// InternalPushTxn resolves conflicts between concurrent txns (or
// between a non-transactional reader or writer and a txn) in several
// ways depending on the statuses and priorities of the conflicting
// transactions. The InternalPushTxn operation is invoked by a
// "pusher" (the writer trying to abort a conflicting txn or the
// reader trying to push a conflicting txn's commit timestamp
// forward), who attempts to resolve a conflict with a "pushee"
// (args.PushTxn -- the pushee txn whose intent(s) caused the
// conflict).
//
// Txn already committed/aborted: If pushee txn is committed or
// aborted return success.
//
// Txn Timeout: If pushee txn entry isn't present or its LastHeartbeat
// timestamp isn't set, use PushTxn.Timestamp as LastHeartbeat. If
// current time - LastHeartbeat > 2 * DefaultHeartbeatInterval, then
// the pushee txn should be either pushed forward, aborted, or
// confirmed not pending, depending on value of Request.PushType.
//
// Old Txn Epoch: If persisted pushee txn entry has a newer Epoch than
// PushTxn.Epoch, return success, as older epoch may be removed.
//
// Lower Txn Priority: If pushee txn has a lower priority than pusher,
// adjust pushee's persisted txn depending on value of
// args.PushType. If args.PushType is ABORT_TXN, set txn.Status to
// ABORTED, and priority to one less than the pusher's priority and
// return success. If args.PushType is PUSH_TIMESTAMP, set
// txn.Timestamp to pusher's Timestamp + 1 (note that we use the
// pusher's Args.Timestamp, not Txn.Timestamp because the args
// timestamp can advance during the txn).
//
// Higher Txn Priority: If pushee txn has a higher priority than
// pusher, return TransactionPushError. Transaction will be retried
// with priority one less than the pushee's higher priority.
func (r *Range) InternalPushTxn(batch engine.Engine, ms *engine.MVCCStats, args *proto.InternalPushTxnRequest, reply *proto.InternalPushTxnResponse) {
if !bytes.Equal(args.Key, args.PusheeTxn.Key) {
reply.SetGoError(util.Errorf("request key %s should match pushee's txn key %s", args.Key, args.PusheeTxn.Key))
return
}
key := keys.TransactionKey(args.PusheeTxn.Key, args.PusheeTxn.ID)
// Fetch existing transaction if possible.
existTxn := &proto.Transaction{}
ok, err := engine.MVCCGetProto(batch, key, proto.ZeroTimestamp,
true /* consistent */, nil /* txn */, existTxn)
if err != nil {
reply.SetGoError(err)
return
}
if ok {
// Start with the persisted transaction record as final transaction.
reply.PusheeTxn = gogoproto.Clone(existTxn).(*proto.Transaction)
// Upgrade the epoch, timestamp and priority as necessary.
if reply.PusheeTxn.Epoch < args.PusheeTxn.Epoch {
reply.PusheeTxn.Epoch = args.PusheeTxn.Epoch
}
reply.PusheeTxn.Timestamp.Forward(args.PusheeTxn.Timestamp)
if reply.PusheeTxn.Priority < args.PusheeTxn.Priority {
reply.PusheeTxn.Priority = args.PusheeTxn.Priority
}
} else {
// Some sanity checks for case where we don't find a transaction record.
if args.PusheeTxn.LastHeartbeat != nil {
reply.SetGoError(proto.NewTransactionStatusError(&args.PusheeTxn,
"no txn persisted, yet intent has heartbeat"))
return
} else if args.PusheeTxn.Status != proto.PENDING {
reply.SetGoError(proto.NewTransactionStatusError(&args.PusheeTxn,
fmt.Sprintf("no txn persisted, yet intent has status %s", args.PusheeTxn.Status)))
return
}
// The transaction doesn't exist yet on disk; use the supplied version.
reply.PusheeTxn = gogoproto.Clone(&args.PusheeTxn).(*proto.Transaction)
}
// If already committed or aborted, return success.
if reply.PusheeTxn.Status != proto.PENDING {
// Trivial noop.
return
}
// If we're trying to move the timestamp forward, and it's already
// far enough forward, return success.
if args.PushType == proto.PUSH_TIMESTAMP && args.Timestamp.Less(reply.PusheeTxn.Timestamp) {
// Trivial noop.
return
}
// pusherWins bool is true in the event the pusher prevails.
var pusherWins bool
// If there's no incoming transaction, the pusher is non-transactional.
