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110705db8d1d80606fc93f6a2cae5a2e313cb1cd
ternfs-XTXMarkets/cpp/cdc/CDCDB.cpp
Francesco Mazzoli 110705db8d EggsFS -> TernFS rename 
Things not done because probably disruptive:

* kmod filesystem string
* sysctl/debugfs/trace
* metrics names
* xmon instance names

Some of these might be renamed too, but starting with a relatively
safe set.
2025-09-03 09:29:53 +01:00

1974 lines
80 KiB
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#include "CDCDB.hpp"
#include <cstdint>
#include <limits>
#include <memory>
#include <rocksdb/iterator.h>
#include <rocksdb/options.h>
#include <rocksdb/statistics.h>
#include <rocksdb/status.h>
#include <rocksdb/utilities/transaction.h>
#include <rocksdb/utilities/optimistic_transaction_db.h>
#include <unordered_set>
#include "Assert.hpp"
#include "AssertiveLock.hpp"
#include "CDCDBData.hpp"
#include "Common.hpp"
#include "Env.hpp"
#include "Exception.hpp"
#include "MsgsGen.hpp"
#include "RocksDBUtils.hpp"
#include "ShardDB.hpp"
#include "Time.hpp"
#include "XmonAgent.hpp"
// The CDC needs to remember about multi-step transactions which it executes by
// talking to the shards. So essentially we need to store a bunch of queued
// queued requests, and a bunch of currently executing transactions, which are
// waiting for shard responses.
//
// Generally speaking we need to make sure to not have transactions step on each
// others toes. This is especially pertinent for edge locking logic -- given our
// requirements for idempotency (we don't know when a request has gone through)
// when we lock an edge we're really locking it so that shard-specific operations
// don't mess things up, rather than other CDC operations.
//
// The strategy that we adopt to achieve that is as follows:
//
// 1. Each request that comes in gets assigned a txn id. The txn ids are sequential:
// later request, higher txn ids.
// 2. We specify a set of directory inode ids that a given request will need to lock
// edges on.
// 3. We store a map InodeId -> []TxnId. The list of TxnIds is ordered. Each TxnId
// is in the list value for all the InodeId keys it needs locks for. Only TxnIds
// that have not completed yet are in this map.
// 4. A txn does not start executing unless it is at the head of all the lists in the
// map above.
//
// This scheme ensures no deadlocks and also fairness (no transaction can ever be
// starved). Divide the requests into the equivalence classes generated by the
// relation "have directories to be locked in common". The scheme above guarantees
// that each class will be run serially, with transactions with earlier txn ids
// being run before txns with later txn ids.
//
// The "move directory" request is a bit of an exception. It needs to do a "no loops"
// check which depends on the entire directory tree. So for simplicity we arrange
// for each move directory request to run serially, by creating a dummy InodeId
// which represents the "move directory lock", so to speak.
//
// The first version of the CDC just executed each transaction serially, but this
// proved way too slow, capping directory creation at around 200req/s. So we did the
// above to pipeline CDC requests. Since this required a change to the CDC RocksDB
// schema, we call the first version of the schema V0, the current one V1.
std::vector<rocksdb::ColumnFamilyDescriptor> CDCDB::getColumnFamilyDescriptors() {
return {
{rocksdb::kDefaultColumnFamilyName, {}},
{"reqQueue", {}},
{"parent", {}},
{"enqueued", {}},
{"executing", {}},
{"dirsToTxns", {}},
};
}
std::ostream& operator<<(std::ostream& out, const CDCShardReq& x) {
out << "CDCShardReq(shid=" << x.shid << ", req=" << x.req << ")";
return out;
}
std::ostream& operator<<(std::ostream& out, const CDCStep& x) {
out << "CDCStep(finishedTxns=[";
for (int i = 0; i < x.finishedTxns.size(); i++) {
if (i > 0) {
out << ", ";
}
const auto& txn = x.finishedTxns[i];
out << "<" << txn.first << ", " << txn.second << ">";
}
out << "], runningTxns=[";
for (int i = 0; i < x.runningTxns.size(); i++) {
if (i > 0) {
out << ", ";
}
const auto& txn = x.runningTxns[i];
out << "<" << txn.first << ", " << txn.second << ">";
}
out << "])";
return out;
}
std::ostream& operator<<(std::ostream& out, CDCTxnId id) {
return out << id.x;
}
std::ostream& operator<<(std::ostream& out, const CDCShardResp& x) {
return out << "CDCShardResp(txnId=" << x.txnId << ", resp=" << x.resp << ")";
}
std::ostream& operator<<(std::ostream& out, const CDCLogEntry& x) {
out << "CDCLogEntry(logIdx= " << x.logIdx() << ", ";
out << "cdcReqs=[";
for (auto& req : x.cdcReqs()) {
out << req << ", ";
}
out << "], shardResps=[";
for (auto& resp: x.shardResps()) {
out << resp << ", ";
}
out << "])";
return out;
}
inline bool createCurrentLockedEdgeRetry(TernError err) {
return
err == TernError::TIMEOUT || err == TernError::MTIME_IS_TOO_RECENT ||
err == TernError::MORE_RECENT_SNAPSHOT_EDGE || err == TernError::MORE_RECENT_CURRENT_EDGE;
}
static constexpr InodeId MOVE_DIRECTORY_LOCK = InodeId::FromU64Unchecked(1ull<<63);
struct DirectoriesNeedingLock {
private:
static constexpr int MAX_SIZE = 3;
std::array<InodeId, MAX_SIZE> _ids;
int _size;
public:
DirectoriesNeedingLock() : _size(0) {
memset(_ids.data(), 0, _ids.size()*sizeof(decltype(_ids)::value_type));
}
int size() const {
return _size;
}
decltype(_ids)::const_iterator begin() const {
return _ids.begin();
}
decltype(_ids)::const_iterator end() const {
return _ids.begin() + _size;
}
void add(InodeId id) {
ALWAYS_ASSERT(_size != MAX_SIZE);
ALWAYS_ASSERT(id != InodeId::FromU64Unchecked(0));
for (InodeId otherId : _ids) {
if (otherId == id) { return; }
}
_ids[_size] = id;
_size++;
}
};
// These are all the directories where we'll lock edges given a request.
// These function _must be pure_! We call it repeatedly as if it's a property
// of the request more than a function.
//
// Technically every well formed request will have distinct inode ids, but there
// are parts in the code where this function is called before we know that the
// request is valid. Hence the set semantics of DirectoriesNeedingLock.
static DirectoriesNeedingLock directoriesNeedingLock(const CDCReqContainer& req) {
DirectoriesNeedingLock toLock;
switch (req.kind()) {
case CDCMessageKind::MAKE_DIRECTORY:
toLock.add(req.getMakeDirectory().ownerId);
break;
case CDCMessageKind::RENAME_FILE:
toLock.add(req.getRenameFile().oldOwnerId);
toLock.add(req.getRenameFile().newOwnerId);
break;
case CDCMessageKind::SOFT_UNLINK_DIRECTORY:
// Lock needs to be acquired on both owner and target directory.
// Lock on owner is needed for remove owner step of the state machine.
// Lock on target is needed so that the target does not get removed by GC after
// we unlink the owner but before we unlock the edge.
toLock.add(req.getSoftUnlinkDirectory().ownerId);
toLock.add(req.getSoftUnlinkDirectory().targetId);
break;
case CDCMessageKind::RENAME_DIRECTORY:
toLock.add(req.getRenameDirectory().oldOwnerId);
toLock.add(req.getRenameDirectory().newOwnerId);
// Moving directories is special: it can introduce loops if we're not careful.
// Instead of trying to not create loops in the context of interleaved transactions,
// we instead only allow one move directory at a time.
toLock.add(MOVE_DIRECTORY_LOCK);
break;
case CDCMessageKind::HARD_UNLINK_DIRECTORY:
toLock.add(req.getHardUnlinkDirectory().dirId);
break;
case CDCMessageKind::CROSS_SHARD_HARD_UNLINK_FILE:
toLock.add(req.getCrossShardHardUnlinkFile().ownerId);
break;
case CDCMessageKind::ERROR:
throw TERN_EXCEPTION("bad req type error");
default:
throw TERN_EXCEPTION("bad req type %s", (uint8_t)req.kind());
}
return toLock;
}
struct StateMachineEnv {
Env& env;
rocksdb::ColumnFamilyHandle* defaultCf;
rocksdb::ColumnFamilyHandle* parentCf;
rocksdb::Transaction& dbTxn;
CDCTxnId txnId;
uint8_t txnStep;
CDCStep& cdcStep;
bool finished;
StateMachineEnv(
Env& env_, rocksdb::ColumnFamilyHandle* defaultCf_, rocksdb::ColumnFamilyHandle* parentCf_, rocksdb::Transaction& dbTxn_, CDCTxnId txnId_, uint8_t step_, CDCStep& cdcStep_
):
env(env_), defaultCf(defaultCf_), parentCf(parentCf_), dbTxn(dbTxn_), txnId(txnId_), txnStep(step_), cdcStep(cdcStep_), finished(false)
{}
InodeId nextDirectoryId(rocksdb::Transaction& dbTxn) {
std::string v;
ROCKS_DB_CHECKED(dbTxn.Get({}, defaultCf, cdcMetadataKey(&NEXT_DIRECTORY_ID_KEY), &v));
ExternalValue<InodeIdValue> nextId(v);
InodeId id = nextId().id();
nextId().setId(InodeId::FromU64(id.u64 + 1));
ROCKS_DB_CHECKED(dbTxn.Put(defaultCf, cdcMetadataKey(&NEXT_DIRECTORY_ID_KEY), nextId.toSlice()));
return id;
}
ShardReqContainer& needsShard(uint8_t step, ShardId shid, bool repeated) {
txnStep = step;
auto& running = cdcStep.runningTxns.emplace_back();
running.first = txnId;
running.second.shid = shid;
running.second.repeated = repeated;
return running.second.req;
}
CDCRespContainer& finish() {
this->finished = true;
auto& finished = cdcStep.finishedTxns.emplace_back();
finished.first = txnId;
return finished.second;
}
void finishWithError(TernError err) {
this->finished = true;
ALWAYS_ASSERT(err != TernError::NO_ERROR);
auto& errored = cdcStep.finishedTxns.emplace_back();
errored.first = txnId;
errored.second.setError() = err;
}
};
constexpr uint8_t TXN_START = 0;
enum MakeDirectoryStep : uint8_t {
MAKE_DIRECTORY_LOOKUP = 1,
MAKE_DIRECTORY_CREATE_DIR = 2,
MAKE_DIRECTORY_LOOKUP_OLD_CREATION_TIME = 3,
MAKE_DIRECTORY_CREATE_LOCKED_EDGE = 4,
MAKE_DIRECTORY_UNLOCK_EDGE = 5,
MAKE_DIRECTORY_ROLLBACK = 6,
};
// Steps:
//
// 1. Lookup if an existing directory exists. If it does, immediately succeed.
