mirror of https://github.com/postgres/postgres
When decoding from a logical slot, it's necessary for xlog reading to be able to read xlog from historical (i.e. not current) timelines; otherwise, decoding fails after failover, because the archives are in the historical timeline. This is required to make "failover logical slots" possible; it currently has no other use, although theoretically it could be used by an extension that creates a slot on a standby and continues to replay from the slot when the standby is promoted. This commit includes a module in src/test/modules with functions to manipulate the slots (which is not otherwise possible in SQL code) in order to enable testing, and a new test in src/test/recovery to ensure that the behavior is as expected. Author: Craig Ringer Reviewed-By: Oleksii Kliukin, Andres Freund, Petr Jelínekpull/11/head
Alvaro Herrera
10 years ago
parent
3b02ea4f07
commit
24c5f1a103
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results/ |
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tmp_check/ |
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log/ |
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# src/test/modules/test_slot_timelines/Makefile
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MODULES = test_slot_timelines
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PGFILEDESC = "test_slot_timelines - test utility for slot timeline following"
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EXTENSION = test_slot_timelines
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DATA = test_slot_timelines--1.0.sql
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EXTRA_INSTALL=contrib/test_decoding
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REGRESS=load_extension
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REGRESS_OPTS = --temp-config=$(top_srcdir)/src/test/modules/test_slot_timelines/test_slot_timelines.conf
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ifdef USE_PGXS |
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PG_CONFIG = pg_config
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PGXS := $(shell $(PG_CONFIG) --pgxs)
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include $(PGXS) |
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else |
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subdir = src/test/modules/test_slot_timelines
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top_builddir = ../../../..
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include $(top_builddir)/src/Makefile.global |
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include $(top_srcdir)/contrib/contrib-global.mk |
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endif |
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A test module for logical decoding failover and timeline following. |
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This module provides a minimal way to maintain logical slots on replicas |
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that mirror the state on the master. It doesn't make decoding possible, |
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just tracking slot state so that a decoding client that's using the master |
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can follow a physical failover to the standby. The master doesn't know |
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about the slots on the standby, they're synced by a client that connects |
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to both. |
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This is intentionally not part of the test_decoding module because that's meant |
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to serve as example code, where this module exercises internal server features |
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by unsafely exposing internal state to SQL. It's not the right way to do |
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failover, it's just a simple way to test it from the perl TAP framework to |
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prove the feature works. |
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In a practical implementation of this approach a bgworker on the master would |
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monitor slot positions and relay them to a bgworker on the standby that applies |
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the position updates without exposing slot internals to SQL. That's too complex |
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for this test framework though. |
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CREATE EXTENSION test_slot_timelines; |
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SELECT test_slot_timelines_create_logical_slot('test_slot', 'test_decoding'); |
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test_slot_timelines_create_logical_slot |
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----------------------------------------- |
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(1 row) |
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SELECT test_slot_timelines_advance_logical_slot('test_slot', txid_current(), txid_current(), pg_current_xlog_location(), pg_current_xlog_location()); |
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test_slot_timelines_advance_logical_slot |
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------------------------------------------ |
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(1 row) |
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SELECT pg_drop_replication_slot('test_slot'); |
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pg_drop_replication_slot |
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-------------------------- |
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(1 row) |
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CREATE EXTENSION test_slot_timelines; |
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SELECT test_slot_timelines_create_logical_slot('test_slot', 'test_decoding'); |
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SELECT test_slot_timelines_advance_logical_slot('test_slot', txid_current(), txid_current(), pg_current_xlog_location(), pg_current_xlog_location()); |
