en,zh: add pause deployment docs of tidb cluster

en/TOC.md

@@ -40,6 +40,7 @@
   - [Migrate TiDB to Kubernetes](migrate-tidb-to-kubernetes.md)
   - [Upgrade TiDB Cluster](upgrade-a-tidb-cluster.md)
   - [Upgrade TiDB Operator](upgrade-tidb-operator.md)
+  - [Pause Sync of TiDB Cluster](pause-sync-of-tidb-cluster.md)
   + Scale TiDB Cluster
     - [Manually Scale](scale-a-tidb-cluster.md)
     - [Automatically Scale](enable-tidb-cluster-auto-scaling.md)

en/pause-sync-of-tidb-cluster.md

@@ -0,0 +1,127 @@
+---
+title: Pause Sync of a TiDB Cluster in Kubernetes
+summary: Introduce how to pause sync of a TiDB cluster in Kubernetes
+---
+
+# Pause Sync of a TiDB Cluster in Kubernetes
+
+This document introduce how to pause sync of a TiDB cluster in Kubernetes with configuration.
+
+## What is sync in TiDB Operator
+
+In TiDB Operator, controller regulates the state of the TiDB cluster in Kubernetes. The controller constantly compares the desired state recorded in the `TidbCluster` object with the actual state of the TiDB cluster. This process is referred to as **sync** generally. For more details, refer to [TiDB Operator Architecture](architecture.md).
+
+## Use scenarios
+
+Here are some cases where you might need to pause sync of a TiDB cluster in Kubernetes.
+
+- Avoiding unexpected rolling update
+
+    In order to prevent the compatibility of the new version TiDB Operator from affecting the TiDB clusters, you can pause sync of TiDB clusters before updating the TiDB Operator. After updating TiDB Operator, resume sync of TiDB clusters one by one or resume sync of TiDB clusters at a specified time, so as to observe the impact of TiDB Operator rolling update on the cluster.
+
+- Avoid multiple rolling restarts
+
+    In some cases, the configuration of a TiDB cluster may be modified several times over a period of time, but you do not want to restart the TiDB cluster many times. In order to avoid multiple rolling restarts, you can pause sync of a TiDB cluster first. During this period, any modification to configuration of the TiDB cluster will not take effect. After the cluster configuration modification is completed, resuming sync of TiDB Cluster. At this time, multiple configuration changes during the sync pausing can be applied in one time rolling restart.
+
+- Maintenance window
+
+    In some situations, you can update or restart TiDB cluster only during a maintenance window. When outside the maintenance window, you can pause sync of the TiDB cluster, so that any modification to spec does not take effect. When inside the maintenance window, you can resume sync of the TiDB cluster to allow TiDB cluster rolling update or restart.
+
+## Pause sync
+
+1. Execute the following command to edit configuration of TiDB cluster. `${cluster_name}` represents the name of TiDB cluster, and `${namespace}` refers to the TiDB cluster namespace.
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    kubectl edit tc ${cluster_name} -n ${namespace}
+    ```
+
+2. Configure the TidbCluster CR with `spec.paused: true` as following, save changes and exit editor, sync of TiDB cluster's components (PD, TiKV, TiDB, TiFlash, TiCDC,Pump) will be paused. 
+
+    {{< copyable "" >}}
+
+    ```yaml
+    apiVersion: pingcap.com/v1alpha1
+    kind: TidbCluster
+    metadata:
+      ...
+    spec:
+      ...
+      paused: true  # Pausing sync of TiDB cluster
+      pd:
+        ...
+      tikv:
+        ...
+      tidb:
+        ...
+    ```
+
+3. Execute the following command to confirm the sync status of a TiDB cluster. `${pod_name}` is the name of tidb-controller-manager Pod, and `${namespace}` is the namespace of TiDB Operator.
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    kubectl logs ${pod_name} -n ${namespace} | grep paused
+    ```
+
+    The expected output is as follows. The sync of all components in the TiDB cluster is paused.
+
+    ```
+    I1207 11:09:59.029949       1 pd_member_manager.go:92] tidb cluster default/basic is paused, skip syncing for pd service
+    I1207 11:09:59.029977       1 pd_member_manager.go:136] tidb cluster default/basic is paused, skip syncing for pd headless service
+    I1207 11:09:59.035437       1 pd_member_manager.go:191] tidb cluster default/basic is paused, skip syncing for pd statefulset
+    I1207 11:09:59.035462       1 tikv_member_manager.go:116] tikv cluster default/basic is paused, skip syncing for tikv service
+    I1207 11:09:59.036855       1 tikv_member_manager.go:175] tikv cluster default/basic is paused, skip syncing for tikv statefulset
+    I1207 11:09:59.036886       1 tidb_member_manager.go:132] tidb cluster default/basic is paused, skip syncing for tidb headless service
+    I1207 11:09:59.036895       1 tidb_member_manager.go:258] tidb cluster default/basic is paused, skip syncing for tidb service
+    I1207 11:09:59.039358       1 tidb_member_manager.go:188] tidb cluster default/basic is paused, skip syncing for tidb statefulset
+    ```
+
+## Resume sync
+
+If you want to resume the sync of the TiDB cluster, configure the TidbCluster CR with `spec.paused: false`.
+
+1. Execute the following command to edit configuration of TiDB cluster. `${cluster_name}` represents the name of TiDB cluster, and `${namespace}` refers to the TiDB cluster namespace.
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    kubectl edit tc ${cluster_name} -n ${namespace}
+    ```
+
+2. Configure the TidbCluster CR with `spec.paused: false` as following, save changes and exit editor, sync of TiDB cluster's components (PD, TiKV, TiDB, TiFlash, TiCDC,Pump) will be resumed. 
+
+    {{< copyable "" >}}
+
+    ```yaml
+    apiVersion: pingcap.com/v1alpha1
+    kind: TidbCluster
+    metadata:
+      ...
+    spec:
+      ...
+      paused: false  # Resuming sync of TiDB cluster
+      pd:
+        ...
+      tikv:
+        ...
+      tidb:
+        ...
+    ```
+
+3. After resuming sync of the TiDB cluster, execute the following command to confirm sync status of the TiDB cluster. `${pod_name}` represents the name of tidb-controller-manager Pod, `${namespace}` represents the namespace of TiDB Operator.
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    kubectl logs ${pod_name} -n ${namespace} | grep "Finished syncing TidbCluster"
+    ```
+
+    The expected output is as follows. The `finished syncing` timestamp is later than the `pausing` timestamp, which indicates that sync of the TiDB cluster has been resumed.
+
+    ```
+    I1207 11:14:59.361353       1 tidb_cluster_controller.go:136] Finished syncing TidbCluster "default/basic" (368.816685ms)
+    I1207 11:15:28.982910       1 tidb_cluster_controller.go:136] Finished syncing TidbCluster "default/basic" (97.486818ms)
+    I1207 11:15:29.360446       1 tidb_cluster_controller.go:136] Finished syncing TidbCluster "default/basic" (377.51187ms)
+    ```

