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ternfs-XTXMarkets/cpp/cdc/CDCDB.cpp
Francesco Mazzoli 6addbdee6a First version of kernel module 
Initial version really by Pawel, but many changes in between.

Big outstanding issues:

* span cache reclamation (unbounded memory otherwise...)
* bad block service detection and workarounds
* corrupted blocks detection and workaround

Co-authored-by: Paweł Dziepak <pawel.dziepak@xtxmarkets.com>
2023-05-18 15:29:41 +00:00

1543 lines
58 KiB
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#include <memory>
#include <rocksdb/db.h>
#include <rocksdb/options.h>
#include <rocksdb/utilities/transaction.h>
#include <rocksdb/utilities/optimistic_transaction_db.h>
#include "Assert.hpp"
#include "Bincode.hpp"
#include "CDCDB.hpp"
#include "AssertiveLock.hpp"
#include "CDCDBData.hpp"
#include "Env.hpp"
#include "Exception.hpp"
#include "Msgs.hpp"
#include "RocksDBUtils.hpp"
#include "ShardDB.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 most obvious way to do this is to lock directory modifications here on
// the CDC servers (e.g. have transactions which need to lock edges in directory
// X to execute serially). Then at every update we can pop stuff from the queue.
//
// For now though, to keep things simple, we just execute _everything_ serially.
//
// So we need to store two things:
//
// * A queue of client requests that we haven't gotten to execute yet;
// * The state for the currently running request.
//
// For now, we just store a queue of requests.
//
// The queue is just indexed by a uint64_t transaction id, which monotonically
// increases. We store this txn id in the database so that we can keep generating
// unique ones even when the queue is empty. We also need to remember it so that
// we can just read/insert without seeking (see
// <https://github.com/facebook/rocksdb/wiki/Implement-Queue-Service-Using-RocksDB>).
//
// So we have one CF which is just a queue with this schema:
//
// * txnid -> cdc req
//
// Then we have another CF with some metadata, specifically:
//
// * LAST_APPLIED_LOG_ENTRY_KEY: to ensure the log entries are applied sequentially
// * LAST_TXN_KEY: last txn enqueued, to generate txn ids (note that we need this on top of the two below to generate globally unique ids)
// * FIRST_TXN_IN_QUEUE_KEY: next in line in the reqs queue, 0 if queue is empty
// * LAST_TXN_IN_QUEUE_KEY: last txn id in the queue, 0 if queue is empty. We need this to
// * EXECUTING_TXN_KEY: txn currently executing. if zero, none.
// * EXECUTING_TXN_STATE_KEY: state of the currently executing txn.
//
// The request stays on the queue until it finishes executing.
//
// The txn state would look something like this:
//
// * uint8_t step
// * ... additional state depending on the request type and step ...
//
// Finally, we store another CF with directory child -> directory parent
// cache, which is updated in directory create and directory moves operations.
// We never delete data from here for now, since even if we stored everything in
// it it wouldn't be very big anyway (~100GiB, assuming an average of 100 files
// per directory).
//
// With regards to log entries, we have three sort of updates:
//
// * A new cdc request arrives;
// * A shard response arrives which we need to advance the current transaction;
// * We want to begin the next transaction.
//
// We separate the action that begins the next transaction to simplify the
// implementation (we don't need "draining" logic in the CDC DB itself),
// and also to offer freedom regarding how to process transactions to what
// uses the CDC DB.
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) {
ALWAYS_ASSERT(!(x.txnFinished != 0 && x.txnNeedsShard != 0));
out << "CDCStep(";
if (x.txnFinished != 0) {
out << "finishedTxn=" << x.txnFinished;
if (x.err != NO_ERROR) {
out << ", err=" << x.err;
} else {
out << ", resp=" << x.resp;
}
}
if (x.txnNeedsShard != 0) {
out << "txnNeedsShard=" << x.txnNeedsShard << ", shardReq=" << x.shardReq;
}
if (x.nextTxn != 0) {
if (x.txnFinished != 0 || x.txnNeedsShard != 0) {
out << ", ";
}
out << "nextTxn=" << x.nextTxn;
}
out << ")";
return out;
}
inline bool createCurrentLockedEdgeRetry(EggsError err) {
return
err == EggsError::TIMEOUT || err == EggsError::MTIME_IS_TOO_RECENT ||
err == EggsError::MORE_RECENT_SNAPSHOT_EDGE || err == EggsError::MORE_RECENT_CURRENT_EDGE;
}
inline bool createCurrentLockedEdgeFatal(EggsError err) {
return
err == EggsError::DIRECTORY_NOT_FOUND || err == EggsError::CANNOT_OVERRIDE_NAME;
}
struct StateMachineEnv {
Env& env;
rocksdb::OptimisticTransactionDB* db;
rocksdb::ColumnFamilyHandle* defaultCf;
rocksdb::ColumnFamilyHandle* parentCf;
rocksdb::Transaction& dbTxn;
EggsTime time;
