docs: Add Noop WAL provider documentation for nightly version (#2180)

Copilot · WenyXu · web-flow · commit baffb4d364c9 · 2025-10-23T14:46:35.000+08:00
Co-authored-by: WenyXu &lt;wenymedia@gmail.com&gt;
diff --git a/docs/user-guide/deployments-administration/configuration.md b/docs/user-guide/deployments-administration/configuration.md
@@ -365,7 +365,8 @@ Read [Performance Tuning Tips](/user-guide/deployments-administration/performanc
 
 ### WAL options
 
-GreptimeDB supports two WAL storage options—Local WAL and Remote WAL. See the [WAL Overview](/user-guide/deployments-administration/wal/overview.md) for a comparison of the two. For detailed configurations, refer to the [Local WAL](/user-guide/deployments-administration/wal/local-wal.md) and [Remote WAL](/user-guide/deployments-administration/wal/remote-wal/configuration.md) documentation.
+GreptimeDB supports three WAL storage options—Local WAL, Remote WAL, and Noop WAL. See the [WAL Overview](/user-guide/deployments-administration/wal/overview.md) for a comparison of the options. For detailed configurations, refer to the [Local WAL](/user-guide/deployments-administration/wal/local-wal.md), [Remote WAL](/user-guide/deployments-administration/wal/remote-wal/configuration.md), and [Noop WAL](/user-guide/deployments-administration/wal/noop-wal.md) documentation.
+
 
 ### Logging options
 
diff --git a/docs/user-guide/deployments-administration/wal/local-wal.md b/docs/user-guide/deployments-administration/wal/local-wal.md
@@ -22,7 +22,7 @@ If you are using Helm Chart to deploy GreptimeDB, you can refer to [Common Helm
 
 | Configuration Option | Description                                                                                                          | Default Value     |
 | -------------------- | -------------------------------------------------------------------------------------------------------------------- | ----------------- |
-| `provider`           | The provider of the WAL. Options: `raft_engine` (local file system storage) or `kafka` (remote WAL storage in Kafka) | `"raft_engine"`   |
+| `provider`           | The provider of the WAL. Options: `raft_engine` (local file system storage), `kafka` (remote WAL storage in Kafka), or `noop` (no-op WAL provider) | `"raft_engine"`   |
 | `dir`                | The directory where to write logs                                                                                    | `{data_home}/wal` |
 | `file_size`          | The size of single WAL log file                                                                                      | `128MB`           |
 | `purge_threshold`    | The threshold of the WAL size to trigger purging                                                                     | `1GB`             |
diff --git a/docs/user-guide/deployments-administration/wal/noop-wal.md b/docs/user-guide/deployments-administration/wal/noop-wal.md
@@ -0,0 +1,41 @@
+---
+keywords: [Configuration, Noop WAL, GreptimeDB Datanode, GreptimeDB, cluster mode]
+description: This section describes how to configure the Noop WAL for GreptimeDB Datanode component in cluster mode.
+---
+# Noop WAL
+
+Noop WAL is a special WAL provider for emergency situations when the configured WAL provider becomes temporarily unavailable. It does not store any WAL data.
+
+## Availability
+
+Noop WAL is **only available in cluster mode**, not in standalone mode.
+
+## Use Cases
+
+- **Temporary WAL Unavailability**: When the WAL provider (e.g., Kafka) is temporarily unavailable, switch the Datanode to Noop WAL to keep the cluster running.
+- **Testing and Development**: Useful for testing scenarios where WAL persistence is not required.
+
+## Data Loss Warning
+
+**When using Noop WAL, all unflushed data will be lost when the Datanode is shutdown or restarted.** Only use this provider temporarily when the normal WAL provider is unavailable. Not recommended for production use except in emergency situations.
+
+## Configuration
+
+To configure Noop WAL for a Datanode:
+
+```toml
+[wal]
+provider = "noop"
+```
+
+In a GreptimeDB cluster, WAL configuration has two parts:
+
+- **Metasrv** - Generates WAL metadata for new regions. Should be set to `raft_engine` or `kafka`.
+- **Datanode** - Reads and writes WAL data. Configure as `noop` when the WAL provider is unavailable.
+
+Note: Noop WAL can only be configured on Datanode, not on Metasrv. When using Noop WAL on Datanode, Metasrv continues using its configured WAL provider.
+
+## Best Practices
+
+- Flush regions regularly using `admin flush_table()` or `admin flush_region()` to minimize data loss.
+- Switch back to the normal WAL provider as soon as it becomes available.
diff --git a/docs/user-guide/deployments-administration/wal/overview.md b/docs/user-guide/deployments-administration/wal/overview.md
@@ -4,11 +4,13 @@ description: This section describes the WAL (Write-Ahead Logging) in GreptimeDB,
 ---
 # Overview
 
