// Send implements the batch.Sender interface. If the request is part of a // transaction, the TxnCoordSender adds the transaction to a map of active // transactions and begins heartbeating it. Every subsequent request for the // same transaction updates the lastUpdate timestamp to prevent live // transactions from being considered abandoned and garbage collected. // Read/write mutating requests have their key or key range added to the // transaction's interval tree of key ranges for eventual cleanup via resolved // write intents; they're tagged to an outgoing EndTransaction request, with // the receiving replica in charge of resolving them. func (tc *TxnCoordSender) Send(ctx context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) { if err := tc.maybeBeginTxn(&ba); err != nil { return nil, roachpb.NewError(err) } ba.CmdID = ba.GetOrCreateCmdID(tc.clock.PhysicalNow()) var startNS int64 // This is the earliest point at which the request has a ClientCmdID and/or // TxnID (if applicable). Begin a Trace which follows this request. trace := tc.tracer.NewTrace(tracer.Coord, &ba) defer trace.Finalize() defer trace.Epoch("sending batch")() ctx = tracer.ToCtx(ctx, trace) var id string // optional transaction ID if ba.Txn != nil { // If this request is part of a transaction... id = string(ba.Txn.ID) // Verify that if this Transaction is not read-only, we have it on // file. If not, refuse writes - the client must have issued a write on // another coordinator previously. if ba.Txn.Writing && ba.IsTransactionWrite() { tc.Lock() _, ok := tc.txns[id] tc.Unlock() if !ok { return nil, roachpb.NewError(util.Errorf("transaction must not write on multiple coordinators")) } } // Set the timestamp to the original timestamp for read-only // commands and to the transaction timestamp for read/write // commands. if ba.IsReadOnly() { ba.Timestamp = ba.Txn.OrigTimestamp } else { ba.Timestamp = ba.Txn.Timestamp } if rArgs, ok := ba.GetArg(roachpb.EndTransaction); ok { et := rArgs.(*roachpb.EndTransactionRequest) if len(et.Key) != 0 { return nil, roachpb.NewError(util.Errorf("EndTransaction must not have a Key set")) } et.Key = ba.Txn.Key // Remember when EndTransaction started in case we want to // be linearizable. startNS = tc.clock.PhysicalNow() if len(et.Intents) > 0 { // TODO(tschottdorf): it may be useful to allow this later. // That would be part of a possible plan to allow txns which // write on multiple coordinators. return nil, roachpb.NewError(util.Errorf("client must not pass intents to EndTransaction")) } tc.Lock() txnMeta, metaOK := tc.txns[id] if id != "" && metaOK { et.Intents = txnMeta.intents() } tc.Unlock() if intents := ba.GetIntents(); len(intents) > 0 { // Writes in Batch, so EndTransaction is fine. Should add // outstanding intents to EndTransaction, though. // TODO(tschottdorf): possible issues when the batch fails, // but the intents have been added anyways. // TODO(tschottdorf): some of these intents may be covered // by others, for example {[a,b), a}). This can lead to // some extra requests when those are non-local to the txn // record. But it doesn't seem worth optimizing now. et.Intents = append(et.Intents, intents...) } else if !metaOK { // If we don't have the transaction, then this must be a retry // by the client. We can no longer reconstruct a correct // request so we must fail. // // TODO(bdarnell): if we had a GetTransactionStatus API then // we could lookup the transaction and return either nil or // TransactionAbortedError instead of this ambivalent error. return nil, roachpb.NewError(util.Errorf("transaction is already committed or aborted")) } if len(et.Intents) == 0 { // If there aren't any intents, then there's factually no // transaction to end. Read-only txns have all of their state in // the client. return nil, roachpb.NewError(util.Errorf("cannot commit a read-only transaction")) } if log.V(1) { for _, intent := range et.Intents { trace.Event(fmt.Sprintf("intent: [%s,%s)", intent.Key, intent.EndKey)) } } } } // Send the command through wrapped sender, taking appropriate measures // on error. var br *roachpb.BatchResponse { var pErr *roachpb.Error br, pErr = tc.wrapped.Send(ctx, ba) if _, ok := pErr.GoError().