PostgreSQL 9.3 Allow a streaming replication standby to follow a timeline switch

Allow a streaming replication standby to follow a timeline switch.

Before this patch, streaming replication would refuse to start replicating
if the timeline in the primary doesn't exactly match the standby. The
situation where it doesn't match is when you have a master, and two
standbys, and you promote one of the standbys to become new master.
Promoting bumps up the timeline ID, and after that bump, the other standby
would refuse to continue.

There's significantly more timeline related logic in streaming replication
now. First of all, when a standby connects to primary, it will ask the
primary for any timeline history files that are missing from the standby.
The missing files are sent using a new replication command TIMELINE_HISTORY,
and stored in standby's pg_xlog directory. Using the timeline history files,
the standby can follow the latest timeline present in the primary
(recovery_target_timeline='latest'), just as it can follow new timelines
appearing in an archive directory.

START_REPLICATION now takes a TIMELINE parameter, to specify exactly which
timeline to stream WAL from. This allows the standby to request the primary
to send over WAL that precedes the promotion. The replication protocol is
changed slightly (in a backwards-compatible way although there's little hope
of streaming replication working across major versions anyway), to allow
replication to stop when the end of timeline reached, putting the walsender
back into accepting a replication command.

Many thanks to Amit Kapila for testing and reviewing various versions of
this patch.

PostgreSQL 9.3 对流复制协议进行了修改, 实现了通过流复制协议实现时间线文件的复制. 非常适合用在角色切换以及多standby的环境.

以前流复制协议并不支持复制时间线文件, 所以每当切换角色后, 都需要手工复制这个文件到standby中.

具体的实现见本文参考部分.

[测试]

一. PostgreSQL 9.2 : 

1.建立standby

主库参数 : 

$PGDATA : /pgdata1919
no other tablespace.

postgresql.conf 

listen_addresses = '0.0.0.0'            # what IP address(es) to listen on;
port = 1919                             # (change requires restart)
max_connections = 100                   # (change requires restart)
superuser_reserved_connections = 13     # (change requires restart)
unix_socket_directory = '.'             # (change requires restart)
unix_socket_permissions = 0700          # begin with 0 to use octal notation
shared_buffers = 1024MB                 # min 128kB
maintenance_work_mem = 512MB            # min 1MB
wal_level = hot_standby                 # minimal, archive, or hot_standby
synchronous_commit = off                # synchronization level;
wal_sync_method = fdatasync             # the default is the first option
wal_buffers = 16384kB                   # min 32kB, -1 sets based on shared_buffers
wal_writer_delay = 10ms         # 1-10000 milliseconds
checkpoint_segments = 32                # in logfile segments, min 1, 16MB each
archive_mode = on               # allows archiving to be done
archive_command = '/bin/date'           # command to use to archive a logfile segment
max_wal_senders = 32            # max number of walsender processes
wal_keep_segments = 64          # in logfile segments, 16MB each; 0 disables
hot_standby = on                        # "on" allows queries during recovery
max_standby_archive_delay = 300s        # max delay before canceling queries
max_standby_streaming_delay = 300s      # max delay before canceling queries
wal_receiver_status_interval = 1s       # send replies at least this often
hot_standby_feedback = on               # send info from standby to prevent
random_page_cost = 2.0                  # same scale as above
effective_cache_size = 8192MB
log_destination = 'csvlog'              # Valid values are combinations of
logging_collector = on          # Enable capturing of stderr and csvlog
log_directory = 'pg_log'                # directory where log files are written,
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log' # log file name pattern,
log_file_mode = 0600                    # creation mode for log files,
log_truncate_on_rotation = on           # If on, an existing log file with the
log_rotation_age = 1d                   # Automatic rotation of logfiles will
log_rotation_size = 10MB                # Automatic rotation of logfiles will
log_checkpoints = on
log_connections = on
log_disconnections = on
log_error_verbosity = verbose           # terse, default, or verbose messages
log_timezone = 'PRC'
autovacuum = on                 # Enable autovacuum subprocess?  'on'
datestyle = 'iso, mdy'
timezone = 'PRC'
lc_messages = 'C'                       # locale for system error message
lc_monetary = 'C'                       # locale for monetary formatting
lc_numeric = 'C'                        # locale for number formatting
lc_time = 'C'                           # locale for time formatting
default_text_search_config = 'pg_catalog.english'
standard_conforming_strings = off

recovery.done 

recovery_target_timeline = 'latest'
standby_mode = on
primary_conninfo = 'host=127.0.0.1 port=11919 user=postgres keepalives_idle=60'         # e.g. 'host=localhost port=5432'

pg_hba.conf 

local   all             all                                     trust
host    all             all             127.0.0.1/32            trust
host    all             all             ::1/128                 trust
local   replication     postgres                                trust
host    replication     postgres        127.0.0.1/32            trust
host all all 0.0.0.0/0 md5

