作者：张乾
外星人2号，现兼任六位喵星人的资深铲屎官。
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手滑误删了数据文件，并且没有可替换的节点时，先别急着提桶跑路，可以考虑利用参数 server_permanent_offline_time 来重建受影响的节点。
原理：
server_permanent_offline_time 是 OceanBase 数据库中用于控制节点永久下线时长的参数。当集群中的某个节点宕机后，系统会根据该参数的设置值来进行相应操作。
如果节点宕机时间小于该参数设置的值，系统会暂时不做处理，以避免频繁的数据迁移；如果宕机时间超过该参数设置的值，该节点被标记为永久下线，RootService 会将该 OBServer 上包含的数据副本从 Paxos 成员组中删除，并在同 zone 内其他可用 OBServer 上补充数据，以保证数据副本 Paxos 成员组完整。该参数默认值是 3600 秒，一般设置较大，以避免不必要的副本复制。此外，当永久下线的节点重新被拉起后，其上的全部数据都需要从其他副本重新拉取。
在本场景下，即是通过调低该参数，让故障节点快速永久下线再重新上线，达到数据重建的目的。
请注意，此过程会占用集群一定的资源，可能会影响性能，因此建议在业务低峰期进行。
官方建议
关于 server_permanent_offline_time 的适用场景和建议值，官方提供如下:
- OceanBase 数据库版本升级场景：建议将该配置项的值设置为72h。
- OBServer 硬件更换场景：建议将该配置项的值设置为4h。
- OBServer 清空上线场景：建议将该配置项的值设置为10m，使集群快速上线。
准备过程
预备一套环境
使用OBD工具快速部署一套3节点OB以及一个OBProxy，再创建好一个租户sysbench_tenant，primary_zone为RANDOM。
注：本文基于OB 3.1.2版本，其他版本需注意另作验证。
准备些数据
使用 sysbench 创建一个表 sbtest1 并插入1W数据。
sysbench ./oltp_insert.lua --mysql-host=10.186.60.3 --mysql-port=2883 --mysql-db=sysbenchdb --mysql-user="sysbench@sysbench_tenant" --mysql-password=sysbench --tables=1 --table_size=10000 --threads=1 --time=600 --report-interval=10 --db-driver=mysql --db-ps-mode=disable --skip-trx=on --mysql-ignore-errors=6002,6004,4012,2013,4016,1062,5157,4038 prepare
这里改写了 sysbench 的建表语句，分了3个区，查询 sbtest1 表分区副本分布如下
MySQL [oceanbase]> select tenant.tenant_name, zone, svr_ip,svr_port, case when role=1 then 'leader' when role=2 then 'follower' else NULL end as role, count(1) as partition_cnt from __all_virtual_meta_table meta inner join __all_tenant tenant on meta.tenant_id=tenant.tenant_id inner join __all_virtual_table tab on meta.tenant_id=tab.tenant_id and meta.table_id=tab.table_id where tenant.tenant_id=1001 and tab.table_name='sbtest1' group by tenant.tenant_name,zone, svr_ip,svr_port, 5 order by tenant.tenant_name, zone, svr_ip, role desc;
+-----------------+-------+--------------+----------+----------+---------------+
| tenant_name | zone | svr_ip | svr_port | role | partition_cnt |
+-----------------+-------+--------------+----------+----------+---------------+
| sysbench_tenant | zone1 | 10.186.64.74 | 2882 | leader | 1 |
| sysbench_tenant | zone1 | 10.186.64.74 | 2882 | follower | 2 |
| sysbench_tenant | zone2 | 10.186.64.75 | 2882 | leader | 1 |
| sysbench_tenant | zone2 | 10.186.64.75 | 2882 | follower | 2 |
| sysbench_tenant | zone3 | 10.186.64.79 | 2882 | leader | 1 |
| sysbench_tenant | zone3 | 10.186.64.79 | 2882 | follower | 2 |
+-----------------+-------+--------------+----------+----------+---------------+开始实验
使用 sysbench 持续写入数据，维持一定的流量，便于在节点重建后对比各节点数据是否一致。
sysbench ./oltp_insert.lua --mysql-host=10.186.60.3 --mysql-port=2883 --mysql-db=sysbenchdb --mysql-user="sysbench@sysbench_tenant" --mysql-password=sysbench --tables=1 --table_size=10000 --threads=1 --time=300 --report-interval=10 --db-driver=mysql --db-ps-mode=disable --skip-trx=on --mysql-ignore-errors=6002,6004,4012,2013,4016,1062,5157,4038 run删除某节点的数据文件
选择zone3下的10.186.64.79节点，将数据文件删除。
[root@localhost data]# rm -rf 1/sstable/block_file
[root@localhost data]# cd 1/sstable/
[root@localhost sstable]# ll
total 0永久下线故障节点
1.调小参数 server_permanent_offline_time ，缩短节点永久下线时间
server_permanent_offline_time 默认值为3600s
MySQL [oceanbase]> alter system set server_permanent_offline_time='60s';
Query OK, 0 rows affected (0.030 sec)
MySQL [oceanbase]> SHOW PARAMETERS LIKE "%server_permanent_offline_time%";