(*roachpb.OpRequiresTxnError); ok { br, pErr = tc.resendWithTxn(ba) } if pErr := tc.updateState(ctx, ba, br, pErr); pErr != nil { return nil, pErr } } if br.Txn == nil { return br, nil } if _, ok := ba.GetArg(roachpb.EndTransaction); !ok { return br, nil } // If the --linearizable flag is set, we want to make sure that // all the clocks in the system are past the commit timestamp // of the transaction. This is guaranteed if either // - the commit timestamp is MaxOffset behind startNS // - MaxOffset ns were spent in this function // when returning to the client. Below we choose the option // that involves less waiting, which is likely the first one // unless a transaction commits with an odd timestamp. if tsNS := br.Txn.Timestamp.WallTime; startNS > tsNS { startNS = tsNS } sleepNS := tc.clock.MaxOffset() - time.Duration(tc.clock.PhysicalNow()-startNS) if tc.linearizable && sleepNS > 0 { defer func() { if log.V(1) { log.Infof("%v: waiting %s on EndTransaction for linearizability", br.Txn.Short(), util.TruncateDuration(sleepNS, time.Millisecond)) } time.Sleep(sleepNS) }() } if br.Txn.Status != roachpb.PENDING { tc.cleanupTxn(trace, *br.Txn) } return br, nil }
// updateState updates the transaction state in both the success and // error cases, applying those updates to the corresponding txnMeta // object when adequate. It also updates certain errors with the // updated transaction for use by client restarts. func (tc *TxnCoordSender) updateState(ctx context.Context, ba roachpb.BatchRequest, br *roachpb.BatchResponse, pErr *roachpb.Error) *roachpb.Error { trace := tracer.FromCtx(ctx) newTxn := &roachpb.Transaction{} newTxn.Update(ba.GetTxn()) // TODO(tamird): remove this clone. It's currently needed to avoid race conditions. pErr = proto.Clone(pErr).(*roachpb.Error) err := pErr.GoError() // TODO(bdarnell): We're writing to errors here (and where using ErrorWithIndex); // since there's no concept of ownership copy-on-write is always preferable. switch t := err.(type) { case nil: newTxn.Update(br.Txn) // Move txn timestamp forward to response timestamp if applicable. // TODO(tschottdorf): see (*Replica).executeBatch and comments within. // Looks like this isn't necessary any more, nor did it prevent a bug // referenced in a TODO there. newTxn.Timestamp.Forward(br.Timestamp) case *roachpb.TransactionStatusError: // Likely already committed or more obscure errors such as epoch or // timestamp regressions; consider txn dead. defer tc.cleanupTxn(trace, t.Txn) case *roachpb.OpRequiresTxnError: panic("OpRequiresTxnError must not happen at this level") case *roachpb.ReadWithinUncertaintyIntervalError: // Mark the host as certain. See the protobuf comment for // Transaction.CertainNodes for details. if t.NodeID == 0 { panic("no replica set in header on uncertainty restart") } newTxn.Update(&t.Txn) newTxn.CertainNodes.Add(t.NodeID) // If the reader encountered a newer write within the uncertainty // interval, move the timestamp forward, just past that write or // up to MaxTimestamp, whichever comes first. candidateTS := newTxn.MaxTimestamp candidateTS.Backward(t.ExistingTimestamp.Add(0, 1)) newTxn.Timestamp.Forward(candidateTS) newTxn.Restart(ba.GetUserPriority(), newTxn.Priority, newTxn.Timestamp) t.Txn = *newTxn case *roachpb.TransactionAbortedError: trace.SetError() newTxn.Update(&t.Txn) // Increase timestamp if applicable. newTxn.Timestamp.Forward(t.Txn.Timestamp) newTxn.Priority = t.Txn.Priority t.Txn = *newTxn // Clean up the freshly aborted transaction in defer(), avoiding a // race with the state update below. defer tc.cleanupTxn(trace, t.Txn) case *roachpb.TransactionPushError: newTxn.Update(t.Txn) // Increase timestamp if applicable, ensuring that we're // just ahead of the pushee. newTxn.Timestamp.Forward(t.PusheeTxn.Timestamp.Add(0, 