
ss->stats.tx_type_cnt[ServerState::NORMAL]++;
}
ss->stats.tx_width_freq_arr[0]++;
}
cb_ptr_ = nullptr;
return local_result_;
}
void Transaction::ReportWritesSquashedMulti(absl::FunctionRef<bool(ShardId)> had_write) {
DCHECK(multi_);
for (unsigned i = 0; i < multi_->shard_journal_write.size(); i++)
multi_->shard_journal_write[i] |= had_write(i);
}
// Runs in the coordinator fiber.
void Transaction::UnlockMulti() {
VLOG(1) << "UnlockMulti " << DebugId();
DCHECK(multi_);
DCHECK_GE(GetUseCount(), 1u); // Greater-equal because there may be callbacks in progress.
if (multi_->mode == NON_ATOMIC)
return;
auto sharded_keys = make_shared<vector<KeyList>>(shard_set->size());
while (!multi_->locks.empty()) {
auto entry = multi_->locks.extract(multi_->locks.begin());
ShardId sid = Shard(entry.value(), sharded_keys->size());
(*sharded_keys)[sid].emplace_back(std::move(entry.value()));
}
unsigned shard_journals_cnt =
ServerState::tlocal()->journal() ? CalcMultiNumOfShardJournals() : 0;
uint32_t prev = run_count_.fetch_add(shard_data_.size(), memory_order_relaxed);
DCHECK_EQ(prev, 0u);
use_count_.fetch_add(shard_data_.size(), std::memory_order_relaxed);
for (ShardId i = 0; i < shard_data_.size(); ++i) {
shard_set->Add(i, [this, sharded_keys, i, shard_journals_cnt]() {
this->UnlockMultiShardCb((*sharded_keys)[i], EngineShard::tlocal(), shard_journals_cnt);
intrusive_ptr_release(this);
});
}
VLOG(1) << "UnlockMultiEnd " << DebugId();
}
uint32_t Transaction::CalcMultiNumOfShardJournals() const {
uint32_t shard_journals_cnt = 0;
for (bool was_shard_write : multi_->shard_journal_write) {
if (was_shard_write) {
++shard_journals_cnt;
}
}
return shard_journals_cnt;
}
void Transaction::Schedule() {
if (multi_ && multi_->role == SQUASHED_STUB)
return;
if (!IsAtomicMulti())
ScheduleInternal();
}
// Runs in coordinator thread.
void Transaction::Execute(RunnableType cb, bool conclude) {
if (multi_ && multi_->role == SQUASHED_STUB) {
RunSquashedMultiCb(cb);
return;
}
DCHECK(coordinator_state_ & COORD_SCHED);
DCHECK(!cb_ptr_);
cb_ptr_ = &cb;
if (IsAtomicMulti()) {
multi_->concluding = conclude;
} else {
coordinator_state_ = conclude ? (coordinator_state_ | COORD_CONCLUDING)
: (coordinator_state_ & ~COORD_CONCLUDING);
}
ExecuteAsync();
DVLOG(1) << "Execute::WaitForCbs " << DebugId();
WaitForShardCallbacks();
DVLOG(1) << "Execute::WaitForCbs " << DebugId() << " completed";
cb_ptr_ = nullptr;
}
// Runs in coordinator thread.
void Transaction::ExecuteAsync() {
DVLOG(1) << "ExecuteAsync " << DebugId();
DCHECK_GT(unique_shard_cnt_, 0u);
DCHECK_GT(use_count_.load(memory_order_relaxed), 0u);
DCHECK(!IsAtomicMulti() || multi_->lock_mode.has_value());
// We do not necessarily Execute this transaction in 'cb' below. It well may be that it will be
// executed by the engine shard once it has been armed and coordinator thread will finish the
// transaction before engine shard thread stops accessing it. Therefore, we increase reference
// by number of callbacks accessing 'this' to allow callbacks to execute shard->Execute(this);
// safely.
use_count_.fetch_add(unique_shard_cnt_, memory_order_relaxed);
// We access sd.is_armed outside of shard-threads but we guard it with run_count_ release.