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SELECT pg_drop_replication_slot('test_slot'); |
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-- complain if script is sourced in psql, rather than via CREATE EXTENSION |
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\echo Use "CREATE EXTENSION test_slot_timelines" to load this file. \quit |
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CREATE OR REPLACE FUNCTION test_slot_timelines_create_logical_slot(slot_name text, plugin text) |
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RETURNS void |
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LANGUAGE c AS 'MODULE_PATHNAME'; |
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COMMENT ON FUNCTION test_slot_timelines_create_logical_slot(text, text) |
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IS 'Create a logical slot at a particular lsn and xid. Do not use in production servers, it is not safe. The slot is created with an invalid xmin and lsn.'; |
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CREATE OR REPLACE FUNCTION test_slot_timelines_advance_logical_slot(slot_name text, new_xmin bigint, new_catalog_xmin bigint, new_restart_lsn pg_lsn, new_confirmed_lsn pg_lsn) |
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RETURNS void |
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LANGUAGE c AS 'MODULE_PATHNAME'; |
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COMMENT ON FUNCTION test_slot_timelines_advance_logical_slot(text, bigint, bigint, pg_lsn, pg_lsn) |
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IS 'Advance a logical slot directly. Do not use this in production servers, it is not safe.'; |
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/*--------------------------------------------------------------------------
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* |
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* test_slot_timelines.c |
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* Test harness code for slot timeline following |
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* |
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* Copyright (c) 2016, PostgreSQL Global Development Group |
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* |
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* IDENTIFICATION |
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* src/test/modules/test_slot_timelines/test_slot_timelines.c |
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* |
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* ------------------------------------------------------------------------- |
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*/ |
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#include "postgres.h" |
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#include "access/transam.h" |
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#include "fmgr.h" |
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#include "miscadmin.h" |
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#include "replication/slot.h" |
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#include "utils/builtins.h" |
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#include "utils/pg_lsn.h" |
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PG_MODULE_MAGIC; |
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PG_FUNCTION_INFO_V1(test_slot_timelines_create_logical_slot); |
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PG_FUNCTION_INFO_V1(test_slot_timelines_advance_logical_slot); |
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static void clear_slot_transient_state(void); |
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/*
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* Create a new logical slot, with invalid LSN and xid, directly. This does not |
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* use the snapshot builder or logical decoding machinery. It's only intended |
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* for creating a slot on a replica that mirrors the state of a slot on an |
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* upstream master. |
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* |
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* Note that this is test harness code. You shouldn't expose slot internals |
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* to SQL like this for any real world usage. See the README. |
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*/ |
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Datum |
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test_slot_timelines_create_logical_slot(PG_FUNCTION_ARGS) |
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{ |
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char *slotname = text_to_cstring(PG_GETARG_TEXT_P(0)); |
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char *plugin = text_to_cstring(PG_GETARG_TEXT_P(1)); |
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CheckSlotRequirements(); |
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ReplicationSlotCreate(slotname, true, RS_PERSISTENT); |
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/* register the plugin name with the slot */ |
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StrNCpy(NameStr(MyReplicationSlot->data.plugin), plugin, NAMEDATALEN); |
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/*
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* Initialize persistent state to placeholders to be set by |
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* test_slot_timelines_advance_logical_slot . |
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*/ |
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MyReplicationSlot->data.xmin = InvalidTransactionId; |
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MyReplicationSlot->data.catalog_xmin = InvalidTransactionId; |
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MyReplicationSlot->data.restart_lsn = InvalidXLogRecPtr; |
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MyReplicationSlot->data.confirmed_flush = InvalidXLogRecPtr; |