1)) newTxn.Restart(ba.GetUserPriority(), t.PusheeTxn.Priority-1, newTxn.Timestamp) t.Txn = newTxn case *roachpb.TransactionRetryError: newTxn.Update(&t.Txn) newTxn.Restart(ba.GetUserPriority(), t.Txn.Priority, newTxn.Timestamp) t.Txn = *newTxn case roachpb.TransactionRestartError: // Assertion: The above cases should exhaust all ErrorDetails which // carry a Transaction. if pErr.Detail != nil { panic(fmt.Sprintf("unhandled TransactionRestartError %T", err)) } default: trace.SetError() } return func() *roachpb.Error { if len(newTxn.ID) <= 0 { return pErr } id := string(newTxn.ID) tc.Lock() defer tc.Unlock() txnMeta := tc.txns[id] // For successful transactional requests, keep the written intents and // the updated transaction record to be sent along with the reply. // The transaction metadata is created with the first writing operation. // A tricky edge case is that of a transaction which "fails" on the // first writing request, but actually manages to write some intents // (for example, due to being multi-range). In this case, there will // be an error, but the transaction will be marked as Writing and the // coordinator must track the state, for the client's retry will be // performed with a Writing transaction which the coordinator rejects // unless it is tracking it (on top of it making sense to track it; // after all, it **has** laid down intents and only the coordinator // can augment a potential EndTransaction call). // consider re-using those. if intents := ba.GetIntents(); len(intents) > 0 && (err == nil || newTxn.Writing) { if txnMeta == nil { if !newTxn.Writing { panic("txn with intents marked as non-writing") } txnMeta = &txnMetadata{ txn: *newTxn, keys: cache.NewIntervalCache(cache.Config{Policy: cache.CacheNone}), firstUpdateNanos: tc.clock.PhysicalNow(), lastUpdateNanos: tc.clock.PhysicalNow(), timeoutDuration: tc.clientTimeout, txnEnd: make(chan struct{}), } tc.txns[id] = txnMeta // If the transaction is already over, there's no point in // launching a one-off coordinator which will shut down right // away. If we ended up here with an error, we'll always start // the coordinator - the transaction has laid down intents, so // we expect it to be committed/aborted at some point in the // future. if _, isEnding := ba.GetArg(roachpb.EndTransaction); err != nil || !isEnding { trace.Event("coordinator spawns") if !tc.stopper.RunAsyncTask(func() { tc.heartbeatLoop(id) }) { // The system is already draining and we can't start the // heartbeat. We refuse new transactions for now because // they're likely not going to have all intents committed. // In principle, we can relax this as needed though. tc.unregisterTxnLocked(id) return roachpb.NewError(&roachpb.NodeUnavailableError{}) } } } for _, intent := range intents { txnMeta.addKeyRange(intent.Key, intent.EndKey) } } // Update our record of this transaction, even on error. if txnMeta != nil { txnMeta.txn = *newTxn if !txnMeta.txn.Writing { panic("tracking a non-writing txn") } txnMeta.setLastUpdate(tc.clock.PhysicalNow()) } if err == nil { // For successful transactional requests, always send the updated txn // record back. br.Txn = newTxn } return pErr }() }
// updateState updates the transaction state in both the success and // error cases, applying those updates to the corresponding txnMeta // object when adequate. It also updates certain errors with the // updated transaction for use by client restarts. func (tc *TxnCoordSender) updateState(ctx context.Context, ba roachpb.BatchRequest, br *roachpb.BatchResponse, pErr *roachpb.Error) *roachpb.Error { trace := tracer.FromCtx(ctx) newTxn := &roachpb.Transaction{} newTxn.Update(ba.GetTxn()) err := pErr.GoError() switch t := err.