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Fix race in incomplete transactions
This commit is contained in:
Neil Alexander
parent
cfbdff3c32
commit
d6c94064af
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@ -18,6 +18,7 @@ import (
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"context"
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"encoding/json"
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"fmt"
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"sync"
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"time"
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"github.com/matrix-org/dendrite/federationsender/storage"
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@ -48,6 +49,7 @@ type destinationQueue struct {
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statistics *types.ServerStatistics // statistics about this remote server
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incomingInvites chan *gomatrixserverlib.InviteV2Request // invites to send
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incomingEDUs chan *gomatrixserverlib.EDU // EDUs to send
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transactionMutex sync.Mutex // protects transactionID and transactionCount
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transactionID gomatrixserverlib.TransactionID // last transaction ID
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transactionCount int // how many events in this transaction so far
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pendingPDUs atomic.Int32 // how many PDUs are waiting to be sent
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@ -93,11 +95,13 @@ func (oq *destinationQueue) sendEvent(nid int64) {
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// one made up yet, or if we've exceeded the number of maximum
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// events allowed in a single tranaction. We'll reset the counter
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// when we do.
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oq.transactionMutex.Lock()
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if oq.transactionID == "" || oq.transactionCount >= maxPDUsPerTransaction {
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now := gomatrixserverlib.AsTimestamp(time.Now())
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oq.transactionID = gomatrixserverlib.TransactionID(fmt.Sprintf("%d-%d", now, oq.statistics.SuccessCount()))
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oq.transactionCount = 0
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}
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oq.transactionMutex.Unlock()
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// Create a database entry that associates the given PDU NID with
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// this destination queue. We'll then be able to retrieve the PDU
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// later.
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@ -164,12 +168,6 @@ func (oq *destinationQueue) backgroundSend() {
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defer oq.running.Store(false)
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for {
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// For now we don't know the next transaction ID. Set it to an
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// empty one. The next step will populate it if we have pending
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// PDUs in the database. Otherwise we'll generate one later on,
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// e.g. in response to EDUs.
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transactionID := gomatrixserverlib.TransactionID("")
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// If we have nothing to do then wait either for incoming events, or
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// until we hit an idle timeout.
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if oq.pendingPDUs.Load() == 0 && len(oq.pendingEDUs) == 0 && len(oq.pendingInvites) == 0 {
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@ -228,17 +226,8 @@ func (oq *destinationQueue) backgroundSend() {
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// If we have pending PDUs or EDUs then construct a transaction.
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if oq.pendingPDUs.Load() > 0 || len(oq.pendingEDUs) > 0 {
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// If we haven't got a transaction ID then we should generate
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// one. Ideally we'd know this already because something queued
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// in the database would give us one, but if we're dealing with
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// EDUs alone, we won't go via the database so we'll make one.
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if transactionID == "" {
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now := gomatrixserverlib.AsTimestamp(time.Now())
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transactionID = gomatrixserverlib.TransactionID(fmt.Sprintf("%d-%d", now, oq.statistics.SuccessCount()))
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}
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// Try sending the next transaction and see what happens.
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transaction, terr := oq.nextTransaction(transactionID, oq.pendingEDUs)
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transaction, terr := oq.nextTransaction(oq.pendingEDUs)
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if terr != nil {
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// We failed to send the transaction.
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if giveUp := oq.statistics.Failure(); giveUp {
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@ -253,7 +242,6 @@ func (oq *destinationQueue) backgroundSend() {
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// If we successfully sent the transaction then clear out
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// the pending events and EDUs, and wipe our transaction ID.
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oq.statistics.Success()
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oq.transactionID = ""
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// Clean up the in-memory buffers.
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oq.cleanPendingEDUs()
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}
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@ -305,9 +293,19 @@ func (oq *destinationQueue) cleanPendingInvites() {
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// queue and sends it. Returns true if a transaction was sent or
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// false otherwise.
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func (oq *destinationQueue) nextTransaction(
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transactionID gomatrixserverlib.TransactionID,
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pendingEDUs []*gomatrixserverlib.EDU,
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) (bool, error) {
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// Before we do anything, we need to roll over the transaction
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// ID that is being used to coalesce events into the next TX.
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// Otherwise it's possible that we'll pick up an incomplete
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// transaction and end up nuking the rest of the events at the
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// cleanup stage.
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oq.transactionMutex.Lock()
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oq.transactionID = ""
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oq.transactionCount = 0
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oq.transactionMutex.Unlock()
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// Create the transaction.
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t := gomatrixserverlib.Transaction{
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PDUs: []json.RawMessage{},
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EDUs: []gomatrixserverlib.EDU{},
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@ -316,42 +314,50 @@ func (oq *destinationQueue) nextTransaction(
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t.Destination = oq.destination
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t.OriginServerTS = gomatrixserverlib.AsTimestamp(time.Now())
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// Ask the database for any pending PDUs from the next transaction.
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// maxPDUsPerTransaction is an upper limit but we probably won't
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// actually retrieve that many events.
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txid, pdus, err := oq.db.GetNextTransactionPDUs(
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context.TODO(), // context
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oq.destination, // server name
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maxPDUsPerTransaction, // how many events to retrieve
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maxPDUsPerTransaction, // max events to retrieve
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)
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if err != nil {
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log.WithError(err).Errorf("failed to get next transaction PDUs for server %q", oq.destination)
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return false, fmt.Errorf("oq.db.GetNextTransactionPDUs: %w", err)
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}
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// If we didn't get anything from the database and there are no
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// pending EDUs then there's nothing to do - stop here.
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if len(pdus) == 0 && len(pendingEDUs) == 0 {
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return false, nil
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}
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if txid != "" {
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// The database supplied us with a transaction ID to use
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// from a failed PDU so use that.
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t.TransactionID = txid
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} else {
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// Otherwise, use the one that the function call gave us.
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// This would happen if it's EDUs only.
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t.TransactionID = transactionID
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// Pick out the transaction ID from the database. If we didn't
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// get a transaction ID (i.e. because there are no PDUs but only
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// EDUs) then generate a transaction ID.
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t.TransactionID = txid
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if t.TransactionID == "" {
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now := gomatrixserverlib.AsTimestamp(time.Now())
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t.TransactionID = gomatrixserverlib.TransactionID(fmt.Sprintf("%d-%d", now, oq.statistics.SuccessCount()))
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}
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// Go through PDUs that we retrieved from the database, if any,
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// and add them into the transaction.
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for _, pdu := range pdus {
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// Append the JSON of the event, since this is a json.RawMessage type in the
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// gomatrixserverlib.Transaction struct
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t.PDUs = append(t.PDUs, (*pdu).JSON())
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}
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// Do the same for pending EDUS in the queue.
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for _, edu := range pendingEDUs {
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t.EDUs = append(t.EDUs, *edu)
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}
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logrus.WithField("server_name", oq.destination).Infof("Sending transaction %q containing %d PDUs, %d EDUs", t.TransactionID, len(t.PDUs), len(t.EDUs))
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// Try to send the transaction to the destination server.
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// TODO: we should check for 500-ish fails vs 400-ish here,
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// since we shouldn't queue things indefinitely in response
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// to a 400-ish error
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@ -367,7 +373,7 @@ func (oq *destinationQueue) nextTransaction(
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t.Destination,
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t.TransactionID,
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); err != nil {
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log.WithError(err).Errorf("failed to clean transaction %q for server %q", transactionID, oq.destination)
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log.WithError(err).Errorf("failed to clean transaction %q for server %q", t.TransactionID, t.Destination)
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}
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return true, nil
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case gomatrix.HTTPError:
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