original post: https://status.openai.com/incidents/ctrsv3lwd797

To create a clear flow chart based on the thought process, we will organize the components and their interactions into a structured diagram. Here’s a step-by-step outline of the flow chart:

Flow Chart Outline #

1. Control Plane #

• API Server
  
  • Connects to etcd for persistent storage.
    
  • Interacts with Scheduler and Controller Manager for cluster management.
    
• Scheduler
  
  • Sends pod scheduling requests to API Server.
    
• Controller Manager
  
  • Manages cluster state through API Server.
    
• etcd
  
  • Stores cluster state data.
    
    

2. DNS Service (CoreDNS) #

• CoreDNS
  
  • Queries API Server for service information.
    
  • Provides DNS resolution to Data Plane.
    
    

3. Data Plane #

• Nodes and Pods
  
  • Use CoreDNS for service name resolution.
    
  • Communicate using resolved IP addresses.
    
    

4. Incident Scenario #

• Telemetry Service
  
  • Sends excessive requests to API Server.
    
• API Server Overload
  
  • Becomes unresponsive due to high load.
    
• CoreDNS Failure
  
  • Cannot query API Server for service information.
    
• Pod Communication Failure
  
  • Unable to resolve service names, leading to communication issues.
    
    

Visual Representation #

[Control Plane]                     [DNS Service]                     [Data Plane]
  | API Server ------------------> [CoreDNS] ------------------> [Nodes and Pods]
  | /            \                 | Queries API Server            | Uses DNS for communication
  v             v                  | for service info              |
[Scheduler]   [Controller Manager]
  |               |
  v               v
[etcd]          [Cluster Management]

Incident Flow #

[Telemetry Service] → [API Server] (Overloaded)
                        ↓
                 [CoreDNS] (Stale or No Updates)
                        ↓
         [Nodes and Pods] (DNS Resolution Fails → Communication Breaks)

Legend #

• Rectangles: Components/services
  
• Arrows: Data flow or interactions
  
• Dashed Arrows: Exception or error paths
  
  

Notes #

• API Server is central, interacting with etcd, Scheduler, and Controller Manager.
  
• CoreDNS depends on API Server for service information.
  
• Pods rely on CoreDNS for name resolution.
  
• Telemetry Service can overload API Server, causing cascading failures.
  
  

This flow chart provides a clear visualization of the Kubernetes architecture and the impact of an overloaded API Server on the overall cluster operation.

以下是中文版的流程图和解释：

---

流程图结构 #

[控制平面]                     [DNS服务]                     [数据平面]
  | API服务器 ------------------> [CoreDNS] ------------------> [节点和Pod]
  | /            \                 | 查询API服务器              | 使用DNS进行通信
  v             v                  | 获取服务信息               |
[调度器]     [控制器管理器]
  |               |
  v               v
[etcd]          [集群管理]

事故流程 #

[监控/Telemetry服务] --> [API服务器] (过载)
                        |
                        v
                     [CoreDNS] (无法解析)
                        |
                        v
                   [节点和Pod] (通信失败)

图例 #

• 矩形框：组件/服务
  
• 箭头：数据流或交互
  
• 虚线箭头：异常或错误路径
  
  

注释 #

• API服务器 是核心，与 etcd、调度器 和 控制器管理器 交互。
  
• CoreDNS 依赖 API服务器 获取服务信息。
  
• Pod 依赖 CoreDNS 进行名称解析。
  
• 监控服务 可能过载 API服务器，导致级联故障。
  
  

---

详细解释 #

1. 控制平面

   • API服务器：连接到etcd进行数据存储，与调度器和控制器管理器交互进行集群管理。
     
   • 调度器：向API服务器发送Pod调度请求。
     
   • 控制器管理器：通过API服务器管理集群状态。
     
   • etcd：存储集群状态数据。
     
     

2. DNS服务（CoreDNS）

   • CoreDNS：查询API服务器获取服务信息，为数据平面提供DNS解析。
     
     

3. 数据平面

   • 节点和Pod：使用CoreDNS进行服务名称解析，通过解析的IP地址进行通信。
     
     

4. 事故场景

   • 监控服务 发送大量请求到API服务器，导致API服务器过载，无法响应。
     
   • CoreDNS 无法查询API服务器获取服务信息，导致Pod之间通信失败。
     
     

---

此流程图提供了Kubernetes架构的清晰可视化，并展示了API服务器过载对整个集群操作的影响。