+-------+----------+--------------+----------+-------------------------------+-----------+-------+-----------------------------------------------------------------------------------------------------------------------------------+--------------+---------+---------+-------------------+
| zone | svr_type | svr_ip | svr_port | name | data_type | value | info | section | scope | source | edit_level |
+-------+----------+--------------+----------+-------------------------------+-----------+-------+-----------------------------------------------------------------------------------------------------------------------------------+--------------+---------+---------+-------------------+
| zone3 | observer | 10.186.64.79 | 2882 | server_permanent_offline_time | NULL | 60s | the time interval between any two heartbeats beyond which a server is considered to be \'permanently\' offline. Range: [20s,+∞) | ROOT_SERVICE | CLUSTER | DEFAULT | DYNAMIC_EFFECTIVE |
| zone1 | observer | 10.186.64.74 | 2882 | server_permanent_offline_time | NULL | 60s | the time interval between any two heartbeats beyond which a server is considered to be \'permanently\' offline. Range: [20s,+∞) | ROOT_SERVICE | CLUSTER | DEFAULT | DYNAMIC_EFFECTIVE |
| zone2 | observer | 10.186.64.75 | 2882 | server_permanent_offline_time | NULL | 60s | the time interval between any two heartbeats beyond which a server is considered to be \'permanently\' offline. Range: [20s,+∞) | ROOT_SERVICE | CLUSTER | DEFAULT | DYNAMIC_EFFECTIVE |
+-------+----------+--------------+----------+-------------------------------+-----------+-------+-----------------------------------------------------------------------------------------------------------------------------------+--------------+---------+---------+-------------------+2.停止故障节点对外提供服务
在kill ob进程前，建议使用隔离(ISOLATE SERVER)或者停止(STOP SERVER)节点的命令，停掉发往该节点的请求，转移副本leader角色。在节点重建恢复后，再开启流量。
# 停掉79节点服务
MySQL [oceanbase]> ALTER SYSTEM STOP SERVER '10.186.64.79:2882' ZONE='zone3';
# 或者隔离
ALTER SYSTEM ISOLATE SERVER '10.186.64.79:2882' ZONE='zone3';3.kill observer进程
执行kill -9 $observer_pid，等待 server_permanent_offline_time 的时间，该ob进入"永久下线”状态。判断ob是否已经永久下线，可以查询表 __all_rootservice_event_history，存在名为 "permanent_offline "的event记录，确认时间和ip都一致后，即可认为ob已经永久下线。
MySQL [oceanbase]> select * from __all_rootservice_event_history where event='permanent_offline' ;
+----------------------------+--------+-------------------+--------+---------------------+-------+--------+-------+--------+-------+--------+-------+--------+-------+--------+------------+--------------+-------------+
| gmt_create | module | event | name1 | value1 | name2 | value2 | name3 | value3 | name4 | value4 | name5 | value5 | name6 | value6 | extra_info | rs_svr_ip | rs_svr_port |
+----------------------------+--------+-------------------+--------+---------------------+-------+--------+-------+--------+-------+--------+-------+--------+-------+--------+------------+--------------+-------------+
| 2023-03-29 17:34:09.596035 | server | permanent_offline | server | "10.186.64.79:2882" | | | | | | | | | | | | 10.186.64.74 | 2882 |
+----------------------------+--------+-------------------+--------+---------------------+-------+--------+-------+--------+-------+--------+-------+--------+-------+--------+------------+--------------+-------------+查询分区副本分布如下，已不存在79节点的分区副本信息，进一步确认了79节点已永久下线。
zone2下的75节点有一个从副本升级为leader角色，此时集群仍然可以继续对外服务。