备库参数 :  

$PGDATA : /pgdata11919
no other tablespace.

postgresql.conf 

port = 11919                             # (change requires restart)
# 其他与primary配置相同

recovery.conf 

recovery_target_timeline = 'latest'
standby_mode = on
primary_conninfo = 'host=127.0.0.1 port=1919 user=postgres keepalives_idle=60'         # e.g. 'host=localhost port=5432'

pg_hba.conf 

local   all             all                                     trust
host    all             all             127.0.0.1/32            trust
host    all             all             ::1/128                 trust
local   replication     postgres                                trust
host    replication     postgres        127.0.0.1/32            trust
host all all 0.0.0.0/0 md5

启动主库和备库后, 确定正常复制.

pg_ctl start -D /pgdata1919

pg_ctl start -D /pgdata11919

ps -ewf|grep pg92 

pg92     11644     1  0 15:27 pts/1    00:00:00 /opt/pgsql9.2.4/bin/postgres
pg92     11645 11644  0 15:27 ?        00:00:00 postgres: logger process
pg92     11647 11644  0 15:27 ?        00:00:00 postgres: checkpointer process
pg92     11648 11644  0 15:27 ?        00:00:00 postgres: writer process
pg92     11649 11644  0 15:27 ?        00:00:00 postgres: wal writer process
pg92     11650 11644  0 15:27 ?        00:00:00 postgres: autovacuum launcher process
pg92     11651 11644  0 15:27 ?        00:00:00 postgres: archiver process
pg92     11652 11644  0 15:27 ?        00:00:00 postgres: stats collector process
pg92     11658     1  0 15:27 pts/1    00:00:00 /opt/pgsql9.2.4/bin/postgres -D /pgdata11919
pg92     11659 11658  0 15:27 ?        00:00:00 postgres: logger process
pg92     11660 11658  0 15:27 ?        00:00:00 postgres: startup process   recovering 0000000100000001000000A1
pg92     11661 11658  0 15:27 ?        00:00:00 postgres: checkpointer process
pg92     11662 11658  0 15:27 ?        00:00:00 postgres: writer process
pg92     11663 11658  0 15:27 ?        00:00:00 postgres: stats collector process
pg92     11729 11658  0 15:28 ?        00:00:00 postgres: wal receiver process   streaming 1/A10245E0
pg92     11730 11644  0 15:28 ?        00:00:00 postgres: wal sender process postgres 127.0.0.1(61278) streaming 1/A10245E0

2.正常关闭primary 

pg_ctl stop -m fast -D /pgdata1919

3.promote standby 

pg92@db-172-16-3-33-> pg_ctl promote -D /pgdata11919
server promoting

4.将primary改成standby启动 

pg92@db-172-16-3-33-> cd /pgdata1919
pg92@db-172-16-3-33-> mv recovery.done recovery.conf
pg92@db-172-16-3-33-> pg_ctl start -D /pgdata1919
server starting

查看日志 

cd /pgdata1919/pg_log
2013-05-08 15:32:05.887 CST,,,11840,,5189ff75.2e40,1,,2013-05-08 15:32:05 CST,,0,FATAL,XX000,"timeline 2 of the primary does not match recovery target timeline 1",,,,,,,,"libpqrcv_connect, libpqwalreceiver.c:154",""

需要手工将时间线文件拷贝到pg_xlog中. 

pg92@db-172-16-3-33-> cp /pgdata11919/pg_xlog/00000002.history /pgdata1919/pg_xlog/

再次查看日志, 正常复制 

2013-05-08 15:33:20.884 CST,,,11763,,5189ff39.2df3,5,,2013-05-08 15:31:05 CST,1/0,0,LOG,00000,"new target timeline is 2",,,,,,,,"rescanLatestTimeLine, xlog.c:4644",""
2013-05-08 15:33:21.177 CST,,,11876,,5189ffc0.2e64,1,,2013-05-08 15:33:20 CST,,0,LOG,00000,"streaming replication successfully connected to primary",,,,,,,,"libpqrcv_connect, libpqwalreceiver.c:171",""
2013-05-08 15:33:21.372 CST,,,11763,,5189ff39.2df3,6,,2013-05-08 15:31:05 CST,1/0,0,LOG,00000,"redo starts at 1/A2000080",,,,,,,,"StartupXLOG, xlog.c:6817",""

