MySQL Shell 9.0  /  ...  /  在 InnoDB ClusterSet 中隔离集群

8.9.1 在 InnoDB ClusterSet 中隔离集群

紧急故障转移 之后,ClusterSet 的不同部分之间的事务集存在差异的风险,您必须隔离集群以防止写入流量或所有流量。

如果发生网络分区,则可能会出现脑裂情况,即实例失去同步并且无法正确通信以定义同步状态。脑裂情况可能发生在以下情况下,例如当 DBA 决定强制选举副本集群成为主集群,从而创建多个主节点,导致脑裂情况。

在这种情况下,DBA 可以选择隔离原始主集群的

  • 写入。

  • 所有流量。

可以使用三种隔离操作

  • <Cluster>.fenceWrites(): 停止对 ClusterSet 主集群的写入流量。副本集群不接受写入,因此此操作对它们没有影响。

    可以在 INVALIDATED 副本集群上使用。此外,如果在禁用了 super_read_only 的副本集群上运行,它将启用它。

  • <Cluster>.unfenceWrites(): 恢复写入流量。此操作可以在之前使用 <Cluster>.fenceWrites() 操作隔离写入流量的集群上运行。

    无法在副本集群上使用 cluster.unfenceWrites()

  • <Cluster>.fenceAllTraffic(): 隔离集群及其中的所有读副本,禁止所有流量。如果您已使用 <Cluster>.fenceAllTraffic() 隔离了集群的所有流量,则必须使用 dba.rebootClusterFromCompleteOutage() MySQL Shell 命令重新启动集群。

    有关 dba.rebootClusterFromCompleteOutage() 的更多信息,请参阅第 7.8.3 节 “从重大故障中重新启动集群”

fenceWrites()

在副本集群上发出 .fenceWrites() 会返回错误

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ERROR: Unable to fence Cluster from write traffic: operation not permitted on REPLICA Clusters Cluster.fenceWrites: The Cluster '<Cluster>' is a REPLICA Cluster of the ClusterSet '<ClusterSet>' (MYSQLSH 51616)

即使您主要在属于集群集的集群上使用隔离,也可以使用 <Cluster>.fenceAllTraffic() 隔离独立集群。

  1. 要隔离主集群的写入流量,请使用 Cluster.fenceWrites 命令,如下所示

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    <Cluster>.fenceWrites()

    运行命令后

    • 集群上的自动 super_read_only 管理被禁用。

    • 集群中所有实例上的 super_read_only 都已启用。

    • 所有应用程序都被阻止在集群上执行写入操作。

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    cluster.fenceWrites() The Cluster 'primary' will be fenced from write traffic * Disabling automatic super_read_only management on the Cluster... * Enabling super_read_only on '127.0.0.1:3311'... * Enabling super_read_only on '127.0.0.1:3312'... * Enabling super_read_only on '127.0.0.1:3313'... NOTE: Applications will now be blocked from performing writes on Cluster 'primary'. Use <Cluster>.unfenceWrites() to resume writes if you are certain a split-brain is not in effect. Cluster successfully fenced from write traffic
  2. 要检查您是否已隔离主集群的写入流量,请使用 <Cluster>.status 命令,如下所示

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    <Cluster>.clusterset.status()

    输出如下

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    clusterset.status() { "clusters": { "primary": { "clusterErrors": [ "WARNING: Cluster is fenced from Write traffic. Use cluster.unfenceWrites() to unfence the Cluster." ], "clusterRole": "PRIMARY", "globalStatus": "OK_FENCED_WRITES", "primary": null, "status": "FENCED_WRITES", "statusText": "Cluster is fenced from Write Traffic." }, "replica": { "clusterRole": "REPLICA", "clusterSetReplicationStatus": "OK", "globalStatus": "OK" } }, "domainName": "primary", "globalPrimaryInstance": null, "primaryCluster": "primary", "status": "UNAVAILABLE", "statusText": "Primary Cluster is fenced from write traffic."
  3. 要解除隔离集群并恢复对主集群的写入流量,请使用 Cluster.fenceWrites 命令,如下所示

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    <Cluster>.unfenceWrites()

    主集群上的自动 super_read_only 管理已启用,并且主集群实例上的 super_read_only 状态已启用。

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    cluster.unfenceWrites() The Cluster 'primary' will be unfenced from write traffic * Enabling automatic super_read_only management on the Cluster... * Disabling super_read_only on the primary '127.0.0.1:3311'... Cluster successfully unfenced from write traffic
  4. 要隔离集群的所有流量,请使用 Cluster.fenceAllTraffic 命令,如下所示

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    <Cluster>.fenceAllTraffic()

    集群实例的主实例上的 super_read_only 状态已启用。在启用集群中所有实例上的 offline_mode 之前

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    cluster.fenceAllTraffic() The Cluster 'primary' will be fenced from all traffic * Enabling super_read_only on the primary '127.0.0.1:3311'... * Enabling offline_mode on the primary '127.0.0.1:3311'... * Enabling offline_mode on '127.0.0.1:3312'... * Stopping Group Replication on '127.0.0.1:3312'... * Enabling offline_mode on '127.0.0.1:3313'... * Stopping Group Replication on '127.0.0.1:3313'... * Stopping Group Replication on the primary '127.0.0.1:3311'... Cluster successfully fenced from all traffic
  5. 要解除隔离集群的所有流量,请使用 dba.rebootClusterFromCompleteOutage() MySQL Shell 命令。恢复集群后,当系统询问您是否要将实例重新加入集群时,选择,即可将实例重新加入集群

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    cluster = dba.rebootClusterFromCompleteOutage() Restoring the cluster 'primary' from complete outage... The instance '127.0.0.1:3312' was part of the cluster configuration. Would you like to rejoin it to the cluster? [y/N]: Y The instance '127.0.0.1:3313' was part of the cluster configuration. Would you like to rejoin it to the cluster? [y/N]: Y * Waiting for seed instance to become ONLINE... 127.0.0.1:3311 was restored. Rejoining '127.0.0.1:3312' to the cluster. Rejoining instance '127.0.0.1:3312' to cluster 'primary'... The instance '127.0.0.1:3312' was successfully rejoined to the cluster. Rejoining '127.0.0.1:3313' to the cluster. Rejoining instance '127.0.0.1:3313' to cluster 'primary'... The instance '127.0.0.1:3313' was successfully rejoined to the cluster. The cluster was successfully rebooted. <Cluster:primary>