MySQL [oceanbase]> select tenant.tenant_name, zone, svr_ip,svr_port, case when role=1 then 'leader' when role=2 then 'follower' else NULL end as role, count(1) as partition_cnt from __all_virtual_meta_table meta inner join __all_tenant tenant on meta.tenant_id=tenant.tenant_id inner join __all_virtual_table tab on meta.tenant_id=tab.tenant_id and meta.table_id=tab.table_id where tenant.tenant_id=1001 and tab.table_name='sbtest1' group by tenant.tenant_name,zone, svr_ip,svr_port, 5 order by tenant.tenant_name, zone, svr_ip, role desc;
+-----------------+-------+--------------+----------+----------+---------------+
| tenant_name | zone | svr_ip | svr_port | role | partition_cnt |
+-----------------+-------+--------------+----------+----------+---------------+
| sysbench_tenant | zone1 | 10.186.64.74 | 2882 | leader | 1 |
| sysbench_tenant | zone1 | 10.186.64.74 | 2882 | follower | 2 |
| sysbench_tenant | zone2 | 10.186.64.75 | 2882 | leader | 2 |
| sysbench_tenant | zone2 | 10.186.64.75 | 2882 | follower | 1 |
+-----------------+-------+--------------+----------+----------+---------------+
4 rows in set (0.005 sec)拉起故障节点，触发数据自动重建
1.启动79节点的ob进程，进程启动后会自动触发重建。
注：防止ob启动失败或存在其他问题，建议启动前将数据文件和事务日志均清空。
[root@localhost data]# rm -rf log1/clog/*
[root@localhost data]# rm -rf log1/ilog/*
[root@localhost data]# rm -rf log1/slog/*
[root@localhost data]# rm -rf 1/sstable/block_file
[root@localhost data]# cd 1/sstable/
[root@localhost sstable]# ll
total 0
[root@localhost sstable]# su admin
bash-4.2$ cd /home/admin/ && ./bin/observer
./bin/observer进程启动后，确认ob心跳恢复状态为active，然后查看分区正在不断补足中
MySQL [oceanbase]> select svr_ip,zone,with_rootserver,status,stop_time,start_service_time,build_version from __all_server;
+--------------+-------+-----------------+--------+-----------+--------------------+----------------------------------------------------------------------------------------+
| svr_ip | zone | with_rootserver | status | stop_time | start_service_time | build_version |
+--------------+-------+-----------------+--------+-----------+--------------------+----------------------------------------------------------------------------------------+
| 10.186.64.74 | zone1 | 1 | active | 0 | 1679984798650860 | 3.1.2_10000392021123010-d4ace121deae5b81d8f0b40afbc4c02705b7fc1d(Dec 30 2021 02:47:29) |
| 10.186.64.75 | zone2 | 0 | active | 0 | 1679984801289281 | 3.1.2_10000392021123010-d4ace121deae5b81d8f0b40afbc4c02705b7fc1d(Dec 30 2021 02:47:29) |
| 10.186.64.79 | zone3 | 0 | active | 1680082329964975 | 1680082511964975 | 3.1.2_10000392021123010-d4ace121deae5b81d8f0b40afbc4c02705b7fc1d(Dec 30 2021 02:47:29) |
+--------------+-------+-----------------+--------+-----------+--------------------+----------------------------------------------------------------------------------------+
3 rows in set (0.002 sec)
MySQL [oceanbase]> select count(*),zone from gv$partition group by zone;
+----------+-------+
| count(*) | zone |
+----------+-------+
| 1322 | zone1 |
| 1322 | zone2 |
| 152 | zone3 |
+----------+-------+
3 rows in set (0.228 sec)
MySQL [oceanbase]> select count(*),zone from gv$partition group by zone;
+----------+-------+
| count(*) | zone |
+----------+-------+
| 1322 | zone1 |
| 1322 | zone2 |
| 664 | zone3 |
+----------+-------+
3 rows in set (0.113 sec)
MySQL [oceanbase]> select count(*),zone from gv$partition group by zone;
+----------+-------+
| count(*) | zone |
+----------+-------+
| 1322 | zone1 |
| 1322 | zone2 |
| 1179 | zone3 |
+----------+-------+
