adapter: Fence Redis reads before snapshots #1167
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@@ -21,6 +21,8 @@ var redisTxnWideSetFencePrefix = []byte("!redis|txn-wide-set|") | |
| var redisTxnWideListFencePrefix = []byte("!redis|txn-wide-list|") | ||
| var redisTxnWideZSetFencePrefix = []byte("!redis|txn-wide-zset|") | ||
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| var errRedisExecSplitShardLeaders = errors.New("ERR EXEC read fence spans multiple shard leaders") | ||
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| type txnCommandHandler func(*txnContext, redcon.Command) (redisResult, error) | ||
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| var txnApplyHandlers = map[string]txnCommandHandler{ | ||
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@@ -38,6 +40,182 @@ var txnApplyHandlers = map[string]txnCommandHandler{ | |
| cmdPExpire: (*txnContext).applyExpireMilliseconds, | ||
| } | ||
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| func redisTxnReadFenceKeys(userKey []byte) [][]byte { | ||
| keys := [][]byte{ | ||
| redisStrKey(userKey), | ||
| redisHLLKey(userKey), | ||
| redisTTLKey(userKey), | ||
| listMetaKey(userKey), | ||
| store.ListMetaDeltaScanPrefix(userKey), | ||
| redisTxnWideListFenceKey(userKey), | ||
| redisHashKey(userKey), | ||
| store.HashMetaKey(userKey), | ||
| store.HashFieldScanPrefix(userKey), | ||
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There was a problem hiding this comment.
When a hash, set, zset, or stream wide-column range is split after its scan-prefix key, this representative fences only the group owning the prefix start, although AGENTS.md reference: AGENTS.md:L24-L25 Useful? React with 👍 / 👎. |
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| store.HashMetaDeltaScanPrefix(userKey), | ||
| redisTxnWideHashFenceKey(userKey), | ||
| redisSetKey(userKey), | ||
| store.SetMetaKey(userKey), | ||
| store.SetMemberScanPrefix(userKey), | ||
| store.SetMetaDeltaScanPrefix(userKey), | ||
| redisTxnWideSetFenceKey(userKey), | ||
| redisZSetKey(userKey), | ||
| store.ZSetMetaKey(userKey), | ||
| store.ZSetMemberScanPrefix(userKey), | ||
| store.ZSetScoreScanPrefix(userKey), | ||
| store.ZSetMetaDeltaScanPrefix(userKey), | ||
| redisTxnWideZSetFenceKey(userKey), | ||
| redisStreamKey(userKey), | ||
| store.StreamMetaKey(userKey), | ||
| store.StreamEntryScanPrefix(userKey), | ||
| } | ||
| if redisLegacyBareReadFenceAllowed(userKey) { | ||
| keys = append(keys, userKey) | ||
| } | ||
| return keys | ||
| } | ||
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| func redisLegacyBareReadFenceAllowed(userKey []byte) bool { | ||
| if isKnownInternalKey(userKey) { | ||
| return false | ||
| } | ||
| return !bytes.HasPrefix(userKey, []byte("!sqs|")) | ||
| } | ||
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| func redisQueuedCommandReadFenceKeys(queue []redcon.Command) [][]byte { | ||
| seen := make(map[string]struct{}, len(queue)) | ||
| keys := make([][]byte, 0, len(queue)) | ||
| appendKey := func(key []byte) { | ||
| keyID := string(key) | ||
| if _, ok := seen[keyID]; ok { | ||
| return | ||
| } | ||
| seen[keyID] = struct{}{} | ||
| keys = append(keys, key) | ||
| } | ||
| for _, cmd := range queue { | ||
| if len(cmd.Args) == 0 { | ||
| continue | ||
| } | ||
| meta, ok := redisCommandTable[strings.ToUpper(string(cmd.Args[0]))] | ||
| if !ok { | ||
| continue | ||
| } | ||
| for _, userKey := range redisCommandGetKeys(meta, cmd.Args) { | ||
| for _, fenceKey := range redisTxnReadFenceKeys(userKey) { | ||
| appendKey(fenceKey) | ||
| } | ||
| } | ||
| } | ||
| return keys | ||
| } | ||
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| type redisTxnProxyRoute struct { | ||
| defaultLeader bool | ||
| key []byte | ||
| } | ||
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| func (r *RedisServer) redisReadFenceGroupKeys(keys [][]byte) [][]byte { | ||
| if r == nil || r.coordinator == nil { | ||
| return nil | ||
| } | ||
| return kv.LeaseReadGroupKeys(r.coordinator, keys) | ||
| } | ||
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| func (r *RedisServer) queuedCommandReadFenceGroupKeys(queue []redcon.Command) [][]byte { | ||
| return r.redisReadFenceGroupKeys(redisQueuedCommandReadFenceKeys(queue)) | ||
| } | ||
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| func (r *RedisServer) readFenceProxyKey(groupKeys [][]byte) ([]byte, bool, error) { | ||
| if r == nil || r.coordinator == nil || len(groupKeys) == 0 { | ||
| return nil, false, nil | ||
| } | ||
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| var targetLeader string | ||
| var proxyKey []byte | ||
| for _, key := range groupKeys { | ||
| leader, localLeader, err := r.readFenceLeader(key) | ||
| if err != nil { | ||
| return nil, false, err | ||
| } | ||
| if err := recordReadFenceTargetLeader(&targetLeader, leader); err != nil { | ||
| return nil, false, err | ||
| } | ||
| if localLeader || len(proxyKey) > 0 { | ||
| continue | ||
| } | ||
| proxyKey = key | ||
| } | ||
| if len(proxyKey) == 0 { | ||
| return nil, false, nil | ||
| } | ||
| return proxyKey, true, nil | ||
| } | ||
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| func (r *RedisServer) readFenceLeader(key []byte) (string, bool, error) { | ||
| localLeader := r.coordinator.IsLeaderForKey(key) | ||
| leader := r.coordinator.RaftLeaderForKey(key) | ||
| if !localLeader && leader == "" { | ||
| return "", false, ErrLeaderNotFound | ||
| } | ||
| return leader, localLeader, nil | ||