二. PostgreSQL 9.3 : 

1.建立standby

主库参数 : 

$PGDATA : /pgdata1999
no other tablespace.

postgresql.conf 

listen_addresses = '0.0.0.0'            # what IP address(es) to listen on;
port = 1999                             # (change requires restart)
max_connections = 100                   # (change requires restart)
superuser_reserved_connections = 13     # (change requires restart)
unix_socket_directories = '.'   # comma-separated list of directories
unix_socket_permissions = 0700          # begin with 0 to use octal notation
tcp_keepalives_idle = 60                # TCP_KEEPIDLE, in seconds;
tcp_keepalives_interval = 60            # TCP_KEEPINTVL, in seconds;
tcp_keepalives_count = 60               # TCP_KEEPCNT;
shared_buffers = 1024MB                 # min 128kB
maintenance_work_mem = 512MB            # min 1MB
max_stack_depth = 8MB                   # min 100kB
wal_level = hot_standby                 # minimal, archive, or hot_standby
synchronous_commit = off                # synchronization level;
wal_sync_method = fdatasync             # the default is the first option
wal_buffers = 16384kB                   # min 32kB, -1 sets based on shared_buffers
wal_writer_delay = 10ms         # 1-10000 milliseconds
commit_delay = 10                       # range 0-100000, in microseconds
commit_siblings = 5                     # range 1-1000
checkpoint_segments = 32                # in logfile segments, min 1, 16MB each
archive_mode = on               # allows archiving to be done
archive_command = '/bin/date'           # command to use to archive a logfile segment
max_wal_senders = 32            # max number of walsender processes
wal_keep_segments = 64          # in logfile segments, 16MB each; 0 disables
hot_standby = on                        # "on" allows queries during recovery
max_standby_archive_delay = 300s        # max delay before canceling queries
max_standby_streaming_delay = 300s      # max delay before canceling queries
wal_receiver_status_interval = 1s       # send replies at least this often
hot_standby_feedback = on               # send info from standby to prevent
random_page_cost = 2.0                  # same scale as above
effective_cache_size = 8192MB
log_destination = 'csvlog'              # Valid values are combinations of
logging_collector = on          # Enable capturing of stderr and csvlog
log_directory = 'pg_log'                # directory where log files are written,
log_filename = 'postgresql-%Y-%m-%d_%H%M%S.log' # log file name pattern,
log_file_mode = 0600                    # creation mode for log files,
log_truncate_on_rotation = on           # If on, an existing log file with the
log_rotation_age = 1d                   # Automatic rotation of logfiles will
log_rotation_size = 10MB                # Automatic rotation of logfiles will
client_min_messages = notice            # values in order of decreasing detail:
log_checkpoints = on
log_connections = on
log_disconnections = on
log_error_verbosity = verbose           # terse, default, or verbose messages
log_timezone = 'PRC'
autovacuum = on                 # Enable autovacuum subprocess?  'on'
datestyle = 'iso, mdy'
timezone = 'PRC'
lc_messages = 'en_US.utf8'                      # locale for system error message
lc_monetary = 'en_US.utf8'                      # locale for monetary formatting
lc_numeric = 'en_US.utf8'                       # locale for number formatting
lc_time = 'en_US.utf8'                          # locale for time formatting
default_text_search_config = 'pg_catalog.english'

recovery.done 

recovery_target_timeline = 'latest'
standby_mode = on
primary_conninfo = 'host=127.0.0.1 port=11999 user=postgres keepalives_idle=60'         # e.g. 'host=localhost port=5432'

pg_hba.conf 

local   all             all                                     trust
host    all             all             127.0.0.1/32            trust
host    all             all             ::1/128                 trust
local   replication     postgres                                trust
host    replication     postgres        127.0.0.1/32            trust
host all all 0.0.0.0/0 md5

备库参数 :  

$PGDATA : /pgdata11999
no other tablespace.