IterateActiveShards(
[](PerShardData& sd, auto i) { sd.is_armed.store(true, memory_order_relaxed); });
uint32_t seq = seqlock_.load(memory_order_relaxed);
// this fence prevents that a read or write operation before a release fence will be reordered
// with a write operation after a release fence. Specifically no writes below will be reordered
// upwards. Important, because it protects non-threadsafe local_mask from being accessed by
// IsArmedInShard in other threads.
run_count_.store(unique_shard_cnt_, memory_order_release);
auto* ss = ServerState::tlocal();
if (unique_shard_cnt_ == 1 && ss->thread_index() == unique_shard_id_ &&
ss->AllowInlineScheduling()) {
DVLOG(1) << "Short-circuit ExecuteAsync " << DebugId();
EngineShard::tlocal()->PollExecution("exec_cb", this);
intrusive_ptr_release(this); // against use_count_.fetch_add above.
return;
}
// We verify seq lock has the same generation number. See below for more info.
auto cb = [seq, this] {
EngineShard* shard = EngineShard::tlocal();
bool is_armed = IsArmedInShard(shard->shard_id());
// First we check that this shard should run a callback by checking IsArmedInShard.
if (is_armed) {
uint32_t seq_after = seqlock_.load(memory_order_relaxed);
DVLOG(3) << "PollExecCb " << DebugId() << " sid(" << shard->shard_id() << ") "
<< run_count_.load(memory_order_relaxed);
// We also make sure that for multi-operation transactions like Multi/Eval
// this callback runs on a correct operation. We want to avoid a situation
// where the first operation is executed and the second operation is armed and
// now this callback from the previous operation finally runs and calls PollExecution.
// It is usually ok, but for single shard operations we abuse index 0 in shard_data_
// Therefore we may end up with a situation where this old callback runs on shard 7,
// accessing shard_data_[0] that now represents shard 5 for the next operation.
// seqlock provides protection for that so each cb will only run on the operation it has
// been tasked with.
// We also must first check is_armed and only then seqlock. The first check ensures that
// the coordinator thread crossed
// "run_count_.store(unique_shard_cnt_, memory_order_release);" barrier and our seqlock_
// is valid.
if (seq_after == seq) {
// shard->PollExecution(this) does not necessarily execute this transaction.
// Therefore, everything that should be handled during the callback execution
// should go into RunInShard.
shard->PollExecution("exec_cb", this);
} else {
VLOG(1) << "Skipping PollExecution " << DebugId() << " sid(" << shard->shard_id() << ")";
}
}
DVLOG(3) << "ptr_release " << DebugId() << " " << seq;
intrusive_ptr_release(this); // against use_count_.fetch_add above.
};
// IsArmedInShard is the protector of non-thread safe data.
IterateActiveShards([&cb](PerShardData& sd, auto i) { shard_set->Add(i, cb); });
}
void Transaction::Conclude() {
if (!IsScheduled())
return;
auto cb = [](Transaction* t, EngineShard* shard) { return OpStatus::OK; };
Execute(std::move(cb), true);
}
void Transaction::Refurbish() {
txid_ = 0;
coordinator_state_ = 0;
cb_ptr_ = nullptr;
}
void Transaction::IterateMultiLocks(ShardId sid, std::function<void(const std::string&)> cb) const {
unsigned shard_num = shard_set->size();
for (const auto& key : multi_->locks) {
ShardId key_sid = Shard(key, shard_num);
if (key_sid == sid) {
cb(key);
}
}
}
void Transaction::EnableShard(ShardId sid) {
unique_shard_cnt_ = 1;
unique_shard_id_ = sid;
shard_data_.resize(1);
shard_data_.front().local_mask |= ACTIVE;
}
void Transaction::EnableAllShards() {
unique_shard_cnt_ = shard_set->size();
unique_shard_id_ = unique_shard_cnt_ == 1 ? 0 : kInvalidSid;
shard_data_.resize(shard_set->size());
for (auto& sd : shard_data_)
sd.local_mask |= ACTIVE;
}
Transaction::RunnableResult Transaction::RunQuickie(EngineShard* shard) {
DCHECK(!IsAtomicMulti());
DCHECK(shard_data_.size() == 1u || multi_->mode == NON_ATOMIC);
DCHECK_NE(unique_shard_id_, kInvalidSid);
DCHECK_EQ(0u, txid_);
auto& sd = shard_data_[SidToId(unique_shard_id_)];
DCHECK_EQ(0, sd.local_mask & (KEYLOCK_ACQUIRED | OUT_OF_ORDER));
DVLOG(1) << "RunQuickSingle " << DebugId() << " " << shard->shard_id();
DCHECK(cb_ptr_) << DebugId() << " " << shard->shard_id();
// Calling the callback in somewhat safe way
RunnableResult result;
try {
result = (*cb_ptr_)(this, shard);
} catch (std::bad_alloc&) {
LOG_FIRST_N(ERROR, 16) << " out of memory";
result = OpStatus::OUT_OF_MEMORY;
} catch (std::exception& e) {
LOG(FATAL) << "Unexpected exception " << e.what();
}
shard->db_slice().OnCbFinish();
// Handling the result, along with conclusion and journaling, is done by the caller
sd.is_armed.store(false, memory_order_relaxed);
cb_ptr_ = nullptr; // We can do it because only a single shard runs the callback.