// 2. Allocate inode id here in the CDC
// 3. Create directory in shard we get from the inode
// 4. Lookup old creation time for the edge we're about to create
// 5. Create locked edge from owner to newly created directory. If this fail because of bad creation time, go back to 4
// 6. Unlock the edge created in 3
//
// If 4 or 5 fails, 3 must be rolled back. 6 does not fail.
//
// 1 is necessary rather than failing on attempted override because otherwise failures
// due to repeated calls are indistinguishable from genuine failures.
struct MakeDirectoryStateMachine {
StateMachineEnv& env;
const MakeDirectoryReq& req;
MakeDirectoryState state;
MakeDirectoryStateMachine(StateMachineEnv& env_, const MakeDirectoryReq& req_, MakeDirectoryState state_):
env(env_), req(req_), state(state_)
{}
void resume(const ShardRespContainer* resp) {
if (env.txnStep == TXN_START) {
start();
return;
}
if (unlikely(resp == nullptr)) { // we're resuming with no response
switch (env.txnStep) {
case MAKE_DIRECTORY_LOOKUP: lookup(); break;
case MAKE_DIRECTORY_CREATE_DIR: createDirectoryInode(); break;
case MAKE_DIRECTORY_LOOKUP_OLD_CREATION_TIME: lookupOldCreationTime(); break;
case MAKE_DIRECTORY_CREATE_LOCKED_EDGE: createLockedEdge(); break;
case MAKE_DIRECTORY_UNLOCK_EDGE: unlockEdge(); break;
case MAKE_DIRECTORY_ROLLBACK: rollback(); break;
default: throw TERN_EXCEPTION("bad step %s", env.txnStep);
}
} else {
switch (env.txnStep) {
case MAKE_DIRECTORY_LOOKUP: afterLookup(*resp); break;
case MAKE_DIRECTORY_CREATE_DIR: afterCreateDirectoryInode(*resp); break;
case MAKE_DIRECTORY_LOOKUP_OLD_CREATION_TIME: afterLookupOldCreationTime(*resp); break;
case MAKE_DIRECTORY_CREATE_LOCKED_EDGE: afterCreateLockedEdge(*resp); break;
case MAKE_DIRECTORY_UNLOCK_EDGE: afterUnlockEdge(*resp); break;
case MAKE_DIRECTORY_ROLLBACK: afterRollback(*resp); break;
default: throw TERN_EXCEPTION("bad step %s", env.txnStep);
}
}
}
void start() {
state.setDirId(env.nextDirectoryId(env.dbTxn));
lookup();
}
void lookup(bool repeated = false) {
auto& shardReq = env.needsShard(MAKE_DIRECTORY_LOOKUP, req.ownerId.shard(), repeated).setLookup();
shardReq.dirId = req.ownerId;
shardReq.name = req.name;
}
void afterLookup(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
lookup(true); // retry
} else if (err == TernError::DIRECTORY_NOT_FOUND) {
env.finishWithError(err);
} else if (err == TernError::NAME_NOT_FOUND) {
// normal case, let's proceed
createDirectoryInode();
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
const auto& lookupResp = resp.getLookup();
if (lookupResp.targetId.type() == InodeType::DIRECTORY) {
// we're good already
auto& cdcResp = env.finish().setMakeDirectory();
cdcResp.creationTime = lookupResp.creationTime;
cdcResp.id = lookupResp.targetId;
} else {
env.finishWithError(TernError::CANNOT_OVERRIDE_NAME);
}
}
}
void createDirectoryInode(bool repeated = false) {
auto& shardReq = env.needsShard(MAKE_DIRECTORY_CREATE_DIR, state.dirId().shard(), repeated).setCreateDirectoryInode();
shardReq.id = state.dirId();
shardReq.ownerId = req.ownerId;
}
void afterCreateDirectoryInode(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
// Try again -- note that the call to create directory inode is idempotent.
createDirectoryInode(true);
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
lookupOldCreationTime();
}
}
void lookupOldCreationTime(bool repeated = false) {
auto& shardReq = env.needsShard(MAKE_DIRECTORY_LOOKUP_OLD_CREATION_TIME, req.ownerId.shard(), repeated).setFullReadDir();
shardReq.dirId = req.ownerId;
shardReq.flags = FULL_READ_DIR_BACKWARDS | FULL_READ_DIR_SAME_NAME | FULL_READ_DIR_CURRENT;
shardReq.limit = 1;
shardReq.startName = req.name;
shardReq.startTime = 0; // we have current set
}
void afterLookupOldCreationTime(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
lookupOldCreationTime(true); // retry
} else if (err == TernError::DIRECTORY_NOT_FOUND) {
// the directory we looked into doesn't even exist anymore --
// we've failed hard and we need to remove the inode.
state.setExitError(err);
rollback();
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
// there might be no existing edge
const auto& fullReadDir = resp.getFullReadDir();
ALWAYS_ASSERT(fullReadDir.results.els.size() < 2); // we have limit=1
if (fullReadDir.results.els.size() == 0) {
state.setOldCreationTime(0); // there was nothing present for this name
} else {
state.setOldCreationTime(fullReadDir.results.els[0].creationTime);
}
// keep going
createLockedEdge();
}
}
void createLockedEdge(bool repeated = false) {
auto& shardReq = env.needsShard(MAKE_DIRECTORY_CREATE_LOCKED_EDGE, req.ownerId.shard(), repeated).setCreateLockedCurrentEdge();
shardReq.dirId = req.ownerId;
shardReq.targetId = state.dirId();
shardReq.name = req.name;
shardReq.oldCreationTime = state.oldCreationTime();
}
void afterCreateLockedEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (createCurrentLockedEdgeRetry(err)) {
createLockedEdge(true); // try again
} else if (err == TernError::CANNOT_OVERRIDE_NAME) {
// this happens when a file gets created between when we looked
// up whether there was something else and now.
state.setExitError(err);
rollback();
} else if (err == TernError::MISMATCHING_CREATION_TIME) {
// lookup the old creation time again
lookupOldCreationTime();
} else {
// We know we cannot get directory not found because we managed to lookup
// old creation time.
//
// We also cannot get MISMATCHING_TARGET since we are the only one
// creating locked edges, and transactions execute serially.
ALWAYS_ASSERT(err == TernError::NO_ERROR);
state.setCreationTime(resp.getCreateLockedCurrentEdge().creationTime);
unlockEdge();
}
}
void unlockEdge(bool repeated = false) {
auto& shardReq = env.needsShard(MAKE_DIRECTORY_UNLOCK_EDGE, req.ownerId.shard(), repeated).setUnlockCurrentEdge();
shardReq.dirId = req.ownerId;
shardReq.name = req.name;
shardReq.targetId = state.dirId();
shardReq.wasMoved = false;
shardReq.creationTime = state.creationTime();
}
void afterUnlockEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT || err == TernError::MTIME_IS_TOO_RECENT) {
// retry
unlockEdge(true);
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
// We're done, record the parent relationship and finish
{
auto k = InodeIdKey::Static(state.dirId());
auto v = InodeIdValue::Static(req.ownerId);
ROCKS_DB_CHECKED(env.dbTxn.Put(env.parentCf, k.toSlice(), v.toSlice()));
}
auto& resp = env.finish().setMakeDirectory();
resp.id = state.dirId();
resp.creationTime = state.creationTime();
}
}
void rollback(bool repeated = false) {
// disown the child, it'll be collected by GC.
auto& shardReq = env.needsShard(MAKE_DIRECTORY_ROLLBACK, state.dirId().shard(), repeated).setRemoveDirectoryOwner();
shardReq.dirId = state.dirId();
// we've just created this directory, it is empty, therefore the policy
// is irrelevant.
shardReq.info = defaultDirectoryInfo();
}
void afterRollback(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
rollback(true); // retry
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
env.finishWithError(state.exitError());
}
}
};
enum HardUnlinkDirectoryStep : uint8_t {
HARD_UNLINK_DIRECTORY_REMOVE_INODE = 1,
};
// The only reason we have this here is for possible conflicts with RemoveDirectoryOwner,
// which might temporarily set the owner of a directory to NULL. Since in the current
// implementation we only ever have one transaction in flight in the CDC, we can just
// execute this.
