From 9069eb95f48c8200f8589faf7adc5e324eed25cd Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Wed, 11 Jul 2018 08:57:18 +0900 Subject: [PATCH] Block replication slot advance for these not yet reserving WAL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Such replication slots are physical slots freshly created without WAL being reserved, which is the default behavior, which have not been used yet as WAL consumption resources to retain WAL. This prevents advancing a slot to a position older than any WAL available, which could falsify calculations for WAL segment recycling. This also cleans up a bit the code, as ReplicationSlotRelease() would be called on ERROR, and improves error messages. Reported-by: Kyotaro Horiguchi Author: Michael Paquier Reviewed-by: Andres Freund, Álvaro Herrera, Kyotaro Horiguchi Discussion: https://postgr.es/m/20180626071305.GH31353@paquier.xyz --- contrib/test_decoding/expected/slot.out | 17 +++++++++++++++++ contrib/test_decoding/sql/slot.sql | 6 ++++++ doc/src/sgml/catalogs.sgml | 3 ++- src/backend/replication/slotfuncs.c | 13 ++++++++----- 4 files changed, 33 insertions(+), 6 deletions(-) diff --git a/contrib/test_decoding/expected/slot.out b/contrib/test_decoding/expected/slot.out index 21e9d56f73..2737a8a301 100644 --- a/contrib/test_decoding/expected/slot.out +++ b/contrib/test_decoding/expected/slot.out @@ -131,3 +131,20 @@ SELECT pg_drop_replication_slot('regression_slot1'); ERROR: replication slot "regression_slot1" does not exist SELECT pg_drop_replication_slot('regression_slot2'); ERROR: replication slot "regression_slot2" does not exist +-- slot advance with physical slot, error with non-reserved slot +SELECT slot_name FROM pg_create_physical_replication_slot('regression_slot3'); + slot_name +------------------ + regression_slot3 +(1 row) + +SELECT pg_replication_slot_advance('regression_slot3', '0/0'); -- invalid LSN +ERROR: invalid target wal lsn +SELECT pg_replication_slot_advance('regression_slot3', '0/1'); -- error +ERROR: cannot advance replication slot that has not previously reserved WAL +SELECT pg_drop_replication_slot('regression_slot3'); + pg_drop_replication_slot +-------------------------- + +(1 row) + diff --git a/contrib/test_decoding/sql/slot.sql b/contrib/test_decoding/sql/slot.sql index 706340c1d8..24cdf7155d 100644 --- a/contrib/test_decoding/sql/slot.sql +++ b/contrib/test_decoding/sql/slot.sql @@ -68,3 +68,9 @@ SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot1', 'test_ -- both should error as they should be dropped on error SELECT pg_drop_replication_slot('regression_slot1'); SELECT pg_drop_replication_slot('regression_slot2'); + +-- slot advance with physical slot, error with non-reserved slot +SELECT slot_name FROM pg_create_physical_replication_slot('regression_slot3'); +SELECT pg_replication_slot_advance('regression_slot3', '0/0'); -- invalid LSN +SELECT pg_replication_slot_advance('regression_slot3', '0/1'); -- error +SELECT pg_drop_replication_slot('regression_slot3'); diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml index 3ed9021c2f..4851bc2e24 100644 --- a/doc/src/sgml/catalogs.sgml +++ b/doc/src/sgml/catalogs.sgml @@ -9867,7 +9867,8 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx The address (LSN) of oldest WAL which still might be required by the consumer of this slot and thus won't be - automatically removed during checkpoints. + automatically removed during checkpoints. NULL + if the LSN of this slot has never been reserved. diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c index 2806e1076c..23af32355b 100644 --- a/src/backend/replication/slotfuncs.c +++ b/src/backend/replication/slotfuncs.c @@ -483,6 +483,12 @@ pg_replication_slot_advance(PG_FUNCTION_ARGS) /* Acquire the slot so we "own" it */ ReplicationSlotAcquire(NameStr(*slotname), true); + /* A slot whose restart_lsn has never been reserved cannot be advanced */ + if (XLogRecPtrIsInvalid(MyReplicationSlot->data.restart_lsn)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("cannot advance replication slot that has not previously reserved WAL"))); + /* * Check if the slot is not moving backwards. Physical slots rely simply * on restart_lsn as a minimum point, while logical slots have confirmed @@ -495,14 +501,11 @@ pg_replication_slot_advance(PG_FUNCTION_ARGS) minlsn = MyReplicationSlot->data.restart_lsn; if (moveto < minlsn) - { - ReplicationSlotRelease(); ereport(ERROR, - (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), - errmsg("cannot move slot to %X/%X, minimum is %X/%X", + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("cannot advance replication slot to %X/%X, minimum is %X/%X", (uint32) (moveto >> 32), (uint32) moveto, (uint32) (minlsn >> 32), (uint32) minlsn))); - } /* Do the actual slot update, depending on the slot type */ if (OidIsValid(MyReplicationSlot->data.database))