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clear_slot_transient_state(); |
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ReplicationSlotRelease(); |
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PG_RETURN_VOID(); |
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} |
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/*
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* Set the state of a slot. |
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* |
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* This doesn't maintain the non-persistent state at all, |
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* but since the slot isn't in use that's OK. |
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* |
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* There's intentionally no check to prevent slots going backwards |
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* because they can actually go backwards if the master crashes when |
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* it hasn't yet flushed slot state to disk then we copy the older |
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* slot state after recovery. |
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* |
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* There's no checking done for xmin or catalog xmin either, since |
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* we can't really do anything useful that accounts for xid wrap-around. |
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* |
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* Note that this is test harness code. You shouldn't expose slot internals |
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* to SQL like this for any real world usage. See the README. |
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*/ |
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Datum |
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test_slot_timelines_advance_logical_slot(PG_FUNCTION_ARGS) |
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{ |
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char *slotname = text_to_cstring(PG_GETARG_TEXT_P(0)); |
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TransactionId new_xmin = (TransactionId) PG_GETARG_INT64(1); |
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TransactionId new_catalog_xmin = (TransactionId) PG_GETARG_INT64(2); |
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XLogRecPtr restart_lsn = PG_GETARG_LSN(3); |
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XLogRecPtr confirmed_lsn = PG_GETARG_LSN(4); |
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CheckSlotRequirements(); |
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ReplicationSlotAcquire(slotname); |
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if (MyReplicationSlot->data.database != MyDatabaseId) |
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elog(ERROR, "Trying to update a slot on a different database"); |
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MyReplicationSlot->data.xmin = new_xmin; |
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MyReplicationSlot->data.catalog_xmin = new_catalog_xmin; |
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MyReplicationSlot->data.restart_lsn = restart_lsn; |
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MyReplicationSlot->data.confirmed_flush = confirmed_lsn; |
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clear_slot_transient_state(); |
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ReplicationSlotMarkDirty(); |
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ReplicationSlotSave(); |
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ReplicationSlotRelease(); |
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ReplicationSlotsComputeRequiredXmin(false); |
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ReplicationSlotsComputeRequiredLSN(); |
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PG_RETURN_VOID(); |
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} |
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static void |
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clear_slot_transient_state(void) |
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{ |
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Assert(MyReplicationSlot != NULL); |
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/*
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* Make sure the slot state is the same as if it were newly loaded from |
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* disk on recovery. |
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*/ |
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MyReplicationSlot->effective_xmin = MyReplicationSlot->data.xmin; |
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MyReplicationSlot->effective_catalog_xmin = MyReplicationSlot->data.catalog_xmin; |
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MyReplicationSlot->candidate_catalog_xmin = InvalidTransactionId; |
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MyReplicationSlot->candidate_xmin_lsn = InvalidXLogRecPtr; |
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MyReplicationSlot->candidate_restart_lsn = InvalidXLogRecPtr; |
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MyReplicationSlot->candidate_restart_valid = InvalidXLogRecPtr; |
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} |
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max_replication_slots=2 |
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wal_level=logical |
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# test_slot_timelines extension |
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comment = 'Test utility for slot timeline following and logical decoding' |
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default_version = '1.0' |
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module_pathname = '$libdir/test_slot_timelines' |
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relocatable = true |
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# Demonstrate that logical can follow timeline switches. |
