// sendAttempt gathers and rearranges the replicas, and makes an RPC call.
func (ds *DistSender) sendAttempt(trace *tracer.Trace, ba roachpb.BatchRequest, desc *roachpb.RangeDescriptor) (*roachpb.BatchResponse, *roachpb.Error) {
defer trace.Epoch("sending RPC")()
leader := ds.leaderCache.Lookup(roachpb.RangeID(desc.RangeID))
// Try to send the call.
replicas := newReplicaSlice(ds.gossip, desc)
// Rearrange the replicas so that those replicas with long common
// prefix of attributes end up first. If there's no prefix, this is a
// no-op.
order := ds.optimizeReplicaOrder(replicas)
// If this request needs to go to a leader and we know who that is, move
// it to the front.
if !(ba.IsReadOnly() && ba.ReadConsistency == roachpb.INCONSISTENT) &&
leader.StoreID > 0 {
if i := replicas.FindReplica(leader.StoreID); i >= 0 {
replicas.MoveToFront(i)
order = rpc.OrderStable
}
}
br, err := ds.sendRPC(trace, desc.RangeID, replicas, order, ba)
if err != nil {
return nil, roachpb.NewError(err)
}
// Untangle the error from the received response.
pErr := br.Error
br.Error = nil // scrub the response error
return br, pErr
}
// redirectOnOrAcquireLeaderLease checks whether this replica has the
// leader lease at the specified timestamp. If it does, returns
// success. If another replica currently holds the lease, redirects by
// returning NotLeaderError. If the lease is expired, a renewal is
// synchronously requested. This method uses the leader lease mutex
// to guarantee only one request to grant the lease is pending.
//
// TODO(spencer): implement threshold regrants to avoid latency in
// the presence of read or write pressure sufficiently close to the
// current lease's expiration.
//
// TODO(spencer): for write commands, don't wait while requesting
// the leader lease. If the lease acquisition fails, the write cmd
// will fail as well. If it succeeds, as is likely, then the write
// will not incur latency waiting for the command to complete.
// Reads, however, must wait.
func (r *Range) redirectOnOrAcquireLeaderLease(trace *tracer.Trace, timestamp proto.Timestamp) error {
r.llMu.Lock()
defer r.llMu.Unlock()
raftNodeID := r.rm.RaftNodeID()
if lease := r.getLease(); lease.Covers(timestamp) {
if lease.OwnedBy(raftNodeID) {
// Happy path: We have an active lease, nothing to do.
return nil
}
// If lease is currently held by another, redirect to holder.
return r.newNotLeaderError(lease, raftNodeID)
}
defer trace.Epoch("request leader lease")()
// Otherwise, no active lease: Request renewal.
err := r.requestLeaderLease(timestamp)
// Getting a LeaseRejectedError back means someone else got there first;
// we can redirect if they cover our timestamp. Note that it can't be us,
// since we're holding a lock here, and even if it were it would be a rare
// extra round-trip.
if _, ok := err.(*proto.LeaseRejectedError); ok {
if lease := r.getLease(); lease.Covers(timestamp) {
return r.newNotLeaderError(lease, raftNodeID)
}
}
return err
}
// sendAttempt is invoked by Send. It temporarily truncates the arguments to
// match the descriptor's EndKey (if necessary) and gathers and rearranges the
// replicas before making a single attempt at sending the request. It returns
// the result of sending the RPC; a potential error contained in the reply has
// to be handled separately by the caller.
func (ds *DistSender) sendAttempt(trace *tracer.Trace, args proto.Request, reply proto.Response, desc *proto.RangeDescriptor) error {
defer trace.Epoch("sending RPC")()
// Truncate the request to our current range, making sure not to
// touch it unless we have to (it is illegal to send EndKey on
// commands which do not operate on ranges).
if endKey := args.Header().EndKey; endKey != nil && !endKey.Less(desc.EndKey) {
defer func(k proto.Key) { args.Header().EndKey = k }(endKey)
args.Header().EndKey = desc.EndKey
}
leader := ds.leaderCache.Lookup(proto.RaftID(desc.RaftID))
// Try to send the call.
replicas := newReplicaSlice(ds.gossip, desc)
// Rearrange the replicas so that those replicas with long common
// prefix of attributes end up first. If there's no prefix, this is a
// no-op.
order := ds.optimizeReplicaOrder(replicas)
// If this request needs to go to a leader and we know who that is, move
// it to the front.
if !(proto.IsRead(args) && args.Header().ReadConsistency == proto.INCONSISTENT) &&
leader.StoreID > 0 {
if i := replicas.FindReplica(leader.StoreID); i >= 0 {
replicas.MoveToFront(i)
order = rpc.OrderStable
}
}
return ds.sendRPC(trace, desc.RaftID, replicas, order, args, reply)
}
func (tc *TxnCoordSender) heartbeat(id string, trace *tracer.Trace, ctx context.Context) bool {
tc.Lock()
proceed := true
txnMeta := tc.txns[id]
// Before we send a heartbeat, determine whether this transaction
// should be considered abandoned. If so, exit heartbeat.
if txnMeta.hasClientAbandonedCoord(tc.clock.PhysicalNow()) {
// TODO(tschottdorf): should we be more proactive here?