uint64_t txnId;
uint8_t txnStep;
CDCStep& cdcStep;
StateMachineEnv(
Env& env_, rocksdb::OptimisticTransactionDB* db_, rocksdb::ColumnFamilyHandle* defaultCf_, rocksdb::ColumnFamilyHandle* parentCf_, rocksdb::Transaction& dbTxn_, EggsTime time_, uint64_t txnId_, uint8_t step_, CDCStep& cdcStep_
):
env(env_), db(db_), defaultCf(defaultCf_), parentCf(parentCf_), dbTxn(dbTxn_), time(time_), txnId(txnId_), txnStep(step_), cdcStep(cdcStep_)
{}
InodeId nextDirectoryId() {
std::string v;
ROCKS_DB_CHECKED(db->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) {
txnStep = step;
cdcStep.txnFinished = 0;
cdcStep.txnNeedsShard = txnId;
cdcStep.shardReq.shid = shid;
return cdcStep.shardReq.req;
}
CDCRespContainer& finish() {
cdcStep.txnFinished = txnId;
cdcStep.err = NO_ERROR;
return cdcStep.resp;
}
void finishWithError(EggsError err) {
ALWAYS_ASSERT(err != NO_ERROR);
cdcStep.txnFinished = txnId;
cdcStep.err = err;
cdcStep.txnNeedsShard = 0;
}
};
constexpr uint8_t TXN_START = 0;
enum MakeDirectoryStep : uint8_t {
MAKE_DIRECTORY_LOOKUP = 1,
MAKE_DIRECTORY_CREATE_DIR = 2,
MAKE_DIRECTORY_CREATE_LOCKED_EDGE = 3,
MAKE_DIRECTORY_UNLOCK_EDGE = 4,
MAKE_DIRECTORY_ROLLBACK = 5,
};
// 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. Create locked edge from owner to newly created directory
// 5. Unlock the edge created in 3
//
// If 4 fails, 3 must be rolled back. 5 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(EggsError err, const ShardRespContainer* resp) {
if (env.txnStep == TXN_START) {
start();
return;
}
if (unlikely(err == NO_ERROR && 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_CREATE_LOCKED_EDGE: createLockedEdge(); break;
case MAKE_DIRECTORY_UNLOCK_EDGE: unlockEdge(); break;
case MAKE_DIRECTORY_ROLLBACK: rollback(); break;
default: throw EGGS_EXCEPTION("bad step %s", env.txnStep);
}
} else {
switch (env.txnStep) {
case MAKE_DIRECTORY_LOOKUP: afterLookup(err, resp); break;
case MAKE_DIRECTORY_CREATE_DIR: afterCreateDirectoryInode(err, resp); break;
case MAKE_DIRECTORY_CREATE_LOCKED_EDGE: afterCreateLockedEdge(err, resp); break;
case MAKE_DIRECTORY_UNLOCK_EDGE: afterUnlockEdge(err, resp); break;
case MAKE_DIRECTORY_ROLLBACK: afterRollback(err, resp); break;
default: throw EGGS_EXCEPTION("bad step %s", env.txnStep);
}
}
}
void start() {
state.setDirId(env.nextDirectoryId());
lookup();
}
void lookup() {
auto& shardReq = env.needsShard(MAKE_DIRECTORY_LOOKUP, req.ownerId.shard()).setLookup();
shardReq.dirId = req.ownerId;
shardReq.name = req.name;
}
void afterLookup(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
lookup(); // retry
} else if (err == EggsError::DIRECTORY_NOT_FOUND) {
env.finishWithError(err);
} else if (err == EggsError::NAME_NOT_FOUND) {
// normal case, let's proceed
createDirectoryInode();
} else {
ALWAYS_ASSERT(err == 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(EggsError::CANNOT_OVERRIDE_NAME);
}
}
}
void createDirectoryInode() {
auto& shardReq = env.needsShard(MAKE_DIRECTORY_CREATE_DIR, state.dirId().shard()).setCreateDirectoryInode();
shardReq.id = state.dirId();
shardReq.ownerId = req.ownerId;
}
void afterCreateDirectoryInode(EggsError shardRespError, const ShardRespContainer* shardResp) {
if (shardRespError == EggsError::TIMEOUT) {
// Try again -- note that the call to create directory inode is idempotent.
createDirectoryInode();
} else {
ALWAYS_ASSERT(shardRespError == NO_ERROR);
createLockedEdge();
}
}
void createLockedEdge() {
auto& shardReq = env.needsShard(MAKE_DIRECTORY_CREATE_LOCKED_EDGE, req.ownerId.shard()).setCreateLockedCurrentEdge();
shardReq.dirId = req.ownerId;
shardReq.targetId = state.dirId();
shardReq.name = req.name;
}
void afterCreateLockedEdge(EggsError err, const ShardRespContainer* resp) {
if (createCurrentLockedEdgeRetry(err)) {
createLockedEdge(); // try again
} else if (createCurrentLockedEdgeFatal(err)) {
// can't go forward
state.setExitError(err);
rollback();
} else {
ALWAYS_ASSERT(err == NO_ERROR);
state.setCreationTime(resp->getCreateLockedCurrentEdge().creationTime);
unlockEdge();
}
}
void unlockEdge() {
auto& shardReq = env.needsShard(MAKE_DIRECTORY_UNLOCK_EDGE, req.ownerId.shard()).setUnlockCurrentEdge();
shardReq.dirId = req.ownerId;
shardReq.name = req.name;
shardReq.targetId = state.dirId();
shardReq.wasMoved = false;
shardReq.creationTime = state.creationTime();
}
void afterUnlockEdge(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
// retry
unlockEdge();
} else {
ALWAYS_ASSERT(err == 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() {
auto& shardReq = env.needsShard(MAKE_DIRECTORY_ROLLBACK, state.dirId().shard()).setRemoveDirectoryOwner();
shardReq.dirId = state.dirId();
// we've just created this directory, it is empty, therefore the policy
// is irrelevant.