postgresql.conf 

port = 11999                             # (change requires restart)
# 其他与primary配置相同

recovery.conf 

recovery_target_timeline = 'latest'
standby_mode = on
primary_conninfo = 'host=127.0.0.1 port=1999 user=postgres keepalives_idle=60'          # e.g. 'host=localhost port=5432'

pg_hba.conf 

local   all             all                                     trust
host    all             all             127.0.0.1/32            trust
host    all             all             ::1/128                 trust
local   replication     postgres                                trust
host    replication     postgres        127.0.0.1/32            trust
host all all 0.0.0.0/0 md5

启动主库和备库后, 确定正常复制.

pg_ctl start -D /pgdata1999

pg_ctl start -D /pgdata11999

ps -ewf|grep pg93 

pg93     12122     1  0 15:39 pts/1    00:00:00 /opt/pgsql9.3/bin/postgres
pg93     12123 12122  0 15:39 ?        00:00:00 postgres: logger process
pg93     12125 12122  0 15:39 ?        00:00:00 postgres: checkpointer process
pg93     12126 12122  0 15:39 ?        00:00:00 postgres: writer process
pg93     12127 12122  0 15:39 ?        00:00:00 postgres: wal writer process
pg93     12128 12122  0 15:39 ?        00:00:00 postgres: autovacuum launcher process
pg93     12129 12122  0 15:39 ?        00:00:00 postgres: archiver process
pg93     12130 12122  0 15:39 ?        00:00:00 postgres: stats collector process
pg93     12135     1  0 15:39 pts/1    00:00:00 /opt/pgsql9.3/bin/postgres -D /pgdata11999
pg93     12136 12135  0 15:39 ?        00:00:00 postgres: logger process
pg93     12137 12135  0 15:39 ?        00:00:00 postgres: startup process   recovering 000000010000000200000050
pg93     12138 12135  0 15:39 ?        00:00:00 postgres: checkpointer process
pg93     12139 12135  0 15:39 ?        00:00:00 postgres: writer process
pg93     12140 12135  0 15:39 ?        00:00:00 postgres: stats collector process
pg93     12141 12135  0 15:39 ?        00:00:00 postgres: wal receiver process
pg93     12142 12122  0 15:39 ?        00:00:00 postgres: wal sender process postgres 127.0.0.1(9639) streaming 2/50000090

2.正常关闭primary 

pg93@db-172-16-3-33-> pg_ctl stop -m fast -D /pgdata1999
waiting for server to shut down.... done
server stopped

3.promote standby 

pg93@db-172-16-3-33-> pg_ctl promote -D /pgdata11999
server promoting

4.将primary改成standby启动 

pg93@db-172-16-3-33-> cd /pgdata1999
pg93@db-172-16-3-33-> mv recovery.done recovery.conf
pg93@db-172-16-3-33-> pg_ctl start
server starting

查看日志, 时间线文件已经自动获取了. 

pg93@db-172-16-3-33-> cd pg_log
2013-05-08 15:43:07.089 CST,,,12196,,518a020b.2fa4,1,,2013-05-08 15:43:07 CST,,0,LOG,00000,"database system was shut down at 2013-05-08 15:42:38 CST",,,,,,,,"StartupXLOG, xlog.c:4885",""
2013-05-08 15:43:07.089 CST,,,12196,,518a020b.2fa4,2,,2013-05-08 15:43:07 CST,,0,LOG,00000,"entering standby mode",,,,,,,,"StartupXLOG, xlog.c:4958",""
2013-05-08 15:43:07.098 CST,,,12196,,518a020b.2fa4,3,,2013-05-08 15:43:07 CST,1/0,0,LOG,00000,"consistent recovery state reached at 2/51000090",,,,,,,,"CheckRecoveryConsistency, xlog.c:6175",""
2013-05-08 15:43:07.098 CST,,,12196,,518a020b.2fa4,4,,2013-05-08 15:43:07 CST,1/0,0,LOG,00000,"record with zero length at 2/51000090",,,,,,,,"ReadRecord, xlog.c:3283",""
2013-05-08 15:43:07.099 CST,,,12194,,518a020a.2fa2,1,,2013-05-08 15:43:06 CST,,0,LOG,00000,"database system is ready to accept read only connections",,,,,,,,"sigusr1_handler, postmaster.c:4656",""
2013-05-08 15:43:07.102 CST,,,12200,,518a020b.2fa8,1,,2013-05-08 15:43:07 CST,,0,LOG,00000,"fetching timeline history file for timeline 2 from primary server",,,,,,,,"WalRcvFetchTimeLineHistoryFiles, walreceiver.c:660",""
2013-05-08 15:43:07.128 CST,,,12200,,518a020b.2fa8,2,,2013-05-08 15:43:07 CST,,0,LOG,00000,"started streaming WAL from primary at 2/51000000 on timeline 1",,,,,,,,"WalReceiverMain, walreceiver.c:365",""
2013-05-08 15:43:07.128 CST,,,12200,,518a020b.2fa8,3,,2013-05-08 15:43:07 CST,,0,LOG,00000,"replication terminated by primary server","End of WAL reached on timeline 1 at 2/51000090",,,,,,,"WalReceiverMain, walreceiver.c:438",""
2013-05-08 15:43:07.128 CST,,,12196,,518a020b.2fa4,5,,2013-05-08 15:43:07 CST,1/0,0,LOG,00000,"new target timeline is 2",,,,,,,,"rescanLatestTimeLine, xlog.c:3455",""
2013-05-08 15:43:07.128 CST,,,12200,,518a020b.2fa8,4,,2013-05-08 15:43:07 CST,,0,LOG,00000,"restarted WAL streaming at 2/51000000 on timeline 2",,,,,,,,"WalReceiverMain, walreceiver.c:370",""
2013-05-08 15:43:07.303 CST,,,12196,,518a020b.2fa4,6,,2013-05-08 15:43:07 CST,1/0,0,LOG,00000,"redo starts at 2/51000090",,,,,,,,"StartupXLOG, xlog.c:5524",""