3 rows in set (0.112 sec)
MySQL [oceanbase]> select count(*),zone from gv$partition group by zone;
+----------+-------+
| count(*) | zone |
+----------+-------+
| 1322 | zone1 |
| 1322 | zone2 |
| 1322 | zone3 |
+----------+-------+
3 rows in set (0.116 sec)当3个zone内的分区个数一致后，同时查看zone3已存在副本信息，认为重建完毕。
由于79节点处于隔离状态，所以还没有leader副本。
MySQL [oceanbase]> select tenant.tenant_name, zone, svr_ip,svr_port, case when role=1 then 'leader' when role=2 then 'follower' else NULL end as role, count(1) as partition_cnt from __all_virtual_meta_table meta inner join __all_tenant tenant on meta.tenant_id=tenant.tenant_id inner join __all_virtual_table tab on meta.tenant_id=tab.tenant_id and meta.table_id=tab.table_id where tenant.tenant_id=1001 and tab.table_name='sbtest1' group by tenant.tenant_name,zone, svr_ip,svr_port, 5 order by tenant.tenant_name, zone, svr_ip, role desc;
+-----------------+-------+--------------+----------+----------+---------------+
| tenant_name | zone | svr_ip | svr_port | role | partition_cnt |
+-----------------+-------+--------------+----------+----------+---------------+
| sysbench_tenant | zone1 | 10.186.64.74 | 2882 | leader | 1 |
| sysbench_tenant | zone1 | 10.186.64.74 | 2882 | follower | 2 |
| sysbench_tenant | zone2 | 10.186.64.75 | 2882 | leader | 2 |
| sysbench_tenant | zone2 | 10.186.64.75 | 2882 | follower | 1 |
| sysbench_tenant | zone3 | 10.186.64.79 | 2882 | follower | 3 |
+-----------------+-------+--------------+----------+----------+---------------+
6 rows in set (0.005 sec)2.开启故障节点服务
执行命令解除79节点的隔离状态。
ALTER SYSTEM START SERVER '10.186.64.79:2882' ZONE='zone3';查询分区副本分布如下，leader角色已迁回79节点。
MySQL [oceanbase]> select tenant.tenant_name, zone, svr_ip,svr_port, case when role=1 then 'leader' when role=2 then 'follower' else NULL end as role, count(1) as partition_cnt from __all_virtual_meta_table meta inner join __all_tenant tenant on meta.tenant_id=tenant.tenant_id inner join __all_virtual_table tab on meta.tenant_id=tab.tenant_id and meta.table_id=tab.table_id where tenant.tenant_id=1001 and tab.table_name='sbtest1' group by tenant.tenant_name,zone, svr_ip,svr_port, 5 order by tenant.tenant_name, zone, svr_ip, role desc;
+-----------------+-------+--------------+----------+----------+---------------+
| tenant_name | zone | svr_ip | svr_port | role | partition_cnt |
+-----------------+-------+--------------+----------+----------+---------------+
| sysbench_tenant | zone1 | 10.186.64.74 | 2882 | leader | 1 |
| sysbench_tenant | zone1 | 10.186.64.74 | 2882 | follower | 2 |
| sysbench_tenant | zone2 | 10.186.64.75 | 2882 | leader | 1 |
| sysbench_tenant | zone2 | 10.186.64.75 | 2882 | follower | 2 |
| sysbench_tenant | zone3 | 10.186.64.79 | 2882 | leader | 1 |
| sysbench_tenant | zone3 | 10.186.64.79 | 2882 | follower | 2 |
+-----------------+-------+--------------+----------+----------+---------------+3.把server_permanent_offline_time参数的预知重新设置为默认的3600s
MySQL [oceanbase]> alter system set server_permanent_offline_time='3600s';
Query OK, 0 rows affected (0.028 sec)
MySQL [oceanbase]> SHOW PARAMETERS LIKE "%server_permanent_offline_time%";
+-------+----------+--------------+----------+-------------------------------+-----------+-------+-----------------------------------------------------------------------------------------------------------------------------------+--------------+---------+---------+-------------------+