shardReq.info = defaultDirectoryInfo();
}
void afterRollback(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
rollback(); // retry
} else {
ALWAYS_ASSERT(err == 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(EggsError err, const ShardRespContainer* resp) {
if (env.txnStep == TXN_START) {
removeInode();
return;
}
if (unlikely(err == NO_ERROR && resp == nullptr)) { // we're resuming with no response
switch (env.txnStep) {
case HARD_UNLINK_DIRECTORY_REMOVE_INODE: removeInode(); break;
default: throw EGGS_EXCEPTION("bad step %s", env.txnStep);
}
} else {
switch (env.txnStep) {
case HARD_UNLINK_DIRECTORY_REMOVE_INODE: afterRemoveInode(err, resp); break;
default: throw EGGS_EXCEPTION("bad step %s", env.txnStep);
}
}
}
void removeInode() {
auto& shardReq = env.needsShard(HARD_UNLINK_DIRECTORY_REMOVE_INODE, req.dirId.shard()).setRemoveInode();
shardReq.id = req.dirId;
}
void afterRemoveInode(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
removeInode(); // try again
} else if (
err == EggsError::DIRECTORY_NOT_FOUND || err == EggsError::DIRECTORY_HAS_OWNER || err == EggsError::DIRECTORY_NOT_EMPTY
) {
env.finishWithError(err);
} else {
ALWAYS_ASSERT(err == NO_ERROR);
env.finish().setHardUnlinkDirectory();
}
}
};
enum RenameFileStep : uint8_t {
RENAME_FILE_LOCK_OLD_EDGE = 1,
RENAME_FILE_CREATE_NEW_LOCKED_EDGE = 2,
RENAME_FILE_UNLOCK_NEW_EDGE = 3,
RENAME_FILE_UNLOCK_OLD_EDGE = 4,
RENAME_FILE_ROLLBACK = 5,
};
// Steps:
//
// 1. lock source current edge
// 2. create destination locked current target edge
// 3. unlock edge in step 2
// 4. unlock source target current edge, and soft unlink it
//
// If we fail at step 2, 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(EggsError err, const ShardRespContainer* resp) {
if (env.txnStep == TXN_START) {
start();
return;
}
if (unlikely(err == NO_ERROR && resp == nullptr)) { // we're resuming with no response
switch (env.txnStep) {
case RENAME_FILE_LOCK_OLD_EDGE: lockOldEdge(); 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 EGGS_EXCEPTION("bad step %s", env.txnStep);
}
} else {
switch (env.txnStep) {
case RENAME_FILE_LOCK_OLD_EDGE: afterLockOldEdge(err, resp); break;
case RENAME_FILE_CREATE_NEW_LOCKED_EDGE: afterCreateNewLockedEdge(err, resp); break;
case RENAME_FILE_UNLOCK_NEW_EDGE: afterUnlockNewEdge(err, resp); break;
case RENAME_FILE_UNLOCK_OLD_EDGE: afterUnlockOldEdge(err, resp); break;
case RENAME_FILE_ROLLBACK: afterRollback(err, resp); break;
default: throw EGGS_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(EggsError::TYPE_IS_NOT_DIRECTORY);
} else if (req.oldOwnerId == req.newOwnerId) {
env.finishWithError(EggsError::SAME_DIRECTORIES);
} else {
lockOldEdge();
}
}
void lockOldEdge() {
auto& shardReq = env.needsShard(RENAME_FILE_LOCK_OLD_EDGE, req.oldOwnerId.shard()).setLockCurrentEdge();
shardReq.dirId = req.oldOwnerId;
shardReq.name = req.oldName;
shardReq.targetId = req.targetId;
shardReq.creationTime = req.oldCreationTime;
}
void afterLockOldEdge(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
lockOldEdge(); // retry
} else if (
err == EggsError::EDGE_NOT_FOUND || err == EggsError::MISMATCHING_CREATION_TIME || err == EggsError::DIRECTORY_NOT_FOUND
) {
// We failed hard and we have nothing to roll back
if (err == EggsError::DIRECTORY_NOT_FOUND) {
err = EggsError::OLD_DIRECTORY_NOT_FOUND;
}
env.finishWithError(err);
} else {
ALWAYS_ASSERT(err == NO_ERROR);
createNewLockedEdge();
}
}
void createNewLockedEdge() {
auto& shardReq = env.needsShard(RENAME_FILE_CREATE_NEW_LOCKED_EDGE, req.newOwnerId.shard()).setCreateLockedCurrentEdge();
shardReq.dirId = req.newOwnerId;
shardReq.name = req.newName;
shardReq.targetId = req.targetId;
}
void afterCreateNewLockedEdge(EggsError err, const ShardRespContainer* resp) {
if (createCurrentLockedEdgeRetry(err)) {
createNewLockedEdge(); // retry
} else if (createCurrentLockedEdgeFatal(err)) {
if (err == EggsError::DIRECTORY_NOT_FOUND) {
err = EggsError::NEW_DIRECTORY_NOT_FOUND;
}
// we failed hard and we need to rollback
state.setExitError(err);
rollback();
} else {
state.setNewCreationTime(resp->getCreateLockedCurrentEdge().creationTime);
unlockNewEdge();
}
}
void unlockNewEdge() {
auto& shardReq = env.needsShard(RENAME_FILE_UNLOCK_NEW_EDGE, req.newOwnerId.shard()).setUnlockCurrentEdge();
shardReq.dirId = req.newOwnerId;
shardReq.targetId = req.targetId;
shardReq.name = req.newName;
shardReq.wasMoved = false;
shardReq.creationTime = state.newCreationTime();
}
void afterUnlockNewEdge(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
unlockNewEdge(); // retry
} else {
ALWAYS_ASSERT(err == NO_ERROR);
unlockOldEdge();
}
}
void unlockOldEdge() {
// 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()).setUnlockCurrentEdge();
shardReq.dirId = req.oldOwnerId;
shardReq.targetId = req.targetId;
shardReq.name = req.oldName;
shardReq.wasMoved = true;
shardReq.creationTime = req.oldCreationTime;
}
void afterUnlockOldEdge(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
unlockOldEdge(); // 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 == NO_ERROR || err == EggsError::EDGE_NOT_FOUND);
// we're finally done
auto& resp = env.finish().setRenameFile();
resp.creationTime = state.newCreationTime();
}
}
void rollback() {
auto& shardReq = env.needsShard(RENAME_FILE_ROLLBACK, req.oldOwnerId.shard()).setUnlockCurrentEdge();
shardReq.dirId = req.oldOwnerId;