return result;
}
// runs in coordinator thread.
// Marks the transaction as expired and removes it from the waiting queue.
void Transaction::ExpireBlocking(WaitKeysProvider wcb) {
DCHECK(!IsGlobal());
DVLOG(1) << "ExpireBlocking " << DebugId();
run_count_.store(unique_shard_cnt_, memory_order_release);
auto expire_cb = [this, &wcb] {
EngineShard* es = EngineShard::tlocal();
ExpireShardCb(wcb(this, es), es);
};
IterateActiveShards([&expire_cb](PerShardData& sd, auto i) { shard_set->Add(i, expire_cb); });
WaitForShardCallbacks();
DVLOG(1) << "ExpireBlocking finished " << DebugId();
}
string_view Transaction::Name() const {
return cid_ ? cid_->name() : "null-command";
}
ShardId Transaction::GetUniqueShard() const {
DCHECK_EQ(GetUniqueShardCnt(), 1U);
return unique_shard_id_;
}
optional<SlotId> Transaction::GetUniqueSlotId() const {
return unique_slot_checker_.GetUniqueSlotId();
}
KeyLockArgs Transaction::GetLockArgs(ShardId sid) const {
KeyLockArgs res;
res.db_index = db_index_;
res.key_step = cid_->opt_mask() & CO::INTERLEAVED_KEYS ? 2 : 1;
res.args = GetShardArgs(sid);
DCHECK(!res.args.empty() || (cid_->opt_mask() & CO::NO_KEY_TRANSACTIONAL));
return res;
}
bool Transaction::IsActive(ShardId sid) const {
// If we have only one shard, we often don't store infromation about all shards, so determine it
// solely by id
if (unique_shard_cnt_ == 1) {
// However the active flag is still supposed to be set for our unique shard
DCHECK((shard_data_[SidToId(unique_shard_id_)].local_mask & ACTIVE));
return sid == unique_shard_id_;
}
return shard_data_[SidToId(sid)].local_mask & ACTIVE;
}
// Runs within a engine shard thread.
// Optimized path that schedules and runs transactions out of order if possible.
// Returns true if eagerly executed, false if the callback will be handled by the transaction
// queue.
bool Transaction::ScheduleUniqueShard(EngineShard* shard) {
DCHECK(!IsAtomicMulti());
DCHECK_EQ(txid_, 0u);
DCHECK(shard_data_.size() == 1u || multi_->mode == NON_ATOMIC);
DCHECK_NE(unique_shard_id_, kInvalidSid);
auto mode = LockMode();
auto lock_args = GetLockArgs(shard->shard_id());
auto& sd = shard_data_[SidToId(unique_shard_id_)];
DCHECK_EQ(TxQueue::kEnd, sd.pq_pos);
bool unlocked_keys =
shard->db_slice().CheckLock(mode, lock_args) && shard->shard_lock()->Check(mode);
bool quick_run = unlocked_keys;
// Fast path. If none of the keys are locked, we can run briefly atomically on the thread
// without acquiring them at all.
