RE: Slot's restart_lsn may point to removed WAL segment after hard restart unexpectedly

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>

From: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>

To: Alexander Korotkov <aekorotkov@gmail.com>

Cc: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Amit Kapila <amit.kapila16@gmail.com>, Vitaly Davydov <v.davydov@postgrespro.ru>, Tom Lane <tgl@sss.pgh.pa.us>, Alexander Lakhin <exclusion@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Masahiko Sawada <sawada.mshk@gmail.com>, "tomas@vondra.me" <tomas@vondra.me>, vignesh C <vignesh21@gmail.com>

Date: 2025-06-25T05:27:27Z

Lists: pgsql-hackers

Commits

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Update comment for ReplicationSlot.last_saved_restart_lsn
- 0810fbb02dbe 19 (unreleased) landed
Fix CheckPointReplicationSlots() with max_replication_slots == 0
- 7195c804bd12 18.0 landed
Remove excess assert from InvalidatePossiblyObsoleteSlot()
- 70d8a91f82f1 18.0 landed
Improve runtime and output of tests for replication slots checkpointing.
- 5ed50f9386f0 17.6 landed
- 4464fddf7b50 18.0 landed
Keep WAL segments by slot's last saved restart LSN
- ca307d5cec90 18.0 landed
Fix an assert in CheckPointReplicationSlots().
- d1ffcc7fa3c5 17.0 cited

Hi,

After commit ca307d5, I noticed another crash when testing
some other logical replication features.

The server with max_replication_slots set to 0 would crash when executing CHECKPOINT.

TRAP: failed Assert("ReplicationSlotCtl != NULL"), File: "slot.c", Line: 1162, PID: 577315
postgres: checkpointer (ExceptionalCondition+0x9e)[0xc046cb]
postgres: checkpointer (ReplicationSlotsComputeRequiredLSN+0x30)[0x99697f]
postgres: checkpointer (CheckPointReplicationSlots+0x191)[0x997dc1]
postgres: checkpointer [0x597b1b]
postgres: checkpointer (CreateCheckPoint+0x6d1)[0x59729e]
postgres: checkpointer (CheckpointerMain+0x559)[0x93ee79]
postgres: checkpointer (postmaster_child_launch+0x15f)[0x940311]
postgres: checkpointer [0x9468b0]
postgres: checkpointer (PostmasterMain+0x1258)[0x9434f8]
postgres: checkpointer (main+0x2fe)[0x7f5f9c]
/lib64/libc.so.6(__libc_start_main+0xe5)[0x7f7585f81d85]
postgres: checkpointer (_start+0x2e)[0x4958ee]

I think it is trying to access the replication slots when the shared memory
for them was not allocated.

Best Regards,
Hou zj