shardReq.name = req.oldName;
shardReq.targetId = req.targetId;
shardReq.wasMoved = false;
shardReq.creationTime = state.newCreationTime();
}
void afterRollback(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
rollback(); // retry
} else {
ALWAYS_ASSERT(err == 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(EggsError err, const ShardRespContainer* resp) {
if (env.txnStep == TXN_START) {
start();
return;
}
if (unlikely(err == NO_ERROR && 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 EGGS_EXCEPTION("bad step %s", env.txnStep);
}
} else {
switch (env.txnStep) {
case SOFT_UNLINK_DIRECTORY_LOCK_EDGE: afterLockEdge(err, resp); break;
case SOFT_UNLINK_DIRECTORY_STAT: afterStat(err, resp); break;
case SOFT_UNLINK_DIRECTORY_REMOVE_OWNER: afterRemoveOwner(err, resp); break;
case SOFT_UNLINK_DIRECTORY_UNLOCK_EDGE: afterUnlockEdge(err, resp); break;
case SOFT_UNLINK_DIRECTORY_ROLLBACK: afterRollback(err, resp); break;
default: throw EGGS_EXCEPTION("bad step %s", env.txnStep);
}
}
}
void start() {
if (req.targetId.type() != InodeType::DIRECTORY) {
env.finishWithError(EggsError::TYPE_IS_NOT_DIRECTORY);
} else {
lockEdge();
}
}
void lockEdge() {
auto& shardReq = env.needsShard(SOFT_UNLINK_DIRECTORY_LOCK_EDGE, req.ownerId.shard()).setLockCurrentEdge();
shardReq.dirId = req.ownerId;
shardReq.name = req.name;
shardReq.targetId = req.targetId;
shardReq.creationTime = req.creationTime;
}
void afterLockEdge(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
lockEdge();
} else if (err == EggsError::MISMATCHING_CREATION_TIME || err == EggsError::EDGE_NOT_FOUND) {
env.finishWithError(err); // no rollback to be done
} else {
ALWAYS_ASSERT(err == NO_ERROR);
state.setStatDirId(req.targetId);
stat();
}
}
void stat() {
auto& shardReq = env.needsShard(SOFT_UNLINK_DIRECTORY_STAT, state.statDirId().shard()).setStatDirectory();
shardReq.id = state.statDirId();
}
void afterStat(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
stat(); // retry
} else {
ALWAYS_ASSERT(err == 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()).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(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
// we don't want to keep the dir info around start again from the last stat
stat();
} else if (err == EggsError::DIRECTORY_NOT_EMPTY) {
state.setExitError(err);
rollback();
} else {
ALWAYS_ASSERT(err == NO_ERROR);
unlockEdge();
}
}
void unlockEdge() {
auto& shardReq = env.needsShard(SOFT_UNLINK_DIRECTORY_UNLOCK_EDGE, req.ownerId.shard()).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(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
unlockEdge();
} 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 == NO_ERROR || err == EggsError::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() {
auto& shardReq = env.needsShard(SOFT_UNLINK_DIRECTORY_ROLLBACK, req.ownerId.shard()).setUnlockCurrentEdge();
shardReq.dirId = req.ownerId;
shardReq.name = req.name;
shardReq.targetId = req.targetId;
shardReq.wasMoved = false;
shardReq.creationTime = req.creationTime;
}
void afterRollback(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
rollback();
} 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 == NO_ERROR || err == EggsError::EDGE_NOT_FOUND);
env.finishWithError(state.exitError());
}
}
};
enum RenameDirectoryStep : uint8_t {
RENAME_DIRECTORY_LOCK_OLD_EDGE = 1,
RENAME_DIRECTORY_CREATE_LOCKED_NEW_EDGE = 2,
RENAME_DIRECTORY_UNLOCK_NEW_EDGE = 3,
RENAME_DIRECTORY_UNLOCK_OLD_EDGE = 4,
RENAME_DIRECTORY_SET_OWNER = 5,
RENAME_DIRECTORY_ROLLBACK = 6,
};
// Steps:
//
// 1. Make sure there's no loop by traversing the parents
// 2. Lock old edge
// 3. Create and lock the new edge
// 4. Unlock the new edge
// 5. Unlock and unlink the old edge
// 6. Update the owner of the moved directory to the new directory
//
// If we fail at step 3, we need to unlock the edge we locked at step 2. Step 4 and 5
// 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(EggsError err, const ShardRespContainer* resp) {
if (env.txnStep == TXN_START) {
start();
return;
}
if (unlikely(err == NO_ERROR && resp == nullptr)) { // we're resuming with no response
switch (env.txnStep) {
case RENAME_DIRECTORY_LOCK_OLD_EDGE: lockOldEdge(); 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 EGGS_EXCEPTION("bad step %s", env.txnStep);
}
} else {
switch (env.txnStep) {
case RENAME_DIRECTORY_LOCK_OLD_EDGE: afterLockOldEdge(err, resp); break;
case RENAME_DIRECTORY_CREATE_LOCKED_NEW_EDGE: afterCreateLockedEdge(err, resp); break;
case RENAME_DIRECTORY_UNLOCK_NEW_EDGE: afterUnlockNewEdge(err, resp); break;
case RENAME_DIRECTORY_UNLOCK_OLD_EDGE: afterUnlockOldEdge(err, resp); break;
case RENAME_DIRECTORY_SET_OWNER: afterSetOwner(err, resp); break;
case RENAME_DIRECTORY_ROLLBACK: afterRollback(err, resp); break;
default: throw EGGS_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(EggsError::TYPE_IS_NOT_DIRECTORY);
} else if (req.oldOwnerId == req.newOwnerId) {
env.finishWithError(EggsError::SAME_DIRECTORIES);
} else if (!loopCheck()) {
// First, check if we'd create a loop
env.finishWithError(EggsError::LOOP_IN_DIRECTORY_RENAME);
} else {
// Now, actually start by locking the old edge
lockOldEdge();
}
}
void lockOldEdge() {
auto& shardReq = env.needsShard(RENAME_DIRECTORY_LOCK_OLD_EDGE, req.oldOwnerId.shard()).setLockCurrentEdge();
shardReq.dirId = req.oldOwnerId;