struct HardUnlinkDirectoryStateMachine {
StateMachineEnv& env;
const HardUnlinkDirectoryReq& req;
HardUnlinkDirectoryState state;
HardUnlinkDirectoryStateMachine(StateMachineEnv& env_, const HardUnlinkDirectoryReq& req_, HardUnlinkDirectoryState state_):
env(env_), req(req_), state(state_)
{}
void resume(const ShardRespContainer* resp) {
if (env.txnStep == TXN_START) {
removeInode();
return;
}
if (unlikely(resp == nullptr)) { // we're resuming with no response
switch (env.txnStep) {
case HARD_UNLINK_DIRECTORY_REMOVE_INODE: removeInode(); break;
default: throw TERN_EXCEPTION("bad step %s", env.txnStep);
}
} else {
switch (env.txnStep) {
case HARD_UNLINK_DIRECTORY_REMOVE_INODE: afterRemoveInode(*resp); break;
default: throw TERN_EXCEPTION("bad step %s", env.txnStep);
}
}
}
void removeInode(bool repeated = false) {
auto& shardReq = env.needsShard(HARD_UNLINK_DIRECTORY_REMOVE_INODE, req.dirId.shard(), repeated).setRemoveInode();
shardReq.id = req.dirId;
}
void afterRemoveInode(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
removeInode(true); // try again
} else if (
err == TernError::DIRECTORY_NOT_FOUND || err == TernError::DIRECTORY_HAS_OWNER || err == TernError::DIRECTORY_NOT_EMPTY
) {
env.finishWithError(err);
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
env.finish().setHardUnlinkDirectory();
}
}
};
enum RenameFileStep : uint8_t {
RENAME_FILE_LOCK_OLD_EDGE = 1,
RENAME_FILE_LOOKUP_OLD_CREATION_TIME = 2,
RENAME_FILE_CREATE_NEW_LOCKED_EDGE = 3,
RENAME_FILE_UNLOCK_NEW_EDGE = 4,
RENAME_FILE_UNLOCK_OLD_EDGE = 5,
RENAME_FILE_ROLLBACK = 6,
};
// Steps:
//
// 1. lock source current edge
// 2. lookup prev creation time for current target edge
// 3. create destination locked current target edge. if it fails because of bad creation time, go back to 2
// 4. unlock edge in step 3
// 5. unlock source target current edge, and soft unlink it
//
// If we fail at step 2 or 3, we need to roll back step 1. Steps 3 and 4 should never fail.
struct RenameFileStateMachine {
StateMachineEnv& env;
const RenameFileReq& req;
RenameFileState state;
RenameFileStateMachine(StateMachineEnv& env_, const RenameFileReq& req_, RenameFileState state_):
env(env_), req(req_), state(state_)
{}
void resume(const ShardRespContainer* resp) {
if (env.txnStep == TXN_START) {
start();
return;
}
if (unlikely(resp == nullptr)) { // we're resuming with no response
switch (env.txnStep) {
case RENAME_FILE_LOCK_OLD_EDGE: lockOldEdge(); break;
case RENAME_FILE_LOOKUP_OLD_CREATION_TIME: lookupOldCreationTime(); break;
case RENAME_FILE_CREATE_NEW_LOCKED_EDGE: createNewLockedEdge(); break;
case RENAME_FILE_UNLOCK_NEW_EDGE: unlockNewEdge(); break;
case RENAME_FILE_UNLOCK_OLD_EDGE: unlockOldEdge(); break;
case RENAME_FILE_ROLLBACK: rollback(); break;
default: throw TERN_EXCEPTION("bad step %s", env.txnStep);
}
} else {
switch (env.txnStep) {
case RENAME_FILE_LOCK_OLD_EDGE: afterLockOldEdge(*resp); break;
case RENAME_FILE_LOOKUP_OLD_CREATION_TIME: afterLookupOldCreationTime(*resp); break;
case RENAME_FILE_CREATE_NEW_LOCKED_EDGE: afterCreateNewLockedEdge(*resp); break;
case RENAME_FILE_UNLOCK_NEW_EDGE: afterUnlockNewEdge(*resp); break;
case RENAME_FILE_UNLOCK_OLD_EDGE: afterUnlockOldEdge(*resp); break;
case RENAME_FILE_ROLLBACK: afterRollback(*resp); break;
default: throw TERN_EXCEPTION("bad step %s", env.txnStep);
}
}
}
void start() {
// We need this explicit check here because moving directories is more complicated,
// and therefore we do it in another transaction type entirely.
if (req.targetId.type() == InodeType::DIRECTORY) {
env.finishWithError(TernError::TYPE_IS_NOT_DIRECTORY);
} else if (req.oldOwnerId == req.newOwnerId) {
env.finishWithError(TernError::SAME_DIRECTORIES);
} else {
lockOldEdge();
}
}
void lockOldEdge(bool repeated = false) {
auto& shardReq = env.needsShard(RENAME_FILE_LOCK_OLD_EDGE, req.oldOwnerId.shard(), repeated).setLockCurrentEdge();
shardReq.dirId = req.oldOwnerId;
shardReq.name = req.oldName;
shardReq.targetId = req.targetId;
shardReq.creationTime = req.oldCreationTime;
}
void afterLockOldEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
lockOldEdge(true); // retry
} else if (
err == TernError::EDGE_NOT_FOUND || err == TernError::MISMATCHING_CREATION_TIME || err == TernError::DIRECTORY_NOT_FOUND
) {
// We failed hard and we have nothing to roll back
if (err == TernError::DIRECTORY_NOT_FOUND) {
err = TernError::OLD_DIRECTORY_NOT_FOUND;
}
env.finishWithError(err);
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
lookupOldCreationTime();
}
}
void lookupOldCreationTime(bool repeated = false) {
auto& shardReq = env.needsShard(RENAME_FILE_LOOKUP_OLD_CREATION_TIME, req.newOwnerId.shard(), repeated).setFullReadDir();
shardReq.dirId = req.newOwnerId;
shardReq.flags = FULL_READ_DIR_BACKWARDS | FULL_READ_DIR_SAME_NAME | FULL_READ_DIR_CURRENT;
shardReq.limit = 1;
shardReq.startName = req.newName;
shardReq.startTime = 0; // we have current set
}
void afterLookupOldCreationTime(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
lookupOldCreationTime(true); // retry
} else if (err == TernError::DIRECTORY_NOT_FOUND) {
// we've failed hard and we need to unlock the old edge.
err = TernError::NEW_DIRECTORY_NOT_FOUND;
state.setExitError(err);
rollback();
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
// there might be no existing edge
const auto& fullReadDir = resp.getFullReadDir();
ALWAYS_ASSERT(fullReadDir.results.els.size() < 2); // we have limit=1
if (fullReadDir.results.els.size() == 0) {
state.setNewOldCreationTime(0); // there was nothing present for this name
} else {
state.setNewOldCreationTime(fullReadDir.results.els[0].creationTime);
}
// keep going
createNewLockedEdge();
}
}
void createNewLockedEdge(bool repeated = false) {
auto& shardReq = env.needsShard(RENAME_FILE_CREATE_NEW_LOCKED_EDGE, req.newOwnerId.shard(), repeated).setCreateLockedCurrentEdge();
shardReq.dirId = req.newOwnerId;
shardReq.name = req.newName;
shardReq.targetId = req.targetId;
shardReq.oldCreationTime = state.newOldCreationTime();
}
void afterCreateNewLockedEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (createCurrentLockedEdgeRetry(err)) {
createNewLockedEdge(true); // retry
} else if (err == TernError::MISMATCHING_CREATION_TIME) {
// we need to lookup the creation time again.
lookupOldCreationTime();
} else if (err == TernError::CANNOT_OVERRIDE_NAME) {
// we failed hard and we need to rollback
state.setExitError(err);
rollback();
} else {
state.setNewCreationTime(resp.getCreateLockedCurrentEdge().creationTime);
unlockNewEdge();
}
}
void unlockNewEdge(bool repeated = false) {
auto& shardReq = env.needsShard(RENAME_FILE_UNLOCK_NEW_EDGE, req.newOwnerId.shard(), repeated).setUnlockCurrentEdge();
shardReq.dirId = req.newOwnerId;
shardReq.targetId = req.targetId;
shardReq.name = req.newName;
shardReq.wasMoved = false;
shardReq.creationTime = state.newCreationTime();
}
void afterUnlockNewEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
unlockNewEdge(true); // retry
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
unlockOldEdge();
}
}
void unlockOldEdge(bool repeated = false) {
// We're done creating the destination edge, now unlock the source, marking it as moved
auto& shardReq = env.needsShard(RENAME_FILE_UNLOCK_OLD_EDGE, req.oldOwnerId.shard(), repeated).setUnlockCurrentEdge();
shardReq.dirId = req.oldOwnerId;
shardReq.targetId = req.targetId;
shardReq.name = req.oldName;
shardReq.wasMoved = true;
shardReq.creationTime = req.oldCreationTime;
}
void afterUnlockOldEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
unlockOldEdge(true); // retry
} else {
// This can only be because of repeated calls from here: we have the edge locked,
// and only the CDC does changes.
// TODO it would be cleaner to verify this with a lookup
ALWAYS_ASSERT(err == TernError::NO_ERROR || err == TernError::EDGE_NOT_FOUND);
// we're finally done
auto& resp = env.finish().setRenameFile();
resp.creationTime = state.newCreationTime();
}
}
void rollback(bool repeated = false) {
auto& shardReq = env.needsShard(RENAME_FILE_ROLLBACK, req.oldOwnerId.shard(), repeated).setUnlockCurrentEdge();
shardReq.dirId = req.oldOwnerId;
shardReq.name = req.oldName;
shardReq.targetId = req.targetId;
shardReq.wasMoved = false;
shardReq.creationTime = state.newCreationTime();
}
void afterRollback(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
rollback(true); // retry
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
env.finishWithError(state.exitError());
}
}
};
enum SoftUnlinkDirectoryStep : uint8_t {
SOFT_UNLINK_DIRECTORY_LOCK_EDGE = 1,
SOFT_UNLINK_DIRECTORY_STAT = 2,
SOFT_UNLINK_DIRECTORY_REMOVE_OWNER = 3,
SOFT_UNLINK_DIRECTORY_UNLOCK_EDGE = 4,
SOFT_UNLINK_DIRECTORY_ROLLBACK = 5,
};
// Steps:
//
// 1. Lock edge going into the directory to remove. This prevents things making
// making it snapshot or similar in the meantime.