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# |
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# Logical replication slots can follow timeline switches but it's |
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# normally not possible to have a logical slot on a replica where |
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# promotion and a timeline switch can occur. The only ways |
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# we can create that circumstance are: |
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# |
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# * By doing a filesystem-level copy of the DB, since pg_basebackup |
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# excludes pg_replslot but we can copy it directly; or |
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# |
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# * by creating a slot directly at the C level on the replica and |
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# advancing it as we go using the low level APIs. It can't be done |
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# from SQL since logical decoding isn't allowed on replicas. |
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# |
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# This module uses the first approach to show that timeline following |
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# on a logical slot works. |
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# |
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use strict; |
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use warnings; |
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use PostgresNode; |
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use TestLib; |
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use Test::More tests => 20; |
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use RecursiveCopy; |
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use File::Copy; |
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my ($stdout, $stderr, $ret); |
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# Initialize master node |
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my $node_master = get_new_node('master'); |
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$node_master->init(allows_streaming => 1, has_archiving => 1); |
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$node_master->append_conf('postgresql.conf', "wal_level = 'logical'\n"); |
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$node_master->append_conf('postgresql.conf', "max_replication_slots = 2\n"); |
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$node_master->append_conf('postgresql.conf', "max_wal_senders = 2\n"); |
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$node_master->append_conf('postgresql.conf', "log_min_messages = 'debug2'\n"); |
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$node_master->dump_info; |
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$node_master->start; |
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diag "Testing logical timeline following with a filesystem-level copy"; |
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$node_master->safe_psql('postgres', |
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"SELECT pg_create_logical_replication_slot('before_basebackup', 'test_decoding');" |
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); |
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$node_master->safe_psql('postgres', "CREATE TABLE decoding(blah text);"); |
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$node_master->safe_psql('postgres', |
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"INSERT INTO decoding(blah) VALUES ('beforebb');"); |
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$node_master->safe_psql('postgres', 'CHECKPOINT;'); |
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my $backup_name = 'b1'; |
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$node_master->backup_fs_hot($backup_name); |
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my $node_replica = get_new_node('replica'); |
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$node_replica->init_from_backup( |
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$node_master, $backup_name, |
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has_streaming => 1, |
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has_restoring => 1); |
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$node_replica->start; |
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$node_master->safe_psql('postgres', |
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"SELECT pg_create_logical_replication_slot('after_basebackup', 'test_decoding');" |
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); |
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$node_master->safe_psql('postgres', |
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"INSERT INTO decoding(blah) VALUES ('afterbb');"); |
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$node_master->safe_psql('postgres', 'CHECKPOINT;'); |
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# Verify that only the before base_backup slot is on the replica |
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$stdout = $node_replica->safe_psql('postgres', |
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'SELECT slot_name FROM pg_replication_slots ORDER BY slot_name'); |
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is($stdout, 'before_basebackup', |
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'Expected to find only slot before_basebackup on replica'); |
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# Boom, crash |
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$node_master->stop('immediate'); |
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$node_replica->promote; |
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$node_replica->poll_query_until('postgres', |
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"SELECT NOT pg_is_in_recovery();"); |
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$node_replica->safe_psql('postgres', |