if (quick_run) {
// TBD add acquire lock here
auto result = RunQuickie(shard);
local_result_ = result.status;
if (result.flags & RunnableResult::AVOID_CONCLUDING) {
// If we want to run again, we have to actually acquire keys, but keep ourselves disarmed
DCHECK_EQ(sd.is_armed, false);
unlocked_keys = false;
} else {
LogAutoJournalOnShard(shard, result);
}
}
// Slow path. Some of the keys are locked, so we schedule on the transaction queue.
if (!unlocked_keys) {
coordinator_state_ |= COORD_SCHED; // safe because single shard
txid_ = op_seq.fetch_add(1, memory_order_relaxed); // -
sd.pq_pos = shard->txq()->Insert(this);
DCHECK_EQ(sd.local_mask & KEYLOCK_ACQUIRED, 0);
shard->db_slice().Acquire(mode, lock_args);
sd.local_mask |= KEYLOCK_ACQUIRED;
DVLOG(1) << "Rescheduling " << DebugId() << " into TxQueue of size " << shard->txq()->size();
// If there are blocked transactons waiting for this tx keys, we will add this transaction
// to the tx-queue (these keys will be contended). This will happen even if the queue was empty.
// In that case we must poll the queue, because there will be no other callback trigerring the
// queue before us.
shard->PollExecution("schedule_unique", nullptr);
}
return quick_run;
}
// This function should not block since it's run via RunBriefInParallel.
bool Transaction::ScheduleInShard(EngineShard* shard) {
ShardId sid = SidToId(shard->shard_id());
auto& sd = shard_data_[sid];
DCHECK(sd.local_mask & ACTIVE);
DCHECK_EQ(sd.local_mask & KEYLOCK_ACQUIRED, 0);
sd.local_mask &= ~OUT_OF_ORDER;
// If a more recent transaction already commited, we abort
if (shard->committed_txid() >= txid_)
return false;
TxQueue* txq = shard->txq();
KeyLockArgs lock_args;
IntentLock::Mode mode = LockMode();
bool lock_granted = false;
// Acquire intent locks. Intent locks are always acquired, even if already locked by others.
if (!IsGlobal()) {
lock_args = GetLockArgs(shard->shard_id());
bool shard_unlocked = shard->shard_lock()->Check(mode);
bool keys_unlocked = shard->db_slice().Acquire(mode, lock_args);
lock_granted = shard_unlocked && keys_unlocked;
sd.local_mask |= KEYLOCK_ACQUIRED;
if (lock_granted) {
sd.local_mask |= OUT_OF_ORDER;
}
DVLOG(3) << "Lock granted " << lock_granted << " for trans " << DebugId();
}
// If the new transaction requires reordering of the pending queue (i.e. it comes before tail)
// and some other transaction already locked its keys we can not reorder 'trans' because
// the transaction could have deduced that it can run OOO and eagerly execute. Hence, we
// fail this scheduling attempt for trans.
if (!txq->Empty() && txid_ < txq->TailScore() && !lock_granted) {
if (sd.local_mask & KEYLOCK_ACQUIRED) {
shard->db_slice().Release(mode, lock_args);
sd.local_mask &= ~KEYLOCK_ACQUIRED;
}
return false;
}
if (IsGlobal()) {
shard->shard_lock()->Acquire(mode);
VLOG(1) << "Global shard lock acquired";
}
TxQueue::Iterator it = txq->Insert(this);
DCHECK_EQ(TxQueue::kEnd, sd.pq_pos);
sd.pq_pos = it;
AnalyzeTxQueue(shard, txq);
DVLOG(1) << "Insert into tx-queue, sid(" << sid << ") " << DebugId() << ", qlen " << txq->size();
return true;
}
bool Transaction::CancelShardCb(EngineShard* shard) {
ShardId idx = SidToId(shard->shard_id());
auto& sd = shard_data_[idx];
auto pos = sd.pq_pos;
if (pos == TxQueue::kEnd)
return false;
sd.pq_pos = TxQueue::kEnd;
TxQueue* txq = shard->txq();
TxQueue::Iterator head = txq->Head();
auto val = txq->At(pos);
Transaction* trans = absl::get<Transaction*>(val);
DCHECK(trans == this) << "Pos " << pos << ", txq size " << txq->size() << ", trans " << trans;
txq->Remove(pos);
if (sd.local_mask & KEYLOCK_ACQUIRED) {
auto mode = LockMode();
auto lock_args = GetLockArgs(shard->shard_id());
DCHECK(lock_args.args.size() > 0);
shard->db_slice().Release(mode, lock_args);
sd.local_mask &= ~KEYLOCK_ACQUIRED;
}
if (IsGlobal()) {
shard->shard_lock()->Release(LockMode());
}
if (pos == head && !txq->Empty()) {
return true;
}
return false;
}
// runs in engine-shard thread.