// 2. Resolve the directory info, since we'll need to store it when we remove the directory owner.
// 3. Remove directory owner from directory that we want to remove. This will fail if there still
// are current edges there.
// 4. Unlock edge going into the directory, making it snapshot.
//
// If 2 or 3 fail, we need to roll back the locking, without making the edge snapshot.
struct SoftUnlinkDirectoryStateMachine {
StateMachineEnv& env;
const SoftUnlinkDirectoryReq& req;
SoftUnlinkDirectoryState state;
DirectoryInfo info;
SoftUnlinkDirectoryStateMachine(StateMachineEnv& env_, const SoftUnlinkDirectoryReq& req_, SoftUnlinkDirectoryState state_):
env(env_), req(req_), state(state_)
{}
void resume(const ShardRespContainer* resp) {
if (env.txnStep == TXN_START) {
start();
return;
}
if (unlikely(resp == nullptr)) { // we're resuming with no response
switch (env.txnStep) {
case SOFT_UNLINK_DIRECTORY_LOCK_EDGE: lockEdge(); break;
case SOFT_UNLINK_DIRECTORY_STAT: stat(); break;
// We don't persist the directory info, so we need to restart the stating when resuming
case SOFT_UNLINK_DIRECTORY_REMOVE_OWNER: stat(); break;
case SOFT_UNLINK_DIRECTORY_UNLOCK_EDGE: unlockEdge(); break;
case SOFT_UNLINK_DIRECTORY_ROLLBACK: rollback(); break;
default: throw TERN_EXCEPTION("bad step %s", env.txnStep);
}
} else {
switch (env.txnStep) {
case SOFT_UNLINK_DIRECTORY_LOCK_EDGE: afterLockEdge(*resp); break;
case SOFT_UNLINK_DIRECTORY_STAT: afterStat(*resp); break;
case SOFT_UNLINK_DIRECTORY_REMOVE_OWNER: afterRemoveOwner(*resp); break;
case SOFT_UNLINK_DIRECTORY_UNLOCK_EDGE: afterUnlockEdge(*resp); break;
case SOFT_UNLINK_DIRECTORY_ROLLBACK: afterRollback(*resp); break;
default: throw TERN_EXCEPTION("bad step %s", env.txnStep);
}
}
}
void start() {
if (req.targetId.type() != InodeType::DIRECTORY) {
env.finishWithError(TernError::TYPE_IS_NOT_DIRECTORY);
} else {
lockEdge();
}
}
void lockEdge(bool repeated = false) {
auto& shardReq = env.needsShard(SOFT_UNLINK_DIRECTORY_LOCK_EDGE, req.ownerId.shard(), repeated).setLockCurrentEdge();
shardReq.dirId = req.ownerId;
shardReq.name = req.name;
shardReq.targetId = req.targetId;
shardReq.creationTime = req.creationTime;
}
void afterLockEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
lockEdge(true);
} else if (err == TernError::MISMATCHING_CREATION_TIME || err == TernError::EDGE_NOT_FOUND || err == TernError::DIRECTORY_NOT_FOUND) {
LOG_INFO(env.env, "failed locking edge in soft unlink for req: %s with err: %s", req, err);
env.finishWithError(err); // no rollback to be done
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
state.setStatDirId(req.targetId);
stat();
}
}
void stat(bool repeated = false) {
auto& shardReq = env.needsShard(SOFT_UNLINK_DIRECTORY_STAT, state.statDirId().shard(), repeated).setStatDirectory();
shardReq.id = state.statDirId();
}
void afterStat(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
stat(true); // retry
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
const auto& statResp = resp.getStatDirectory();
// insert tags
for (const auto& newEntry : statResp.info.entries.els) {
bool found = false;
for (const auto& entry: info.entries.els) {
if (entry.tag == newEntry.tag) {
found = true;
break;
}
}
if (!found) {
info.entries.els.emplace_back(newEntry);
}
}
if (info.entries.els.size() == REQUIRED_DIR_INFO_TAGS.size()) { // we've found everything
auto& shardReq = env.needsShard(SOFT_UNLINK_DIRECTORY_REMOVE_OWNER, req.targetId.shard(), false).setRemoveDirectoryOwner();
shardReq.dirId = req.targetId;
shardReq.info = info;
} else {
ALWAYS_ASSERT(statResp.owner != NULL_INODE_ID);
// keep walking upwards
state.setStatDirId(statResp.owner);
stat();
}
}
}
void afterRemoveOwner(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
// we don't want to keep the dir info around start again from the last stat
stat();
} else if (err == TernError::DIRECTORY_NOT_EMPTY) {
state.setExitError(err);
rollback();
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR, "Unexpected error when removing owner, ownerId=%s name=%s creationTime=%s targetId=%s: %s", req.ownerId, GoLangQuotedStringFmt(req.name.ref().data(), req.name.ref().size()), req.creationTime, req.targetId, err);
unlockEdge();
}
}
void unlockEdge(bool repeated = false) {
auto& shardReq = env.needsShard(SOFT_UNLINK_DIRECTORY_UNLOCK_EDGE, req.ownerId.shard(), repeated).setUnlockCurrentEdge();
shardReq.dirId = req.ownerId;
shardReq.name = req.name;
shardReq.targetId = req.targetId;
// Note that here we used wasMoved even if the subsequent
// snapshot edge will be non-owned, since we're dealing with
// a directory, rather than a file.
shardReq.wasMoved = true;
shardReq.creationTime = req.creationTime;
}
void afterUnlockEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
unlockEdge(true);
} else {
// This can only be because of repeated calls from here: we have the edge locked,
// and only the CDC does changes.
// TODO it would be cleaner to verify this with a lookup
ALWAYS_ASSERT(err == TernError::NO_ERROR || err == TernError::EDGE_NOT_FOUND);
auto& cdcResp = env.finish().setSoftUnlinkDirectory();
// Update parent map
{
auto k = InodeIdKey::Static(req.targetId);
ROCKS_DB_CHECKED(env.dbTxn.Delete(env.parentCf, k.toSlice()));
}
}
}
void rollback(bool repeated = false) {
auto& shardReq = env.needsShard(SOFT_UNLINK_DIRECTORY_ROLLBACK, req.ownerId.shard(), repeated).setUnlockCurrentEdge();
shardReq.dirId = req.ownerId;
shardReq.name = req.name;
shardReq.targetId = req.targetId;
shardReq.wasMoved = false;
shardReq.creationTime = req.creationTime;
}
void afterRollback(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
rollback(true);
} else {
// This can only be because of repeated calls from here: we have the edge locked,
// and only the CDC does changes.
// TODO it would be cleaner to verify this with a lookup
ALWAYS_ASSERT(err == TernError::NO_ERROR || err == TernError::EDGE_NOT_FOUND);
env.finishWithError(state.exitError());
}
}
};
enum RenameDirectoryStep : uint8_t {
RENAME_DIRECTORY_LOCK_OLD_EDGE = 1,
RENAME_DIRECTORY_LOOKUP_OLD_CREATION_TIME = 2,
RENAME_DIRECTORY_CREATE_LOCKED_NEW_EDGE = 3,
RENAME_DIRECTORY_UNLOCK_NEW_EDGE = 4,
RENAME_DIRECTORY_UNLOCK_OLD_EDGE = 5,
RENAME_DIRECTORY_SET_OWNER = 6,
RENAME_DIRECTORY_ROLLBACK = 7,
};
// Steps:
//
// 1. Make sure there's no loop by traversing the parents
// 2. Lock old edge
// 3. Lookup old creation time for the edge
// 4. Create and lock the new edge
// 5. Unlock the new edge
// 6. Unlock and unlink the old edge
// 7. Update the owner of the moved directory to the new directory
//
// If we fail at step 3 or 4, we need to unlock the edge we locked at step 2. Step 5 and 6
// should never fail.
struct RenameDirectoryStateMachine {
StateMachineEnv& env;
const RenameDirectoryReq& req;
RenameDirectoryState state;
RenameDirectoryStateMachine(StateMachineEnv& env_, const RenameDirectoryReq& req_, RenameDirectoryState state_):
env(env_), req(req_), state(state_)
{}
void resume(const ShardRespContainer* resp) {
if (env.txnStep == TXN_START) {
start();
return;
}
if (unlikely(resp == nullptr)) { // we're resuming with no response
switch (env.txnStep) {
case RENAME_DIRECTORY_LOCK_OLD_EDGE: lockOldEdge(); break;
case RENAME_DIRECTORY_LOOKUP_OLD_CREATION_TIME: lookupOldCreationTime(); break;
case RENAME_DIRECTORY_CREATE_LOCKED_NEW_EDGE: createLockedNewEdge(); break;
case RENAME_DIRECTORY_UNLOCK_NEW_EDGE: unlockNewEdge(); break;
case RENAME_DIRECTORY_UNLOCK_OLD_EDGE: unlockOldEdge(); break;
case RENAME_DIRECTORY_SET_OWNER: setOwner(); break;
case RENAME_DIRECTORY_ROLLBACK: rollback(); break;
default: throw TERN_EXCEPTION("bad step %s", env.txnStep);
}
} else {
switch (env.txnStep) {
case RENAME_DIRECTORY_LOCK_OLD_EDGE: afterLockOldEdge(*resp); break;
case RENAME_DIRECTORY_LOOKUP_OLD_CREATION_TIME: afterLookupOldCreationTime(*resp); break;
case RENAME_DIRECTORY_CREATE_LOCKED_NEW_EDGE: afterCreateLockedEdge(*resp); break;
case RENAME_DIRECTORY_UNLOCK_NEW_EDGE: afterUnlockNewEdge(*resp); break;
case RENAME_DIRECTORY_UNLOCK_OLD_EDGE: afterUnlockOldEdge(*resp); break;
case RENAME_DIRECTORY_SET_OWNER: afterSetOwner(*resp); break;
case RENAME_DIRECTORY_ROLLBACK: afterRollback(*resp); break;
default: throw TERN_EXCEPTION("bad step %s", env.txnStep);
}
}
}
// Check that changing this parent-child relationship wouldn't create
// loops in directory structure.