// We make a random priority, biased by specified
// args.Header().UserPriority in this case.
var priority int32
if args.Txn != nil {
priority = args.Txn.Priority
} else {
// Make sure we have a deterministic random number when generating
// a priority for this txn-less request, so all replicas see same priority.
randGen := rand.New(rand.NewSource(int64(reply.PusheeTxn.Priority) ^ args.Timestamp.WallTime))
priority = proto.MakePriority(randGen, args.GetUserPriority())
}
// Check for txn timeout.
if reply.PusheeTxn.LastHeartbeat == nil {
reply.PusheeTxn.LastHeartbeat = &reply.PusheeTxn.Timestamp
}
if args.Now.Equal(proto.ZeroTimestamp) {
reply.SetGoError(util.Error("the field Now must be provided"))
return
}
// Compute heartbeat expiration (all replicas must see the same result).
expiry := args.Now
expiry.Forward(args.Timestamp) // if Timestamp is ahead, use that
expiry.WallTime -= 2 * DefaultHeartbeatInterval.Nanoseconds()
if reply.PusheeTxn.LastHeartbeat.Less(expiry) {
if log.V(1) {
log.Infof("pushing expired txn %s", reply.PusheeTxn)
}
pusherWins = true
} else if reply.PusheeTxn.Isolation == proto.SNAPSHOT && args.PushType == proto.PUSH_TIMESTAMP {
if log.V(1) {
log.Infof("pushing timestamp for snapshot isolation txn")
}
pusherWins = true
} else if args.PushType == proto.CLEANUP_TXN {
// If just attempting to cleanup old or already-committed txns, don't push.
pusherWins = false
} else if reply.PusheeTxn.Priority < priority ||
(reply.PusheeTxn.Priority == priority && args.Txn != nil &&
args.Txn.Timestamp.Less(reply.PusheeTxn.Timestamp)) {
// Pusher wins based on priority; if priorities are equal, order
// by lower txn timestamp.
if log.V(1) {
log.Infof("pushing intent from txn with lower priority %s vs %d", reply.PusheeTxn, priority)
}
pusherWins = true
}
if !pusherWins {
err := proto.NewTransactionPushError(args.Txn, reply.PusheeTxn)
if log.V(1) {
log.Info(err)
}
reply.SetGoError(err)
return
}
// Upgrade priority of pushed transaction to one less than pusher's.
reply.PusheeTxn.UpgradePriority(priority - 1)
// If aborting transaction, set new status and return success.
if args.PushType == proto.ABORT_TXN {
reply.PusheeTxn.Status = proto.ABORTED
} else if args.PushType == proto.PUSH_TIMESTAMP {
// Otherwise, update timestamp to be one greater than the request's timestamp.
reply.PusheeTxn.Timestamp = args.Timestamp
reply.PusheeTxn.Timestamp.Logical++
}
// Persist the pushed transaction using zero timestamp for inline value.
if err := engine.MVCCPutProto(batch, ms, key, proto.ZeroTimestamp, nil, reply.PusheeTxn); err != nil {
reply.SetGoError(err)
return
}
}
// InternalPushTxn resolves conflicts between concurrent txns (or
// between a non-transactional reader or writer and a txn) in several
// ways depending on the statuses and priorities of the conflicting
// transactions. The InternalPushTxn operation is invoked by a
// "pusher" (the writer trying to abort a conflicting txn or the
// reader trying to push a conflicting txn's commit timestamp
// forward), who attempts to resolve a conflict with a "pushee"
// (args.PushTxn -- the pushee txn whose intent(s) caused the
// conflict).
//
// Txn already committed/aborted: If pushee txn is committed or
// aborted return success.
//
// Txn Timeout: If pushee txn entry isn't present or its LastHeartbeat
// timestamp isn't set, use PushTxn.Timestamp as LastHeartbeat. If
// current time - LastHeartbeat > 2 * DefaultHeartbeatInterval, then
// the pushee txn should be either pushed forward or aborted,
// depending on value of Request.Abort.
//
// Old Txn Epoch: If persisted pushee txn entry has a newer Epoch than
// PushTxn.Epoch, return success, as older epoch may be removed.
//
// Lower Txn Priority: If pushee txn has a lower priority than pusher,
// adjust pushee's persisted txn depending on value of args.Abort. If
// args.Abort is true, set txn.Status to ABORTED, and priority to one
// less than the pusher's priority and return success. If args.Abort
// is false, set txn.Timestamp to pusher's txn.Timestamp + 1.