(type) { case nil: newTxn.Update(br.GetTxn()) // Move txn timestamp forward to response timestamp if applicable. // TODO(tschottdorf): see (*Replica).executeBatch and comments within. // Looks like this isn't necessary any more, nor did it prevent a bug // referenced in a TODO there. newTxn.Timestamp.Forward(br.Timestamp) case *roachpb.TransactionStatusError: // Likely already committed or more obscure errors such as epoch or // timestamp regressions; consider txn dead. defer tc.cleanupTxn(trace, t.Txn) case *roachpb.OpRequiresTxnError: // TODO(tschottdorf): range-spanning autowrap currently broken. panic("TODO(tschottdorf): disabled") case *roachpb.ReadWithinUncertaintyIntervalError: // Mark the host as certain. See the protobuf comment for // Transaction.CertainNodes for details. if t.NodeID == 0 { panic("no replica set in header on uncertainty restart") } newTxn.CertainNodes.Add(t.NodeID) // If the reader encountered a newer write within the uncertainty // interval, move the timestamp forward, just past that write or // up to MaxTimestamp, whichever comes first. candidateTS := newTxn.MaxTimestamp candidateTS.Backward(t.ExistingTimestamp.Add(0, 1)) newTxn.Timestamp.Forward(candidateTS) newTxn.Restart(ba.GetUserPriority(), newTxn.Priority, newTxn.Timestamp) t.Txn = *newTxn case *roachpb.TransactionAbortedError: // Increase timestamp if applicable. newTxn.Timestamp.Forward(t.Txn.Timestamp) newTxn.Priority = t.Txn.Priority t.Txn = *newTxn // Clean up the freshly aborted transaction in defer(), avoiding a // race with the state update below. defer tc.cleanupTxn(trace, t.Txn) case *roachpb.TransactionPushError: // Increase timestamp if applicable, ensuring that we're // just ahead of the pushee. newTxn.Timestamp.Forward(t.PusheeTxn.Timestamp.Add(0, 1)) newTxn.Restart(ba.GetUserPriority(), t.PusheeTxn.Priority-1, newTxn.Timestamp) t.Txn = newTxn case *roachpb.TransactionRetryError: // Increase timestamp if applicable. newTxn.Timestamp.Forward(t.Txn.Timestamp) newTxn.Restart(ba.GetUserPriority(), t.Txn.Priority, newTxn.Timestamp) t.Txn = *newTxn case roachpb.TransactionRestartError: // Assertion: The above cases should exhaust all ErrorDetails which // carry a Transaction. if pErr.Detail != nil { panic(fmt.Sprintf("unhandled TransactionRestartError %T", err)) } } return func() *roachpb.Error { if len(newTxn.ID) <= 0 { return pErr } id := string(newTxn.ID) tc.Lock() defer tc.Unlock() txnMeta := tc.txns[id] // For successful transactional requests, keep the written intents and // the updated transaction record to be sent along with the reply. // The transaction metadata is created with the first writing operation // TODO(tschottdorf): already computed the intents prior to sending, // consider re-using those. if intents := ba.GetIntents(); len(intents) > 0 && err == nil { if txnMeta == nil { newTxn.Writing = true txnMeta = &txnMetadata{ txn: *newTxn, keys: cache.NewIntervalCache(cache.Config{Policy: cache.CacheNone}), firstUpdateNanos: tc.clock.PhysicalNow(), lastUpdateNanos: tc.clock.PhysicalNow(), timeoutDuration: tc.clientTimeout, txnEnd: make(chan struct{}), } tc.txns[id] = txnMeta // If the transaction is already over, there's no point in // launching a one-off coordinator which will shut down right // away. if _, isEnding := ba.GetArg(roachpb.EndTransaction); !isEnding { trace.Event("coordinator spawns") if !tc.stopper.RunAsyncTask(func() { tc.heartbeatLoop(id) }) { // The system is already draining and we can't start the // heartbeat. We refuse new transactions for now because // they're likely not going to have all intents committed. // In principle, we can relax this as needed though. tc.unregisterTxnLocked(id) return roachpb.NewError(&roachpb.NodeUnavailableError{}) } } } for _, intent := range intents { txnMeta.addKeyRange(intent.Key, intent.EndKey) } } // Update our record of this transaction, even on error. if txnMeta != nil { txnMeta.txn.Update(newTxn) // better to replace after #2300 if !txnMeta.txn.Writing { panic("tracking a non-writing txn") } txnMeta.setLastUpdate(tc.clock.PhysicalNow()) } if err == nil { // For successful transactional requests, always send the updated txn // record back. if br.Txn == nil { br.Txn = &roachpb.Transaction{} } *br.Txn = *newTxn } return pErr }() }