bool loopCheck() {
std::unordered_set<InodeId> visited;
InodeId cursor = req.targetId;
for (;;) {
if (visited.count(cursor) > 0) {
LOG_INFO(env.env, "Re-encountered %s in loop check, will return false", cursor);
return false;
}
LOG_DEBUG(env.env, "Performing loop check for %s", cursor);
visited.insert(cursor);
if (cursor == req.targetId) {
cursor = req.newOwnerId;
} else {
auto k = InodeIdKey::Static(cursor);
std::string v;
ROCKS_DB_CHECKED(env.dbTxn.Get({}, env.parentCf, k.toSlice(), &v));
cursor = ExternalValue<InodeIdValue>(v)().id();
}
if (cursor == ROOT_DIR_INODE_ID) {
break;
}
}
return true;
}
void start() {
if (req.targetId.type() != InodeType::DIRECTORY) {
env.finishWithError(TernError::TYPE_IS_NOT_DIRECTORY);
} else if (req.oldOwnerId == req.newOwnerId) {
env.finishWithError(TernError::SAME_DIRECTORIES);
} else if (!loopCheck()) {
// First, check if we'd create a loop
env.finishWithError(TernError::LOOP_IN_DIRECTORY_RENAME);
} else {
// Now, actually start by locking the old edge
lockOldEdge();
}
}
void lockOldEdge(bool repeated = false) {
auto& shardReq = env.needsShard(RENAME_DIRECTORY_LOCK_OLD_EDGE, req.oldOwnerId.shard(), repeated).setLockCurrentEdge();
shardReq.dirId = req.oldOwnerId;
shardReq.name = req.oldName;
shardReq.targetId = req.targetId;
shardReq.creationTime = req.oldCreationTime;
}
void afterLockOldEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
lockOldEdge(true); // retry
} else if (
err == TernError::DIRECTORY_NOT_FOUND || err == TernError::EDGE_NOT_FOUND || err == TernError::MISMATCHING_CREATION_TIME
) {
if (err == TernError::DIRECTORY_NOT_FOUND) {
err = TernError::OLD_DIRECTORY_NOT_FOUND;
}
env.finishWithError(err);
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
lookupOldCreationTime();
}
}
void lookupOldCreationTime(bool repeated = false) {
auto& shardReq = env.needsShard(RENAME_FILE_LOOKUP_OLD_CREATION_TIME, req.newOwnerId.shard(), repeated).setFullReadDir();
shardReq.dirId = req.newOwnerId;
shardReq.flags = FULL_READ_DIR_BACKWARDS | FULL_READ_DIR_SAME_NAME | FULL_READ_DIR_CURRENT;
shardReq.limit = 1;
shardReq.startName = req.newName;
shardReq.startTime = 0; // we have current set
}
void afterLookupOldCreationTime(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
lookupOldCreationTime(true); // retry
} else if (err == TernError::DIRECTORY_NOT_FOUND) {
// we've failed hard and we need to unlock the old edge.
state.setExitError(err);
rollback();
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
// there might be no existing edge
const auto& fullReadDir = resp.getFullReadDir();
ALWAYS_ASSERT(fullReadDir.results.els.size() < 2); // we have limit=1
if (fullReadDir.results.els.size() == 0) {
state.setNewOldCreationTime(0); // there was nothing present for this name
} else {
state.setNewOldCreationTime(fullReadDir.results.els[0].creationTime);
}
// keep going
createLockedNewEdge();
}
}
void createLockedNewEdge(bool repeated = false) {
auto& shardReq = env.needsShard(RENAME_DIRECTORY_CREATE_LOCKED_NEW_EDGE, req.newOwnerId.shard(), repeated).setCreateLockedCurrentEdge();
shardReq.dirId = req.newOwnerId;
shardReq.name = req.newName;
shardReq.targetId = req.targetId;
shardReq.oldCreationTime = state.newOldCreationTime();
}
void afterCreateLockedEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (createCurrentLockedEdgeRetry(err)) {
createLockedNewEdge(true);
} else if (err == TernError::MISMATCHING_CREATION_TIME) {
// we need to lookup the creation time again.
lookupOldCreationTime();
} else if (err == TernError::CANNOT_OVERRIDE_NAME) {
state.setExitError(err);
rollback();
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
state.setNewCreationTime(resp.getCreateLockedCurrentEdge().creationTime);
unlockNewEdge();
}
}
void unlockNewEdge(bool repeated = false) {
auto& shardReq = env.needsShard(RENAME_DIRECTORY_UNLOCK_NEW_EDGE, req.newOwnerId.shard(), repeated).setUnlockCurrentEdge();
shardReq.dirId = req.newOwnerId;
shardReq.name = req.newName;
shardReq.targetId = req.targetId;
shardReq.wasMoved = false;
shardReq.creationTime = state.newCreationTime();
}
void afterUnlockNewEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
unlockNewEdge(true);
} else if (err == TernError::EDGE_NOT_FOUND) {
// This can only be because of repeated calls from here: we have the edge locked,
// and only the CDC does changes.
// TODO it would be cleaner to verify this with a lookup
unlockOldEdge();
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
unlockOldEdge();
}
}
void unlockOldEdge(bool repeated = false) {
auto& shardReq = env.needsShard(RENAME_DIRECTORY_UNLOCK_OLD_EDGE, req.oldOwnerId.shard(), repeated).setUnlockCurrentEdge();
shardReq.dirId = req.oldOwnerId;
shardReq.name = req.oldName;
shardReq.targetId = req.targetId;
shardReq.wasMoved = true;
shardReq.creationTime = req.oldCreationTime;
}
void afterUnlockOldEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
unlockOldEdge(true);
} else if (err == TernError::EDGE_NOT_FOUND) {
// This can only be because of repeated calls from here: we have the edge locked,
// and only the CDC does changes.
// TODO it would be cleaner to verify this with a lookup
setOwner();
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
setOwner();
}
}
void setOwner(bool repeated = false) {
auto& shardReq = env.needsShard(RENAME_DIRECTORY_SET_OWNER, req.targetId.shard(), repeated).setSetDirectoryOwner();
shardReq.ownerId = req.newOwnerId;
shardReq.dirId = req.targetId;
}
void afterSetOwner(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
setOwner(true);
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
auto& resp = env.finish().setRenameDirectory();
resp.creationTime = state.newCreationTime();
// update cache
{
auto k = InodeIdKey::Static(req.targetId);
auto v = InodeIdValue::Static(req.newOwnerId);
ROCKS_DB_CHECKED(env.dbTxn.Put(env.parentCf, k.toSlice(), v.toSlice()));
}
}
}
void rollback(bool repeated = false) {
auto& shardReq = env.needsShard(RENAME_DIRECTORY_ROLLBACK, req.oldOwnerId.shard(), repeated).setUnlockCurrentEdge();
shardReq.dirId = req.oldOwnerId;
shardReq.name = req.oldName;
shardReq.targetId = req.targetId;
shardReq.wasMoved = false;
shardReq.creationTime = state.newCreationTime();
}
void afterRollback(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
rollback(true);
} else {
env.finishWithError(state.exitError());
}
}
};
enum CrossShardHardUnlinkFileStep : uint8_t {
CROSS_SHARD_HARD_UNLINK_FILE_REMOVE_EDGE = 1,
CROSS_SHARD_HARD_UNLINK_FILE_MAKE_TRANSIENT = 2,
};
// Steps:
//
// 1. Remove owning edge in one shard
// 2. Make file transient in other shard
//
// Step 2 cannot fail.