//
// Higher Txn Priority: If pushee txn has a higher priority than
// pusher, return TransactionRetryError. Transaction will be retried
// with priority one less than the pushee's higher priority.
func (r *Range) InternalPushTxn(args *proto.InternalPushTxnRequest, reply *proto.InternalPushTxnResponse) {
if !bytes.Equal(args.Key, args.PusheeTxn.ID) {
reply.SetGoError(util.Errorf("request key %q should match pushee's txn ID %q", args.Key, args.PusheeTxn.ID))
return
}
// Create the actual key to the system-local transaction table.
key := engine.MakeKey(engine.KeyLocalTransactionPrefix, args.Key)
// Fetch existing transaction if possible.
existTxn := &proto.Transaction{}
ok, err := engine.GetProto(r.engine, key, existTxn)
if err != nil {
reply.SetGoError(err)
return
}
if ok {
// Start with the persisted transaction record as final transaction.
reply.PusheeTxn = gogoproto.Clone(existTxn).(*proto.Transaction)
// Upgrade the epoch and timestamp as necessary.
if reply.PusheeTxn.Epoch < args.PusheeTxn.Epoch {
reply.PusheeTxn.Epoch = args.PusheeTxn.Epoch
}
if reply.PusheeTxn.Timestamp.Less(args.PusheeTxn.Timestamp) {
reply.PusheeTxn.Timestamp = args.PusheeTxn.Timestamp
}
} else {
// Some sanity checks for case where we don't find a transaction record.
if args.PusheeTxn.LastHeartbeat != nil {
reply.SetGoError(proto.NewTransactionStatusError(&args.PusheeTxn,
"no txn persisted, yet intent has heartbeat"))
return
} else if args.PusheeTxn.Status != proto.PENDING {
reply.SetGoError(proto.NewTransactionStatusError(&args.PusheeTxn,
fmt.Sprintf("no txn persisted, yet intent has status %s", args.PusheeTxn.Status)))
return
}
// The transaction doesn't exist yet on disk; use the supplied version.
reply.PusheeTxn = gogoproto.Clone(&args.PusheeTxn).(*proto.Transaction)
}
// If already committed or aborted, return success.
if reply.PusheeTxn.Status != proto.PENDING {
// Trivial noop.
return
}
// If we're trying to move the timestamp forward, and it's already
// far enough forward, return success.
if !args.Abort && args.Timestamp.Less(reply.PusheeTxn.Timestamp) {
// Trivial noop.
return
}
// pusherWins bool is true in the event the pusher prevails.
var pusherWins bool
// Check for txn timeout.
if reply.PusheeTxn.LastHeartbeat == nil {
reply.PusheeTxn.LastHeartbeat = &reply.PusheeTxn.Timestamp
}
// Compute heartbeat expiration.
expiry := r.clock.Now()
expiry.WallTime -= 2 * DefaultHeartbeatInterval.Nanoseconds()
if reply.PusheeTxn.LastHeartbeat.Less(expiry) {
log.V(1).Infof("pushing expired txn %+v", reply.PusheeTxn)
pusherWins = true
} else if args.PusheeTxn.Epoch < reply.PusheeTxn.Epoch {
// Check for an intent from a prior epoch.
log.V(1).Infof("pushing intent from previous epoch for txn %+v", reply.PusheeTxn)
pusherWins = true
} else if reply.PusheeTxn.Priority < args.Txn.Priority ||
(reply.PusheeTxn.Priority == args.Txn.Priority && args.Txn.Timestamp.Less(reply.PusheeTxn.Timestamp)) {
// Finally, choose based on priority; if priorities are equal, order by lower txn timestamp.
log.V(1).Infof("pushing intent from txn with lower priority %+v vs %+v", reply.PusheeTxn, args.Txn)
pusherWins = true
}
if !pusherWins {
log.V(1).Infof("failed to push intent %+v vs %+v", reply.PusheeTxn, args.Txn)
reply.SetGoError(proto.NewTransactionRetryError(reply.PusheeTxn))
return
}
// If aborting transaction, set new status and return success.
if args.Abort {
reply.PusheeTxn.Status = proto.ABORTED
} else {
// Otherwise, update timestamp to be one greater than the request's timestamp.
reply.PusheeTxn.Timestamp = args.Timestamp
reply.PusheeTxn.Timestamp.Logical++
}
// Persist the pushed transaction.
if err := engine.PutProto(r.engine, key, reply.PusheeTxn); err != nil {
reply.SetGoError(err)
return
}
}