PolarDB for PostgreSQL 备份并恢复一个 Standby 节点

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PolarDB for PostgreSQL 备份并恢复一个 Standby 节点

基础备份也可以用于搭建一个新的 Standby 节点。如下图所示，Standby 节点与 Primary / Replica 节点各自使用独立的共享存储，与 Primary 节点使用物理复制保持同步。Standby 节点可用于作为主共享存储的灾备。

PFS 文件系统格式化和挂载

假设此时用于部署 Standby 计算节点的机器已经准备好用于后备的共享存储 nvme2n1：

$ lsblk

NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT

nvme0n1 259:1 0 40G 0 disk

└─nvme0n1p1 259:2 0 40G 0 part /etc/hosts

nvme2n1 259:3 0 70G 0 disk

nvme1n1 259:0 0 60G 0 disk

将这个共享存储格式化为 PFS 格式，并启动 PFSD 守护进程挂载到 PFS 文件系统：

sudo pfs -C disk mkfs nvme2n1

sudo /usr/local/polarstore/pfsd/bin/start_pfsd.sh -p nvme2n1 -w 2

备份数据到本地存储和共享存储

在用于部署 Standby 节点的机器上执行备份，以 ~/standby 作为本地数据目录，以 /nvme2n1/shared_data 作为共享存储目录：

polar_basebackup \

--host=[Primary节点所在IP] \

--port=[Primary节点所在端口号] \

-D /home/postgres/standby \

--polardata=/nvme2n1/shared_data/ \

--polar_storage_cluster_name=disk \

--polar_disk_name=nvme2n1 \

--polar_host_id=3 \

-X stream --progress --write-recovery-conf -v

将会看到如下输出。其中，除了 polar_basebackup 的输出以外，还有 PFS 的输出日志：

[PFSD_SDK INF Jan 11 10:11:27.247112][99]pfs_mount_prepare 103: begin prepare mount cluster(disk), PBD(nvme2n1), hostid(3),flags(0x13)

[PFSD_SDK INF Jan 11 10:11:27.247161][99]pfs_mount_prepare 165: pfs_mount_prepare success for nvme2n1 hostid 3

[PFSD_SDK INF Jan 11 10:11:27.293900][99]chnl_connection_poll_shm 1238: ack data update s_mount_epoch 1

[PFSD_SDK INF Jan 11 10:11:27.293912][99]chnl_connection_poll_shm 1266: connect and got ack data from svr, err = 0, mntid 0

[PFSD_SDK INF Jan 11 10:11:27.293979][99]pfsd_sdk_init 191: pfsd_chnl_connect success

[PFSD_SDK INF Jan 11 10:11:27.293987][99]pfs_mount_post 208: pfs_mount_post err : 0

[PFSD_SDK ERR Jan 11 10:11:27.297257][99]pfsd_opendir 1437: opendir /nvme2n1/shared_data/ error: No such file or directory

[PFSD_SDK INF Jan 11 10:11:27.297396][99]pfsd_mkdir 1320: mkdir /nvme2n1/shared_data

polar_basebackup: initiating base backup, waiting for checkpoint to complete

WARNING: a labelfile "/nvme1n1/shared_data//polar_non_exclusive_backup_label" is already on disk

HINT: POLAR: we overwrite it

polar_basebackup: checkpoint completed

polar_basebackup: write-ahead log start point: 0/16C91F8 on timeline 1

polar_basebackup: starting background WAL receiver

polar_basebackup: created temporary replication slot "pg_basebackup_373"

...

[PFSD_SDK INF Jan 11 10:11:32.992005][99]pfsd_open 539: open /nvme2n1/shared_data/polar_non_exclusive_backup_label with inode 6325, fd 0

[PFSD_SDK INF Jan 11 10:11:32.993074][99]pfsd_open 539: open /nvme2n1/shared_data/global/pg_control with inode 8373, fd 0

851396/851396 kB (100%), 2/2 tablespaces

polar_basebackup: write-ahead log end point: 0/16C9300

polar_basebackup: waiting for background process to finish streaming ...

polar_basebackup: base backup completed

[PFSD_SDK INF Jan 11 10:11:52.378220][99]pfsd_umount_force 247: pbdname nvme2n1

[PFSD_SDK INF Jan 11 10:11:52.378229][99]pfs_umount_prepare 269: pfs_umount_prepare. pbdname:nvme2n1

[PFSD_SDK INF Jan 11 10:11:52.404010][99]chnl_connection_release_shm 1164: client umount return : deleted /var/run/pfsd//nvme2n1/99.pid

[PFSD_SDK INF Jan 11 10:11:52.404171][99]pfs_umount_post 281: pfs_umount_post. pbdname:nvme2n1

[PFSD_SDK INF Jan 11 10:11:52.404174][99]pfsd_umount_force 261: umount success for nvme2n1

上述命令会在当前机器的本地存储上备份 Primary 节点的本地数据目录，在参数指定的共享存储目录上备份共享数据目录。

重新配置 Standby 节点

重新编辑 Standby 节点的配置文件 ~/standby/postgresql.conf：

-polar_hostid=1

+polar_hostid=3

-polar_disk_name='nvme1n1'

-polar_datadir='/nvme1n1/shared_data/'

+polar_disk_name='nvme2n1'

+polar_datadir='/nvme2n1/shared_data/'

-synchronous_standby_names='replica1'

在 Standby 节点的复制配置文件 ~/standby/recovery.conf 中添加：

+recovery_target_timeline = 'latest'

+primary_slot_name = 'standby1'

Standby 节点启动

在 Primary 节点上创建用于与 Standby 进行物理复制的复制槽：

$ psql \

--host=[Primary节点所在IP] --port=5432 \

-d postgres \

-c "SELECT * FROM pg_create_physical_replication_slot('standby1');"

slot_name | lsn

-----------+-----

standby1 |

(1 row)

启动 Standby 节点：

pg_ctl -D $HOME/standby start

Standby 节点验证

在 Primary 节点上创建表并插入数据，在 Standby 节点上可以查询到数据：

$ psql -q \

-h [Primary节点所在IP] \

-p 5432 \

-d postgres \

-c "CREATE TABLE t (t1 INT PRIMARY KEY, t2 INT); INSERT INTO t VALUES (1, 1),(2, 3),(3, 3);"

$ psql -q \

-h [Standby节点所在IP] \

-p 5432 \

-d postgres \

-c "SELECT * FROM t;"

t1 | t2

----+----

1 | 1

2 | 3

3 | 3

(3 rows)