// The client might be continuing the transaction
// through another coordinator, but in the most likely
// case it's just gone and the open transaction record
// could block concurrent operations.
if log.V(1) {
log.Infof("transaction %s abandoned; stopping heartbeat",
txnMeta.txn)
}
proceed = false
}
// txnMeta.txn is possibly replaced concurrently,
// so grab a copy before unlocking.
txn := txnMeta.txn
tc.Unlock()
if !proceed {
return false
}
request := &proto.HeartbeatTxnRequest{
RequestHeader: proto.RequestHeader{
Key: txn.Key,
Txn: &txn,
},
}
request.Header().Timestamp = tc.clock.Now()
reply := &proto.HeartbeatTxnResponse{}
call := proto.Call{
Args: request,
Reply: reply,
}
epochEnds := trace.Epoch("heartbeat")
tc.wrapped.Send(ctx, call)
epochEnds()
// If the transaction is not in pending state, then we can stop
// the heartbeat. It's either aborted or committed, and we resolve
// write intents accordingly.
if reply.GoError() != nil {
log.Warningf("heartbeat to %s failed: %s", txn, reply.GoError())
}
// TODO(bdarnell): once we have gotten a heartbeat response with
// Status != PENDING, future heartbeats are useless. However, we
// need to continue the heartbeatLoop until the client either
// commits or abandons the transaction. We could save a little
// pointless work by restructuring this loop to stop sending
// heartbeats between the time that the transaction is aborted and
// the client finds out. Furthermore, we could use this information
// to send TransactionAbortedErrors to the client so it can restart
// immediately instead of running until its EndTransaction.
return true
}
// sendSingleRange gathers and rearranges the replicas, and makes an RPC call.
func (ds *DistSender) sendSingleRange(trace *tracer.Trace, ba roachpb.BatchRequest, desc *roachpb.RangeDescriptor) (*roachpb.BatchResponse, *roachpb.Error) {
defer trace.Epoch("sending RPC")()
leader := ds.leaderCache.Lookup(roachpb.RangeID(desc.RangeID))
// Try to send the call.
replicas := newReplicaSlice(ds.gossip, desc)
// Rearrange the replicas so that those replicas with long common
// prefix of attributes end up first. If there's no prefix, this is a
// no-op.
order := ds.optimizeReplicaOrder(replicas)
// If this request needs to go to a leader and we know who that is, move
// it to the front.
if !(ba.IsReadOnly() && ba.ReadConsistency == roachpb.INCONSISTENT) &&
leader.StoreID > 0 {
if i := replicas.FindReplica(leader.StoreID); i >= 0 {
replicas.MoveToFront(i)
order = rpc.OrderStable
}
}
// Increase the sequence counter in the per-range loop (not
// outside) since we might hit the same range twice by
// accident. For example, we might send multiple requests to
// the same Replica if (1) the descriptor cache has post-split
// descriptors that are still write intents and (2) the split
// has not yet been completed.
ba.SetNewRequest()
br, pErr := ds.sendRPC(trace, desc.RangeID, replicas, order, ba)
if pErr != nil {
return nil, pErr
}
// Untangle the error from the received response.
pErr = br.Error
br.Error = nil // scrub the response error
return br, pErr
}
// heartbeat periodically sends a HeartbeatTxn RPC to an extant
// transaction, stopping in the event the transaction is aborted or
// committed after attempting to resolve the intents. When the
// heartbeat stops, the transaction is unregistered from the
// coordinator,
func (tc *TxnCoordSender) heartbeat(id string) {
var tickChan <-chan time.Time
{
ticker := time.NewTicker(tc.heartbeatInterval)
tickChan = ticker.C
defer ticker.Stop()
}
defer tc.unregisterTxn(id)
var closer <-chan struct{}
var trace *tracer.Trace
{
tc.Lock()
txnMeta := tc.txns[id] // do not leak to outer scope
closer = txnMeta.txnEnd
trace = tc.tracer.NewTrace(&txnMeta.txn)
tc.Unlock()
}
if closer == nil {
// Avoid race in which a Txn is cleaned up before the heartbeat
// goroutine gets a chance to start.
return
}
ctx := tracer.ToCtx(context.Background(), trace)
defer trace.Finalize()
// Loop with ticker for periodic heartbeats.
for {
select {
case <-tickChan:
tc.Lock()
proceed := true
txnMeta := tc.txns[id]
// Before we send a heartbeat, determine whether this transaction
// should be considered abandoned. If so, exit heartbeat.
if txnMeta.hasClientAbandonedCoord(tc.clock.PhysicalNow()) {
// TODO(tschottdorf): should we be more proactive here?