struct CrossShardHardUnlinkFileStateMachine {
StateMachineEnv& env;
const CrossShardHardUnlinkFileReq& req;
CrossShardHardUnlinkFileState state;
CrossShardHardUnlinkFileStateMachine(StateMachineEnv& env_, const CrossShardHardUnlinkFileReq& req_, CrossShardHardUnlinkFileState state_):
env(env_), req(req_), state(state_)
{}
void resume(const ShardRespContainer* resp) {
if (env.txnStep == TXN_START) {
start();
return;
}
if (unlikely(resp == nullptr)) { // we're resuming with no response
switch (env.txnStep) {
case CROSS_SHARD_HARD_UNLINK_FILE_REMOVE_EDGE: removeEdge(); break;
case CROSS_SHARD_HARD_UNLINK_FILE_MAKE_TRANSIENT: makeTransient(); break;
default: throw TERN_EXCEPTION("bad step %s", env.txnStep);
}
} else {
switch (env.txnStep) {
case CROSS_SHARD_HARD_UNLINK_FILE_REMOVE_EDGE: afterRemoveEdge(*resp); break;
case CROSS_SHARD_HARD_UNLINK_FILE_MAKE_TRANSIENT: afterMakeTransient(*resp); break;
default: throw TERN_EXCEPTION("bad step %s", env.txnStep);
}
}
}
void start() {
if (req.ownerId.shard() == req.targetId.shard()) {
env.finishWithError(TernError::SAME_SHARD);
} else if (req.targetId.type() == InodeType::DIRECTORY) {
env.finishWithError(TernError::TYPE_IS_DIRECTORY);
} else {
removeEdge();
}
}
void removeEdge(bool repeated = false) {
auto& shardReq = env.needsShard(CROSS_SHARD_HARD_UNLINK_FILE_REMOVE_EDGE, req.ownerId.shard(), repeated).setRemoveOwnedSnapshotFileEdge();
shardReq.ownerId = req.ownerId;
shardReq.targetId = req.targetId;
shardReq.name = req.name;
shardReq.creationTime = req.creationTime;
}
void afterRemoveEdge(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT || err == TernError::MTIME_IS_TOO_RECENT) {
removeEdge(true);
} else if (err == TernError::DIRECTORY_NOT_FOUND) {
env.finishWithError(err);
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR);
makeTransient();
}
}
void makeTransient(bool repeated = false) {
auto& shardReq = env.needsShard(CROSS_SHARD_HARD_UNLINK_FILE_MAKE_TRANSIENT, req.targetId.shard(), repeated).setMakeFileTransient();
shardReq.id = req.targetId;
shardReq.note = req.name;
}
void afterMakeTransient(const ShardRespContainer& resp) {
auto err = resp.kind() == ShardMessageKind::ERROR ? resp.getError() : TernError::NO_ERROR;
if (err == TernError::TIMEOUT) {
makeTransient(true);
} else {
ALWAYS_ASSERT(err == TernError::NO_ERROR || err == TernError::FILE_NOT_FOUND);
env.finish().setCrossShardHardUnlinkFile();
}
}
};
void CDCShardResp::pack(BincodeBuf& buf) const {
buf.packScalar(txnId.x);
checkPoint.pack(buf);
resp.pack(buf);
}
void CDCShardResp::unpack(BincodeBuf& buf) {
txnId.x = buf.unpackScalar<uint64_t>();
checkPoint.unpack(buf);
resp.unpack(buf);
}
size_t CDCShardResp::packedSize() const {
return sizeof(uint64_t) + checkPoint.packedSize() + resp.packedSize();
}
void CDCLogEntry::prepareLogEntries(std::vector<CDCReqContainer>& cdcReqs, std::vector<CDCShardResp>& shardResps, size_t maxPackedSize, std::vector<CDCLogEntry>& entriesOut) {
size_t usedSize = std::numeric_limits<size_t>::max();
CDCLogEntry* curEntry{nullptr};
for (auto& shardResp : shardResps) {
auto respSize = shardResp.packedSize();
ALWAYS_ASSERT(respSize < maxPackedSize);
if (unlikely(maxPackedSize - respSize < usedSize)) {
curEntry = &entriesOut.emplace_back();
usedSize = curEntry->packedSize();
}
curEntry->_shardResps.emplace_back(std::move(shardResp));
usedSize += respSize;
ALWAYS_ASSERT(usedSize <= maxPackedSize);
}
for (auto& cdcReq : cdcReqs) {
auto reqSize = cdcReq.packedSize();
ALWAYS_ASSERT(reqSize < maxPackedSize);
if (unlikely(maxPackedSize - reqSize < usedSize)) {
curEntry = &entriesOut.emplace_back();
usedSize = curEntry->packedSize();
}
curEntry->_cdcReqs.emplace_back(std::move(cdcReq));
usedSize += reqSize;
ALWAYS_ASSERT(usedSize <= maxPackedSize);
}
cdcReqs.clear();
shardResps.clear();
}
CDCLogEntry CDCLogEntry::prepareBootstrapEntry() {
CDCLogEntry entry;
entry._bootstrapEntry = true;
return entry;
}
void CDCLogEntry::pack(BincodeBuf& buf) const {
buf.packScalar<bool>(_bootstrapEntry);
buf.packScalar<uint32_t>(_cdcReqs.size());
for (auto& cdcReq : _cdcReqs) {
cdcReq.pack(buf);
}
buf.packScalar<uint32_t>(_shardResps.size());
for (auto& shardResp : _shardResps) {
shardResp.pack(buf);
}
}
void CDCLogEntry::unpack(BincodeBuf& buf) {
_bootstrapEntry = buf.unpackScalar<bool>();
_cdcReqs.resize(buf.unpackScalar<uint32_t>());
for (auto& cdcReq : _cdcReqs) {
cdcReq.unpack(buf);
}
_shardResps.resize(buf.unpackScalar<uint32_t>());
for (auto& shardResp : _shardResps) {
shardResp.unpack(buf);
}
}
size_t CDCLogEntry::packedSize() const {
size_t size{1 + 2 * sizeof(uint32_t)};
for (auto& cdcReq : _cdcReqs) {
size += cdcReq.packedSize();
}
for (auto& shardResp : _shardResps) {
size += shardResp.packedSize();
}
return size;
}
struct CDCDBImpl {
Env _env;
// The reason why we insist in storing everything in RocksDB is that we can do
// everything in a single transaction, so it's easier to reason about atomic
// modifications. _dirsToTxnsCf for example would be much simpler as a
// simple unordered_map.
//
// It also has the nice advantage that we don't need to reconstruct the state
// when starting up, it's all already there.
// The general pattern in this file is to use a txn for everything,
// hence this naming.
rocksdb::OptimisticTransactionDB* _dbDontUseDirectly;
rocksdb::ColumnFamilyHandle* _defaultCf;
rocksdb::ColumnFamilyHandle* _parentCf;
rocksdb::ColumnFamilyHandle* _enqueuedCf; // V1, txnId -> CDC req, only for executing or waiting to be executed requests
rocksdb::ColumnFamilyHandle* _executingCf; // V1, txnId -> CDC state machine, for requests that are executing
// V1, data structure storing a dir to txn ids mapping:
// InodeId -> txnId -- sentinel telling us what the first txn in line is. If none, zero.
// we need the sentinel to skip over tombstones quickly.
// InodeId, txnId set with the queue
rocksdb::ColumnFamilyHandle* _dirsToTxnsCf;
// legacy
rocksdb::ColumnFamilyHandle* _reqQueueCfLegacy; // V0, txnId -> CDC req, for all the requests (including historical)
AssertiveLock _processLock;
std::shared_ptr<rocksdb::Statistics> _dbStatistics;
std::string _dbStatisticsFile;
// ----------------------------------------------------------------
// initialization
CDCDBImpl() = delete;
CDCDBImpl& operator=(const CDCDBImpl&) = delete;
CDCDBImpl(Logger& logger, std::shared_ptr<XmonAgent>& xmon, SharedRocksDB& sharedDb) : _env(logger, xmon, "cdc_db") {
_defaultCf = sharedDb.getCF(rocksdb::kDefaultColumnFamilyName);
_reqQueueCfLegacy = sharedDb.getCF("reqQueue");
_parentCf = sharedDb.getCF("parent");
_enqueuedCf = sharedDb.getCF("enqueued");
_executingCf = sharedDb.getCF("executing");
_dirsToTxnsCf = sharedDb.getCF("dirsToTxns");
_dbDontUseDirectly = sharedDb.transactionDB();
_initDb();
}
// Getting/setting txn ids from our txn ids keys
#define TXN_ID_SETTER_GETTER(key, getterName, setterName) \
uint64_t getterName(rocksdb::Transaction& dbTxn) { \
std::string v; \
ROCKS_DB_CHECKED(dbTxn.Get({}, _defaultCf, cdcMetadataKey(&key), &v)); \
ExternalValue<U64Value> txnIdV(v); \
return txnIdV().u64(); \
} \
void setterName(rocksdb::Transaction& dbTxn, uint64_t x) { \
auto v = U64Value::Static(x); \
ROCKS_DB_CHECKED(dbTxn.Put(_defaultCf, cdcMetadataKey(&key), v.toSlice())); \
}
TXN_ID_SETTER_GETTER(LAST_TXN_KEY, _lastTxn, _setLastTxn)
TXN_ID_SETTER_GETTER(EXECUTING_TXN_KEY, _executingTxnLegacy, _setExecutingTxnLegacy)
#undef TXN_ID_SETTER_GETTER
// returns -1 if the version key was not set
int64_t _version(rocksdb::Transaction& dbTxn) {
std::string value;
auto status = dbTxn.Get({}, _defaultCf, cdcMetadataKey(&VERSION_KEY), &value);
if (status.IsNotFound()) {
return -1;
} else {
ROCKS_DB_CHECKED(status);
ExternalValue<U64Value> vV(value);
return vV().u64();
}
}
void _setVersion(rocksdb::Transaction& dbTxn, uint64_t version) {
auto v = U64Value::Static(version);
ROCKS_DB_CHECKED(dbTxn.Put(_defaultCf, cdcMetadataKey(&VERSION_KEY), v.toSlice()));
}
void _initDbV0(rocksdb::Transaction& dbTxn) {
LOG_INFO(_env, "initializing V0 db");
const auto keyExists = [&dbTxn](rocksdb::ColumnFamilyHandle* cf, const rocksdb::Slice& key) -> bool {
std::string value;
auto status = dbTxn.Get({}, cf, key, &value);
if (status.IsNotFound()) {
return false;
} else {
ROCKS_DB_CHECKED(status);
return true;
}
};
if (!keyExists(_defaultCf, cdcMetadataKey(&NEXT_DIRECTORY_ID_KEY))) {
LOG_INFO(_env, "initializing next directory id");
auto id = InodeIdValue::Static(InodeId::FromU64(ROOT_DIR_INODE_ID.u64 + 1));
ROCKS_DB_CHECKED(dbTxn.Put({}, cdcMetadataKey(&NEXT_DIRECTORY_ID_KEY), id.toSlice()));
}
const auto initZeroValue = [this, &keyExists, &dbTxn](const std::string& what, const CDCMetadataKey& key) {
if (!keyExists(_defaultCf, cdcMetadataKey(&key))) {
LOG_INFO(_env, "initializing %s", what);
StaticValue<U64Value> v;
v().setU64(0);
ROCKS_DB_CHECKED(dbTxn.Put({}, cdcMetadataKey(&key), v.toSlice()));
}
};
initZeroValue("last txn", LAST_TXN_KEY);
initZeroValue("first txn in queue", FIRST_TXN_IN_QUEUE_KEY);
initZeroValue("last txn in queue", LAST_TXN_IN_QUEUE_KEY);
initZeroValue("executing txn", EXECUTING_TXN_KEY);
initZeroValue("last applied log index", LAST_APPLIED_LOG_ENTRY_KEY);
}
void _initDbV1(rocksdb::Transaction& dbTxn) {
LOG_INFO(_env, "initializing V1 db");
// Pick up the executing txn, if any, and move it to the executing CF.
// We preserve the executing txn to preserve integrity.
