系統變數group_replication_group_seeds為空導致MySQL節點無法啟動組複製

潇湘隐者發表於2024-11-06
變數MySql

MySQL InnoDB Cluster叢集中一個節點，在伺服器重啟過後，啟動MySQL例項後，發現status為MISSING，另外memberState為OFFLINE狀態。如下所示：

 MySQL  mysqldbu02:7306 ssl  JS > cluster.status()
{
    "clusterName": "yssps", 
    "defaultReplicaSet": {
        "name": "default", 
        "primary": "mysqldbu02:7306", 
        "ssl": "REQUIRED", 
        "status": "OK_NO_TOLERANCE_PARTIAL", 
        "statusText": "Cluster is NOT tolerant to any failures. 1 member is not active.", 
        "topology": {
            "mysqldbu01:7306": {
                "address": "mysqldbu01:7306", 
                "instanceErrors": [
                    "NOTE: group_replication is stopped."
                ], 
                "memberRole": "SECONDARY", 
                "memberState": "OFFLINE", 
                "mode": "n/a", 
                "readReplicas": {}, 
                "role": "HA", 
                "status": "(MISSING)", 
                "version": "8.0.35"
            }, 
            "mysqldbu02:7306": {
                "address": "mysqldbu02:7306", 
                "memberRole": "PRIMARY", 
                "mode": "R/W", 
                "readReplicas": {}, 
                "replicationLag": "applier_queue_applied", 
                "role": "HA", 
                "status": "ONLINE", 
                "version": "8.0.35"
            }, 
            "mysqldbu03:7306": {
                "address": "mysqldbu03:7306", 
                "memberRole": "SECONDARY", 
                "mode": "R/O", 
                "readReplicas": {}, 
                "replicationLag": "applier_queue_applied", 
                "role": "HA", 
                "status": "ONLINE", 
                "version": "8.0.35"
            }
        }, 
        "topologyMode": "Single-Primary"
    }, 
    "groupInformationSourceMember": "mysqldbu02:7306"
}
 MySQL  mysqldbu02:7306 ssl  JS >

從錯誤提示資訊來看是組複製沒有啟動(group_replication is stopped)。其實MySQL InnoDB Cluster的節點重啟操作在生產環境和測試環境都做過多次，還是第一次遇到這種情況。

另外，在這個節點上檢視節點的狀態如下：

mysql> select * from performance_schema.replication_group_members order by member_host\G
*************************** 1. row ***************************
              CHANNEL_NAME: group_replication_applier
                 MEMBER_ID: 5ad73846-3fce-11ee-a86c-5254003c1c6e
               MEMBER_HOST: mysqldbu01
               MEMBER_PORT: 7306
              MEMBER_STATE: OFFLINE
               MEMBER_ROLE: 
            MEMBER_VERSION: 
MEMBER_COMMUNICATION_STACK: MySQL
1 row in set (0.00 sec)

mysql>

具體的錯誤日誌如下所示

2024-11-06T10:03:19.369090+08:00 29 [Warning] [MY-011735] [Repl] Plugin group_replication reported: '[GCS] Automatically adding IPv4
 localhost address to the allowlist. It is mandatory that it is added.'
2024-11-06T10:03:19.369171+08:00 29 [Warning] [MY-011735] [Repl] Plugin group_replication reported: '[GCS] Automatically adding IPv6
 localhost address to the allowlist. It is mandatory that it is added.'
2024-11-06T10:03:19.371586+08:00 40 [System] [MY-010597] [Repl] 'CHANGE REPLICATION SOURCE TO FOR CHANNEL 'group_replication_applier
' executed'. Previous state source_host='<NULL>', source_port= 0, source_log_file='', source_log_pos= 4, source_bind=''. New state s
ource_host='<NULL>', source_port= 0, source_log_file='', source_log_pos= 4, source_bind=''.
2024-11-06T10:03:19.391449+08:00 29 [ERROR] [MY-011735] [Repl] Plugin group_replication reported: '[GCS] Unable to join the group: peers not configured. '
2024-11-06T10:03:19.391512+08:00 29 [ERROR] [MY-011639] [Repl] Plugin group_replication reported: 'Error on group communication engine start'
2024-11-06T10:03:19.391581+08:00 29 [ERROR] [MY-011735] [Repl] Plugin group_replication reported: '[GCS] The member is leaving a group without being on one.'

關鍵資訊為：[Repl] Plugin group_replication reported: '[GCS] Unable to join the group: peers not configured.

這個錯誤資訊意味著沒有配置系統變數group_replication_group_seeds。 另外，手工啟動組複製，錯誤日誌依然報同樣的錯誤，執行啟動組複製命令的錯誤資訊如下所示：

mysql> start group_replication;
ERROR 3097 (HY000): The START GROUP_REPLICATION command failed as there was an error when joining the communication group.
mysql>

檢查發現系統變數group_replication_group_seeds的值為空(my.cnf中沒有設定這個系統變數，在mysqld-auto.cnf中系統變數為空值)，因為是測試環境，不清楚什麼時候動過這個系統變數，，畢竟測試環境經常被折騰來折騰去。

mysql> show variables like 'group_replication_local_address';
+---------------------------------+---------------------+
| Variable_name                   | Value               |
+---------------------------------+---------------------+
| group_replication_local_address | mysqldbu01:7306     |
+---------------------------------+---------------------+
1 row in set (0.01 sec)

mysql> 
mysql>  show variables like 'group_replication_group_seeds';
+-------------------------------+-------+
| Variable_name                 | Value |
+-------------------------------+-------+
| group_replication_group_seeds |       |
+-------------------------------+-------+
1 row in set (0.00 sec)

mysql> select * from performance_schema.persisted_variables where variable_name='group_replication_group_seeds';
+-------------------------------+----------------+
| VARIABLE_NAME                 | VARIABLE_VALUE |
+-------------------------------+----------------+
| group_replication_group_seeds |                |
+-------------------------------+----------------+
1 row in set (0.01 sec)

mysql>

設定系統變數group_replication_group_seeds的值後，重啟組複製就正常了。

mysql> set persist group_replication_group_seeds='mysqldbu02:7306';
Query OK, 0 rows affected (0.01 sec)

mysql> start group_replication;
Query OK, 0 rows affected, 1 warning (11.28 sec)

mysql>

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