| zone | svr_type | svr_ip | svr_port | name | data_type | value | info | section | scope | source | edit_level |
+-------+----------+--------------+----------+-------------------------------+-----------+-------+-----------------------------------------------------------------------------------------------------------------------------------+--------------+---------+---------+-------------------+
| zone2 | observer | 10.186.64.75 | 2882 | server_permanent_offline_time | NULL | 3600s | the time interval between any two heartbeats beyond which a server is considered to be \'permanently\' offline. Range: [20s,+∞) | ROOT_SERVICE | CLUSTER | DEFAULT | DYNAMIC_EFFECTIVE |
| zone1 | observer | 10.186.64.74 | 2882 | server_permanent_offline_time | NULL | 3600s | the time interval between any two heartbeats beyond which a server is considered to be \'permanently\' offline. Range: [20s,+∞) | ROOT_SERVICE | CLUSTER | DEFAULT | DYNAMIC_EFFECTIVE |
| zone3 | observer | 10.186.64.79 | 2882 | server_permanent_offline_time | NULL | 3600s | the time interval between any two heartbeats beyond which a server is considered to be \'permanently\' offline. Range: [20s,+∞) | ROOT_SERVICE | CLUSTER | DEFAULT | DYNAMIC_EFFECTIVE |
+-------+----------+--------------+----------+-------------------------------+-----------+-------+-----------------------------------------------------------------------------------------------------------------------------------+--------------+---------+---------+-------------------+
3 rows in set (0.007 sec)校验各ob节点数据量
sysbench已运行结束，直连各observer，校验数据量是一致的。
[root@localhost ~]# obclient -h10.186.64.74 -P2881 -usysbench@sysbench_tenant -Dsysbenchdb -A -psysbench
Welcome to the OceanBase. Commands end with ; or \g.
Your MySQL connection id is 3221545401
Server version: 5.7.25 OceanBase 3.1.2 (r10000392021123010-d4ace121deae5b81d8f0b40afbc4c02705b7fc1d) (Built Dec 30 2021 02:47:29)
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MySQL [sysbenchdb]> select count(*) from sbtest1;
+----------+
| count(*) |
+----------+
| 53195 |
+----------+
1 row in set (0.036 sec)
MySQL [sysbenchdb]> exit
Bye
[root@localhost ~]# obclient -h10.186.64.75 -P2881 -usysbench@sysbench_tenant -Dsysbenchdb -A -psysbench
Welcome to the OceanBase. Commands end with ; or \g.
Your MySQL connection id is 3221823448
Server version: 5.7.25 OceanBase 3.1.2 (r10000392021123010-d4ace121deae5b81d8f0b40afbc4c02705b7fc1d) (Built Dec 30 2021 02:47:29)
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MySQL [sysbenchdb]> select count(*) from sbtest1;
+----------+
| count(*) |
+----------+
| 53195 |
+----------+
1 row in set (0.040 sec)
MySQL [sysbenchdb]> exit
Bye
[root@localhost ~]# obclient -h10.186.64.79 -P2881 -usysbench@sysbench_tenant -Dsysbenchdb -A -psysbench
Welcome to the OceanBase. Commands end with ; or \g.
Your MySQL connection id is 3222011907
Server version: 5.7.25 OceanBase 3.1.2 (r10000392021123010-d4ace121deae5b81d8f0b40afbc4c02705b7fc1d) (Built Dec 30 2021 02:47:29)
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
MySQL [sysbenchdb]> select count(*) from sbtest1;
+----------+
| count(*) |
+----------+
| 53195 |
+----------+
1 row in set (0.037 sec)
MySQL [sysbenchdb]>总结
数据文件损坏或者丢失时，可通过调整参数 server_permanent_offline_time 来重建受影响的节点。
1.设小 server_permanent_offline_time 阈值
2.停止故障节点对外服务
3.终止该节点进程。
4.超过阈值后，节点将被标记为永久下线，系统会自动清空副本以及向同zone内其他节点迁移数据。
5.启动 OB 进程，自动触发重建节点数据。
6.开启故障节点服务。
7.把server_permanent_offline_time参数改回原来的值