ArgSlice Transaction::GetShardArgs(ShardId sid) const {
DCHECK(!multi_ || multi_->role != SQUASHER);
// We can read unique_shard_cnt_ only because ShardArgsInShard is called after IsArmedInShard
// barrier.
if (unique_shard_cnt_ == 1) {
return args_;
}
const auto& sd = shard_data_[sid];
return ArgSlice{args_.data() + sd.arg_start, sd.arg_count};
}
// from local index back to original arg index skipping the command.
// i.e. returns (first_key_pos -1) or bigger.
size_t Transaction::ReverseArgIndex(ShardId shard_id, size_t arg_index) const {
if (unique_shard_cnt_ == 1)
return reverse_index_[arg_index];
const auto& sd = shard_data_[shard_id];
return reverse_index_[sd.arg_start + arg_index];
}
OpStatus Transaction::WaitOnWatch(const time_point& tp, WaitKeysProvider wkeys_provider,
KeyReadyChecker krc) {
DVLOG(2) << "WaitOnWatch " << DebugId();
using namespace chrono;
auto cb = [&](Transaction* t, EngineShard* shard) {
auto keys = wkeys_provider(t, shard);
return t->WatchInShard(keys, shard, krc);
};
Execute(std::move(cb), true);
coordinator_state_ |= COORD_BLOCKED;
auto wake_cb = [this] {
return (coordinator_state_ & COORD_CANCELLED) ||
wakeup_requested_.load(memory_order_relaxed) > 0;
};
auto* stats = ServerState::tl_connection_stats();
++stats->num_blocked_clients;
if (DCHECK_IS_ON()) {
int64_t ms = -1;
if (tp != time_point::max())
ms = duration_cast<milliseconds>(tp - time_point::clock::now()).count();
DVLOG(1) << "WaitOnWatch TimeWait for " << ms << " ms " << DebugId();
}
cv_status status = cv_status::no_timeout;
if (tp == time_point::max()) {
blocking_ec_.await(std::move(wake_cb));
} else {
status = blocking_ec_.await_until(std::move(wake_cb), tp);
}
DVLOG(1) << "WaitOnWatch done " << int(status) << " " << DebugId();
--stats->num_blocked_clients;
OpStatus result = OpStatus::OK;
if (status == cv_status::timeout) {
result = OpStatus::TIMED_OUT;
} else if (coordinator_state_ & COORD_CANCELLED) {
result = local_result_;
}
if (result != OpStatus::OK)
ExpireBlocking(wkeys_provider);
coordinator_state_ &= ~COORD_BLOCKED;
return result;
}
// Runs only in the shard thread.
