## 模块 3: 隔离可用区 1 中的子网 1
### 步骤 1：模拟可用区 1 的完全故障
+ 返回[终端 1](ssh://monitor1-ssh#1) 并执行脚本，通过阻止子网 `demo-subnet-1` (可用区 1 中的子网 10.90.1.0/24)，模拟可用区的完全故障。
```bash
VPC_ID=`aws ec2 describe-vpcs \
--filters "Name=tag:Name,Values=${LAB:USER_UNIQUE_TAG}" \
--query "Vpcs[0].VpcId" \
--output text \
--region ${LAB:REGION_CODE}`
SUBNET_ID=`aws ec2 describe-subnets \
--filters "Name=vpc-id,Values=${VPC_ID}" "Name=tag:Name,Values=demo-subnet-1" \
--query "Subnets[0].SubnetId" \
--output text \
--region ${LAB:REGION_CODE}`
CAGE_NACL_ID=`aws ec2 describe-network-acls \
--filters "Name=vpc-id,Values=${VPC_ID}" "Name=default,Values=false" "Name=tag:Name,Values=cage" \
--query "NetworkAcls[0].NetworkAclId" \
--output text \
--region ${LAB:REGION_CODE}`
ASSOC_ID=`aws ec2 describe-network-acls \
--filters "Name=vpc-id,Values=${VPC_ID}" "Name=default,Values=true" \
--query "NetworkAcls[0].Associations" \
--output text \
--region ${LAB:REGION_CODE} | grep ${SUBNET_ID} | awk -F" " '{print $1}'`
aws ec2 replace-network-acl-association \
--association-id ${ASSOC_ID} \
--network-acl-id ${CAGE_NACL_ID} \
--region ${LAB:REGION_CODE}
```
```output
{
"NewAssociationId": "aclassoc-0402a6103febf799f"
}
```
### 步骤 2：验证若干组件已断开连接
+ 在[终端 1](ssh://monitor1-ssh#1) 中，查看集群状态以验证若干组件，包括 PD、TiDB 和 TiKV 服务器由于可用区故障而断开连接/隔离。
+ 在示例输出中，受影响的服务器为 `10.90.1.208:2379 pd`、`10.90.1.247:4000 tidb` 和 `10.90.1.122:20160 tikv`。因此，集群的三分之一组件丢失连接。
```bash
tiup cluster display tidb-demo
```
```output
Cluster type: tidb
Cluster name: tidb-demo
Cluster version: v${LAB:TIDB_VERSION}
Deploy user: ec2-user
SSH type: builtin
Dashboard URL: http://${LAB:HOST_PD1_PUBLIC_IP}:2379/dashboard
Grafana URL: http://${LAB:HOST_MONITOR1_PRIVATE_IP}:3000
ID Role Host Ports OS/Arch Status Data Dir Deploy Dir
-- ---- ---- ----- ------- ------ -------- ----------
${LAB:HOST_MONITOR1_PRIVATE_IP}:9093 alertmanager ${LAB:HOST_MONITOR1_PRIVATE_IP} 9093/9094 linux/x86_64 Up /tidb-data/alertmanager-9093 /tidb-deploy/alertmanager-9093
${LAB:HOST_MONITOR1_PRIVATE_IP}:3000 grafana ${LAB:HOST_MONITOR1_PRIVATE_IP} 3000 linux/x86_64 Up - /tidb-deploy/grafana-3000
${LAB:HOST_PD1_PRIVATE_IP}:2379 pd ${LAB:HOST_PD1_PRIVATE_IP} 2379/2380 linux/x86_64 Down /tidb-data/pd-2379 /tidb-deploy/pd-2379
${LAB:HOST_PD2_PRIVATE_IP}:2379 pd ${LAB:HOST_PD2_PRIVATE_IP} 2379/2380 linux/x86_64 Up|L /tidb-data/pd-2379 /tidb-deploy/pd-2379
${LAB:HOST_PD3_PRIVATE_IP}:2379 pd ${LAB:HOST_PD3_PRIVATE_IP} 2379/2380 linux/x86_64 Up /tidb-data/pd-2379 /tidb-deploy/pd-2379
