On Fri, Jun 13, 2025 at 1:00 PM Perumal Raj <peruci...@gmail.com> wrote: > > Yes Shveta! > > I could see repeated message in New-replica . > > 2025-06-13 06:20:30.146 UTC [277861] LOG: could not synchronize replication > slot "kafka_logical_slot" because remote slot precedes local slot > 2025-06-13 06:20:30.146 UTC [277861] DETAIL: The remote slot has LSN > 0/6D0000B8 and catalog xmin 1085, but the local slot has LSN 0/6F000000 and > catalog xmin 1088. > 2025-06-13 06:21:00.176 UTC [277861] LOG: could not synchronize replication > slot "kafka_logical_slot" because remote slot precedes local slot > 2025-06-13 06:21:00.176 UTC [277861] DETAIL: The remote slot has LSN > 0/6D0000B8 and catalog xmin 1085, but the local slot has LSN 0/6F000000 and > catalog xmin 1088. > 2025-06-13 06:21:30.207 UTC [277861] LOG: could not synchronize replication > slot "kafka_logical_slot" because remote slot precedes local slot > 2025-06-13 06:21:30.207 UTC [277861] DETAIL: The remote slot has LSN > 0/6D0000B8 and catalog xmin 1085, but the local slot has LSN 0/6F000000 and > catalog xmin 1088. > 2025-06-13 06:22:00.238 UTC [277861] LOG: could not synchronize replication > slot "kafka_logical_slot" because remote slot precedes local slot > 2025-06-13 06:22:00.238 UTC [277861] DETAIL: The remote slot has LSN > 0/6D0000B8 and catalog xmin 1085, but the local slot has LSN 0/6F000000 and > catalog xmin 1088. > 2025-06-13 06:22:30.268 UTC [277861] LOG: could not synchronize replication > slot "kafka_logical_slot" because remote slot precedes local slot > 2025-06-13 06:22:30.268 UTC [277861] DETAIL: The remote slot has LSN > 0/6D0000B8 and catalog xmin 1085, but the local slot has LSN 0/6F000000 and > catalog xmin 1088. > 2025-06-13 06:23:00.299 UTC [277861] LOG: could not synchronize replication > slot "kafka_logical_slot" because remote slot precedes local slot > 2025-06-13 06:23:00.299 UTC [277861] DETAIL: The remote slot has LSN > 0/6D0000B8 and catalog xmin 1085, but the local slot has LSN 0/6F000000 and > catalog xmin 1088. > 2025-06-13 06:23:30.329 UTC [277861] LOG: could not synchronize replication > slot "kafka_logical_slot" because remote slot precedes local slot > 2025-06-13 06:23:30.329 UTC [277861] DETAIL: The remote slot has LSN > 0/6D0000B8 and catalog xmin 1085, but the local slot has LSN 0/6F000000 and > catalog xmin 1088. > 2025-06-13 06:24:00.360 UTC [277861] LOG: could not synchronize replication > slot "kafka_logical_slot" because remote slot precedes local slot > 2025-06-13 06:24:00.360 UTC [277861] DETAIL: The remote slot has LSN > 0/6D0000B8 and catalog xmin 1085, but the local slot has LSN 0/6F000000 and > catalog xmin 1088. > 2025-06-13 06:24:30.391 UTC [277861] LOG: could not synchronize replication > slot "kafka_logical_slot" because remote slot precedes local slot > 2025-06-13 06:24:30.391 UTC [277861] DETAIL: The remote slot has LSN > 0/6D0000B8 and catalog xmin 1085, but the local slot has LSN 0/6F000000 and > catalog xmin 1088. > 2025-06-13 06:25:00.421 UTC [277861] LOG: could not synchronize replication > slot "kafka_logical_slot" because remote slot precedes local slot > 2025-06-13 06:25:00.421 UTC [277861] DETAIL: The remote slot has LSN > 0/6D0000B8 and catalog xmin 1085, but the local slot has LSN 0/6F000000 and > catalog xmin 1088. > 2025-06-13 06:25:30.452 UTC [277861] LOG: could not synchronize replication > slot "kafka_logical_slot" because remote slot precedes local slot > 2025-06-13 06:25:30.452 UTC [277861] DETAIL: The remote slot has LSN > 0/6D0000B8 and catalog xmin 1085, but the local slot has LSN 0/6F000000 and > catalog xmin 1088. > > > It appears that my Debezium connectors have stopped consuming data, resulting > in an outdated restart_lsn of "0/6D0000B8". >
Yes, if there are no consumers consuming the changes on the failover slot on primary, and meanwhile slot synchronization is started, the initial sync may have such a temporary state of synced slot. This is intentionally done to prevent the inconsistent state of the synced slot and avoid unexpected behaviour if failover is performed at that moment. > In contrast, the New_replica has a restart_lsn that matches the primary > server's most recent confirmed_flush_lsn, indicating it is up to date. > > As soon as I recreate that replication slot, it got sync with > New_Replica(temporary=false) . > > 2025-06-13 06:26:00.484 UTC [277861] LOG: dropped replication slot > "kafka_logical_slot" of database with OID 16384 > > 2025-06-13 06:26:30.520 UTC [277861] LOG: starting logical decoding for slot > "kafka_logical_slot" > > 2025-06-13 06:26:30.520 UTC [277861] DETAIL: Streaming transactions > committing after 0/0, reading WAL from 0/76003140. > > 2025-06-13 06:26:30.520 UTC [277861] LOG: logical decoding found consistent > point at 0/76003140 > > 2025-06-13 06:26:30.520 UTC [277861] DETAIL: There are no running > transactions. > > 2025-06-13 06:26:30.526 UTC [277861] LOG: newly created replication slot > "kafka_logical_slot" is sync-ready now > > 2025-06-13 06:35:39.212 UTC [277857] LOG: restartpoint starting: time > > 2025-06-13 06:35:42.022 UTC [277857] LOG: restartpoint complete: wrote 29 > buffers (0.2%); 0 WAL file(s) added, 0 removed, 0 recycled; write=2.805 s, > sync=0.002 s, total=2.810 s; sync files=26, longest=0.002 s, average=0.001 s; > distance=16496 kB, estimate=16496 kB; lsn=0/7701F480, redo lsn=0/7701F428 > > 2025-06-13 06:35:42.022 UTC [277857] LOG: recovery restart point at > 0/7701F428 > > 2025-06-13 06:35:42.022 UTC [277857] DETAIL: Last completed transaction was > at log time 2025-06-13 06:33:31.675341+00. > > Until the synchronization is complete, the slot type is marked as > temporary=true, as you mentioned. > > is there any manual way to advance "restart_lsn" of logical replication slot > ? This is to ensure slot synchronization. > 1) The first and recommended option is to get the connector running again and let it advance the slot by consuming the changes. 2) Another option is to manually advance the slot on the primary by using pg_logical_slot_get_binary_changes(). However, if the logical replication setup is intended to consume these changes but is currently inactive, then slot's consumer will not be able to reprocess those changes upon restarting. So the said API should be used only after analyzing the current state of logical replication setup and if we are okay with those changes not shipped to logical replication consumers. thanks Shveta