shardReq.name = req.oldName;
shardReq.targetId = req.targetId;
shardReq.creationTime = req.oldCreationTime;
}
void afterLockOldEdge(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
lockOldEdge(); // retry
} else if (
err == EggsError::DIRECTORY_NOT_FOUND || err == EggsError::EDGE_NOT_FOUND || err == EggsError::MISMATCHING_CREATION_TIME
) {
if (err == EggsError::DIRECTORY_NOT_FOUND) {
err = EggsError::OLD_DIRECTORY_NOT_FOUND;
}
env.finishWithError(err);
} else {
ALWAYS_ASSERT(err == NO_ERROR);
createLockedNewEdge();
}
}
void createLockedNewEdge() {
auto& shardReq = env.needsShard(RENAME_DIRECTORY_CREATE_LOCKED_NEW_EDGE, req.newOwnerId.shard()).setCreateLockedCurrentEdge();
shardReq.dirId = req.newOwnerId;
shardReq.name = req.newName;
shardReq.targetId = req.targetId;
}
void afterCreateLockedEdge(EggsError err, const ShardRespContainer* resp) {
if (createCurrentLockedEdgeRetry(err)) {
createLockedNewEdge();
} else if (createCurrentLockedEdgeFatal(err)) {
state.setExitError(err);
rollback();
} else {
ALWAYS_ASSERT(err == NO_ERROR);
state.setNewCreationTime(resp->getCreateLockedCurrentEdge().creationTime);
unlockNewEdge();
}
}
void unlockNewEdge() {
auto& shardReq = env.needsShard(RENAME_DIRECTORY_UNLOCK_NEW_EDGE, req.newOwnerId.shard()).setUnlockCurrentEdge();
shardReq.dirId = req.newOwnerId;
shardReq.name = req.newName;
shardReq.targetId = req.targetId;
shardReq.wasMoved = false;
shardReq.creationTime = state.newCreationTime();
}
void afterUnlockNewEdge(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
unlockNewEdge();
} else if (err == EggsError::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 == NO_ERROR);
unlockOldEdge();
}
}
void unlockOldEdge() {
auto& shardReq = env.needsShard(RENAME_DIRECTORY_UNLOCK_OLD_EDGE, req.oldOwnerId.shard()).setUnlockCurrentEdge();
shardReq.dirId = req.oldOwnerId;
shardReq.name = req.oldName;
shardReq.targetId = req.targetId;
shardReq.wasMoved = true;
shardReq.creationTime = req.oldCreationTime;
}
void afterUnlockOldEdge(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
unlockOldEdge();
} else if (err == EggsError::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 == NO_ERROR);
setOwner();
}
}
void setOwner() {
auto& shardReq = env.needsShard(RENAME_DIRECTORY_SET_OWNER, req.targetId.shard()).setSetDirectoryOwner();
shardReq.ownerId = req.newOwnerId;
shardReq.dirId = req.targetId;
}
void afterSetOwner(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
setOwner();
} else {
ALWAYS_ASSERT(err == 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() {
auto& shardReq = env.needsShard(RENAME_DIRECTORY_ROLLBACK, req.oldOwnerId.shard()).setUnlockCurrentEdge();
shardReq.dirId = req.oldOwnerId;
shardReq.name = req.oldName;
shardReq.targetId = req.targetId;
shardReq.wasMoved = false;
shardReq.creationTime = state.newCreationTime();
}
void afterRollback(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
rollback();
} 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(EggsError err, const ShardRespContainer* resp) {
if (env.txnStep == TXN_START) {
start();
return;
}
if (unlikely(err == NO_ERROR && 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 EGGS_EXCEPTION("bad step %s", env.txnStep);
}
} else {
switch (env.txnStep) {
case CROSS_SHARD_HARD_UNLINK_FILE_REMOVE_EDGE: afterRemoveEdge(err, resp); break;
case CROSS_SHARD_HARD_UNLINK_FILE_MAKE_TRANSIENT: afterMakeTransient(err, resp); break;
default: throw EGGS_EXCEPTION("bad step %s", env.txnStep);
}
}
}
void start() {
if (req.ownerId.shard() == req.targetId.shard()) {
env.finishWithError(EggsError::SAME_SHARD);
} else {
removeEdge();
}
}
void removeEdge() {
auto& shardReq = env.needsShard(CROSS_SHARD_HARD_UNLINK_FILE_REMOVE_EDGE, req.ownerId.shard()).setRemoveOwnedSnapshotFileEdge();
shardReq.ownerId = req.ownerId;
shardReq.targetId = req.targetId;
shardReq.name = req.name;
shardReq.creationTime = req.creationTime;
}
void afterRemoveEdge(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT || err == EggsError::MTIME_IS_TOO_RECENT) {
removeEdge();
} else if (err == EggsError::DIRECTORY_NOT_FOUND) {
env.finishWithError(err);
} else {
ALWAYS_ASSERT(err == NO_ERROR);
makeTransient();
}
}
void makeTransient() {
auto& shardReq = env.needsShard(CROSS_SHARD_HARD_UNLINK_FILE_MAKE_TRANSIENT, req.targetId.shard()).setMakeFileTransient();
shardReq.id = req.targetId;
shardReq.note = req.name;
}
void afterMakeTransient(EggsError err, const ShardRespContainer* resp) {
if (err == EggsError::TIMEOUT) {
makeTransient();
} else {
ALWAYS_ASSERT(err == NO_ERROR);
env.finish().setCrossShardHardUnlinkFile();
}
}
};
// Wrapper types to pack/unpack with kind
struct PackCDCReq {
const CDCReqContainer& req;
PackCDCReq(const CDCReqContainer& req_): req(req_) {}
void pack(BincodeBuf& buf) const {
buf.packScalar<CDCMessageKind>(req.kind());
req.pack(buf);
}
uint16_t packedSize() const {
return 1 + req.packedSize();
}
};
struct UnpackCDCReq {
CDCReqContainer& req;
UnpackCDCReq(CDCReqContainer& req_): req(req_) {}
void unpack(BincodeBuf& buf) {
auto kind = buf.unpackScalar<CDCMessageKind>();
req.unpack(buf, kind);
}
};
struct CDCDBImpl {
Env _env;
// TODO it would be good to store basically all of the metadata in memory,
// so that we'd just read from it, but this requires a bit of care when writing
// if we want to be able to not write the batch at the end.