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"INSERT INTO decoding(blah) VALUES ('after failover');"); |
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# Shouldn't be able to read from slot created after base backup |
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($ret, $stdout, $stderr) = $node_replica->psql('postgres', |
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"SELECT data FROM pg_logical_slot_peek_changes('after_basebackup', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');" |
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); |
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is($ret, 3, 'replaying from after_basebackup slot fails'); |
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like( |
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$stderr, |
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qr/replication slot "after_basebackup" does not exist/, |
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'after_basebackup slot missing'); |
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# Should be able to read from slot created before base backup |
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($ret, $stdout, $stderr) = $node_replica->psql( |
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'postgres', |
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"SELECT data FROM pg_logical_slot_peek_changes('before_basebackup', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');", |
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timeout => 30); |
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is($ret, 0, 'replay from slot before_basebackup succeeds'); |
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is( $stdout, q(BEGIN |
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table public.decoding: INSERT: blah[text]:'beforebb' |
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COMMIT |
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BEGIN |
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table public.decoding: INSERT: blah[text]:'afterbb' |
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COMMIT |
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BEGIN |
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table public.decoding: INSERT: blah[text]:'after failover' |
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COMMIT), 'decoded expected data from slot before_basebackup'); |
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is($stderr, '', 'replay from slot before_basebackup produces no stderr'); |
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# We don't need the standby anymore |
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$node_replica->teardown_node(); |
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# OK, time to try the same thing again, but this time we'll be using slot |
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# mirroring on the standby and a pg_basebackup of the master. |
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diag "Testing logical timeline following with test_slot_timelines module"; |
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$node_master->start(); |
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# Clean up after the last test |
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$node_master->safe_psql('postgres', 'DELETE FROM decoding;'); |
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is( $node_master->psql( |
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'postgres', |
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'SELECT pg_drop_replication_slot(slot_name) FROM pg_replication_slots;'), |
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0, |
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'dropping slots succeeds via pg_drop_replication_slot'); |
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# Same as before, we'll make one slot before basebackup, one after. This time |
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# the basebackup will be with pg_basebackup so it'll omit both slots, then |
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# we'll use SQL functions provided by the test_slot_timelines test module to sync |
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# them to the replica, do some work, sync them and fail over then test again. |
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# This time we should have both the before- and after-basebackup slots working. |
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is( $node_master->psql( |
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'postgres', |
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"SELECT pg_create_logical_replication_slot('before_basebackup', 'test_decoding');" |
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), |
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0, |
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'creating slot before_basebackup succeeds'); |
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$node_master->safe_psql('postgres', |
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"INSERT INTO decoding(blah) VALUES ('beforebb');"); |
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|
|
||||||
|
$backup_name = 'b2'; |
||||||
|
$node_master->backup($backup_name); |
||||||
|
|
||||||
|
is( $node_master->psql( |
||||||
|
'postgres', |
||||||
|
"SELECT pg_create_logical_replication_slot('after_basebackup', 'test_decoding');" |
||||||
|
), |
||||||
|
0, |
||||||
|
'creating slot after_basebackup succeeds'); |
||||||
|
|
||||||
|
$node_master->safe_psql('postgres', |
||||||
|
"INSERT INTO decoding(blah) VALUES ('afterbb');"); |
||||||
|
|
||||||
|
$node_replica = get_new_node('replica2'); |
||||||
|
$node_replica->init_from_backup( |
||||||
|
$node_master, $backup_name, |
||||||
|
has_streaming => 1, |
||||||
|
has_restoring => 1); |
||||||
|
|
||||||
|
$node_replica->start; |
||||||
|
|
||||||
|
# Verify the slots are both absent on the replica |
||||||
|
$stdout = $node_replica->safe_psql('postgres', |
||||||
|
'SELECT slot_name FROM pg_replication_slots ORDER BY slot_name'); |
||||||
|
is($stdout, '', 'No slots exist on the replica'); |
||||||
|
|
||||||
|