zh/TOC.md

@@ -40,6 +40,7 @@
   - [迁移 TiDB 至 Kubernetes](migrate-tidb-to-kubernetes.md)
   - [升级 TiDB 集群](upgrade-a-tidb-cluster.md)
   - [升级 TiDB Operator](upgrade-tidb-operator.md)
+  - [暂停 TiDB 集群同步](pause-sync-of-tidb-cluster.md)
   + TiDB 集群伸缩
     - [手动扩缩容](scale-a-tidb-cluster.md)
     - [自动弹性伸缩](enable-tidb-cluster-auto-scaling.md)

zh/pause-sync-of-tidb-cluster.md

@@ -0,0 +1,127 @@
+---
+title: 暂停同步 Kubernetes 上的 TiDB 集群
+summary: 介绍如何暂停同步 Kubernetes 上的 TiDB 集群
+---
+
+# 暂停同步 Kubernetes 上的 TiDB 集群
+
+本文介绍如何通过配置暂停同步 Kubernetes 上的 TiDB 集群。
+
+## 什么是同步
+
+在 TiDB Operator 中，控制器会不断对比 `TidbCluster` 对象中记录的期望状态与 TiDB 集群的实际状态，并调整 Kubernetes 中的资源以驱动 TiDB 集群满足期望状态。这个不断调整的过程通常被称为**同步**。更多细节参见[TiDB Operator架构](architecture.md)。
+
+## 暂停同步的应用场景
+
+以下为一些暂停同步的应用场景。
+
+- 避免意外的滚动升级
+
+    为防止 TiDB Operator 新版本的兼容性问题影响集群，升级 TiDB Operator 之前，可以先暂停同步集群。升级 TiDB Operator 之后，逐个恢复同步集群或者在指定时间恢复同步集群，以此来观察 TiDB Operator 版本升级对集群的影响。
+
+- 避免多次滚动重启集群
+
+    在某些情况下，一段时间内可能会多次修改 TiDB 集群配置，但是又不想多次滚动重启集群。为了避免多次滚动重启集群，可以先暂停同步集群，在此期间，对 TiDB 集群的任何配置都不会生效。集群配置修改完成后，恢复集群同步，此时暂停同步期间的所有配置修改都能在一次重启过程中被应用。
+
+- 维护时间窗口
+
+    在某些情况下，只允许在特定时间窗口内滚动升级或重启 TiDB 集群。因此可以在维护时间窗口之外的时间段暂停 TiDB 集群的同步过程，这样在维护时间窗口之外对 TiDB 集群的任何配置都不会生效；在维护时间窗口内，可以通过恢复 TiDB 集群同步来允许滚动升级或者重启 TiDB 集群。
+
+## 暂停同步 TiDB 集群
+
+1. 使用以下命令修改集群配置，其中 `${cluster_name}` 表示 TiDB 集群名称, `${namespace}` 表示 TiDB 集群所在的 namespace。
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    kubectl edit tc ${cluster_name} -n ${namespace}
+    ```
+
+2. 在 TidbCluster CR 中以如下方式配置 `spec.paused: true`，保存配置并退出编辑器。TiDB 集群各组件 (PD、TiKV、TiDB、TiFlash、TiCDC、Pump) 的同步过程将会被暂停。
+
+    {{< copyable "" >}}
+
+    ```yaml
+    apiVersion: pingcap.com/v1alpha1
+    kind: TidbCluster
+    metadata:
+      ...
+    spec:
+      ...
+      paused: true  # 暂停同步
+      pd:
+        ...
+      tikv:
+        ...
+      tidb:
+        ...
+    ```
+
+3. TiDB 集群同步暂停后，可以使用以下命令查看 tidb-controller-manager Pod 日志确认 TiDB 集群同步状态。其中 `${pod_name}` 表示 tidb-controller-manager Pod 的名称，`${namespace}` 表示 TiDB Operator 所在的 namespace。
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    kubectl logs ${pod_name} -n ${namespace} | grep paused
+    ```
+
+    输出类似下方结果则表示 TiDB 集群同步已经暂停。
+
+    ```
+    I1207 11:09:59.029949       1 pd_member_manager.go:92] tidb cluster default/basic is paused, skip syncing for pd service