| } | ||
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| func recordReadFenceTargetLeader(target *string, leader string) error { | ||
| if leader == "" { | ||
| return nil | ||
| } | ||
| if *target == "" { | ||
| *target = leader | ||
| return nil | ||
| } | ||
| if *target != leader { | ||
| return errRedisExecSplitShardLeaders | ||
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Comment on lines
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When a request reaches a node that is not the leader of either involved group, two groups led by the same remote process still normally report different Raft endpoints because each group has its own listener, while AGENTS.md reference: AGENTS.md:L25-L27 Useful? React with 👍 / 👎. |
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| } | ||
| return nil | ||
| } | ||
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| func (r *RedisServer) transactionProxyRoute(queue []redcon.Command) (redisTxnProxyRoute, error) { | ||
| if r == nil || r.coordinator == nil { | ||
| return redisTxnProxyRoute{}, nil | ||
| } | ||
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| groupKeys := r.queuedCommandReadFenceGroupKeys(queue) | ||
| if len(groupKeys) == 0 { | ||
| if !r.coordinator.IsLeader() { | ||
| return redisTxnProxyRoute{defaultLeader: true}, nil | ||
| } | ||
| return redisTxnProxyRoute{}, nil | ||
| } | ||
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| proxyKey, ok, err := r.readFenceProxyKey(groupKeys) | ||
| if err != nil { | ||
| return redisTxnProxyRoute{}, err | ||
| } | ||
| if ok { | ||
| return redisTxnProxyRoute{key: proxyKey}, nil | ||
| } | ||
| return redisTxnProxyRoute{}, nil | ||
| } | ||
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| func (r *RedisServer) leaseRedisReadFenceGroups(ctx context.Context, groupKeys [][]byte) error { | ||
| if r == nil || r.coordinator == nil { | ||
| return nil | ||
| } | ||
| for _, key := range groupKeys { | ||
| if _, err := kv.LeaseReadForKeyThrough(r.coordinator, ctx, key); err != nil { | ||
| return errors.WithStack(err) | ||
| } | ||
| } | ||
| return nil | ||
| } | ||
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| func (r *RedisServer) leaseQueuedCommandReadGroups(ctx context.Context, queue []redcon.Command) error { | ||
| if r.coordinator == nil { | ||
| return nil | ||
| } | ||
| return r.leaseRedisReadFenceGroups(ctx, r.queuedCommandReadFenceGroupKeys(queue)) | ||
| } | ||
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| // MULTI/EXEC/DISCARD handling | ||
| func (r *RedisServer) multi(conn redcon.Conn, _ redcon.Command) { | ||
| state := getConnState(conn) | ||
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@@ -72,13 +250,19 @@ func (r *RedisServer) exec(conn redcon.Conn, _ redcon.Command) { | |
| state.inTxn = false | ||
| state.queue = nil | ||
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| route, err := r.transactionProxyRoute(queue) | ||
| if err != nil { | ||
| writeRedisError(conn, err) | ||
| return | ||
| } | ||
| if route.defaultLeader { | ||
| r.proxyTransactionToLeader(conn, queue) | ||
| return | ||
| } | ||
| if len(route.key) > 0 { | ||
| r.proxyTransactionToLeaderForKey(conn, route.key, queue) | ||
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When Useful? React with 👍 / 👎. |
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| return | ||
| } | ||
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| results, err := r.runTransaction(queue) | ||
| if err != nil { | ||
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@@ -2379,6 +2563,10 @@ func (r *RedisServer) runTransactionDirect(queue []redcon.Command) ([]redisResul | |
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| var results []redisResult | ||
| err := r.retryRedisWrite(dispatchCtx, func() error { | ||
| if err := r.leaseQueuedCommandReadGroups(dispatchCtx, queue); err != nil { | ||
| return err | ||
| } | ||
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| startTS := r.txnStartTS() | ||
| readPin := r.pinReadTS(startTS) | ||
| defer readPin.Release() | ||
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@@ -2593,6 +2781,10 @@ func (r *RedisServer) runTransactionWithDedup(queue []redcon.Command) ([]redisRe | |
| // from runTransactionWithDedup to keep that loop under the cyclop | ||
| // budget; the dedup rationale lives there. | ||
| func (r *RedisServer) firstExecAttempt(dispatchCtx context.Context, queue []redcon.Command) ([]redisResult, *reusableExecTxn, error) { | ||
| if err := r.leaseQueuedCommandReadGroups(dispatchCtx, queue); err != nil { | ||
| return nil, nil, err | ||
| } | ||
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| startTS := r.txnStartTS() | ||
| readPin := r.pinReadTS(startTS) | ||
| defer readPin.Release() | ||
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When this new per-shard proxy path targets a node whose EXEC returns the newly introduced
errRedisExecRouteChangedAfterAmbiguousAttempt, go-redis reports the top-level non-array EXEC error as the pipeline error and copies it onto the queued command handles. Neither proxy error handler recognizes this error, soproxyTransactionToLeaderAddrwrites an EXEC result array containing per-command errors instead of preserving the top-level ambiguous-transaction failure; clients can therefore treat the transaction as having executed with ordinary command failures. Promote this EXEC-level error in the proxy handlers before writing the result array.Useful? React with 👍 / 👎.