rocksdb::OptimisticTransactionDB* _db;
rocksdb::ColumnFamilyHandle* _defaultCf;
rocksdb::ColumnFamilyHandle* _reqQueueCf;
rocksdb::ColumnFamilyHandle* _parentCf;
AssertiveLock _processLock;
// Used to deserialize into
CDCReqContainer _cdcReq;
// ----------------------------------------------------------------
// initialization
CDCDBImpl() = delete;
CDCDBImpl& operator=(const CDCDBImpl&) = delete;
CDCDBImpl(Logger& logger, const std::string& path) : _env(logger, "cdc_db") {
rocksdb::Options options;
options.create_if_missing = true;
options.create_missing_column_families = true;
options.compression = rocksdb::kLZ4Compression;
std::vector<rocksdb::ColumnFamilyDescriptor> familiesDescriptors{
{rocksdb::kDefaultColumnFamilyName, {}},
{"reqQueue", {}},
{"parent", {}},
};
std::vector<rocksdb::ColumnFamilyHandle*> familiesHandles;
auto dbPath = path + "/db";
LOG_INFO(_env, "initializing CDC RocksDB in %s", dbPath);
ROCKS_DB_CHECKED_MSG(
rocksdb::OptimisticTransactionDB::Open(options, dbPath, familiesDescriptors, &familiesHandles, &_db),
"could not open RocksDB %s", dbPath
);
ALWAYS_ASSERT(familiesDescriptors.size() == familiesHandles.size());
_defaultCf = familiesHandles[0];
_reqQueueCf = familiesHandles[1];
_parentCf = familiesHandles[2];
_initDb();
}
void close() {
LOG_INFO(_env, "destroying column families and closing database");
ROCKS_DB_CHECKED(_db->DestroyColumnFamilyHandle(_defaultCf));
ROCKS_DB_CHECKED(_db->DestroyColumnFamilyHandle(_reqQueueCf));
ROCKS_DB_CHECKED(_db->DestroyColumnFamilyHandle(_parentCf));
ROCKS_DB_CHECKED(_db->Close());
}
~CDCDBImpl() {
delete _db;
}
// 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(FIRST_TXN_IN_QUEUE_KEY, _firstTxnInQueue, _setFirstTxnInQueue)
TXN_ID_SETTER_GETTER(LAST_TXN_IN_QUEUE_KEY, _lastTxnInQueue, _setLastTxnInQueue)
TXN_ID_SETTER_GETTER(EXECUTING_TXN_KEY, _executingTxn, _setExecutingTxn)
#undef TXN_ID_SETTER_GETTER
void _initDb() {
const auto keyExists = [this](rocksdb::ColumnFamilyHandle* cf, const rocksdb::Slice& key) -> bool {
std::string value;
auto status = _db->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(_db->Put({}, cdcMetadataKey(&NEXT_DIRECTORY_ID_KEY), id.toSlice()));
}
const auto initZeroValue = [this, &keyExists](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(_db->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);
}
// Processing
// ----------------------------------------------------------------
uint64_t _lastAppliedLogEntry() {
std::string value;
ROCKS_DB_CHECKED(_db->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();
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()));
}
// Pushes a new request onto the queue.
void _reqQueuePush(rocksdb::Transaction& dbTxn, uint64_t txnId, const CDCReqContainer& req) {
// Check metadata
uint64_t last = _lastTxnInQueue(dbTxn);
ALWAYS_ASSERT(last == 0 || txnId == last + 1);
// Write to queue
{
auto k = U64Key::Static(txnId);
std::string v = bincodeToRocksValue(PackCDCReq(req));
ROCKS_DB_CHECKED(dbTxn.Put(_reqQueueCf, k.toSlice(), v));
}
// Update metadata
if (last == 0) {
_setFirstTxnInQueue(dbTxn, txnId);
}
_setLastTxnInQueue(dbTxn, txnId);
}
// Returns 0 if the queue was empty, otherwise what was popped
uint64_t _reqQueuePeek(rocksdb::Transaction& dbTxn, CDCReqContainer& req) {
uint64_t first = _firstTxnInQueue(dbTxn);
if (first == 0) {
return 0;
}
// Read
{
auto k = U64Key::Static(first);
std::string v;
ROCKS_DB_CHECKED(dbTxn.Get({}, _reqQueueCf, k.toSlice(), &v));
UnpackCDCReq ureq(req);
bincodeFromRocksValue(v, ureq);
}
return first;
}
// Returns 0 if the queue was empty, otherwise what was popped
uint64_t _reqQueuePop(rocksdb::Transaction& dbTxn) {
uint64_t first = _firstTxnInQueue(dbTxn);
if (first == 0) {
LOG_DEBUG(_env, "txn queue empty, returning 0");
return 0;
}
// Update metadata
uint64_t last = _lastTxnInQueue(dbTxn);
if (first == last) { // empty queue
_setFirstTxnInQueue(dbTxn, 0);
_setLastTxnInQueue(dbTxn, 0);
} else {
_setFirstTxnInQueue(dbTxn, first+1);
}
LOG_DEBUG(_env, "popped txn %s from queue", first);
return first;
}
// Moves the state forward, filling in `step` appropriatedly, and writing
// out the updated state.