${LAB:HOST_MONITOR1_PRIVATE_IP}:9090 prometheus ${LAB:HOST_MONITOR1_PRIVATE_IP} 9090/12020 linux/x86_64 Up /tidb-data/prometheus-9090 /tidb-deploy/prometheus-9090
${LAB:HOST_DB1_PRIVATE_IP}:4000 tidb ${LAB:HOST_DB1_PRIVATE_IP} 4000/10080 linux/x86_64 Down - /tidb-deploy/tidb-4000
${LAB:HOST_DB2_PRIVATE_IP}:4000 tidb ${LAB:HOST_DB2_PRIVATE_IP} 4000/10080 linux/x86_64 Up - /tidb-deploy/tidb-4000
${LAB:HOST_KV1_PRIVATE_IP}:20160 tikv ${LAB:HOST_KV1_PRIVATE_IP} 20160/20180 linux/x86_64 Disconnected /tidb-data/tikv-20160 /tidb-deploy/tikv-20160
${LAB:HOST_KV2_PRIVATE_IP}:20160 tikv ${LAB:HOST_KV2_PRIVATE_IP} 20160/20180 linux/x86_64 Up /tidb-data/tikv-20160 /tidb-deploy/tikv-20160
${LAB:HOST_KV3_PRIVATE_IP}:20160 tikv ${LAB:HOST_KV3_PRIVATE_IP} 20160/20180 linux/x86_64 Up /tidb-data/tikv-20160 /tidb-deploy/tikv-20160
Total nodes: 11
```
### 步骤 3：验证您的 INSERT 和 QUERY 负载仍在运行
+ 在[终端 2](ssh://monitor1-ssh#2) 和[终端 3](ssh://monitor1-ssh#3) 中，验证您的示例 INSERT/QUERY 负载仍在运行。请注意，现在 INSERT 和 QUERY 负载仅与一个 TiDB 服务器实例工作。
```output
Worker 1 -> TiDB:Mon May 13 05:51:52 UTC 2024 at ${LAB:HOST_DB2_PRIVATE_IP}
Worker 2 -> TiDB:Mon May 13 05:51:52 UTC 2024 at ${LAB:HOST_DB2_PRIVATE_IP}
Worker 1 -> TiDB:Mon May 13 05:51:53 UTC 2024 at ${LAB:HOST_DB2_PRIVATE_IP}
Worker 2 -> TiDB:Mon May 13 05:51:53 UTC 2024 at ${LAB:HOST_DB2_PRIVATE_IP}
Worker 1 -> TiDB:Mon May 13 05:51:54 UTC 2024 at ${LAB:HOST_DB2_PRIVATE_IP}
...
```
```output
Mon May 13 05:51:51 UTC 2024
COUNT(event)
5481
Mon May 13 05:51:54 UTC 2024
COUNT(event)
5485
...
```
### 步骤 4：恢复可用区 1 的连接
+ 在[终端 1](ssh://monitor1-ssh#1) 中，运行脚本以恢复 `demo-subnet-1` 的连接。在 TiDB Cloud 的真实场景中，你无需自行执行此类脚本——由 TiDB Cloud 负责恢复。若可用区问题短暂，网络恢复后断开的组件会自动重新加入集群。若数据中心长时间不可用，TiDB Cloud 可在健康的可用区扩展容量并驱逐不可达节点。无论哪种方式，应用都可继续使用健康的 TiDB 端点——与本自管部署实验中观察到的结果相同。欲了解更多高级 TiDB 技能，请访问 [https://tidb.io/education/](https://tidb.io/education/)。
```bash
VPC_ID=`aws ec2 describe-vpcs \
--filters "Name=tag:Name,Values=${LAB:USER_UNIQUE_TAG}" \
--query "Vpcs[0].VpcId" \
--output text \
--region ${LAB:REGION_CODE}`
SUBNET_ID=`aws ec2 describe-subnets \
--filters "Name=vpc-id,Values=${VPC_ID}" "Name=tag:Name,Values=demo-subnet-1" \
--query "Subnets[0].SubnetId" \
--output text \
--region ${LAB:REGION_CODE}`
DEFAULT_NACL_ID=`aws ec2 describe-network-acls \
--filters "Name=vpc-id,Values=${VPC_ID}" "Name=default,Values=true" \
--query "NetworkAcls[0].NetworkAclId" \
--output text \
--region ${LAB:REGION_CODE}`
ASSOC_ID=`aws ec2 describe-network-acls \