-The [Write-Ahead Logging](/contributor-guide/datanode/wal.md#introduction)(WAL) is a crucial component in GreptimeDB that persistently records every data modification to ensure no memory-cached data loss. GreptimeDB provides two WAL storage options:
+The [Write-Ahead Logging](/contributor-guide/datanode/wal.md#introduction)(WAL) is a crucial component in GreptimeDB that persistently records every data modification to ensure no memory-cached data loss. GreptimeDB provides three WAL storage options:
 
 - **Local WAL**: Uses an embedded storage engine([raft-engine](https://github.com/tikv/raft-engine)) within the [Datanode](/user-guide/concepts/why-greptimedb.md).
 
-- **Remote WAL**: Uses [Apache Kafka](https://kafka.apache.org/) as the external(remote) WAL storage component. 
+- **Remote WAL**: Uses [Apache Kafka](https://kafka.apache.org/) as the external(remote) WAL storage component.
+
+- **Noop WAL**: A no-op WAL provider for emergency situations when WAL becomes unavailable. Does not store any data. 
 
 ## Local WAL
 
@@ -40,9 +42,16 @@ The [Write-Ahead Logging](/contributor-guide/datanode/wal.md#introduction)(WAL)
 
 - **Network overhead**: Since WAL data needs to be transmitted over the network, careful planning of cluster network bandwidth is required to ensure low latency and high throughput, especially under write-heavy workloads.
 
+## Noop WAL
+
+Noop WAL is a special WAL provider for emergency situations when the configured WAL provider becomes temporarily unavailable. It does not store any WAL data and is only available in cluster mode.
+
+For detailed configuration, see the [Noop WAL](/user-guide/deployments-administration/wal/noop-wal.md) page.
 
 ## Next steps
 
 - To configure the Local WAL storage, please refer to [Local WAL](/user-guide/deployments-administration/wal/local-wal.md).
 
-- To learn more about the Remote WAL, please refer to [Remote WAL](/user-guide/deployments-administration/wal/remote-wal/configuration.md).
+- To learn more about the Remote WAL, please refer to [Remote WAL](/user-guide/deployments-administration/wal/remote-wal/configuration.md).
+
+- To learn more about the Noop WAL, please refer to [Noop WAL](/user-guide/deployments-administration/wal/noop-wal.md).
diff --git a/i18n/zh/docusaurus-plugin-content-docs/current/user-guide/deployments-administration/configuration.md b/i18n/zh/docusaurus-plugin-content-docs/current/user-guide/deployments-administration/configuration.md
@@ -357,7 +357,8 @@ write_cache_size = "10GiB"
 
 ### WAL 选项
 
-GreptimeDB 支持两种 WAL 存储方式：本地 WAL 和 Remote WAL。关于它们的对比，请参见 [WAL 概述](/user-guide/deployments-administration/wal/overview.md)。具体配置可参考 [本地 WAL](/user-guide/deployments-administration/wal/local-wal.md) 和 [Remote WAL](/user-guide/deployments-administration/wal/remote-wal/configuration.md) 文档。
+GreptimeDB 支持三种 WAL 存储方式：本地 WAL、Remote WAL 和 Noop WAL。关于它们的对比，请参见 [WAL 概述](/user-guide/deployments-administration/wal/overview.md)。具体配置可参考 [本地 WAL](/user-guide/deployments-administration/wal/local-wal.md)、[Remote WAL](/user-guide/deployments-administration/wal/remote-wal/configuration.md) 和 [Noop WAL](/user-guide/deployments-administration/wal/noop-wal.md) 文档。
+
 