OpStatus Transaction::WatchInShard(ArgSlice keys, EngineShard* shard, KeyReadyChecker krc) {
ShardId idx = SidToId(shard->shard_id());
auto& sd = shard_data_[idx];
CHECK_EQ(0, sd.local_mask & SUSPENDED_Q);
auto* bc = shard->EnsureBlockingController();
bc->AddWatched(keys, std::move(krc), this);
sd.local_mask |= SUSPENDED_Q;
sd.local_mask &= ~OUT_OF_ORDER;
DVLOG(2) << "AddWatched " << DebugId() << " local_mask:" << sd.local_mask
<< ", first_key:" << keys.front();
return OpStatus::OK;
}
void Transaction::ExpireShardCb(ArgSlice wkeys, EngineShard* shard) {
auto lock_args = GetLockArgs(shard->shard_id());
shard->db_slice().Release(LockMode(), lock_args);
unsigned sd_idx = SidToId(shard->shard_id());
auto& sd = shard_data_[sd_idx];
sd.local_mask |= EXPIRED_Q;
sd.local_mask &= ~KEYLOCK_ACQUIRED;
shard->blocking_controller()->FinalizeWatched(wkeys, this);
DCHECK(!shard->blocking_controller()->awakened_transactions().contains(this));
// Resume processing of transaction queue
shard->PollExecution("unwatchcb", nullptr);
DecreaseRunCnt();
}
OpStatus Transaction::RunSquashedMultiCb(RunnableType cb) {
DCHECK(multi_ && multi_->role == SQUASHED_STUB);
DCHECK_EQ(unique_shard_cnt_, 1u);
auto* shard = EngineShard::tlocal();
auto result = cb(this, shard);
shard->db_slice().OnCbFinish();
LogAutoJournalOnShard(shard, result);
DCHECK_EQ(result.flags, 0); // if it's sophisticated, we shouldn't squash it
return result;
}
void Transaction::UnlockMultiShardCb(const KeyList& sharded_keys, EngineShard* shard,
uint32_t shard_journals_cnt) {
DCHECK(multi_ && multi_->lock_mode);
auto journal = shard->journal();
if (journal != nullptr && multi_->shard_journal_write[shard->shard_id()]) {
journal->RecordEntry(txid_, journal::Op::EXEC, db_index_, shard_journals_cnt,
unique_slot_checker_.GetUniqueSlotId(), {}, true);
}
if (multi_->mode == GLOBAL) {
shard->shard_lock()->Release(IntentLock::EXCLUSIVE);
} else {
for (const auto& key : sharded_keys) {
shard->db_slice().ReleaseNormalized(*multi_->lock_mode, db_index_, key, 1);
}
}
ShardId sid = shard->shard_id();
auto& sd = shard_data_[SidToId(sid)];
sd.local_mask |= UNLOCK_MULTI;
// It does not have to be that all shards in multi transaction execute this tx.
// Hence it could stay in the tx queue. We perform the necessary cleanup and remove it from
// there. The transaction is not guaranteed to be at front.
if (sd.pq_pos != TxQueue::kEnd) {
DVLOG(1) << "unlockmulti: TxRemove " << DebugId();
TxQueue* txq = shard->txq();
DCHECK(!txq->Empty());
DCHECK_EQ(absl::get<Transaction*>(txq->At(sd.pq_pos)), this);
txq->Remove(sd.pq_pos);
sd.pq_pos = TxQueue::kEnd;
}
shard->RemoveContTx(this);
// Wake only if no tx queue head is currently running
if (shard->blocking_controller() && shard->GetContTx() == nullptr)
shard->blocking_controller()->NotifyPending();
shard->PollExecution("unlockmulti", nullptr);
this->DecreaseRunCnt();
}
void Transaction::DecreaseRunCnt() {
// to protect against cases where Transaction is destroyed before run_ec_.notify
// finishes running. We can not put it inside the (res == 1) block because then it's too late.
::boost::intrusive_ptr guard(this);
// We use release so that no stores will be reordered after.
// It's needed because we need to enforce that all stores executed before this point
// are visible right after run_count_ is unblocked in the coordinator thread.
// The fact that run_ec_.notify() does release operation is not enough, because
// WaitForCallbacks might skip reading run_ec_ if run_count_ is already 0.
uint32_t res = run_count_.fetch_sub(1, memory_order_release);
CHECK_GE(res, 1u) << unique_shard_cnt_ << " " << unique_shard_id_ << " " << cid_->name() << " "
<< use_count_.load(memory_order_relaxed) << " " << uint32_t(coordinator_state_);
if (res == 1) {
run_ec_.notify();
}
}
bool Transaction::IsGlobal() const {
// Please note that a transaction can be non-global even if multi_->mode == GLOBAL.
// It happens when a transaction is squashed and switches to execute differrent commands.
return global_;
}
// Runs only in the shard thread.
// Returns true if the transacton has changed its state from suspended to awakened,
// false, otherwise.
bool Transaction::NotifySuspended(TxId committed_txid, ShardId sid, string_view key) {
unsigned idx = SidToId(sid);
auto& sd = shard_data_[idx];
unsigned local_mask = sd.local_mask;
if (local_mask & Transaction::EXPIRED_Q) {
return false;
}
// Wake a transaction only once on the first notify.