数据库进程正常 

pg93     12135     1  0 15:39 pts/1    00:00:00 /opt/pgsql9.3/bin/postgres -D /pgdata11999
pg93     12136 12135  0 15:39 ?        00:00:00 postgres: logger process
pg93     12138 12135  0 15:39 ?        00:00:00 postgres: checkpointer process
pg93     12139 12135  0 15:39 ?        00:00:00 postgres: writer process
pg93     12140 12135  0 15:39 ?        00:00:00 postgres: stats collector process
pg93     12179 12135  0 15:42 ?        00:00:00 postgres: wal writer process
pg93     12180 12135  0 15:42 ?        00:00:00 postgres: autovacuum launcher process
pg93     12181 12135  0 15:42 ?        00:00:00 postgres: archiver process   last was 00000002.history
pg93     12194     1  0 15:43 pts/1    00:00:00 /opt/pgsql9.3/bin/postgres
pg93     12195 12194  0 15:43 ?        00:00:00 postgres: logger process
pg93     12196 12194  0 15:43 ?        00:00:00 postgres: startup process   recovering 000000020000000200000051
pg93     12197 12194  0 15:43 ?        00:00:00 postgres: checkpointer process
pg93     12198 12194  0 15:43 ?        00:00:00 postgres: writer process
pg93     12199 12194  0 15:43 ?        00:00:00 postgres: stats collector process
pg93     12200 12194  0 15:43 ?        00:00:00 postgres: wal receiver process   streaming 2/5100EC10
pg93     12201 12135  0 15:43 ?        00:00:00 postgres: wal sender process postgres 127.0.0.1(61597) streaming 2/5100EC10
pg93     12211 12135  0 15:43 ?        00:00:00 postgres: autovacuum worker process   postgres

[参考]
1. http://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=abfd192b1b5ba5216ac4b1f31dcd553106304b19

2. http://www.postgresql.org/docs/devel/static/protocol-replication.html

流复制协议新增了TIMELINE_HISTORY 命令, 同时对START_REPLICATION命令做了修改支持TIMELINE参数. 

TIMELINE_HISTORY tli
Requests the server to send over the timeline history file for timeline tli. Server replies with a result set of a single row, containing two fields:

filename
Filename of the timeline history file, e.g 00000002.history.

content
Contents of the timeline history file.

START_REPLICATION XXX/XXX TIMELINE tli

3. src/backend/replication/walreceiver.c 

+           ereport(LOG,
+                   (errmsg("fetching timeline history file for timeline %u from primary server",
+                           tli)));
时间： 2024-10-26 05:51:21

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背景 为了降低备份对数据库的性能影响,我们在有standby的情况下,可以选择从standby备份PostgreSQL. pg_rman是一个备份工具,同样支持从standby备份数据库,但是有一些使用的注意事项. 例如需要连接主库,需要能读取归档目录,需要告诉主库和备库的连接地址,需要备库的$PGDATA等等. 为什么既要连接主库,还要能力连接备库. pg_rman需要连接到主库执行pg_start_backup,pg_stop_backup. 同时需要连接到standby数据库查看pg_la