{
uint64_t executingTxn = _executingTxnLegacy(dbTxn);
if (executingTxn != 0) {
LOG_INFO(_env, "migrating txn %s", executingTxn);
// _reqQueueCf -> _enqueuedCf
auto txnK = CDCTxnIdKey::Static(CDCTxnId(executingTxn));
std::string reqV;
ROCKS_DB_CHECKED(dbTxn.Get({}, _reqQueueCfLegacy, txnK.toSlice(), &reqV));
CDCReqContainer req;
bincodeFromRocksValue(reqV, req);
ROCKS_DB_CHECKED(dbTxn.Put(_enqueuedCf, txnK.toSlice(), reqV));
// EXECUTING_TXN_KEY -> _executingCf
std::string txnStateV;
ROCKS_DB_CHECKED(dbTxn.Get({}, _defaultCf, cdcMetadataKey(&EXECUTING_TXN_STATE_KEY), &txnStateV));
ROCKS_DB_CHECKED(dbTxn.Put(_executingCf, txnK.toSlice(), txnStateV));
// Add to _dirsToTxnsCf, will lock since things are empty
_addToDirsToTxns(dbTxn, txnK().id(), req);
}
}
// Throw away everything legacy. The clients will just retry.
ROCKS_DB_CHECKED(dbTxn.Delete(cdcMetadataKey(&FIRST_TXN_IN_QUEUE_KEY)));
ROCKS_DB_CHECKED(dbTxn.Delete(cdcMetadataKey(&LAST_TXN_IN_QUEUE_KEY)));
ROCKS_DB_CHECKED(dbTxn.Delete(cdcMetadataKey(&EXECUTING_TXN_KEY)));
ROCKS_DB_CHECKED(dbTxn.Delete(cdcMetadataKey(&EXECUTING_TXN_STATE_KEY)));
// We delete the _reqQueueCfLegacy CF outside the transaction, because it's just too expensive
// to delete here one-by-one.
}
void _initDb() {
rocksdb::WriteOptions options;
options.sync = true;
std::unique_ptr<rocksdb::Transaction> dbTxn(_dbDontUseDirectly->BeginTransaction(options));
if (_version(*dbTxn) == -1) {
_initDbV0(*dbTxn);
_setVersion(*dbTxn, 0);
}
if (_version(*dbTxn) == 0) {
_initDbV1(*dbTxn);
_setVersion(*dbTxn, 1);
}
commitTransaction(*dbTxn);
// This means that it'll be recreated and dropped each time, but that's OK.
_dbDontUseDirectly->DropColumnFamily(_reqQueueCfLegacy);
LOG_INFO(_env, "DB initialization done");
}
// ----------------------------------------------------------------
// retrying txns
void commitTransaction(rocksdb::Transaction& txn) {
XmonNCAlert alert(10_sec);
for (;;) {
auto status = txn.Commit();
if (likely(status.ok())) {
_env.clearAlert(alert);
return;
}
if (likely(status.IsTryAgain())) {
_env.updateAlert(alert, "got try again in CDC transaction, will sleep for a second and try again");
(1_sec).sleepRetry();
continue;
}
// We don't expect any other kind of error. The docs state:
//
// If this transaction was created by an OptimisticTransactionDB(),
// Status::Busy() may be returned if the transaction could not guarantee
// that there are no write conflicts. Status::TryAgain() may be returned
// if the memtable history size is not large enough
// (See max_write_buffer_size_to_maintain).
//
// However we never run transactions concurrently. So we should never get busy.
//
// This is just a way to throw the right exception.
ROCKS_DB_CHECKED(status);
}
}
// Processing
// ----------------------------------------------------------------
uint64_t _lastAppliedLogEntryDB() {
std::string value;
ROCKS_DB_CHECKED(_dbDontUseDirectly->Get({}, cdcMetadataKey(&LAST_APPLIED_LOG_ENTRY_KEY), &value));
ExternalValue<U64Value> v(value);
return v().u64();
}
uint64_t _lastAppliedLogEntry(rocksdb::Transaction& dbTxn) {
std::string value;
ROCKS_DB_CHECKED(dbTxn.Get({}, cdcMetadataKey(&LAST_APPLIED_LOG_ENTRY_KEY), &value));
ExternalValue<U64Value> v(value);
return v().u64();
}
void _advanceLastAppliedLogEntry(rocksdb::Transaction& dbTxn, uint64_t index) {
uint64_t oldIndex = _lastAppliedLogEntry(dbTxn);
ALWAYS_ASSERT(oldIndex+1 == index, "old index is %s, expected %s, got %s", oldIndex, oldIndex+1, index);
LOG_DEBUG(_env, "bumping log index from %s to %s", oldIndex, index);
StaticValue<U64Value> v;
v().setU64(index);
ROCKS_DB_CHECKED(dbTxn.Put({}, cdcMetadataKey(&LAST_APPLIED_LOG_ENTRY_KEY), v.toSlice()));
}
void _addToDirsToTxns(rocksdb::Transaction& dbTxn, CDCTxnId txnId, const CDCReqContainer& req) {
for (const auto dirId: directoriesNeedingLock(req)) {
LOG_DEBUG(_env, "adding dir %s for txn %s", dirId, txnId);
{
// into the set
StaticValue<DirsToTxnsKey> k;
k().setDirId(dirId);
k().setTxnId(txnId);
ROCKS_DB_CHECKED(dbTxn.Put(_dirsToTxnsCf, k.toSlice(), ""));
}
{
// sentinel, if necessary
StaticValue<DirsToTxnsKey> k;
k().setDirId(dirId);
k().setSentinel();
std::string v;
auto status = dbTxn.Get({}, _dirsToTxnsCf, k.toSlice(), &v);
if (status.IsNotFound()) { // we're the first ones here, add the sentinel
auto v = CDCTxnIdValue::Static(txnId);
ROCKS_DB_CHECKED(dbTxn.Put(_dirsToTxnsCf, k.toSlice(), v.toSlice()));
} else {
ROCKS_DB_CHECKED(status);
}
}
}
}
// Returns the txn ids that might be free to work now. Note that we don't
// know that for sure because they might not hold locks for all dirs. This
// function does not check that.
void _removeFromDirsToTxns(rocksdb::Transaction& dbTxn, CDCTxnId txnId, const CDCReqContainer& req, std::vector<CDCTxnId>& mightBeReady) {
for (const auto dirId: directoriesNeedingLock(req)) {
LOG_DEBUG(_env, "removing dir %s for txn %s", dirId, txnId);
StaticValue<DirsToTxnsKey> k;
k().setDirId(dirId);
k().setTxnId(txnId);
// Check if there's a next key in line. We know that we won't
// have to step over many deleted keys here because we go through the
// list in order, and we seek from the list element we've just deleted.
// It is however important to set the iteration upper bound as of to
// not spill over and possibly trip over deleted keys.
StaticValue<DirsToTxnsKey> upperBoundK;
upperBoundK().setDirId(dirId);
upperBoundK().setTxnId(CDCTxnId(~(uint64_t)0));
rocksdb::Slice upperBoundSlice = upperBoundK.toSlice();
rocksdb::ReadOptions itOptions;
itOptions.iterate_upper_bound = &upperBoundSlice;
std::unique_ptr<rocksdb::Iterator> it(dbTxn.GetIterator(itOptions, _dirsToTxnsCf));
it->Seek(k.toSlice());
// we must find the key here -- we're removing it.
ALWAYS_ASSERT(it->Valid());
{
// Additional safety check: the key is what we expect.
auto foundKey = ExternalValue<DirsToTxnsKey>::FromSlice(it->key());
ALWAYS_ASSERT(!foundKey().isSentinel() && foundKey().txnId() == txnId);
}
// now that we've done our checks, we can remove the key
ROCKS_DB_CHECKED(dbTxn.Delete(_dirsToTxnsCf, k.toSlice()));
// then we look for the next one, if there's anything,
// and overwrite/delete the sentinel
StaticValue<DirsToTxnsKey> sentinelK;
sentinelK().setDirId(dirId);
sentinelK().setSentinel();
it->Next();
if (it->Valid()) { // there's something, set the sentinel
auto nextK = ExternalValue<DirsToTxnsKey>::FromSlice(it->key());
auto sentinelV = CDCTxnIdValue::Static(nextK().txnId());
LOG_DEBUG(_env, "selected %s as next in line after finishing %s", nextK().txnId(), txnId);
mightBeReady.emplace_back(nextK().txnId());
ROCKS_DB_CHECKED(dbTxn.Put(_dirsToTxnsCf, sentinelK.toSlice(), sentinelV.toSlice()));
} else { // we were the last ones here, remove sentinel
ROCKS_DB_CHECKED(it->status());
ROCKS_DB_CHECKED(dbTxn.Delete(_dirsToTxnsCf, sentinelK.toSlice()));
}
}
}
// Check if we have a lock on all the directories that matter to the txn id.
// It is assumed that the txnId in question is already in _dirsToTxnsCf.
bool _isReadyToGo(rocksdb::Transaction& dbTxn, CDCTxnId txnId, const CDCReqContainer& req) {
for (const auto dirId: directoriesNeedingLock(req)) {
// the sentinel _must_ be present -- at the very least us!