// We don't care about preserving the strict order with multiple operations running on blocking
// keys in parallel, because the internal order is not observable from outside either way.
if (wakeup_requested_.fetch_add(1, memory_order_relaxed) > 0)
return false;
DVLOG(1) << "NotifySuspended " << DebugId() << ", local_mask:" << local_mask << " by commited_id "
<< committed_txid;
// local_mask could be awaked (i.e. not suspended) if the transaction has been
// awakened by another key or awakened by the same key multiple times.
if (local_mask & SUSPENDED_Q) {
DCHECK_EQ(0u, local_mask & AWAKED_Q);
sd.local_mask &= ~SUSPENDED_Q;
sd.local_mask |= AWAKED_Q;
// Find index of awakened key.
auto args = GetShardArgs(sid);
auto it =
find_if(args.begin(), args.end(), [key](auto arg) { return facade::ToSV(arg) == key; });
DCHECK(it != args.end());
sd.wake_key_pos = it - args.begin();
}
blocking_ec_.notify();
return true;
}
optional<string_view> Transaction::GetWakeKey(ShardId sid) const {
auto& sd = shard_data_[SidToId(sid)];
if ((sd.local_mask & AWAKED_Q) == 0)
return nullopt;
CHECK_NE(sd.wake_key_pos, UINT16_MAX);
return GetShardArgs(sid).at(sd.wake_key_pos);
}
void Transaction::LogAutoJournalOnShard(EngineShard* shard, RunnableResult result) {
// TODO: For now, we ignore non shard coordination.
if (shard == nullptr)
return;
// Ignore technical squasher hops.
if (multi_ && multi_->role == SQUASHER)
return;
// Only write commands and/or no-key-transactional commands are logged
if (cid_->IsWriteOnly() == 0 && (cid_->opt_mask() & CO::NO_KEY_TRANSACTIONAL) == 0)
return;
auto journal = shard->journal();
if (journal == nullptr)
return;
if (result.status != OpStatus::OK) {
// We log NOOP even for NO_AUTOJOURNAL commands because the non-success status could have been
// due to OOM in a single shard, while other shards succeeded
journal->RecordEntry(txid_, journal::Op::NOOP, db_index_, unique_shard_cnt_,
unique_slot_checker_.GetUniqueSlotId(), journal::Entry::Payload{}, true);
return;
}
// If autojournaling was disabled and not re-enabled, skip it
if ((cid_->opt_mask() & CO::NO_AUTOJOURNAL) && !renabled_auto_journal_.load(memory_order_relaxed))
return;
// TODO: Handle complex commands like LMPOP correctly once they are implemented.
journal::Entry::Payload entry_payload;
string_view cmd{cid_->name()};
if (unique_shard_cnt_ == 1 || args_.empty()) {
entry_payload = make_pair(cmd, full_args_);
} else {
entry_payload = make_pair(cmd, GetShardArgs(shard->shard_id()));
}
LogJournalOnShard(shard, std::move(entry_payload), unique_shard_cnt_, false, true);
}
void Transaction::LogJournalOnShard(EngineShard* shard, journal::Entry::Payload&& payload,
uint32_t shard_cnt, bool multi_commands,
bool allow_await) const {
auto journal = shard->journal();
CHECK(journal);
if (multi_ && multi_->role != SQUASHED_STUB)
multi_->shard_journal_write[shard->shard_id()] = true;
bool is_multi = multi_commands || IsAtomicMulti();
auto opcode = is_multi ? journal::Op::MULTI_COMMAND : journal::Op::COMMAND;
journal->RecordEntry(txid_, opcode, db_index_, shard_cnt, unique_slot_checker_.GetUniqueSlotId(),
std::move(payload), allow_await);
}
void Transaction::FinishLogJournalOnShard(EngineShard* shard, uint32_t shard_cnt) const {
if (multi_) {
return;
}
