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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 696b0c5fd0
commit 691d79a079
3 changed files with 36 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
src/backend/replication/logical/logical.c
View File

@ -79,6 +79,11 @@ CheckLogicalDecodingRequirements(void)
{
CheckSlotRequirements();
/*
* NB: Adding a new requirement likely means that RestoreSlotFromDisk()
* needs the same check.
*/
if (wal_level < WAL_LEVEL_LOGICAL)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),

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

@ -971,6 +971,11 @@ restart:
void
CheckSlotRequirements(void)
{
/*
* NB: Adding a new requirement likely means that RestoreSlotFromDisk()
* needs the same check.
*/
if (max_replication_slots == 0)
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
@ -1502,6 +1507,31 @@ RestoreSlotFromDisk(const char *name)
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 */
for (i = 0; i < max_replication_slots; i++)
{

23
src/test/recovery/t/006_logical_decoding.pl
View File

@ -7,7 +7,7 @@ use strict;
use warnings;
use PostgresNode;
use TestLib;
use Test::More tests => 16;
use Test::More tests => 10;
use Config;
# Initialize master node
@ -135,26 +135,5 @@ is($node_master->psql('postgres', 'DROP DATABASE otherdb'),
is($node_master->slot('otherdb_slot')->{'slot_name'},
undef, 'logical slot was actually dropped with DB');
# Restarting a node with wal_level = logical that has existing
# slots must succeed, but decoding from those slots must fail.
$node_master->safe_psql('postgres', 'ALTER SYSTEM SET wal_level = replica');
is($node_master->safe_psql('postgres', 'SHOW wal_level'),
'logical', 'wal_level is still logical before restart');
$node_master->restart;
is($node_master->safe_psql('postgres', 'SHOW wal_level'),
'replica', 'wal_level is replica');
isnt($node_master->slot('test_slot')->{'catalog_xmin'},
'0', 'restored slot catalog_xmin is nonzero');
is( $node_master->psql(
'postgres',
qq[SELECT pg_logical_slot_get_changes('test_slot', NULL, NULL);]),
3,
'reading from slot with wal_level < logical fails');
is( $node_master->psql(
'postgres', q[SELECT pg_drop_replication_slot('test_slot')]),
0,
'can drop logical slot while wal_level = replica');
is($node_master->slot('test_slot')->{'catalog_xmin'}, '', 'slot was dropped');
# done with the node
$node_master->stop;