//
// This will _not_ start a new transaction automatically if the old one
// finishes.
template<template<typename> typename V>
void _advance(
EggsTime time,
rocksdb::Transaction& dbTxn,
uint64_t txnId,
const CDCReqContainer& req,
// If `shardRespError` and `shardResp` are null, we're starting to execute.
// Otherwise, (err == NO_ERROR) == (req != nullptr).
EggsError shardRespError,
const ShardRespContainer* shardResp,
V<TxnState> state,
CDCStep& step
) {
LOG_DEBUG(_env, "advancing txn %s of kind %s", txnId, req.kind());
StateMachineEnv sm(_env, _db, _defaultCf, _parentCf, dbTxn, time, txnId, state().step(), step);
switch (req.kind()) {
case CDCMessageKind::MAKE_DIRECTORY:
MakeDirectoryStateMachine(sm, req.getMakeDirectory(), state().getMakeDirectory()).resume(shardRespError, shardResp);
break;
case CDCMessageKind::HARD_UNLINK_DIRECTORY:
HardUnlinkDirectoryStateMachine(sm, req.getHardUnlinkDirectory(), state().getHardUnlinkDirectory()).resume(shardRespError, shardResp);
break;
case CDCMessageKind::RENAME_FILE:
RenameFileStateMachine(sm, req.getRenameFile(), state().getRenameFile()).resume(shardRespError, shardResp);
break;
case CDCMessageKind::SOFT_UNLINK_DIRECTORY:
SoftUnlinkDirectoryStateMachine(sm, req.getSoftUnlinkDirectory(), state().getSoftUnlinkDirectory()).resume(shardRespError, shardResp);
break;
case CDCMessageKind::RENAME_DIRECTORY:
RenameDirectoryStateMachine(sm, req.getRenameDirectory(), state().getRenameDirectory()).resume(shardRespError, shardResp);
break;
case CDCMessageKind::CROSS_SHARD_HARD_UNLINK_FILE:
CrossShardHardUnlinkFileStateMachine(sm, req.getCrossShardHardUnlinkFile(), state().getCrossShardHardUnlinkFile()).resume(shardRespError, shardResp);
break;
default:
throw EGGS_EXCEPTION("bad cdc message kind %s", req.kind());
}
state().setStep(sm.txnStep);
ALWAYS_ASSERT(step.txnFinished == 0 || step.txnFinished == txnId);
ALWAYS_ASSERT(step.txnNeedsShard == 0 || step.txnNeedsShard == txnId);
ALWAYS_ASSERT(step.txnFinished == txnId || step.txnNeedsShard == txnId);
if (step.txnFinished == txnId) {
// we're done, clear the transaction from the system
ALWAYS_ASSERT(_reqQueuePop(dbTxn) == txnId);
_setExecutingTxn(dbTxn, 0);
// not strictly necessary, it'll just be overwritten next time, but let's be tidy
ROCKS_DB_CHECKED(dbTxn.Delete(_defaultCf, cdcMetadataKey(&EXECUTING_TXN_STATE_KEY)));
// also, fill in whether we've got something next
step.nextTxn = _firstTxnInQueue(dbTxn);
} else {
// we're _not_ done, write out the state
ROCKS_DB_CHECKED(dbTxn.Put(_defaultCf, cdcMetadataKey(&EXECUTING_TXN_STATE_KEY), state.toSlice()));
}
}
// Starts executing the next transaction in line, if possible. If it managed
// to start something, it immediately advances it as well (no point delaying
// that). Returns the txn id that was started, if any.
uint64_t _startExecuting(EggsTime time, rocksdb::Transaction& dbTxn, CDCStep& step) {
uint64_t executingTxn = _executingTxn(dbTxn);
if (executingTxn != 0) {
LOG_DEBUG(_env, "another transaction %s is already executing, can't start", executingTxn);
return 0;
}
uint64_t txnToExecute = _reqQueuePeek(dbTxn, _cdcReq);
if (txnToExecute == 0) {
LOG_DEBUG(_env, "no transactions in queue found, can't start");
return 0;
}
_setExecutingTxn(dbTxn, txnToExecute);
LOG_DEBUG(_env, "starting to execute txn %s with req %s", txnToExecute, _cdcReq);
StaticValue<TxnState> txnState;
txnState().start(_cdcReq.kind());
_advance(time, dbTxn, txnToExecute, _cdcReq, NO_ERROR, nullptr, txnState, step);
return txnToExecute;
}
uint64_t processCDCReq(
bool sync,
EggsTime time,
uint64_t logIndex,
const CDCReqContainer& req,
CDCStep& step
) {
auto locked = _processLock.lock();
rocksdb::WriteOptions options;
options.sync = sync;
std::unique_ptr<rocksdb::Transaction> dbTxn(_db->BeginTransaction(options));
step.clear();
_advanceLastAppliedLogEntry(*dbTxn, logIndex);
// Enqueue req
uint64_t txnId;
{
// Generate new txn id
txnId = _lastTxn(*dbTxn) + 1;
_setLastTxn(*dbTxn, txnId);
// Push to queue
_reqQueuePush(*dbTxn, txnId, req);
LOG_DEBUG(_env, "enqueued CDC req %s with txn id %s", req.kind(), txnId);
}
// Start executing, if we can
_startExecuting(time, *dbTxn, step);
LOG_DEBUG(_env, "committing transaction");
dbTxn->Commit();
return txnId;
}
void processShardResp(
bool sync, // Whether to persist synchronously. Unneeded if log entries are persisted already.