// The client might be continuing the transaction
// through another coordinator, but in the most likely
// case it's just gone and the open transaction record
// could block concurrent operations.
if log.V(1) {
log.Infof("transaction %s abandoned; stopping heartbeat",
txnMeta.txn)
}
proceed = false
}
// txnMeta.txn is possibly replaced concurrently,
// so grab a copy before unlocking.
txn := txnMeta.txn
tc.Unlock()
if !proceed {
return
}
request := &proto.HeartbeatTxnRequest{
RequestHeader: proto.RequestHeader{
Key: txn.Key,
User: security.RootUser,
Txn: &txn,
},
}
request.Header().Timestamp = tc.clock.Now()
reply := &proto.HeartbeatTxnResponse{}
call := proto.Call{
Args: request,
Reply: reply,
}
epochEnds := trace.Epoch("heartbeat")
tc.wrapped.Send(ctx, call)
epochEnds()
// If the transaction is not in pending state, then we can stop
// the heartbeat. It's either aborted or committed, and we resolve
// write intents accordingly.
if reply.GoError() != nil {
log.Warningf("heartbeat to %s failed: %s", txn, reply.GoError())
} else if reply.Txn != nil && reply.Txn.Status != proto.PENDING {
// Signal cleanup. Doesn't do much but stop this goroutine, but
// let's be future-proof.
tc.cleanupTxn(trace, *reply.Txn)
return
}
case <-closer:
// Transaction finished normally.
return
}
}
}
// resolve sends resolve intent commands for all key ranges this transaction
// has covered. Any keys listed in the resolved slice have already been
// resolved and are skipped.
func (tm *txnMetadata) resolve(trace *tracer.Trace, resolved []proto.Key, sender client.Sender) {
txn := &tm.txn
if tm.keys.Len() > 0 {
if log.V(2) {
log.Infof("cleaning up %d intent(s) for transaction %s", tm.keys.Len(), txn)
}
}
// TODO(tschottdorf): Should create a Batch here. However, we're resolving
// intents and if those are on meta records, there may be a certain order
// in which they need to be resolved so that they can get routed to the
// correct range. Since a batch runs its commands one by one and we don't
// know the correct order, we prefer to fire them off in parallel.
var wg sync.WaitGroup
for _, o := range tm.keys.GetOverlaps(proto.KeyMin, proto.KeyMax) {
// If the op was range based, end key != start key: resolve a range.
var call proto.Call
key := o.Key.Start().(proto.Key)
endKey := o.Key.End().(proto.Key)
if !key.Next().Equal(endKey) {
call.Args = &proto.InternalResolveIntentRangeRequest{
RequestHeader: proto.RequestHeader{
Timestamp: txn.Timestamp,
Key: key,
EndKey: endKey,
User: security.RootUser,
Txn: txn,
},
}
call.Reply = &proto.InternalResolveIntentRangeResponse{}
} else {
// Check if the key has already been resolved; skip if yes.
found := false
for _, k := range resolved {
if key.Equal(k) {
if log.V(2) {
log.Warningf("skipping previously resolved intent at %q", k)
}
found = true
}
}
if found {
continue
}
call.Args = &proto.InternalResolveIntentRequest{
RequestHeader: proto.RequestHeader{
Timestamp: txn.Timestamp,
Key: key,
User: security.RootUser,
Txn: txn,
},
}
call.Reply = &proto.InternalResolveIntentResponse{}
}
ctx := tracer.ToCtx(context.Background(), trace.Fork())
if log.V(2) {
log.Infof("cleaning up intent %q for txn %s", call.Args.Header().Key, txn)
}
// Each operation gets their own goroutine. We only want to return to
// the caller after the operations have finished.
wg.Add(1)
go func() {
sender.Send(ctx, call)
wg.Done()
if call.Reply.Header().Error != nil {
log.Warningf("failed to cleanup %q intent: %s", call.Args.Header().Key, call.Reply.Header().GoError())
}
}()
}
defer trace.Epoch("waiting for intent resolution")()
wg.Wait()
tm.keys.Clear()
}