+    I1207 11:09:59.029977       1 pd_member_manager.go:136] tidb cluster default/basic is paused, skip syncing for pd headless service
+    I1207 11:09:59.035437       1 pd_member_manager.go:191] tidb cluster default/basic is paused, skip syncing for pd statefulset
+    I1207 11:09:59.035462       1 tikv_member_manager.go:116] tikv cluster default/basic is paused, skip syncing for tikv service
+    I1207 11:09:59.036855       1 tikv_member_manager.go:175] tikv cluster default/basic is paused, skip syncing for tikv statefulset
+    I1207 11:09:59.036886       1 tidb_member_manager.go:132] tidb cluster default/basic is paused, skip syncing for tidb headless service
+    I1207 11:09:59.036895       1 tidb_member_manager.go:258] tidb cluster default/basic is paused, skip syncing for tidb service
+    I1207 11:09:59.039358       1 tidb_member_manager.go:188] tidb cluster default/basic is paused, skip syncing for tidb statefulset
+    ```
+
+## 恢复同步 TiDB 集群
+
+如果想要恢复 TiDB 集群的同步，可以在 TidbCluster CR 中配置 `spec.paused: false`，恢复同步 TiDB 集群。
+
+1. 使用以下命令修改集群配置，其中 `${cluster_name}` 表示 TiDB 集群名称, `${namespace}` 表示 TiDB 集群所在的 namespace。
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    kubectl edit tc ${cluster_name} -n ${namespace}
+    ```
+
+2. 在 TidbCluster CR 中以如下方式配置 `spec.paused: false`，保存配置并退出编辑器。TiDB 集群各组件 (PD、TiKV、TiDB、TiFlash、TiCDC、Pump) 的同步过程将会被恢复。
+
+    {{< copyable "" >}}
+
+    ```yaml
+    apiVersion: pingcap.com/v1alpha1
+    kind: TidbCluster
+    metadata:
+      ...
+    spec:
+      ...
+      paused: false  # 恢复同步
+      pd:
+        ...
+      tikv:
+        ...
+      tidb:
+        ...
+    ```
+
+3. 恢复 TiDB 集群同步后，可以使用以下命令查看 tidb-controller-manager Pod 日志确认 TiDB 集群同步状态。其中 `${pod_name}` 表示 tidb-controller-manager Pod 的名称，`${namespace}` 表示 TiDB Operator 所在的 namespace。
+
+    {{< copyable "shell-regular" >}}
+
+    ```shell
+    kubectl logs ${pod_name} -n ${namespace} | grep "Finished syncing TidbCluster"
+    ```
+
+    输出类似下方结果，可以看到同步成功时间戳大于暂停同步日志中显示的时间戳，表示 TiDB 集群同步已经被恢复。
+
+    ```
+    I1207 11:14:59.361353       1 tidb_cluster_controller.go:136] Finished syncing TidbCluster "default/basic" (368.816685ms)
+    I1207 11:15:28.982910       1 tidb_cluster_controller.go:136] Finished syncing TidbCluster "default/basic" (97.486818ms)
+    I1207 11:15:29.360446       1 tidb_cluster_controller.go:136] Finished syncing TidbCluster "default/basic" (377.51187ms)
+    ```