 ### Logging 选项
 
diff --git a/i18n/zh/docusaurus-plugin-content-docs/current/user-guide/deployments-administration/wal/local-wal.md b/i18n/zh/docusaurus-plugin-content-docs/current/user-guide/deployments-administration/wal/local-wal.md
@@ -23,7 +23,7 @@ sync_write = false
 
 | 配置项            | 描述                                                                                            | 默认值            |
 | ----------------- | ----------------------------------------------------------------------------------------------- | ----------------- |
-| `provider`        | WAL 的提供者。可选项：`raft_engine`（本地文件系统存储）或 `kafka`（使用 Kafka 的远程 WAL 存储） | `"raft_engine"`   |
+| `provider`        | WAL 的提供者。可选项：`raft_engine`（本地文件系统存储）、`kafka`（使用 Kafka 的远程 WAL 存储）或 `noop`（无操作 WAL 提供者） | `"raft_engine"`   |
 | `dir`             | 日志写入目录                                                                                    | `{data_home}/wal` |
 | `file_size`       | 单个 WAL 日志文件的大小                                                                         | `128MB`           |
 | `purge_threshold` | 触发清理的 WAL 总大小阈值                                                                       | `1GB`             |
diff --git a/i18n/zh/docusaurus-plugin-content-docs/current/user-guide/deployments-administration/wal/noop-wal.md b/i18n/zh/docusaurus-plugin-content-docs/current/user-guide/deployments-administration/wal/noop-wal.md
@@ -0,0 +1,41 @@
+---
+keywords: [配置, Noop WAL, GreptimeDB Datanode, GreptimeDB, 集群模式]
+description: 介绍如何在集群模式下为 GreptimeDB Datanode 组件配置 Noop WAL。
+---
+# Noop WAL
+
+Noop WAL 是一种特殊的 WAL 提供者，用于 WAL 暂时不可用时的紧急情况。它不会存储任何 WAL 数据。
+
+## 可用性
+
+Noop WAL **仅在集群模式下可用**，单机模式不支持。
+
+## 使用场景
+
+- **WAL 暂时不可用**：当 WAL 提供者（如 Kafka）暂时不可用时，可以将 Datanode 切换到 Noop WAL 保持集群运行。
+- **测试和开发**：适用于不需要 WAL 持久化的测试场景。
+
+## 数据丢失警告
+
+**使用 Noop WAL 时，Datanode 关闭或重启会导致所有未刷新的数据丢失。** 仅应在 WAL 提供者不可用时临时使用，不建议用于生产环境，除非是紧急情况。
+
+## 配置
+
+为 Datanode 配置 Noop WAL：
+
+```toml
+[wal]
+provider = "noop"
+```
+
+在 GreptimeDB 集群中，WAL 配置分为两部分：
+
+- **Metasrv** - 负责为新 Region 生成 WAL 元数据，应配置为 `raft_engine` 或 `kafka`。
+- **Datanode** - 负责 WAL 数据读写，可在 WAL 提供者不可用时配置为 `noop`。
+
+注意：Noop WAL 只能配置在 Datanode 上，Metasrv 不支持。使用 Noop WAL 时，Metasrv 仍使用原配置的 WAL 提供者。
+
+## 最佳实践
+
+- 定期使用 `admin flush_table()` 或 `admin flush_region()` 刷新 Region，减少数据丢失。
+- WAL 提供者恢复后，尽快切换回正常配置。
diff --git a/i18n/zh/docusaurus-plugin-content-docs/current/user-guide/deployments-administration/wal/overview.md b/i18n/zh/docusaurus-plugin-content-docs/current/user-guide/deployments-administration/wal/overview.md
@@ -4,13 +4,15 @@ description: 介绍 GreptimeDB 中的 WAL（预写日志），包括本地 WAL 
 ---
 # 概述
 