StaticValue<DirsToTxnsKey> k;
k().setDirId(dirId);
k().setSentinel();
std::string v;
ROCKS_DB_CHECKED(dbTxn.Get({}, _dirsToTxnsCf, k.toSlice(), &v));
ExternalValue<CDCTxnIdValue> otherTxnId(v);
if (otherTxnId().id() != txnId) {
return false;
}
}
return true;
}
// Adds a request to the enqueued requests. Also adds it to dirsToTxns, which will implicitly
// acquire locks.
void _addToEnqueued(rocksdb::Transaction& dbTxn, CDCTxnId txnId, const CDCReqContainer& req) {
{
auto k = CDCTxnIdKey::Static(txnId);
std::string v = bincodeToRocksValue(req);
ROCKS_DB_CHECKED(dbTxn.Put(_enqueuedCf, k.toSlice(), v));
}
_addToDirsToTxns(dbTxn, txnId, req);
}
// Moves the state forward, filling in `step` appropriatedly, and writing
// out the updated state.
template<template<typename> typename V>
void _advance(
rocksdb::Transaction& dbTxn,
CDCTxnId txnId,
const CDCReqContainer& req,
const ShardRespContainer* shardResp,
V<TxnState>& state,
CDCStep& step,
// to collect things that might be able to start now because
// we've finished doing other stuff
std::vector<CDCTxnId>& txnIds
) {
LOG_DEBUG(_env, "advancing txn %s of kind %s with state", txnId, req.kind());
StateMachineEnv sm(_env, _defaultCf, _parentCf, dbTxn, txnId, state().step(), step);
switch (req.kind()) {
case CDCMessageKind::MAKE_DIRECTORY:
MakeDirectoryStateMachine(sm, req.getMakeDirectory(), state().getMakeDirectory()).resume(shardResp);
break;
case CDCMessageKind::HARD_UNLINK_DIRECTORY:
HardUnlinkDirectoryStateMachine(sm, req.getHardUnlinkDirectory(), state().getHardUnlinkDirectory()).resume(shardResp);
break;
case CDCMessageKind::RENAME_FILE:
RenameFileStateMachine(sm, req.getRenameFile(), state().getRenameFile()).resume(shardResp);
break;
case CDCMessageKind::SOFT_UNLINK_DIRECTORY:
SoftUnlinkDirectoryStateMachine(sm, req.getSoftUnlinkDirectory(), state().getSoftUnlinkDirectory()).resume(shardResp);
break;
case CDCMessageKind::RENAME_DIRECTORY:
RenameDirectoryStateMachine(sm, req.getRenameDirectory(), state().getRenameDirectory()).resume(shardResp);
break;
case CDCMessageKind::CROSS_SHARD_HARD_UNLINK_FILE:
CrossShardHardUnlinkFileStateMachine(sm, req.getCrossShardHardUnlinkFile(), state().getCrossShardHardUnlinkFile()).resume(shardResp);
break;
default:
throw TERN_EXCEPTION("bad cdc message kind %s", req.kind());
}
state().setStep(sm.txnStep);
if (sm.finished) {
// we finished immediately
LOG_DEBUG(_env, "txn %s with req %s finished", txnId, req);
_finishExecuting(dbTxn, txnId, req, txnIds);
} else {
// we still have something to do, persist
_setExecuting(dbTxn, txnId, state);
}
}
bool _isExecuting(rocksdb::Transaction& dbTxn, CDCTxnId txnId) {
auto k = CDCTxnIdKey::Static(txnId);
std::string v;
auto status = dbTxn.Get({}, _executingCf, k.toSlice(), &v);
if (status.IsNotFound()) {
return false;
}
ROCKS_DB_CHECKED(status);
return true;
}
template<template<typename> typename V>
void _setExecuting(rocksdb::Transaction& dbTxn, CDCTxnId txnId, V<TxnState>& state) {
auto k = CDCTxnIdKey::Static(txnId);
ROCKS_DB_CHECKED(dbTxn.Put(_executingCf, k.toSlice(), state.toSlice()));
}
void _finishExecuting(rocksdb::Transaction& dbTxn, CDCTxnId txnId, const CDCReqContainer& req, std::vector<CDCTxnId>& txnIds) {
{
// delete from _executingCf
auto k = CDCTxnIdKey::Static(txnId);
ROCKS_DB_CHECKED(dbTxn.Delete(_executingCf, k.toSlice()));
}
// delete from dirsToTxnIds
_removeFromDirsToTxns(dbTxn, txnId, req, txnIds);
}
// Starts executing the given transactions, if possible. If it managed
// to start something, it immediately advances it as well (no point delaying
// that).
//
// It modifies `txnIds` with new transactions we looked at if we immediately
// finish executing txns that we start here.
void _startExecuting(rocksdb::Transaction& dbTxn, std::vector<CDCTxnId>& txnIds, CDCStep& step) {
CDCReqContainer req;
for (int i = 0; i < txnIds.size(); i++) {
CDCTxnId txnId = txnIds[i];
auto reqK = CDCTxnIdKey::Static(txnId);
std::string reqV;
ROCKS_DB_CHECKED(dbTxn.Get({}, _enqueuedCf, reqK.toSlice(), &reqV));
bincodeFromRocksValue(reqV, req);
if (!_isExecuting(dbTxn, txnId)) {
if (_isReadyToGo(dbTxn, txnId, req)) {
LOG_DEBUG(_env, "starting to execute txn %s with req %s, since it is ready to go and not executing already", txnId, req);
StaticValue<TxnState> txnState;
txnState().start(req.kind());
_setExecuting(dbTxn, txnId, txnState);
_advance(dbTxn, txnId, req, nullptr, txnState, step, txnIds);
} else {
LOG_DEBUG(_env, "waiting before executing txn %s with req %s, since it is not ready to go", txnId, req);
}
}
}
}
void _enqueueCDCReqs(
rocksdb::Transaction& dbTxn,
const std::vector<CDCReqContainer>& reqs,
CDCStep& step,
// we need two lists because one (`cdcReqsTxnIds`) is specifically
// to return to the user, while the other is used for other purposes,
// too.
std::vector<CDCTxnId>& txnIdsToStart,
std::vector<CDCTxnId>& cdcReqsTxnIds
) {
for (const auto& req: reqs) {
uint64_t txnId;
{
// Generate new txn id
txnId = _lastTxn(dbTxn) + 1;
_setLastTxn(dbTxn, txnId);
// Push to queue
_addToEnqueued(dbTxn, txnId, req);
LOG_DEBUG(_env, "enqueued CDC req %s with txn id %s", req.kind(), txnId);
}
txnIdsToStart.emplace_back(txnId);
cdcReqsTxnIds.emplace_back(txnId);
}
}
void _advanceWithResp(
rocksdb::Transaction& dbTxn,
CDCTxnId txnId,
const ShardRespContainer* resp,
CDCStep& step,
std::vector<CDCTxnId>& txnIdsToStart
) {
auto txnIdK = CDCTxnIdKey::Static(txnId);
// Get the req
CDCReqContainer cdcReq;
{
std::string reqV;
ROCKS_DB_CHECKED(dbTxn.Get({}, _enqueuedCf, txnIdK.toSlice(), &reqV));
bincodeFromRocksValue(reqV, cdcReq);
}
// Get the state
std::string txnStateV;
ROCKS_DB_CHECKED(dbTxn.Get({}, _executingCf, txnIdK.toSlice(), &txnStateV));
ExternalValue<TxnState> txnState(txnStateV);
// Advance with response
_advance(dbTxn, txnId, cdcReq, resp, txnState, step, txnIdsToStart);
}
void update(
bool sync,
uint64_t logIndex,
const std::vector<CDCReqContainer>& cdcReqs,
const std::vector<CDCShardResp>& shardResps,
CDCStep& step,
std::vector<CDCTxnId>& cdcReqsTxnIds
) {
auto locked = _processLock.lock();
rocksdb::WriteOptions options;
options.sync = sync;
std::unique_ptr<rocksdb::Transaction> dbTxn(_dbDontUseDirectly->BeginTransaction(options));
_advanceLastAppliedLogEntry(*dbTxn, logIndex);
step.clear();
cdcReqsTxnIds.clear();
{
std::vector<CDCTxnId> txnIdsToStart;
_enqueueCDCReqs(*dbTxn, cdcReqs, step, txnIdsToStart, cdcReqsTxnIds);
for (const auto& resp: shardResps) {
_advanceWithResp(*dbTxn, resp.txnId, &resp.resp, step, txnIdsToStart);
}
_startExecuting(*dbTxn, txnIdsToStart, step);
}
commitTransaction(*dbTxn);
}
void bootstrap(
bool sync,
uint64_t logIndex,
CDCStep& step
) {
auto locked = _processLock.lock();
rocksdb::WriteOptions options;
options.sync = sync;
std::unique_ptr<rocksdb::Transaction> dbTxn(_dbDontUseDirectly->BeginTransaction(options));
step.clear();
_advanceLastAppliedLogEntry(*dbTxn, logIndex);
std::vector<CDCTxnId> txnIdsToStart;
// Just collect all executing txns, and run them
std::unique_ptr<rocksdb::Iterator> it(dbTxn->GetIterator({}, _executingCf));
for (it->SeekToFirst(); it->Valid(); it->Next()) {
auto txnIdK = ExternalValue<CDCTxnIdKey>::FromSlice(it->key());
_advanceWithResp(*dbTxn, txnIdK().id(), nullptr, step, txnIdsToStart);
}
ROCKS_DB_CHECKED(it->status());
_startExecuting(*dbTxn, txnIdsToStart, step);
commitTransaction(*dbTxn);
}
};
CDCDB::CDCDB(Logger& logger, std::shared_ptr<XmonAgent>& xmon, SharedRocksDB& sharedDb) {
_impl = new CDCDBImpl(logger, xmon, sharedDb);
}
CDCDB::~CDCDB() {
delete ((CDCDBImpl*)_impl);
}
void CDCDB::applyLogEntry(bool sync, const CDCLogEntry& entry, CDCStep& step, std::vector<CDCTxnId>& cdcReqsTxnIds) {
if (unlikely(entry.bootstrapEntry())) {
((CDCDBImpl*)_impl)->bootstrap(sync, entry.logIdx(), step);
} else {
((CDCDBImpl*)_impl)->update(sync, entry.logIdx(), entry.cdcReqs(), entry.shardResps(), step, cdcReqsTxnIds);
}
}
uint64_t CDCDB::lastAppliedLogEntry() {
return ((CDCDBImpl*)_impl)->_lastAppliedLogEntryDB();
}
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