auto journal = shard->journal();
CHECK(journal);
journal->RecordEntry(txid_, journal::Op::EXEC, db_index_, shard_cnt,
unique_slot_checker_.GetUniqueSlotId(), {}, false);
}
void Transaction::CancelBlocking(std::function<OpStatus(ArgSlice)> status_cb) {
if ((coordinator_state_ & COORD_BLOCKED) == 0)
return;
OpStatus status = OpStatus::CANCELLED;
if (status_cb) {
vector<string_view> all_keys;
IterateActiveShards([this, &all_keys](PerShardData&, auto i) {
auto shard_keys = GetShardArgs(i);
all_keys.insert(all_keys.end(), shard_keys.begin(), shard_keys.end());
});
status = status_cb(absl::MakeSpan(all_keys));
}
if (status == OpStatus::OK)
return;
coordinator_state_ |= COORD_CANCELLED;
local_result_ = status;
blocking_ec_.notify();
}
OpResult<KeyIndex> DetermineKeys(const CommandId* cid, CmdArgList args) {
if (cid->opt_mask() & (CO::GLOBAL_TRANS | CO::NO_KEY_TRANSACTIONAL))
return KeyIndex::Empty();
KeyIndex key_index;
int num_custom_keys = -1;
if (cid->opt_mask() & CO::VARIADIC_KEYS) {
// ZUNION/INTER <num_keys> <key1> [<key2> ...]
// EVAL <script> <num_keys>
// XREAD ... STREAMS ...
if (args.size() < 2) {
return OpStatus::SYNTAX_ERR;
}
string_view name{cid->name()};
if (name == "XREAD" || name == "XREADGROUP") {
for (size_t i = 0; i < args.size(); ++i) {
string_view arg = ArgS(args, i);
if (absl::EqualsIgnoreCase(arg, "STREAMS")) {
size_t left = args.size() - i - 1;
if (left < 2 || left % 2 != 0)
return OpStatus::SYNTAX_ERR;
key_index.start = i + 1;
key_index.end = key_index.start + (left / 2);
key_index.step = 1;
return key_index;
}
}
return OpStatus::SYNTAX_ERR;
}
if (absl::EndsWith(name, "STORE"))
key_index.bonus = 0; // Z<xxx>STORE <key> commands
unsigned num_keys_index;
if (absl::StartsWith(name, "EVAL"))
num_keys_index = 1;
else
num_keys_index = key_index.bonus ? *key_index.bonus + 1 : 0;
string_view num = ArgS(args, num_keys_index);
if (!absl::SimpleAtoi(num, &num_custom_keys) || num_custom_keys < 0)
return OpStatus::INVALID_INT;
if (num_custom_keys == 0 &&
(absl::StartsWith(name, "ZDIFF") || absl::StartsWith(name, "ZUNION") ||
absl::StartsWith(name, "ZINTER"))) {
return OpStatus::AT_LEAST_ONE_KEY;
}
if (args.size() < size_t(num_custom_keys) + num_keys_index + 1)
return OpStatus::SYNTAX_ERR;
}
if (cid->first_key_pos() > 0) {
key_index.start = cid->first_key_pos() - 1;
int last = cid->last_key_pos();
if (num_custom_keys >= 0) {
key_index.end = key_index.start + num_custom_keys;
} else {
key_index.end = last > 0 ? last : (int(args.size()) + last + 1);
}
key_index.step = cid->opt_mask() & CO::INTERLEAVED_KEYS ? 2 : 1;
if (cid->opt_mask() & CO::STORE_LAST_KEY) {
string_view name{cid->name()};
if (name == "GEORADIUSBYMEMBER" && args.size() >= 5) {
// key member radius .. STORE destkey
string_view opt = ArgS(args, args.size() - 2);
if (absl::EqualsIgnoreCase(opt, "STORE") || absl::EqualsIgnoreCase(opt, "STOREDIST")) {
key_index.bonus = args.size() - 1;
}
}
}
return key_index;
}
LOG(FATAL) << "TBD: Not supported " << cid->name();
return key_index;
}
std::vector<Transaction::PerShardCache>& Transaction::TLTmpSpace::GetShardIndex(unsigned size) {
shard_cache.resize(size);
for (auto& v : shard_cache)
v.Clear();
return shard_cache;
}
} // namespace dfly
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