-[预写日志](/contributor-guide/datanode/wal.md#introduction)(WAL) 是 GreptimeDB 的关键组件之一，负责持久化记录每次数据修改操作，以确保内存中的数据在故障发生时不会丢失。GreptimeDB 支持两种 WAL 存储方案：
+[预写日志](/contributor-guide/datanode/wal.md#introduction)(WAL) 是 GreptimeDB 的关键组件之一，负责持久化记录每次数据修改操作，以确保内存中的数据在故障发生时不会丢失。GreptimeDB 支持三种 WAL 存储方案：
 
 
 - **本地 WAL**: 使用嵌入式存储引擎 [raft-engine](https://github.com/tikv/raft-engine) ，直接集成在 [Datanode](/user-guide/concepts/why-greptimedb.md) 服务中。
 
 - **Remote WAL**: 使用 [Apache Kafka](https://kafka.apache.org/) 作为外部的 WAL 存储组件。
 
+- **Noop WAL**: 无操作 WAL 提供者，用于 WAL 暂时不可用的紧急情况，不存储任何数据。
+
 ## 本地 WAL
 
 ### 优点
@@ -34,7 +36,7 @@ description: 介绍 GreptimeDB 中的 WAL（预写日志），包括本地 WAL 
 - **低 RTO**: 通过将 WAL 与 Datanode 解耦，[恢复时间目标](https://en.wikipedia.org/wiki/Disaster_recovery#Recovery_Time_Objective) (RTO) 得以最小化。当 Datanode 崩溃时，Metasrv 会发起 [Region Failover](/user-guide/deployments-administration/manage-data/region-failover.md) ，将受影响 Region 迁移至健康节点，无需本地重放 WAL。
 
 
-- **多消费者订阅**:Remote WAL 支持多个消费者同时订阅 WAL 日志，实现 Region 热备和 [Region Migration](/user-guide/deployments-administration/manage-data/region-migration.md) 等功能，提升系统的高可用性和灵活性。
+- **多消费者订阅**: Remote WAL 支持多个消费者同时订阅 WAL 日志，实现 Region 热备和 [Region Migration](/user-guide/deployments-administration/manage-data/region-migration.md) 等功能，提升系统的高可用性和灵活性。
 
 
 ### 缺点
@@ -43,9 +45,16 @@ description: 介绍 GreptimeDB 中的 WAL（预写日志），包括本地 WAL 
 
 - **网络开销**: WAL 数据需通过网络传输，需合理规划集群网络带宽，确保低延迟与高吞吐量，尤其在写入密集型负载下。
 
+## Noop WAL
+
+Noop WAL 是一种特殊的 WAL 提供者，用于 WAL 暂时不可用的紧急情况。它不会存储任何 WAL 数据，仅在集群模式下可用。
+
+详细配置说明请参阅 [Noop WAL](/user-guide/deployments-administration/wal/noop-wal.md)。
 
 ## 后续步骤
 
 - 如需配置本地 WAL 存储，请参阅[本地 WAL](/user-guide/deployments-administration/wal/local-wal.md)。
 
-- 想了解更多 Remote WAL 相关信息，请参阅 [Remote WAL](/user-guide/deployments-administration/wal/remote-wal/configuration.md)。
+- 想了解更多 Remote WAL 相关信息，请参阅 [Remote WAL](/user-guide/deployments-administration/wal/remote-wal/configuration.md)。
+
+- 想了解更多 Noop WAL 相关信息，请参阅 [Noop WAL](/user-guide/deployments-administration/wal/noop-wal.md)。
diff --git a/sidebars.ts b/sidebars.ts
@@ -311,6 +311,7 @@ const sidebars: SidebarsConfig = {
                     'user-guide/deployments-administration/wal/remote-wal/manage-kafka',
                   ]
                 },
+                'user-guide/deployments-administration/wal/noop-wal',
               ],
             },
             'user-guide/deployments-administration/configuration',

Original file line number	Diff line number	Diff line change
`@@ -311,6 +311,7 @@ const sidebars: SidebarsConfig = {`
`311`	`311`	`'user-guide/deployments-administration/wal/remote-wal/manage-kafka',`
`312`	`312`	`]`
`313`	`313`	`},`
	`314`	`+ 'user-guide/deployments-administration/wal/noop-wal',`
`314`	`315`	`],`
`315`	`316`	`},`
`316`	`317`	`'user-guide/deployments-administration/configuration',`