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Disallow starting server with insufficient wal_level for existing slot.

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Previously it was possible to create a slot, change wal_level, and
restart, even if the new wal_level was insufficient for the
slot. That's a problem for both logical and physical slots, because
the necessary WAL records are not generated.

This removes a few tests in newer versions that, somewhat
inexplicably, whether restarting with a too low wal_level worked (a
buggy behaviour!).

Reported-By: Joshua D. Drake
Author: Andres Freund
Discussion: https://postgr.es/m/20181029191304.lbsmhshkyymhw22w@alap3.anarazel.de
Backpatch: 9.4-, where replication slots where introduced
This commit is contained in:
Andres Freund 2018-10-31 14:47:41 -07:00
parent 558571afc7
commit d35fd17cb5
2 changed files with 35 additions and 0 deletions
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5
src/backend/replication/logical/logical.c
View File

@ -77,6 +77,11 @@ CheckLogicalDecodingRequirements(void)
{ {
CheckSlotRequirements(); CheckSlotRequirements();
/*
* NB: Adding a new requirement likely means that RestoreSlotFromDisk()
* needs the same check.
*/
if (wal_level < WAL_LEVEL_LOGICAL) if (wal_level < WAL_LEVEL_LOGICAL)
ereport(ERROR, ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),

30
src/backend/replication/slot.c
View File

@ -783,6 +783,11 @@ ReplicationSlotsCountDBSlots(Oid dboid, int *nslots, int *nactive)
void void
CheckSlotRequirements(void) CheckSlotRequirements(void)
{ {
/*
* NB: Adding a new requirement likely means that RestoreSlotFromDisk()
* needs the same check.
*/
if (max_replication_slots == 0) if (max_replication_slots == 0)
ereport(ERROR, ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
@ -1286,6 +1291,31 @@ RestoreSlotFromDisk(const char *name)
return; return;
} }
/*
* Verify that requirements for the specific slot type are met. That's
* important because if these aren't met we're not guaranteed to retain
* all the necessary resources for the slot.
*
* NB: We have to do so *after* the above checks for ephemeral slots,
* because otherwise a slot that shouldn't exist anymore could prevent
* restarts.
*
* NB: Changing the requirements here also requires adapting
* CheckSlotRequirements() and CheckLogicalDecodingRequirements().
*/
if (cp.slotdata.database != InvalidOid && wal_level < WAL_LEVEL_LOGICAL)
ereport(FATAL,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("logical replication slots \"%s\" exists, but wal_level < logical",
NameStr(cp.slotdata.name)),
errhint("Change wal_level to be replica or higher.")));
else if (wal_level < WAL_LEVEL_REPLICA)
ereport(FATAL,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("physical replication slots \"%s\" exists, but wal_level < replica",
NameStr(cp.slotdata.name)),
errhint("Change wal_level to be replica or higher.")));
/* nothing can be active yet, don't lock anything */ /* nothing can be active yet, don't lock anything */
for (i = 0; i < max_replication_slots; i++) for (i = 0; i < max_replication_slots; i++)
{ {