# Now do our magic to sync the slot states across. Normally |
||||||
|
# this would be being done continuously by a bgworker but |
||||||
|
# we're just doing it by hand for this test. This is exposing |
||||||
|
# postgres innards to SQL so it's unsafe except for testing. |
||||||
|
$node_master->safe_psql('postgres', 'CREATE EXTENSION test_slot_timelines;'); |
||||||
|
my $slotinfo = $node_master->safe_psql('postgres', |
||||||
|
'SELECT slot_name, plugin, xmin, catalog_xmin, restart_lsn, confirmed_flush_lsn FROM pg_replication_slots ORDER BY slot_name' |
||||||
|
); |
||||||
|
diag "Copying slots to replica"; |
||||||
|
open my $fh, '<', \$slotinfo or die $!; |
||||||
|
while (<$fh>) |
||||||
|
{ |
||||||
|
print $_; |
||||||
|
chomp $_; |
||||||
|
my ($slot_name, $plugin, $xmin, $catalog_xmin, $restart_lsn, |
||||||
|
$confirmed_flush_lsn) |
||||||
|
= map { |
||||||
|
if ($_ ne '') { "'$_'" } |
||||||
|
else { 'NULL' } |
||||||
|
} split qr/\|/, $_; |
||||||
|
|
||||||
|
print |
||||||
|
"# Copying slot $slot_name,$plugin,$xmin,$catalog_xmin,$restart_lsn,$confirmed_flush_lsn\n"; |
||||||
|
$node_replica->safe_psql('postgres', |
||||||
|
"SELECT test_slot_timelines_create_logical_slot($slot_name, $plugin);" |
||||||
|
); |
||||||
|
$node_replica->safe_psql('postgres', |
||||||
|
"SELECT test_slot_timelines_advance_logical_slot($slot_name, $xmin, $catalog_xmin, $restart_lsn, $confirmed_flush_lsn);" |
||||||
|
); |
||||||
|
} |
||||||
|
close $fh or die $!; |
||||||
|
|
||||||
|
# Now both slots are present on the replica and exactly match the master |
||||||
|
$stdout = $node_replica->safe_psql('postgres', |
||||||
|
'SELECT slot_name FROM pg_replication_slots ORDER BY slot_name'); |
||||||
|
is( $stdout, |
||||||
|
"after_basebackup\nbefore_basebackup", |
||||||
|
'both slots now exist on replica'); |
||||||
|
|
||||||
|
$stdout = $node_replica->safe_psql( |
||||||
|
'postgres', |
||||||
|
qq{SELECT slot_name, plugin, xmin, catalog_xmin, |
||||||
|
restart_lsn, confirmed_flush_lsn |
||||||
|
FROM pg_replication_slots |
||||||
|
ORDER BY slot_name}); |
||||||
|
is($stdout, $slotinfo, |
||||||
|
"slot data read back from replica matches slot data on master"); |
||||||
|
|
||||||
|
# We now have to copy some extra WAL to satisfy the requirements of the oldest |
||||||
|
# replication slot. pg_basebackup doesn't know to copy the extra WAL for slots |
||||||
|
# so we have to help out. We know the WAL is still retained on the master |
||||||
|
# because we haven't advanced the slots there. |
||||||
|
# |
||||||
|
# Figure out what the oldest segment we need is by looking at the restart_lsn |
||||||
|
# of the oldest slot. |
||||||
|
# |
||||||
|
# It only makes sense to do this once the slots are created on the replica, |
||||||
|
# otherwise it might just delete the segments again. |
||||||
|
|
||||||
|
my $oldest_needed_segment = $node_master->safe_psql( |
||||||
|
'postgres', |
||||||
|
qq{SELECT pg_xlogfile_name(( |
||||||
|
SELECT restart_lsn |
||||||
|
FROM pg_replication_slots |
||||||
|
ORDER BY restart_lsn ASC |
||||||
|
LIMIT 1 |
||||||
|
));} |
||||||
|
); |
||||||
|
|
||||||
|
diag "oldest needed xlog seg is $oldest_needed_segment "; |
||||||
|
|
||||||
|
# WAL segment names sort lexically so we can just grab everything > than this |
||||||
|
# segment. |
||||||
|
opendir(my $pg_xlog, $node_master->data_dir . "/pg_xlog") or die $!; |
||||||
|
while (my $seg = readdir $pg_xlog) |
||||||
|
{ |
||||||
|
next unless $seg >= $oldest_needed_segment && $seg =~ /^[0-9]{24}/; |
||||||
|
diag "copying xlog seg $seg"; |
||||||
|
copy( |
||||||
|
$node_master->data_dir . "/pg_xlog/" . $seg, |
||||||
|
$node_replica->data_dir . "/pg_xlog/" . $seg |
||||||
|
) or die "copy of xlog seg $seg failed: $!"; |
||||||
|
} |
||||||
|
closedir $pg_xlog; |
||||||
|
|
||||||
|
# Boom, crash the master |
||||||
|
$node_master->stop('immediate'); |
||||||
|
|
||||||
|
$node_replica->promote; |
||||||
|
$node_replica->poll_query_until('postgres', |
||||||
|
"SELECT NOT pg_is_in_recovery();"); |
||||||
|
|
||||||
|
$node_replica->safe_psql('postgres', |
||||||
|
"INSERT INTO decoding(blah) VALUES ('after failover');"); |
||||||
|
|
||||||
|
# This time we can read from both slots |
||||||
|
($ret, $stdout, $stderr) = $node_replica->psql( |
||||||
|
'postgres', |
||||||
|
"SELECT data FROM pg_logical_slot_peek_changes('after_basebackup', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');", |
||||||
|
timeout => 30); |
||||||
|
is($ret, 0, 'replay from slot after_basebackup succeeds'); |
||||||
|
is( $stdout, q(BEGIN |
||||||
|
table public.decoding: INSERT: blah[text]:'afterbb' |
||||||
|
COMMIT |
||||||
|
BEGIN |
||||||
|
table public.decoding: INSERT: blah[text]:'after failover' |
||||||
|
COMMIT), 'decoded expected data from slot after_basebackup'); |
||||||
|
is($stderr, '', 'replay from slot after_basebackup produces no stderr'); |
||||||
|
|
||||||
|
# Should be able to read from slot created before base backup |
||||||
|
# |
||||||
|
# This would fail with an error about missing WAL segments if we hadn't |
||||||
|
# copied extra WAL earlier. |
||||||
|
($ret, $stdout, $stderr) = $node_replica->psql( |
||||||
|
'postgres', |
||||||
|
"SELECT data FROM pg_logical_slot_peek_changes('before_basebackup', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');", |
||||||
|
timeout => 30); |
||||||
|
is($ret, 0, 'replay from slot before_basebackup succeeds'); |
||||||
|
is( $stdout, q(BEGIN |
||||||
|
table public.decoding: INSERT: blah[text]:'beforebb' |
||||||
|
COMMIT |
||||||
|
BEGIN |
||||||
|
table public.decoding: INSERT: blah[text]:'afterbb' |
||||||
|
COMMIT |
||||||
|
BEGIN |
||||||
|
table public.decoding: INSERT: blah[text]:'after failover' |
||||||
|
COMMIT), 'decoded expected data from slot before_basebackup'); |
||||||
|
is($stderr, '', 'replay from slot before_basebackup produces no stderr'); |
||||||
|
|
||||||
|
($ret, $stdout, $stderr) = $node_replica->psql('postgres', |
||||||
|
'SELECT pg_drop_replication_slot(slot_name) FROM pg_replication_slots;'); |
||||||
|
is($ret, 0, 'dropping slots succeeds via pg_drop_replication_slot'); |
||||||
|
is($stderr, '', 'dropping slots produces no stderr output'); |
||||||
|
|
||||||
|
1; |
||||||
Loading…
Reference in new issue