--filters "Name=vpc-id,Values=${VPC_ID}" "Name=default,Values=false" \
--query "NetworkAcls[0].Associations" \
--output text \
--region ${LAB:REGION_CODE} | grep ${SUBNET_ID} | awk -F" " '{print $1}'`
aws ec2 replace-network-acl-association \
--association-id ${ASSOC_ID} \
--network-acl-id ${DEFAULT_NACL_ID} \
--region ${LAB:REGION_CODE}
```
```output
{
"NewAssociationId": "aclassoc-0df1e05cfc70356a8"
}
```
### 步骤 5：验证所有集群组件已同步
+ 验证集群状态以确保之前断开的组件现已同步。
```bash
tiup cluster display tidb-demo
```
```output
Cluster type: tidb
Cluster name: tidb-demo
Cluster version: v${LAB:TIDB_VERSION}
Deploy user: ec2-user
SSH type: builtin
Dashboard URL: http://${LAB:HOST_PD1_PUBLIC_IP}:2379/dashboard
Grafana URL: http://${LAB:HOST_MONITOR1_PRIVATE_IP}:3000
ID Role Host Ports OS/Arch Status Data Dir Deploy Dir
-- ---- ---- ----- ------- ------ -------- ----------
${LAB:HOST_MONITOR1_PRIVATE_IP}:9093 alertmanager ${LAB:HOST_MONITOR1_PRIVATE_IP} 9093/9094 linux/x86_64 Up /tidb-data/alertmanager-9093 /tidb-deploy/alertmanager-9093
${LAB:HOST_MONITOR1_PRIVATE_IP}:3000 grafana ${LAB:HOST_MONITOR1_PRIVATE_IP} 3000 linux/x86_64 Up - /tidb-deploy/grafana-3000
${LAB:HOST_PD1_PRIVATE_IP}:2379 pd ${LAB:HOST_PD1_PRIVATE_IP} 2379/2380 linux/x86_64 Up /tidb-data/pd-2379 /tidb-deploy/pd-2379
${LAB:HOST_PD2_PRIVATE_IP}:2379 pd ${LAB:HOST_PD2_PRIVATE_IP} 2379/2380 linux/x86_64 Up|L /tidb-data/pd-2379 /tidb-deploy/pd-2379
${LAB:HOST_PD3_PRIVATE_IP}:2379 pd ${LAB:HOST_PD3_PRIVATE_IP} 2379/2380 linux/x86_64 Up /tidb-data/pd-2379 /tidb-deploy/pd-2379
${LAB:HOST_MONITOR1_PRIVATE_IP}:9090 prometheus ${LAB:HOST_MONITOR1_PRIVATE_IP} 9090/12020 linux/x86_64 Up /tidb-data/prometheus-9090 /tidb-deploy/prometheus-9090
${LAB:HOST_DB1_PRIVATE_IP}:4000 tidb ${LAB:HOST_DB1_PRIVATE_IP} 4000/10080 linux/x86_64 Up - /tidb-deploy/tidb-4000
${LAB:HOST_DB2_PRIVATE_IP}:4000 tidb ${LAB:HOST_DB2_PRIVATE_IP} 4000/10080 linux/x86_64 Up - /tidb-deploy/tidb-4000
${LAB:HOST_KV1_PRIVATE_IP}:20160 tikv ${LAB:HOST_KV1_PRIVATE_IP} 20160/20180 linux/x86_64 Up /tidb-data/tikv-20160 /tidb-deploy/tikv-20160
${LAB:HOST_KV2_PRIVATE_IP}:20160 tikv ${LAB:HOST_KV2_PRIVATE_IP} 20160/20180 linux/x86_64 Up /tidb-data/tikv-20160 /tidb-deploy/tikv-20160
${LAB:HOST_KV3_PRIVATE_IP}:20160 tikv ${LAB:HOST_KV3_PRIVATE_IP} 20160/20180 linux/x86_64 Up /tidb-data/tikv-20160 /tidb-deploy/tikv-20160
Total nodes: 11
```
+ 按 Ctrl+C 停止[终端 2](ssh://monitor1-ssh#2) 和[终端 3](ssh://monitor1-ssh#3) 上的两个负载。