EggsTime time,
uint64_t logIndex,
EggsError respError,
const ShardRespContainer* resp,
CDCStep& step
) {
auto locked = _processLock.lock();
rocksdb::WriteOptions options;
options.sync = sync;
std::unique_ptr<rocksdb::Transaction> dbTxn(_db->BeginTransaction(options));
step.clear();
_advanceLastAppliedLogEntry(*dbTxn, logIndex);
// Find the txn
uint64_t txnId = _executingTxn(*dbTxn);
ALWAYS_ASSERT(txnId != 0);
// Get the req
{
auto k = U64Key::Static(txnId);
std::string reqV;
ROCKS_DB_CHECKED(dbTxn->Get({}, _reqQueueCf, k.toSlice(), &reqV));
UnpackCDCReq ureq(_cdcReq);
bincodeFromRocksValue(reqV, ureq);
}
// Get the state
std::string txnStateV;
ROCKS_DB_CHECKED(dbTxn->Get({}, _defaultCf, cdcMetadataKey(&EXECUTING_TXN_STATE_KEY), &txnStateV));
ExternalValue<TxnState> txnState(txnStateV);
// Advance
_advance(time, *dbTxn, txnId, _cdcReq, respError, resp, txnState, step);
dbTxn->Commit();
}
void startNextTransaction(
bool sync, // Whether to persist synchronously. Unneeded if log entries are persisted already.
EggsTime time,
uint64_t logIndex,
CDCStep& step
) {
auto locked = _processLock.lock();
rocksdb::WriteOptions options;
options.sync = sync;
std::unique_ptr<rocksdb::Transaction> dbTxn(_db->BeginTransaction(options));
step.clear();
_advanceLastAppliedLogEntry(*dbTxn, logIndex);
uint64_t txnId = _startExecuting(time, *dbTxn, step);
if (txnId == 0) {
// no txn could be started, see if one is executing already to fill in the `step`
txnId = _executingTxn(*dbTxn);
if (txnId != 0) {
LOG_DEBUG(_env, "transaction %s is already executing, will resume it", txnId);
// Get the req
{
auto k = U64Key::Static(txnId);
std::string reqV;
ROCKS_DB_CHECKED(dbTxn->Get({}, _reqQueueCf, k.toSlice(), &reqV));
UnpackCDCReq ureq(_cdcReq);
bincodeFromRocksValue(reqV, ureq);
}
// Get the state
std::string txnStateV;
ROCKS_DB_CHECKED(dbTxn->Get({}, _defaultCf, cdcMetadataKey(&EXECUTING_TXN_STATE_KEY), &txnStateV));
ExternalValue<TxnState> txnState(txnStateV);
// Advance
_advance(time, *dbTxn, txnId, _cdcReq, NO_ERROR, nullptr, txnState, step);
}
}
dbTxn->Commit();
}
void status(CDCStatus& resp) {
memset(&resp, 0, sizeof(resp));
std::unique_ptr<rocksdb::Transaction> dbTxn(_db->BeginTransaction({}));
uint64_t txnId = _executingTxn(*dbTxn);
if (txnId != 0) {
// Get the req kind
{
auto k = U64Key::Static(txnId);
std::string reqV;
ROCKS_DB_CHECKED(dbTxn->Get({}, _reqQueueCf, k.toSlice(), &reqV));
BincodeBuf bbuf(reqV);
resp.executingTxnKind = (CDCMessageKind)bbuf.unpackScalar<uint8_t>();
}
// Get the step
{
std::string txnStateV;
ROCKS_DB_CHECKED(dbTxn->Get({}, _defaultCf, cdcMetadataKey(&EXECUTING_TXN_STATE_KEY), &txnStateV));
ExternalValue<TxnState> txnState(txnStateV);
resp.executingTxnStep = txnState().step();
}
}
resp.queuedTxns = _lastTxnInQueue(*dbTxn) - _firstTxnInQueue(*dbTxn);
}
};
CDCDB::CDCDB(Logger& logger, const std::string& path) {
_impl = new CDCDBImpl(logger, path);
}
void CDCDB::close() {
((CDCDBImpl*)_impl)->close();
}
CDCDB::~CDCDB() {
delete ((CDCDBImpl*)_impl);
}
uint64_t CDCDB::processCDCReq(bool sync, EggsTime time, uint64_t logIndex, const CDCReqContainer& req, CDCStep& step) {
return ((CDCDBImpl*)_impl)->processCDCReq(sync, time, logIndex, req, step);
}
void CDCDB::processShardResp(bool sync, EggsTime time, uint64_t logIndex, EggsError respError, const ShardRespContainer* resp, CDCStep& step) {
return ((CDCDBImpl*)_impl)->processShardResp(sync, time, logIndex, respError, resp, step);
}
void CDCDB::startNextTransaction(bool sync, EggsTime time, uint64_t logIndex, CDCStep& step) {
return ((CDCDBImpl*)_impl)->startNextTransaction(sync, time, logIndex, step);
}
uint64_t CDCDB::lastAppliedLogEntry() {
return ((CDCDBImpl*)_impl)->_lastAppliedLogEntry();
}
void CDCDB::status(CDCStatus& resp) {
return ((CDCDBImpl*)_impl)->status(resp);
}
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