/*------------------------------------------------------------------------- * * twophase.c * Two-phase commit support functions. * * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION * $PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.39.2.3 2009/11/23 09:59:00 heikki Exp $ * * NOTES * Each global transaction is associated with a global transaction * identifier (GID). The client assigns a GID to a postgres * transaction with the PREPARE TRANSACTION command. * * We keep all active global transactions in a shared memory array. * When the PREPARE TRANSACTION command is issued, the GID is * reserved for the transaction in the array. This is done before * a WAL entry is made, because the reservation checks for duplicate * GIDs and aborts the transaction if there already is a global * transaction in prepared state with the same GID. * * A global transaction (gxact) also has a dummy PGPROC that is entered * into the ProcArray array; this is what keeps the XID considered * running by TransactionIdIsInProgress. It is also convenient as a * PGPROC to hook the gxact's locks to. * * In order to survive crashes and shutdowns, all prepared * transactions must be stored in permanent storage. This includes * locking information, pending notifications etc. All that state * information is written to the per-transaction state file in * the pg_twophase directory. * *------------------------------------------------------------------------- */ #include "postgres.h" #include #include #include #include #include #include "access/heapam.h" #include "access/xlogmm.h" #include "access/subtrans.h" #include "access/transam.h" #include "access/twophase.h" #include "access/twophase_rmgr.h" #include "access/xact.h" #include "catalog/pg_type.h" #include "funcapi.h" #include "miscadmin.h" #include "pgstat.h" #include "replication/walsender.h" #include "replication/syncrep.h" #include "storage/fd.h" #include "storage/ipc.h" #include "storage/procarray.h" #include "storage/smgr.h" #include "utils/builtins.h" #include "utils/faultinjector.h" #include "utils/guc.h" #include "utils/memutils.h" #include "access/distributedlog.h" #include "storage/backendid.h" #include "cdb/cdbtm.h" #include "cdb/cdbvars.h" #include "cdb/cdbpersistentrecovery.h" #include "cdb/cdbpersistentrelation.h" #include "cdb/cdbmirroredflatfile.h" #include "cdb/cdbmirroredfilesysobj.h" #include "cdb/cdbpersistentfilesysobj.h" /* GUC variable, can't be changed after startup */ int max_prepared_xacts = 5; /* * This struct describes one global transaction that is in prepared state * or attempting to become prepared. * * The first component of the struct is a dummy PGPROC that is inserted * into the global ProcArray so that the transaction appears to still be * running and holding locks. It must be first because we cast pointers * to PGPROC and pointers to GlobalTransactionData back and forth. * * The lifecycle of a global transaction is: * * 1. After checking that the requested GID is not in use, set up an entry in * the TwoPhaseState->prepXacts array with the correct GID and valid = false, * and mark it as locked by my backend. * * 2. After successfully completing prepare, set valid = true and enter the * contained PGPROC into the global ProcArray. * * 3. To begin COMMIT PREPARED or ROLLBACK PREPARED, check that the entry is * valid and not locked, then mark the entry as locked by storing my current * backend ID into locking_backend. This prevents concurrent attempts to * commit or rollback the same prepared xact. * * 4. On completion of COMMIT PREPARED or ROLLBACK PREPARED, remove the entry * from the ProcArray and the TwoPhaseState->prepXacts array and return it to * the freelist. * * Note that if the preparing transaction fails between steps 1 and 2, the * entry must be removed so that the GID and the GlobalTransaction struct * can be reused. See AtAbort_Twophase(). * * typedef struct GlobalTransactionData *GlobalTransaction appears in * twophase.h */ #define GIDSIZE 200 extern List *expectedTLIs; typedef struct GlobalTransactionData { PGPROC proc; /* dummy proc */ BackendId dummyBackendId; /* similar to backend id for backends */ TimestampTz prepared_at; /* time of preparation */ XLogRecPtr prepare_begin_lsn; /* XLOG begging offset of prepare record */ XLogRecPtr prepare_lsn; /* XLOG offset of prepare record */ Oid owner; /* ID of user that executed the xact */ BackendId locking_backend; /* backend currently working on the xact */ bool valid; /* TRUE if PGPROC entry is in proc array */ char gid[GIDSIZE]; /* The GID assigned to the prepared xact */ int prepareAppendOnlyIntentCount; /* * The Append-Only Resync EOF intent count for * a non-crashed prepared transaction. */ } GlobalTransactionData; /* * Two Phase Commit shared state. Access to this struct is protected * by TwoPhaseStateLock. */ typedef struct TwoPhaseStateData { /* Head of linked list of free GlobalTransactionData structs */ SHMEM_OFFSET freeGXacts; /* Number of valid prepXacts entries. */ int numPrepXacts; /* * There are max_prepared_xacts items in this array, but C wants a * fixed-size array. */ GlobalTransaction prepXacts[1]; /* VARIABLE LENGTH ARRAY */ } TwoPhaseStateData; /* VARIABLE LENGTH STRUCT */ static TwoPhaseStateData *TwoPhaseState; /* * The following list is */ static HTAB *crashRecoverPostCheckpointPreparedTransactions_map_ht = NULL; static void add_recover_post_checkpoint_prepared_transactions_map_entry(TransactionId xid, XLogRecPtr *m, char *caller); static void remove_recover_post_checkpoint_prepared_transactions_map_entry(TransactionId xid, char *caller); static TwoPhaseStateData *TwoPhaseState; /* * Global transaction entry currently locked by us, if any. */ static GlobalTransaction MyLockedGxact = NULL; static bool twophaseExitRegistered = false; static void RecordTransactionCommitPrepared(TransactionId xid, const char *gid, int nchildren, TransactionId *children, PersistentEndXactRecObjects *persistentPrepareObjects); static void RecordTransactionAbortPrepared(TransactionId xid, int nchildren, TransactionId *children, PersistentEndXactRecObjects *persistentPrepareObjects); static void ProcessRecords(char *bufptr, TransactionId xid, const TwoPhaseCallback callbacks[]); static void RemoveGXact(GlobalTransaction gxact); /* * Generic initialisation of hash table. */ static HTAB * init_hash(const char *name, Size keysize, Size entrysize, int initialSize) { HASHCTL ctl; memset(&ctl, 0, sizeof(ctl)); ctl.keysize = keysize; ctl.entrysize = entrysize; ctl.hash = tag_hash; return hash_create(name, initialSize, &ctl, HASH_ELEM | HASH_FUNCTION); } /* end init_hash */ /* * Add a new mapping to the recover post checkpoint prepared transactions hash table. */ static void add_recover_post_checkpoint_prepared_transactions_map_entry(TransactionId xid, XLogRecPtr *m, char *caller) { prpt_map *entry = NULL; bool found = false; if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "add_recover_post_checkpoint_prepared_transactions_map_entry: start of function." ); /* * The table is lazily initialised. */ if (crashRecoverPostCheckpointPreparedTransactions_map_ht == NULL) { if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "add_recover_post_checkpoint_prepared_transactions_map_entry: initial setup of global hash table. Caller = %s", caller); crashRecoverPostCheckpointPreparedTransactions_map_ht = init_hash("two phase post checkpoint prepared transactions map", sizeof(TransactionId), /* keysize */ sizeof(prpt_map), 10 /* initialize for 10 entries */); } if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "add_recover_post_checkpoint_prepared_transactions_map_entry: add entry xid = %u, XLogRecPtr = %s, caller = %s", xid, XLogLocationToString(m), caller); entry = hash_search(crashRecoverPostCheckpointPreparedTransactions_map_ht, &xid, HASH_ENTER, &found); /* * KAS should probably put out an error if found == true (i.e. it already exists). */ if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "add_recover_post_checkpoint_prepared_transactions_map_entry: add entry xid = %u, address prpt_map = %p", xid, entry); /* * If this is a new entry, we need to add the data, if we found * an entry, we need to update it, so just copy our data * right over the top. */ memcpy(&entry->xlogrecptr, m, sizeof(XLogRecPtr)); if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "Transaction id = %u, XLog Rec Ptr = %s, caller = %s", xid, XLogLocationToString(m), caller); } /* end add_recover_post_checkpoint_prepared_transactions_map_entry */ /* * Find a mapping in the recover post checkpoint prepared transactions hash table. */ bool TwoPhaseFindRecoverPostCheckpointPreparedTransactionsMapEntry(TransactionId xid, XLogRecPtr *m, char *caller) { prpt_map *entry = NULL; bool found = false; if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "find_recover_post_checkpoint_prepared_transactions_map_entry: start of function." ); MemSet(m, 0, sizeof(XLogRecPtr)); /* * The table is lazily initialised. */ if (crashRecoverPostCheckpointPreparedTransactions_map_ht == NULL) { if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "find_recover_post_checkpoint_prepared_transactions_map_entry: initial setup of global hash table. Caller = %s", caller); crashRecoverPostCheckpointPreparedTransactions_map_ht = init_hash("two phase post checkpoint prepared transactions map", sizeof(TransactionId), /* keysize */ sizeof(prpt_map), 10 /* initialize for 10 entries */); } entry = hash_search(crashRecoverPostCheckpointPreparedTransactions_map_ht, &xid, HASH_FIND, &found); if (entry == NULL) { if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "find_recover_post_checkpoint_prepared_transactions_map_entry: did not find entry xid = %u, caller = %s", xid, caller); return false; } memcpy(m, &entry->xlogrecptr, sizeof(XLogRecPtr)); if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "find_recover_post_checkpoint_prepared_transactions_map_entry: found entry xid = %u, XLogRecPtr = %s, caller = %s", xid, XLogLocationToString(m), caller); return true; } /* * Remove a mapping from the recover post checkpoint prepared transactions hash table. */ static void remove_recover_post_checkpoint_prepared_transactions_map_entry(TransactionId xid, char *caller) { prpt_map *entry = NULL; bool found = false;; if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "remove_recover_post_checkpoint_prepared_transactions_map_entry: entering..." ); if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "remove_recover_post_checkpoint_prepared_transactions_map_entry: TransactionId = %u", xid); if (crashRecoverPostCheckpointPreparedTransactions_map_ht != NULL) { entry = hash_search(crashRecoverPostCheckpointPreparedTransactions_map_ht, &xid, HASH_REMOVE, &found); } /* KAS should probably put out an error if it is not found. */ if (found == true) { if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "remove_recover_post_checkpoint_prepared_transaction_map_entry found = TRUE"); } else { if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "remove_recover_post_checkpoint_prepared_transaction_map_entry found = FALSE"); } } /* end remove_recover_post_checkpoint_prepared_transactions_map_entry */ /* * Initialization of shared memory */ Size TwoPhaseShmemSize(void) { Size size; /* Need the fixed struct, the array of pointers, and the GTD structs */ size = offsetof(TwoPhaseStateData, prepXacts); size = add_size(size, mul_size(max_prepared_xacts, sizeof(GlobalTransaction))); size = MAXALIGN(size); size = add_size(size, mul_size(max_prepared_xacts, sizeof(GlobalTransactionData))); return size; } void TwoPhaseShmemInit(void) { bool found; TwoPhaseState = ShmemInitStruct("Prepared Transaction Table", TwoPhaseShmemSize(), &found); if (!IsUnderPostmaster) { GlobalTransaction gxacts; int i; Assert(!found); TwoPhaseState->freeGXacts = INVALID_OFFSET; TwoPhaseState->numPrepXacts = 0; /* * Initialize the linked list of free GlobalTransactionData structs */ gxacts = (GlobalTransaction) ((char *) TwoPhaseState + MAXALIGN(offsetof(TwoPhaseStateData, prepXacts) + sizeof(GlobalTransaction) * max_prepared_xacts)); for (i = 0; i < max_prepared_xacts; i++) { gxacts[i].proc.links.next = TwoPhaseState->freeGXacts; TwoPhaseState->freeGXacts = MAKE_OFFSET(&gxacts[i]); /* * Assign a unique ID for each dummy proc, so that the range of * dummy backend IDs immediately follows the range of normal * backend IDs. We don't dare to assign a real backend ID to * dummy procs, because prepared transactions don't take part in * cache invalidation like a real backend ID would imply, but * having a unique ID for them is nevertheless handy. This * arrangement allows you to allocate an array of size * (MaxBackends + max_prepared_xacts + 1), and have a slot for * every backend and prepared transaction. Currently multixact.c * uses that technique. */ gxacts[i].dummyBackendId = MaxBackends + 1 + i; } } else { Assert(found); } } /* * Exit hook to unlock the global transaction entry we're working on. */ static void AtProcExit_Twophase(int code, Datum arg) { /* same logic as abort */ AtAbort_Twophase(); } /* * Abort hook to unlock the global transaction entry we're working on. */ void AtAbort_Twophase(void) { if (MyLockedGxact == NULL) return; /* * What to do with the locked global transaction entry? If we were in * the process of preparing the transaction, but haven't written the WAL * record and state file yet, the transaction must not be considered as * prepared. Likewise, if we are in the process of finishing an * already-prepared transaction, and fail after having already written * the 2nd phase commit or rollback record to the WAL, the transaction * should not be considered as prepared anymore. In those cases, just * remove the entry from shared memory. * * Otherwise, the entry must be left in place so that the transaction * can be finished later, so just unlock it. * * If we abort during prepare, after having written the WAL record, we * might not have transfered all locks and other state to the prepared * transaction yet. Likewise, if we abort during commit or rollback, * after having written the WAL record, we might not have released * all the resources held by the transaction yet. In those cases, the * in-memory state can be wrong, but it's too late to back out. */ if (!MyLockedGxact->valid) { RemoveGXact(MyLockedGxact); } else { LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE); MyLockedGxact->locking_backend = InvalidBackendId; LWLockRelease(TwoPhaseStateLock); } MyLockedGxact = NULL; } /* * This is called after we have finished transfering state to the prepared * PGXACT entry. */ void PostPrepare_Twophase() { LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE); MyLockedGxact->locking_backend = InvalidBackendId; LWLockRelease(TwoPhaseStateLock); MyLockedGxact = NULL; } /* * MarkAsPreparing * Reserve the GID for the given transaction. * * Internally, this creates a gxact struct and puts it into the active array. * NOTE: this is also used when reloading a gxact after a crash; so avoid * assuming that we can use very much backend context. */ GlobalTransaction MarkAsPreparing(TransactionId xid, LocalDistribXactData *localDistribXactRef, const char *gid, TimestampTz prepared_at, Oid owner, Oid databaseid , XLogRecPtr *xlogrecptr) { GlobalTransaction gxact; int i; int idlen = strlen(gid); /* on first call, register the exit hook */ if (!twophaseExitRegistered) { on_shmem_exit(AtProcExit_Twophase, 0); twophaseExitRegistered = true; } if (idlen >= GIDSIZE) ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE), errmsg("transaction identifier \"%s\" is too long (%d > %d max)", gid, idlen, GIDSIZE))); LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE); /* Check for conflicting GID */ for (i = 0; i < TwoPhaseState->numPrepXacts; i++) { gxact = TwoPhaseState->prepXacts[i]; if (strcmp(gxact->gid, gid) == 0) { ereport(ERROR, (errcode(ERRCODE_DUPLICATE_OBJECT), errmsg("transaction identifier \"%s\" is already in use", gid))); } } /* Get a free gxact from the freelist */ if (TwoPhaseState->freeGXacts == INVALID_OFFSET) ereport(ERROR, (errcode(ERRCODE_OUT_OF_MEMORY), errmsg("maximum number of prepared transactions reached"), errhint("Increase max_prepared_transactions (currently %d).", max_prepared_xacts))); gxact = (GlobalTransaction) MAKE_PTR(TwoPhaseState->freeGXacts); TwoPhaseState->freeGXacts = gxact->proc.links.next; /* Initialize it */ MemSet(&gxact->proc, 0, sizeof(PGPROC)); SHMQueueElemInit(&(gxact->proc.links)); gxact->proc.waitStatus = STATUS_OK; /* We set up the gxact's VXID as InvalidBackendId/XID */ gxact->proc.lxid = (LocalTransactionId) xid; gxact->proc.xid = xid; gxact->proc.xmin = InvalidTransactionId; gxact->proc.pid = 0; gxact->proc.backendId = InvalidBackendId; gxact->proc.databaseId = databaseid; gxact->proc.roleId = owner; gxact->proc.inCommit = false; gxact->proc.vacuumFlags = 0; gxact->proc.serializableIsoLevel = false; gxact->proc.inDropTransaction = false; gxact->proc.lwWaiting = false; gxact->proc.lwExclusive = false; gxact->proc.lwWaitLink = NULL; gxact->proc.waitLock = NULL; gxact->proc.waitProcLock = NULL; gxact->proc.localDistribXactData = *localDistribXactRef; for (i = 0; i < NUM_LOCK_PARTITIONS; i++) SHMQueueInit(&(gxact->proc.myProcLocks[i])); /* subxid data must be filled later by GXactLoadSubxactData */ gxact->proc.subxids.overflowed = false; gxact->proc.subxids.nxids = 0; gxact->prepared_at = prepared_at; /* initialize LSN to 0 (start of WAL) */ gxact->prepare_lsn.xlogid = 0; gxact->prepare_lsn.xrecoff = 0; if (xlogrecptr == NULL) { gxact->prepare_begin_lsn.xlogid = 0; gxact->prepare_begin_lsn.xrecoff = 0; } else { gxact->prepare_begin_lsn.xlogid = xlogrecptr->xlogid; gxact->prepare_begin_lsn.xrecoff = xlogrecptr->xrecoff; /* Assert(xlogrecptr->xrecoff > 0 || xlogrecptr->xlogid > 0); */ } gxact->owner = owner; gxact->locking_backend = MyBackendId; gxact->valid = false; strcpy(gxact->gid, gid); gxact->prepareAppendOnlyIntentCount = 0; if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "MarkAsPreparing: gxact->proc.xid = %d, gxact->prepare_begin_lsn = %s, and set valid = false", gxact->proc.xid, XLogLocationToString(&gxact->prepare_begin_lsn)); /* And insert it into the active array */ Assert(TwoPhaseState->numPrepXacts < max_prepared_xacts); if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "MarkAsPreparing: TwoPhaseState->numPrepXacts = %d, adding one", TwoPhaseState->numPrepXacts); TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts++] = gxact; /* * Remember that we have this GlobalTransaction entry locked for us. * If we abort after this, we must release it. */ MyLockedGxact = gxact; LWLockRelease(TwoPhaseStateLock); return gxact; } /* * GXactLoadSubxactData * * If the transaction being persisted had any subtransactions, this must * be called before MarkAsPrepared() to load information into the dummy * PGPROC. */ static void GXactLoadSubxactData(GlobalTransaction gxact, int nsubxacts, TransactionId *children) { /* We need no extra lock since the GXACT isn't valid yet */ if (nsubxacts > PGPROC_MAX_CACHED_SUBXIDS) { gxact->proc.subxids.overflowed = true; nsubxacts = PGPROC_MAX_CACHED_SUBXIDS; } if (nsubxacts > 0) { memcpy(gxact->proc.subxids.xids, children, nsubxacts * sizeof(TransactionId)); gxact->proc.subxids.nxids = nsubxacts; } } /* * MarkAsPrepared * Mark the GXACT as fully valid, and enter it into the global ProcArray. */ static void MarkAsPrepared(GlobalTransaction gxact) { /* Lock here may be overkill, but I'm not convinced of that ... */ LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE); Assert(!gxact->valid); if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "MarkAsPrepared: gxact->proc.xid = %d and set valid = true", gxact->proc.xid); gxact->valid = true; LWLockRelease(TwoPhaseStateLock); elog((Debug_print_full_dtm ? LOG : DEBUG5),"MarkAsPrepared marking GXACT gid = %s as valid (prepared)", gxact->gid); LocalDistribXact_ChangeState(&gxact->proc, LOCALDISTRIBXACT_STATE_PREPARED); /* * Put it into the global ProcArray so TransactionIdIsInProgress considers * the XID as still running. */ ProcArrayAdd(&gxact->proc); } /* * LockGXact * Locate the prepared transaction and mark it busy for COMMIT or PREPARE. */ static GlobalTransaction LockGXact(const char *gid, Oid user, bool raiseErrorIfNotFound) { int i; elog((Debug_print_full_dtm ? LOG : DEBUG5),"LockGXact called to lock identifier = %s.",gid); /* on first call, register the exit hook */ if (!twophaseExitRegistered) { on_shmem_exit(AtProcExit_Twophase, 0); twophaseExitRegistered = true; } LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE); for (i = 0; i < TwoPhaseState->numPrepXacts; i++) { GlobalTransaction gxact = TwoPhaseState->prepXacts[i]; elog((Debug_print_full_dtm ? LOG : DEBUG5), "LockGXact checking identifier = %s.",gxact->gid); /* Ignore not-yet-valid GIDs */ if (!gxact->valid) continue; if (strcmp(gxact->gid, gid) != 0) continue; /* Found it, but has someone else got it locked? */ if (gxact->locking_backend != InvalidBackendId) ereport(ERROR, (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), errmsg("prepared transaction with identifier \"%s\" is busy", gid))); if (user != gxact->owner && !superuser_arg(user)) { LWLockRelease(TwoPhaseStateLock); ereport(ERROR, (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE), errmsg("permission denied to finish prepared transaction"), errhint("Must be superuser or the user that prepared the transaction."))); } /* * Note: it probably would be possible to allow committing from * another database; but at the moment NOTIFY is known not to work and * there may be some other issues as well. Hence disallow until * someone gets motivated to make it work. */ if (MyDatabaseId != gxact->proc.databaseId && (Gp_role != GP_ROLE_EXECUTE)) ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), errmsg("prepared transaction belongs to another database"), errhint("Connect to the database where the transaction was prepared to finish it."))); /* OK for me to lock it */ /* we *must* have it locked with a valid xid here! */ Assert(MyBackendId != InvalidBackendId); gxact->locking_backend = MyBackendId; MyLockedGxact = gxact; LWLockRelease(TwoPhaseStateLock); return gxact; } LWLockRelease(TwoPhaseStateLock); if (raiseErrorIfNotFound) { ereport(ERROR, (errcode(ERRCODE_UNDEFINED_OBJECT), errmsg("prepared transaction with identifier \"%s\" does not exist", gid))); } return NULL; } /* * FindCurrentPrepareGXact * Locate the current prepare transaction. */ static GlobalTransaction FindPrepareGXact(const char *gid) { int i; elog((Debug_print_full_dtm ? LOG : DEBUG5),"FindCurrentPrepareGXact called to lock identifier = %s.",gid); LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE); for (i = 0; i < TwoPhaseState->numPrepXacts; i++) { GlobalTransaction gxact = TwoPhaseState->prepXacts[i]; elog((Debug_print_full_dtm ? LOG : DEBUG5), "FindCurrentPrepareGXact checking identifier = %s.",gxact->gid); if (strcmp(gxact->gid, gid) != 0) continue; LWLockRelease(TwoPhaseStateLock); return gxact; } LWLockRelease(TwoPhaseStateLock); ereport(ERROR, (errcode(ERRCODE_UNDEFINED_OBJECT), errmsg("prepared transaction with identifier \"%s\" does not exist", gid))); /* NOTREACHED */ return NULL; } /* * RemoveGXact * Remove the prepared transaction from the shared memory array. * * NB: caller should have already removed it from ProcArray */ static void RemoveGXact(GlobalTransaction gxact) { int i; if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "RemoveGXact: entering..."); LWLockAcquire(TwoPhaseStateLock, LW_EXCLUSIVE); for (i = 0; i < TwoPhaseState->numPrepXacts; i++) { if (gxact == TwoPhaseState->prepXacts[i]) { if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "RemoveGXact: about to remove xid = %d", gxact->proc.xid); /* remove from the active array */ if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "RemoveGXact: TwoPhaseState->numPrepXacts = %d, subtracting 1", TwoPhaseState->numPrepXacts); TwoPhaseState->numPrepXacts--; TwoPhaseState->prepXacts[i] = TwoPhaseState->prepXacts[TwoPhaseState->numPrepXacts]; /* and put it back in the freelist */ gxact->proc.links.next = TwoPhaseState->freeGXacts; TwoPhaseState->freeGXacts = MAKE_OFFSET(gxact); LWLockRelease(TwoPhaseStateLock); return; } } LWLockRelease(TwoPhaseStateLock); elog(ERROR, "failed to find %p in GlobalTransaction array", gxact); } /* * Returns an array of all prepared transactions for the user-level * function pg_prepared_xact. * * The returned array and all its elements are copies of internal data * structures, to minimize the time we need to hold the TwoPhaseStateLock. * * WARNING -- we return even those transactions that are not fully prepared * yet. The caller should filter them out if he doesn't want them. * * The returned array is palloc'd. */ static int GetPreparedTransactionList(GlobalTransaction *gxacts) { GlobalTransaction array; int num; int i; LWLockAcquire(TwoPhaseStateLock, LW_SHARED); if (TwoPhaseState->numPrepXacts == 0) { LWLockRelease(TwoPhaseStateLock); *gxacts = NULL; return 0; } num = TwoPhaseState->numPrepXacts; array = (GlobalTransaction) palloc(sizeof(GlobalTransactionData) * num); *gxacts = array; for (i = 0; i < num; i++) memcpy(array + i, TwoPhaseState->prepXacts[i], sizeof(GlobalTransactionData)); LWLockRelease(TwoPhaseStateLock); return num; } /* Working status for pg_prepared_xact */ typedef struct { GlobalTransaction array; int ngxacts; int currIdx; } Working_State; /* * pg_prepared_xact * Produce a view with one row per prepared transaction. * * This function is here so we don't have to export the * GlobalTransactionData struct definition. */ Datum pg_prepared_xact(PG_FUNCTION_ARGS) { FuncCallContext *funcctx; Working_State *status; if (SRF_IS_FIRSTCALL()) { TupleDesc tupdesc; MemoryContext oldcontext; /* create a function context for cross-call persistence */ funcctx = SRF_FIRSTCALL_INIT(); /* * Switch to memory context appropriate for multiple function calls */ oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx); /* build tupdesc for result tuples */ /* this had better match pg_prepared_xacts view in system_views.sql */ tupdesc = CreateTemplateTupleDesc(5, false); TupleDescInitEntry(tupdesc, (AttrNumber) 1, "transaction", XIDOID, -1, 0); TupleDescInitEntry(tupdesc, (AttrNumber) 2, "gid", TEXTOID, -1, 0); TupleDescInitEntry(tupdesc, (AttrNumber) 3, "prepared", TIMESTAMPTZOID, -1, 0); TupleDescInitEntry(tupdesc, (AttrNumber) 4, "ownerid", OIDOID, -1, 0); TupleDescInitEntry(tupdesc, (AttrNumber) 5, "dbid", OIDOID, -1, 0); funcctx->tuple_desc = BlessTupleDesc(tupdesc); /* * Collect all the 2PC status information that we will format and send * out as a result set. */ status = (Working_State *) palloc(sizeof(Working_State)); funcctx->user_fctx = (void *) status; status->ngxacts = GetPreparedTransactionList(&status->array); status->currIdx = 0; MemoryContextSwitchTo(oldcontext); } funcctx = SRF_PERCALL_SETUP(); status = (Working_State *) funcctx->user_fctx; while (status->array != NULL && status->currIdx < status->ngxacts) { GlobalTransaction gxact = &status->array[status->currIdx++]; Datum values[5]; bool nulls[5]; HeapTuple tuple; Datum result; if (!gxact->valid) continue; /* * Form tuple with appropriate data. */ MemSet(values, 0, sizeof(values)); MemSet(nulls, 0, sizeof(nulls)); values[0] = TransactionIdGetDatum(gxact->proc.xid); values[1] = DirectFunctionCall1(textin, CStringGetDatum(gxact->gid)); values[2] = TimestampTzGetDatum(gxact->prepared_at); values[3] = ObjectIdGetDatum(gxact->owner); values[4] = ObjectIdGetDatum(gxact->proc.databaseId); tuple = heap_form_tuple(funcctx->tuple_desc, values, nulls); result = HeapTupleGetDatum(tuple); SRF_RETURN_NEXT(funcctx, result); } SRF_RETURN_DONE(funcctx); } /* * TwoPhaseGetDummyProc * Get the dummy backend ID for prepared transaction specified by XID * * Dummy backend IDs are similar to real backend IDs of real backends. * They start at MaxBackends + 1, and are unique across all currently active * real backends and prepared transactions. */ BackendId TwoPhaseGetDummyBackendId(TransactionId xid) { PGPROC *proc = TwoPhaseGetDummyProc(xid); return ((GlobalTransaction) proc)->dummyBackendId; } /* * TwoPhaseGetDummyProc * Get the PGPROC that represents a prepared transaction specified by XID */ PGPROC * TwoPhaseGetDummyProc(TransactionId xid) { PGPROC *result = NULL; int i; static TransactionId cached_xid = InvalidTransactionId; static PGPROC *cached_proc = NULL; /* * During a recovery, COMMIT PREPARED, or ABORT PREPARED, we'll be called * repeatedly for the same XID. We can save work with a simple cache. */ if (xid == cached_xid) return cached_proc; LWLockAcquire(TwoPhaseStateLock, LW_SHARED); for (i = 0; i < TwoPhaseState->numPrepXacts; i++) { GlobalTransaction gxact = TwoPhaseState->prepXacts[i]; if (gxact->proc.xid == xid) { result = &gxact->proc; break; } } LWLockRelease(TwoPhaseStateLock); if (result == NULL) /* should not happen */ elog(ERROR, "failed to find dummy PGPROC for xid %u (%d entries)", xid, TwoPhaseState->numPrepXacts); cached_xid = xid; cached_proc = result; return result; } /************************************************************************/ /* State file support */ /************************************************************************/ #define TwoPhaseFilePath(path, xid) \ snprintf(path, MAXPGPATH, TWOPHASE_DIR "/%08X", xid) #define TwoPhaseSimpleFileName(path, xid) \ snprintf(path, MAXPGPATH, "/%08X", xid) /* * 2PC state file format: * * 1. TwoPhaseFileHeader * 2. TransactionId[] (subtransactions) * 3. RelFileNode[] (files to be deleted at commit) * 4. RelFileNode[] (files to be deleted at abort) * 5. TwoPhaseRecordOnDisk * 6. ... * 7. TwoPhaseRecordOnDisk (end sentinel, rmid == TWOPHASE_RM_END_ID) * 8. CRC32 * * Each segment except the final CRC32 is MAXALIGN'd. */ /* * Header for a 2PC state file */ #define TWOPHASE_MAGIC 0x57F94531 /* format identifier */ typedef struct TwoPhaseFileHeader { uint32 magic; /* format identifier */ uint32 total_len; /* actual file length */ TransactionId xid; /* original transaction XID */ Oid database; /* OID of database it was in */ TimestampTz prepared_at; /* time of preparation */ Oid owner; /* user running the transaction */ int32 nsubxacts; /* number of following subxact XIDs */ int16 persistentPrepareObjectCount; /* number of PersistentEndXactRec style objects */ char gid[GIDSIZE]; /* GID for transaction */ } TwoPhaseFileHeader; /* * Header for each record in a state file * * NOTE: len counts only the rmgr data, not the TwoPhaseRecordOnDisk header. * The rmgr data will be stored starting on a MAXALIGN boundary. */ typedef struct TwoPhaseRecordOnDisk { uint32 len; /* length of rmgr data */ TwoPhaseRmgrId rmid; /* resource manager for this record */ uint16 info; /* flag bits for use by rmgr */ } TwoPhaseRecordOnDisk; /* * During prepare, the state file is assembled in memory before writing it * to WAL and the actual state file. We use a chain of XLogRecData blocks * so that we will be able to pass the state file contents directly to * XLogInsert. */ static struct xllist { XLogRecData *head; /* first data block in the chain */ XLogRecData *tail; /* last block in chain */ uint32 bytes_free; /* free bytes left in tail block */ uint32 total_len; /* total data bytes in chain */ } records; /* * Append a block of data to records data structure. * * NB: each block is padded to a MAXALIGN multiple. This must be * accounted for when the file is later read! * * The data is copied, so the caller is free to modify it afterwards. */ static void save_state_data(const void *data, uint32 len) { uint32 padlen = MAXALIGN(len); if (padlen > records.bytes_free) { records.tail->next = palloc0(sizeof(XLogRecData)); records.tail = records.tail->next; records.tail->buffer = InvalidBuffer; records.tail->len = 0; records.tail->next = NULL; records.bytes_free = Max(padlen, 512); records.tail->data = palloc(records.bytes_free); } memcpy(((char *) records.tail->data) + records.tail->len, data, len); records.tail->len += padlen; records.bytes_free -= padlen; records.total_len += padlen; } /* * Start preparing a state file. * * Initializes data structure and inserts the 2PC file header record. */ void StartPrepare(GlobalTransaction gxact) { TransactionId xid = gxact->proc.xid; TwoPhaseFileHeader hdr; TransactionId *children; int32 persistentPrepareSerializeLen; PersistentEndXactRecObjects persistentPrepareObjects; /* Initialize linked list */ records.head = palloc0(sizeof(XLogRecData)); records.head->buffer = InvalidBuffer; records.head->len = 0; records.head->next = NULL; records.bytes_free = Max(sizeof(TwoPhaseFileHeader), 512); records.head->data = palloc(records.bytes_free); records.tail = records.head; records.total_len = 0; /* Create header */ hdr.magic = TWOPHASE_MAGIC; hdr.total_len = 0; /* EndPrepare will fill this in */ hdr.xid = xid; hdr.database = gxact->proc.databaseId; hdr.prepared_at = gxact->prepared_at; hdr.owner = gxact->owner; hdr.nsubxacts = xactGetCommittedChildren(&children); persistentPrepareSerializeLen = PersistentEndXactRec_FetchObjectsFromSmgr( &persistentPrepareObjects, EndXactRecKind_Prepare, &hdr.persistentPrepareObjectCount); StrNCpy(hdr.gid, gxact->gid, GIDSIZE); save_state_data(&hdr, sizeof(TwoPhaseFileHeader)); /* Add the additional info about subxacts and deletable files */ if (hdr.nsubxacts > 0) { save_state_data(children, hdr.nsubxacts * sizeof(TransactionId)); /* While we have the child-xact data, stuff it in the gxact too */ GXactLoadSubxactData(gxact, hdr.nsubxacts, children); } if (hdr.persistentPrepareObjectCount > 0) { char *persistentPrepareBuffer; int16 objectCount; Assert(persistentPrepareSerializeLen > 0); persistentPrepareBuffer = (char*) palloc(persistentPrepareSerializeLen); PersistentEndXactRec_Serialize( &persistentPrepareObjects, EndXactRecKind_Prepare, &objectCount, (uint8*)persistentPrepareBuffer, persistentPrepareSerializeLen); if (Debug_persistent_print) { elog(Persistent_DebugPrintLevel(), "StartPrepare: persistentPrepareSerializeLen %d", persistentPrepareSerializeLen); PersistentEndXactRec_Print("StartPrepare", &persistentPrepareObjects); } save_state_data(persistentPrepareBuffer, persistentPrepareSerializeLen); pfree(persistentPrepareBuffer); } SIMPLE_FAULT_INJECTOR(StartPrepareTx); } /* * Finish preparing state file. * * Writes state file (the prepare record) to WAL. */ void EndPrepare(GlobalTransaction gxact) { TransactionId xid = gxact->proc.xid; TwoPhaseFileHeader *hdr; char path[MAXPGPATH]; MIRRORED_LOCK_DECLARE; if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "EndPrepare: xid = %d", xid); /* Add the end sentinel to the list of 2PC records */ RegisterTwoPhaseRecord(TWOPHASE_RM_END_ID, 0, NULL, 0); /* Go back and fill in total_len in the file header record */ hdr = (TwoPhaseFileHeader *) records.head->data; Assert(hdr->magic == TWOPHASE_MAGIC); hdr->total_len = records.total_len + sizeof(pg_crc32); /* * If the file size exceeds MaxAllocSize, we won't be able to read it in * ReadTwoPhaseFile. Check for that now, rather than fail at commit time. */ if (hdr->total_len > MaxAllocSize) ereport(ERROR, (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED), errmsg("two-phase state file maximum length exceeded"))); /* * Create the 2PC state file. * * Note: because we use BasicOpenFile(), we are responsible for ensuring * the FD gets closed in any error exit path. Once we get into the * critical section, though, it doesn't matter since any failure causes * PANIC anyway. */ TwoPhaseFilePath(path, xid); /* * The MirroredLock will cover BOTH mirrored writes to the pg_twophase directory * and the Prepared XLOG record. * * The lock order is: MirroredLock then CheckpointStartLock. */ MIRRORED_LOCK; /* * We have to set inCommit here, too; otherwise a checkpoint starting * immediately after the WAL record is inserted could complete without * fsync'ing our state file. (This is essentially the same kind of race * condition as the COMMIT-to-clog-write case that RecordTransactionCommit * uses inCommit for; see notes there.) * * We save the PREPARE record's location in the gxact for later use by * CheckPointTwoPhase. * * NOTE: Critical section and CheckpointStartLock were moved up. */ START_CRIT_SECTION(); MyProc->inCommit = true; gxact->prepare_lsn = XLogInsert(RM_XACT_ID, XLOG_XACT_PREPARE, records.head); gxact->prepare_begin_lsn = XLogLastInsertBeginLoc(); /* Add the prepared record to our global list */ add_recover_post_checkpoint_prepared_transactions_map_entry(xid, &gxact->prepare_begin_lsn, "EndPrepare"); XLogFlush(gxact->prepare_lsn); /* * Now we may update the CLOG, if we wrote COMMIT record above */ if (max_wal_senders > 0) WalSndWakeup(); /* If we crash now, we have prepared: WAL replay will fix things */ if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "EndPrepare: proc.xid %u, prepare_lsn %s, gid %s", xid, XLogLocationToString(&gxact->prepare_lsn), gxact->gid); if (Debug_abort_after_segment_prepared) { elog(PANIC, "Raise an error as directed by Debug_abort_after_segment_prepared"); } /* * Mark the prepared transaction as valid. As soon as xact.c marks MyProc * as not running our XID (which it will do immediately after this * function returns), others can commit/rollback the xact. * * NB: a side effect of this is to make a dummy ProcArray entry for the * prepared XID. This must happen before we clear the XID from MyProc, * else there is a window where the XID is not running according to * TransactionIdIsInProgress, and onlookers would be entitled to assume * the xact crashed. Instead we have a window where the same XID appears * twice in ProcArray, which is OK. */ MarkAsPrepared(gxact); /* * Remember that we have this GlobalTransaction entry locked for us. If * we crash after this point, it's too late to abort, but we must unlock * it so that the prepared transaction can be committed or rolled back. */ MyLockedGxact = gxact; END_CRIT_SECTION(); /* * Now we can mark ourselves as out of the commit critical section: a * checkpoint starting after this will certainly see the gxact as a * candidate for fsyncing. */ MyProc->inCommit = false; MIRRORED_UNLOCK; SIMPLE_FAULT_INJECTOR(EndPreparedTwoPhaseSleep); /* * Wait for synchronous replication, if required. */ Assert(gxact->prepare_lsn.xrecoff != 0); SyncRepWaitForLSN(gxact->prepare_lsn); records.tail = records.head = NULL; } /* end EndPrepare */ /* * Register a 2PC record to be written to state file. */ void RegisterTwoPhaseRecord(TwoPhaseRmgrId rmid, uint16 info, const void *data, uint32 len) { TwoPhaseRecordOnDisk record; record.rmid = rmid; record.info = info; record.len = len; save_state_data(&record, sizeof(TwoPhaseRecordOnDisk)); if (len > 0) save_state_data(data, len); } void PrepareIntentAppendOnlyCommitWork(char *gid) { GlobalTransaction gxact; gxact = FindPrepareGXact(gid); Assert(gxact->prepareAppendOnlyIntentCount >= 0); gxact->prepareAppendOnlyIntentCount++; } void PrepareDecrAppendOnlyCommitWork(char *gid) { GlobalTransaction gxact; gxact = FindPrepareGXact(gid); Assert(gxact->prepareAppendOnlyIntentCount >= 1); gxact->prepareAppendOnlyIntentCount--; } /* * FinishPreparedTransaction: execute COMMIT PREPARED or ROLLBACK PREPARED */ bool FinishPreparedTransaction(const char *gid, bool isCommit, bool raiseErrorIfNotFound) { MIRRORED_LOCK_DECLARE; GlobalTransaction gxact; TransactionId xid; char *buf; char *bufptr; char *dummy; TwoPhaseFileHeader *hdr; TransactionId latestXid; TransactionId *children; PersistentEndXactRecObjects persistentPrepareObjects; int32 deserializeLen; int prepareAppendOnlyIntentCount; XLogRecPtr tfXLogRecPtr; XLogRecord *tfRecord = NULL; /* * Validate the GID, and lock the GXACT to ensure that two backends do not * try to commit the same GID at once. */ gxact = LockGXact(gid, GetUserId(), raiseErrorIfNotFound); if (!raiseErrorIfNotFound && gxact == NULL) { return false; } xid = gxact->proc.xid; tfXLogRecPtr = gxact->prepare_begin_lsn; elog((Debug_print_full_dtm ? LOG : DEBUG5), "FinishPreparedTransaction(): got xid %d for gid '%s'", xid, gid); /* * Check for recovery control file, and if so set up state for offline * recovery */ XLogReadRecoveryCommandFile(DEBUG5); /* Now we can determine the list of expected TLIs */ expectedTLIs = XLogReadTimeLineHistory(ThisTimeLineID); /* get the two phase information from the xlog */ XLogCloseReadRecord(); tfRecord = XLogReadRecord(&tfXLogRecPtr, false, LOG); if (tfRecord == NULL) { /* * Invalid XLOG record means record is corrupted. * Failover is required, hopefully mirror is in healthy state. */ ereport(WARNING, (errmsg("primary failure, " "xlog record is invalid, " "failover requested"), errhint("run gprecoverseg to re-establish mirror connectivity"))); FileRep_SetSegmentState(SegmentStateFault, FaultTypeIO); ereport(ERROR, (errcode(ERRCODE_DATA_CORRUPTED), errmsg("xlog record is invalid"), errSendAlert(true))); } buf = XLogRecGetData(tfRecord); if (buf == NULL) ereport(ERROR, (errcode(ERRCODE_DATA_CORRUPTED), errmsg("two-phase state information for transaction %u is corrupt", xid), errSendAlert(true))); /* * Disassemble the header area */ hdr = (TwoPhaseFileHeader *) buf; Assert(TransactionIdEquals(hdr->xid, xid)); bufptr = buf + MAXALIGN(sizeof(TwoPhaseFileHeader)); children = (TransactionId *) bufptr; bufptr += MAXALIGN(hdr->nsubxacts * sizeof(TransactionId)); /* * Although we return the end of the PersistentEndXactRec object, we really want the * rounded-up aligned next buffer. So, that is why we compute the deserialized length * and calculated the next buffer with it. */ deserializeLen = PersistentEndXactRec_DeserializeLen( (uint8*) bufptr, hdr->persistentPrepareObjectCount); PersistentEndXactRec_Deserialize( (uint8*) bufptr, hdr->persistentPrepareObjectCount, &persistentPrepareObjects, (uint8**) &dummy); if (Debug_persistent_print) { elog(Persistent_DebugPrintLevel(), "FinishPreparedTransaction: deserializedLen %d, persistentPrepareObjectCount %d", deserializeLen, hdr->persistentPrepareObjectCount); PersistentEndXactRec_Print("FinishPreparedTransaction", &persistentPrepareObjects); } bufptr += MAXALIGN(deserializeLen); // NOTE: This use to be inside RecordTransactionCommitPrepared and // NOTE: RecordTransactionAbortPrepared. Moved out here so the mirrored // NOTE: can cover both the XLOG record and the mirrored pg_twophase file // NOTE: work. START_CRIT_SECTION(); /* * Use the MirroredLock to cover both the XLOG of the {COMMIT|ABORT} PREPARED * record and the removal the of the two phase file from the pg_twophase directory. */ MIRRORED_LOCK; /* * We have to lock out checkpoint start here when updating persistent relation information * like Appendonly segment's committed EOF. Otherwise there might be a window between * the time some data is added to an appendonly segment file and its EOF updated in the * persistent relation tables. If there is a checkpoint before updating the persistent tables * and the system crash after the checkpoint, then during crash recovery we would not resync * to the right EOFs (MPP-18261). */ MyProc->inCommit = true; /* compute latestXid among all children */ latestXid = TransactionIdLatest(xid, hdr->nsubxacts, children); /* * The order of operations here is critical: make the XLOG entry for * commit or abort, then mark the transaction committed or aborted in * pg_clog, then remove its PGPROC from the global ProcArray (which means * TransactionIdIsInProgress will stop saying the prepared xact is in * progress), then run the post-commit or post-abort callbacks. The * callbacks will release the locks the transaction held. */ if (isCommit) RecordTransactionCommitPrepared(xid, gid, hdr->nsubxacts, children, &persistentPrepareObjects); else RecordTransactionAbortPrepared(xid, hdr->nsubxacts, children, &persistentPrepareObjects); prepareAppendOnlyIntentCount = gxact->prepareAppendOnlyIntentCount; ProcArrayRemove(&gxact->proc, latestXid); /* * In case we fail while running the callbacks, mark the gxact invalid so * no one else will try to commit/rollback, and so it will be recycled * if we fail after this point. It is still locked by our backend so it * won't go away yet. * * (We assume it's safe to do this without taking TwoPhaseStateLock.) */ if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "FinishPreparedTransaction: gxact->proc.xid = %d and set valid = false", gxact->proc.xid); gxact->valid = false; /* * We have to remove any files that were supposed to be dropped. For * consistency with the regular xact.c code paths, must do this before * releasing locks, so do it before running the callbacks. * * NB: this code knows that we couldn't be dropping any temp rels ... */ PersistentFileSysObj_PreparedEndXactAction( xid, gid, &persistentPrepareObjects, isCommit, prepareAppendOnlyIntentCount); /* And now do the callbacks */ if (isCommit) ProcessRecords(bufptr, xid, twophase_postcommit_callbacks); else ProcessRecords(bufptr, xid, twophase_postabort_callbacks); /* Count the prepared xact as committed or aborted */ AtEOXact_PgStat(isCommit); /* * And now we can clean up our mess. */ remove_recover_post_checkpoint_prepared_transactions_map_entry(xid, "FinishPreparedTransaction"); RemoveGXact(gxact); MyLockedGxact = NULL; /* Checkpoint can proceed now */ MyProc->inCommit = false; MIRRORED_UNLOCK; END_CRIT_SECTION(); SIMPLE_FAULT_INJECTOR(FinishPreparedAfterRecordCommitPrepared); /* Need to figure out the memory allocation and deallocationfor "buffer". For now, just let it leak. */ return true; } /* * Scan a 2PC state file (already read into memory by ReadTwoPhaseFile) * and call the indicated callbacks for each 2PC record. */ static void ProcessRecords(char *bufptr, TransactionId xid, const TwoPhaseCallback callbacks[]) { for (;;) { TwoPhaseRecordOnDisk *record = (TwoPhaseRecordOnDisk *) bufptr; Assert(record->rmid <= TWOPHASE_RM_MAX_ID); if (record->rmid == TWOPHASE_RM_END_ID) break; bufptr += MAXALIGN(sizeof(TwoPhaseRecordOnDisk)); if (callbacks[record->rmid] != NULL) callbacks[record->rmid] (xid, record->info, (void *) bufptr, record->len); bufptr += MAXALIGN(record->len); } } /* * Remove the 2PC file for the specified XID. * * If giveWarning is false, do not complain about file-not-present; * this is an expected case during WAL replay. */ void RemoveTwoPhaseFile(TransactionId xid, bool giveWarning) { remove_recover_post_checkpoint_prepared_transactions_map_entry(xid, "RemoveTwoPhaseFile: Removing from list"); } /* * This is used in WAL replay. * */ void RecreateTwoPhaseFile(TransactionId xid, void *content, int len, XLogRecPtr *xlogrecptr) { if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "RecreateTwoPhaseFile: entering..."); add_recover_post_checkpoint_prepared_transactions_map_entry(xid, xlogrecptr, "RecreateTwoPhaseFile: add entry to hash list"); } /* * CheckPointTwoPhase -- handle 2PC component of checkpointing. * * We must fsync the state file of any GXACT that is valid and has a PREPARE * LSN <= the checkpoint's redo horizon. (If the gxact isn't valid yet or * has a later LSN, this checkpoint is not responsible for fsyncing it.) * * This is deliberately run as late as possible in the checkpoint sequence, * because GXACTs ordinarily have short lifespans, and so it is quite * possible that GXACTs that were valid at checkpoint start will no longer * exist if we wait a little bit. * * If a GXACT remains valid across multiple checkpoints, it'll be fsynced * each time. This is considered unusual enough that we don't bother to * expend any extra code to avoid the redundant fsyncs. (They should be * reasonably cheap anyway, since they won't cause I/O.) */ void CheckPointTwoPhase(XLogRecPtr redo_horizon) { /* * I think this is not needed with the new two phase logic. * We have already attached all the prepared transactions to * the checkpoint record. For now, just return from this. */ return; } /* * PrescanPreparedTransactions * * This function will return the oldest valid XID, and will also set * the ShmemVariableCache->nextXid to the next available XID. * * This function is run during database startup, after we have completed * reading WAL. ShmemVariableCache->nextXid has been set to one more than * the highest XID for which evidence exists in WAL. The * crashRecoverPostCheckpointPreparedTransactions_map_ht has already been * populated with all pre and post checkpoint inflight transactions. * * We will advance nextXid beyond any subxact XIDs belonging to valid * prepared xacts. We need to do this since subxact commit doesn't * write a WAL entry, and so there might be no evidence in WAL of those * subxact XIDs. * * Our other responsibility is to determine and return the oldest valid XID * among the prepared xacts (if none, return ShmemVariableCache->nextXid). * This is needed to synchronize pg_subtrans startup properly. */ TransactionId PrescanPreparedTransactions(void) { prpt_map *entry = NULL; TransactionId origNextXid = ShmemVariableCache->nextXid; TransactionId result = origNextXid; XLogRecPtr *tfXLogRecPtr = NULL; XLogRecord *tfRecord = NULL; HASH_SEQ_STATUS hsStatus; TwoPhaseFileHeader *hdr = NULL; TransactionId xid; TransactionId *subxids; if (crashRecoverPostCheckpointPreparedTransactions_map_ht != NULL) { hash_seq_init(&hsStatus,crashRecoverPostCheckpointPreparedTransactions_map_ht); entry = (prpt_map *)hash_seq_search(&hsStatus); if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "PrescanPreparedTransactions: address entry = %p", entry); if (entry != NULL) tfXLogRecPtr = (XLogRecPtr *) &entry->xlogrecptr; } while (tfXLogRecPtr != NULL) { if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "PrescanPreparedTransactions: XLogRecPtr = %s", XLogLocationToString(tfXLogRecPtr)); tfRecord = XLogReadRecord(tfXLogRecPtr, false, LOG); hdr = (TwoPhaseFileHeader *) XLogRecGetData(tfRecord); xid = hdr->xid; if (TransactionIdDidCommit(xid) == false && TransactionIdDidAbort(xid) == false) { int i; /* * Incorporate xid into the running-minimum result. */ if (TransactionIdPrecedes(xid, result)) result = xid; /* * Examine subtransaction XIDs ... they should all follow main * XID, and they may force us to advance nextXid. */ subxids = (TransactionId *) ((char *)hdr + MAXALIGN(sizeof(TwoPhaseFileHeader))); for (i = 0; i < hdr->nsubxacts; i++) { TransactionId subxid = subxids[i]; Assert(TransactionIdFollows(subxid, xid)); if (TransactionIdFollowsOrEquals(subxid, ShmemVariableCache->nextXid)) { ShmemVariableCache->nextXid = subxid; TransactionIdAdvance(ShmemVariableCache->nextXid); } } } /* Get the next entry */ entry = (prpt_map *)hash_seq_search(&hsStatus); if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "PrescanPreparedTransactions: address entry = %p", entry); if (entry != NULL) tfXLogRecPtr = (XLogRecPtr *) &entry->xlogrecptr; else tfXLogRecPtr = NULL; } return result; } /* * Retrieve all the prepared transactions on the checkpoint, and add them to our local list. */ void SetupCheckpointPreparedTransactionList(XLogRecord *record) { prepared_transaction_agg_state *ptas = NULL; XLogRecPtr *tfXLogRecPtr = NULL; TransactionId xid; prpt_map *m = NULL; /* Under some cercumstances, and old style checkpoint may exist (upgrade switch xlog...). */ /* Check to see if it looks like an old checkpoin, size of a checkpoint plus size of an empty DTX list or less */ if (record->xl_len <= (sizeof(CheckPoint) + TMGXACT_CHECKPOINT_BYTES(0))) { /* * This is an old checkpoint (pre-removal of two phase) or a bad checkpoint record. * Assume it is old and return. */ if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "SetupCheckpointPreparedTransactionList: Looks like an old style checkpoint record, so just return"); return; } ptas = (prepared_transaction_agg_state *)mmxlog_get_checkpoint_record_suffix(record); if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "SetupCheckpointPreparedTransactionList: prepared transaciton agg state length = %d", ptas->count); m = ptas->maps; for (int iPrep = 0; iPrep < ptas->count; iPrep++) { xid = m[iPrep].xid; tfXLogRecPtr = &(m[iPrep]).xlogrecptr; add_recover_post_checkpoint_prepared_transactions_map_entry(xid, tfXLogRecPtr, "SetupCheckpointPreparedTransactionList: add entry to hash list"); } } /* end SetupCheckpointPreparedTransactionList */ /* * RecoverPreparedTransactions * * Scan the global list of post checkpoint records and reload shared-memory state for each * prepared transaction (reacquire locks, etc). This is run during database * startup. */ void RecoverPreparedTransactions(void) { prpt_map *entry = NULL; XLogRecPtr *tfXLogRecPtr = NULL; XLogRecord *tfRecord = NULL; PersistentEndXactRecObjects persistentPrepareObjects; LocalDistribXactData localDistribXactData; TwoPhaseFileHeader *hdr = NULL; HASH_SEQ_STATUS hsStatus; if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "Entering RecoverPreparedTransactions"); if (crashRecoverPostCheckpointPreparedTransactions_map_ht != NULL) { hash_seq_init(&hsStatus,crashRecoverPostCheckpointPreparedTransactions_map_ht); entry = (prpt_map *)hash_seq_search(&hsStatus); if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "RecoverPreparedTransactions: address entry = %p", entry); if (entry != NULL) tfXLogRecPtr = (XLogRecPtr *) &entry->xlogrecptr; } while (tfXLogRecPtr != NULL) { TransactionId xid; char *bufptr; TransactionId *subxids; GlobalTransaction gxact; DistributedTransactionTimeStamp distribTimeStamp; DistributedTransactionId distribXid; if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "RecoverPreparedTransactions: XLogRecPtr = %s", XLogLocationToString(tfXLogRecPtr)); tfRecord = XLogReadRecord(tfXLogRecPtr, false, LOG); hdr = (TwoPhaseFileHeader *) XLogRecGetData(tfRecord); elog(Persistent_DebugPrintLevel(), "RecoverPreparedTransactions: prepared twophase record total_len = %u, xid = %d", hdr->total_len, hdr->xid); xid = hdr->xid; bufptr = (char *) hdr + MAXALIGN(sizeof(TwoPhaseFileHeader)); subxids = (TransactionId *) bufptr; bufptr += MAXALIGN(hdr->nsubxacts * sizeof(TransactionId)); PersistentEndXactRec_Deserialize((uint8 *) bufptr, hdr->persistentPrepareObjectCount, &persistentPrepareObjects, (uint8 **) &bufptr); if (Debug_persistent_print) { elog( Persistent_DebugPrintLevel(), "RecoverPreparedTransactions: deserializeLen %d, persistentPrepareObjectCount %d", PersistentEndXactRec_DeserializeLen((uint8*) bufptr, hdr->persistentPrepareObjectCount), hdr->persistentPrepareObjectCount); PersistentEndXactRec_Print("RecoverPreparedTransactions", &persistentPrepareObjects); } /* * Reconstruct subtrans state for the transaction --- needed * because pg_subtrans is not preserved over a restart. Note that * we are linking all the subtransactions directly to the * top-level XID; there may originally have been a more complex * hierarchy, but there's no need to restore that exactly. */ for (int iSub = 0; iSub < hdr->nsubxacts; iSub++) SubTransSetParent(subxids[iSub], xid); /* * Crack open the gid to get the DTM start time and distributed * transaction id. */ dtxCrackOpenGid(hdr->gid, &distribTimeStamp, &distribXid); /* * Recreate its GXACT and dummy PGPROC * * Note: since we don't have the PREPARE record's WAL location at * hand, we leave prepare_lsn zeroes. This means the GXACT will * be fsync'd on every future checkpoint. We assume this * situation is infrequent enough that the performance cost is * negligible (especially since we know the state file has already * been fsynced). */ elog(Persistent_DebugPrintLevel(), "RecoverPreparedTransactions: Calling MarkAsPreparing on id = %s with distribTimeStamp %u and distribXid %u", hdr->gid, distribTimeStamp, distribXid); localDistribXactData.state = LOCALDISTRIBXACT_STATE_ACTIVE; localDistribXactData.distribTimeStamp = distribTimeStamp; localDistribXactData.distribXid = distribXid; gxact = MarkAsPreparing(xid, &localDistribXactData, hdr->gid, hdr->prepared_at, hdr->owner, hdr->database, tfXLogRecPtr); GXactLoadSubxactData(gxact, hdr->nsubxacts, subxids); MarkAsPrepared(gxact); /* * Recover other state (notably locks) using resource managers */ ProcessRecords(bufptr, xid, twophase_recover_callbacks); /* Get the next entry */ entry = (prpt_map *)hash_seq_search(&hsStatus); if (Debug_persistent_print) elog(Persistent_DebugPrintLevel(), "RecoverPreparedTransactions: address entry = %p", entry); if (entry != NULL) tfXLogRecPtr = (XLogRecPtr *) &entry->xlogrecptr; else tfXLogRecPtr = NULL; } /* end while (xlogrecptr = (XLogRecPtr *)hash_seq_search(&hsStatus)) */ } /* * RecordTransactionCommitPrepared * * This is basically the same as RecordTransactionCommit: in particular, * we must set the inCommit flag to avoid a race condition. * * We know the transaction made at least one XLOG entry (its PREPARE), * so it is never possible to optimize out the commit record. */ static void RecordTransactionCommitPrepared(TransactionId xid, const char *gid, int nchildren, TransactionId *children, PersistentEndXactRecObjects *persistentPrepareObjects) { int16 persistentCommitObjectCount; char *persistentCommitBuffer = NULL; XLogRecData rdata[3]; int lastrdata = 0; xl_xact_commit_prepared xlrec; XLogRecPtr recptr; DistributedTransactionTimeStamp distribTimeStamp; DistributedTransactionId distribXid; /* * Look at the prepare information with respect to a commit. */ persistentCommitObjectCount = PersistentEndXactRec_ObjectCount( persistentPrepareObjects, EndXactRecKind_Commit); /* * Ensure the caller already has MirroredLock and has set MyProc->isCommit. */ Assert(MyProc->inCommit); /* Emit the XLOG commit record */ xlrec.xid = xid; xlrec.crec.xtime = time(NULL); xlrec.crec.persistentCommitObjectCount = persistentCommitObjectCount; xlrec.crec.nsubxacts = nchildren; rdata[0].data = (char *) (&xlrec); rdata[0].len = MinSizeOfXactCommitPrepared; rdata[0].buffer = InvalidBuffer; /* dump persistent commit objects */ if (persistentCommitObjectCount > 0) { int32 persistentCommitSerializeLen; int16 objectCount; persistentCommitSerializeLen = PersistentEndXactRec_SerializeLen( persistentPrepareObjects, EndXactRecKind_Commit); Assert(persistentCommitSerializeLen > 0); persistentCommitBuffer = (char *) palloc(persistentCommitSerializeLen); PersistentEndXactRec_Serialize( persistentPrepareObjects, EndXactRecKind_Commit, &objectCount, (uint8 *) persistentCommitBuffer, persistentCommitSerializeLen); if (Debug_persistent_print) { elog(Persistent_DebugPrintLevel(), "RecordTransactionCommitPrepared: persistentCommitSerializeLen %d, objectCount %d", persistentCommitSerializeLen, objectCount); PersistentEndXactRec_Print("RecordTransactionCommitPrepared", persistentPrepareObjects); } rdata[0].next = &(rdata[1]); rdata[1].data = persistentCommitBuffer; rdata[1].len = persistentCommitSerializeLen; rdata[1].buffer = InvalidBuffer; lastrdata = 1; } /* dump committed child Xids */ if (nchildren > 0) { rdata[lastrdata].next = &(rdata[2]); rdata[2].data = (char *) children; rdata[2].len = nchildren * sizeof(TransactionId); rdata[2].buffer = InvalidBuffer; lastrdata = 2; } rdata[lastrdata].next = NULL; SIMPLE_FAULT_INJECTOR(TwoPhaseTransactionCommitPrepared); recptr = XLogInsert(RM_XACT_ID, XLOG_XACT_COMMIT_PREPARED, rdata); /* * We don't currently try to sleep before flush here ... nor is there any * support for async commit of a prepared xact (the very idea is probably * a contradiction) */ /* Flush XLOG to disk */ XLogFlush(recptr); if (max_wal_senders > 0) WalSndWakeup(); /* * Crack open the gid to get the DTM start time and distributed * transaction id. */ dtxCrackOpenGid(gid, &distribTimeStamp, &distribXid); /* UNDONE: What are the locking issues here? */ /* * Mark the distributed transaction committed. */ DistributedLog_SetCommitted( xid, distribTimeStamp, distribXid, /* isRedo */ false); /* Mark the transaction committed in pg_clog */ TransactionIdCommit(xid); /* to avoid race conditions, the parent must commit first */ TransactionIdCommitTree(nchildren, children); /* * Wait for synchronous replication, if required. * * Note that at this stage we have marked clog, but still show as running * in the procarray and continue to hold locks. */ SyncRepWaitForLSN(recptr); if (persistentCommitBuffer != NULL) pfree(persistentCommitBuffer); } /* * RecordTransactionAbortPrepared * * This is basically the same as RecordTransactionAbort. * * We know the transaction made at least one XLOG entry (its PREPARE), * so it is never possible to optimize out the abort record. */ static void RecordTransactionAbortPrepared(TransactionId xid, int nchildren, TransactionId *children, PersistentEndXactRecObjects *persistentPrepareObjects) { int16 persistentAbortObjectCount; char *persistentAbortBuffer = NULL; XLogRecData rdata[3]; int lastrdata = 0; xl_xact_abort_prepared xlrec; XLogRecPtr recptr; /* * Catch the scenario where we aborted partway through * RecordTransactionCommitPrepared ... */ if (TransactionIdDidCommit(xid)) elog(PANIC, "cannot abort transaction %u, it was already committed", xid); /* * Look at the prepare information with respect to an abort. */ persistentAbortObjectCount = PersistentEndXactRec_ObjectCount( persistentPrepareObjects, EndXactRecKind_Abort); /* Emit the XLOG abort record */ xlrec.xid = xid; xlrec.arec.xact_time = GetCurrentTimestamp(); xlrec.arec.persistentAbortObjectCount = persistentAbortObjectCount; xlrec.arec.nsubxacts = nchildren; rdata[0].data = (char *) (&xlrec); rdata[0].len = MinSizeOfXactAbortPrepared; rdata[0].buffer = InvalidBuffer; /* dump persistent abort objects */ if (persistentAbortObjectCount > 0) { int32 persistentAbortSerializeLen; int16 objectCount; persistentAbortSerializeLen = PersistentEndXactRec_SerializeLen( persistentPrepareObjects, EndXactRecKind_Abort); Assert(persistentAbortSerializeLen > 0); persistentAbortBuffer = (char *) palloc(persistentAbortSerializeLen); PersistentEndXactRec_Serialize( persistentPrepareObjects, EndXactRecKind_Abort, &objectCount, (uint8 *) persistentAbortBuffer, persistentAbortSerializeLen); if (Debug_persistent_print) { elog(Persistent_DebugPrintLevel(), "RecordTransactionAbortPrepared: persistentAbortSerializeLen %d", persistentAbortSerializeLen); PersistentEndXactRec_Print("RecordTransactionAbortPrepared", persistentPrepareObjects); } rdata[0].next = &(rdata[1]); rdata[1].data = persistentAbortBuffer; rdata[1].len = persistentAbortSerializeLen; rdata[1].buffer = InvalidBuffer; lastrdata = 1; } /* dump committed child Xids */ if (nchildren > 0) { rdata[lastrdata].next = &(rdata[2]); rdata[2].data = (char *) children; rdata[2].len = nchildren * sizeof(TransactionId); rdata[2].buffer = InvalidBuffer; lastrdata = 2; } rdata[lastrdata].next = NULL; SIMPLE_FAULT_INJECTOR(TwoPhaseTransactionAbortPrepared); recptr = XLogInsert(RM_XACT_ID, XLOG_XACT_ABORT_PREPARED, rdata); /* Always flush, since we're about to remove the 2PC state file */ XLogFlush(recptr); if (max_wal_senders > 0) WalSndWakeup(); /* * Mark the transaction aborted in clog. This is not absolutely necessary * but we may as well do it while we are here. */ TransactionIdAbort(xid); TransactionIdAbortTree(nchildren, children); /* * Wait for synchronous replication, if required. * * Note that at this stage we have marked clog, but still show as running * in the procarray and continue to hold locks. */ Assert(recptr.xrecoff != 0); SyncRepWaitForLSN(recptr); if (persistentAbortBuffer != NULL) pfree(persistentAbortBuffer); } int TwoPhaseRecoverMirror(void) { int retval = 0; /* No need to do anything. */ return retval; } /* * This function will gather up all the current prepared transaction xlog pointers, * and pass that information back to the caller. */ void getTwoPhasePreparedTransactionData(prepared_transaction_agg_state **ptas, char *caller) { int numberOfPrepareXacts = TwoPhaseState->numPrepXacts; GlobalTransaction *globalTransactionArray = TwoPhaseState->prepXacts; TransactionId xid; XLogRecPtr *recordPtr = NULL; int maxCount; elog(PersistentRecovery_DebugPrintLevel(), "getTwoPhasePreparedTransactionData: start of function from caller %s", caller); Assert(*ptas == NULL); TwoPhaseAddPreparedTransactionInit(ptas, &maxCount); elog(PersistentRecovery_DebugPrintLevel(), "getTwoPhasePreparedTransactionData: numberOfPrepareXacts = %d", numberOfPrepareXacts); for (int i = 0; i < numberOfPrepareXacts; i++) { if ((globalTransactionArray[i])->valid == false) /* Skip any invalid prepared transacitons. */ continue; xid = (globalTransactionArray[i])->proc.xid; recordPtr = &(globalTransactionArray[i])->prepare_begin_lsn; elog(PersistentRecovery_DebugPrintLevel(), "getTwoPhasePreparedTransactionData: add entry xid = %u, XLogRecPtr = %s, caller = %s", xid, XLogLocationToString(recordPtr), caller); TwoPhaseAddPreparedTransaction(ptas, &maxCount, xid, recordPtr, caller); } } /* end getTwoPhasePreparedTransactionData */ /* * This function will allocate enough space to accomidate maxCount values. */ void TwoPhaseAddPreparedTransactionInit(prepared_transaction_agg_state **ptas, int *maxCount) { int len; Assert (*ptas == NULL); *maxCount = 10; // Start off with at least this much room. len = PREPARED_TRANSACTION_CHECKPOINT_BYTES(*maxCount); *ptas = (prepared_transaction_agg_state*)palloc0(len); } /* end TwoPhaseAddPreparedTransactionInit */ /* * This function adds another entry to the list of prepared transactions. */ void TwoPhaseAddPreparedTransaction(prepared_transaction_agg_state **ptas, int *maxCount, TransactionId xid, XLogRecPtr *xlogPtr, char *caller) { int len; int count; prpt_map *m; Assert(*ptas != NULL); Assert(*maxCount > 0); count = (*ptas)->count; Assert(count <= *maxCount); if (count == *maxCount) { prepared_transaction_agg_state *oldPtas; oldPtas = *ptas; (*maxCount) *= 2; // Double. len = PREPARED_TRANSACTION_CHECKPOINT_BYTES(*maxCount); *ptas = (prepared_transaction_agg_state*)palloc0(len); memcpy(*ptas, oldPtas, PREPARED_TRANSACTION_CHECKPOINT_BYTES(count)); pfree(oldPtas); } m = &(*ptas)->maps[count]; m->xid = xid; m->xlogrecptr.xlogid = xlogPtr->xlogid; m->xlogrecptr.xrecoff = xlogPtr->xrecoff; if (Debug_persistent_recovery_print) { SUPPRESS_ERRCONTEXT_DECLARE; SUPPRESS_ERRCONTEXT_PUSH(); elog(PersistentRecovery_DebugPrintLevel(), "TwoPhaseAddPreparedTransaction: add entry XLogRecPtr = %s, caller = %s", XLogLocationToString(xlogPtr), caller); SUPPRESS_ERRCONTEXT_POP(); } (*ptas)->count++; } /* end TwoPhaseAddPreparedTransaction */ /* * Return a pointer to the oldest XLogRecPtr in the list or NULL if the list is empty. */ XLogRecPtr * getTwoPhaseOldestPreparedTransactionXLogRecPtr(XLogRecData *rdata) { prepared_transaction_agg_state *ptas = (prepared_transaction_agg_state *)rdata->data; int map_count = ptas->count; prpt_map *m = ptas->maps; XLogRecPtr *oldest = NULL; elog(PersistentRecovery_DebugPrintLevel(), "getTwoPhaseOldestPreparedTransactionXLogRecPtr: map_count = %d", map_count); if (map_count > 0) { oldest = &(m[0].xlogrecptr); for (int i = 1; i < map_count; i++) { elog(PersistentRecovery_DebugPrintLevel(), "getTwoPhaseOldestPreparedTransactionXLogRecPtr: checkpoint prepared pointer %d = %s", i, XLogLocationToString(oldest)); if (XLByteLE(m[i].xlogrecptr, *oldest)) oldest = &(m[i].xlogrecptr); } } return oldest; } /* end getTwoPhaseOldestPreparedTransactionXLogRecPtr */