[筆記] AWS EventBridge

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AWS的事件中心

流程為所有Event都會被傳入 event bus, 其中透過Rule來過濾事件, 符合條件的事件, 會trigger 特定組件 ( e.g. lambda,SQS/SNS…), 不符合則是忽略

graph LR
    S3_Event --> EventBus
    EC2_Instance --> EventBus
    CloudTail --> EventBus
    Cron --> EventBus

    subgraph EventBridge
        EventBus --> A{match rule ?} -->|Yes ,json trigger| Lambda
        A -->|No| Ignore
    end

Event Bus

可以視為 EventBridge的處理事件的中心, 所有事件都會傳入 Event Bus , 才開始後續動作

Event Bus 可以藉由 AWS Account中的 Resource-based policies 來控制存取權限
Event 進入至 Event Bus 後, 可以透過Rule來過濾事件
Event Bus archive(需額外費用), 可以將事件封存 (一段期限或是永久), default archive為關閉, 若開啟, archive期限default為永久
可 replay event (如某個event可驅動特定lambda, 之後可無限重複使用該event來驅動該lambda)

Event Bus Source

傳入Event Bus的來源, 可以是以下幾種

AWS Service

來自AWS服務的所有事件

例如以下

定時執行任務 schedule or cron
EC2 Instance被啟動
CodeBuild 建立失敗
S3 Upload object
Trusted Advisor, 有新發現
CloudTail 任何API被調用

AWS Partner

也可以是 AWS合作的SaaS, e.g. Zendesk,DataDog,Auth0 …
可將這些服務所發生的事件傳入 Event Bus

Custom Apps

自定義的app

Event Bridge Rule

Event進入 event bus後 , Rule 會過濾事件的, 符合條件的事件, 才會trigger

創建Rule

Rule type

擇一

Rule with an event pattern : 特定event驅動
Schedule: 定期性任務

Event Source

擇一

AWS service
Other (Custom , partner or other)
All Event

Sample Event (Optional)

json格式, 定義 Event的範例, 主要用於開發或調適, 可驗證規則

e.g. EC2狀態改變, 被停止

{
  "version": "0",
  "id": "651d5f8b-947c-4c0f-acb7-5ac4e41a1b8a",
  "detail-type": "EC2 Instance State-change Notification",
  "source": "aws.ec2",
  "account": "123456789012",
  "time": "2015-11-11T21:33:19Z",
  "region": "us-east-1",
  "resources": [
    "arn:aws:ec2:us-east-1:123456789012:instance/i-abcd3333"
  ],
  "detail": {
    "instance-id": "i-abcd3333",
    "state": "stopped"
  }
}

Event Pattern

定義 Event的條件, 符合條件的事件才會trigger application

e.g. EC2被關閉或是終止

{
  "source": [
    "aws.ec2"
  ],
  "detail-type": [
    "EC2 Instance State-change Notification"
  ],
  "detail": {
    "state": [
      "stopped",
      "terminated"
    ]
  }
}

Schema Registry

可以將 event 的 json schema 產生 java/python/Typescript/go 的 code, 用於 marshalling / unmarshalling
詳細用途待驗證 …

Resource-Base Policy

用於管理特定EventBus的存取權限 e.g. allow / deny 來自其他AWS Account or Region 的事件

允許其他AWS帳號的event 進入event bus

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "AWS": "1112222333"
        // AWS Account ID
      },
      "Action": "events:PutEvents",
      "Resource": "arn:aws:events:us-east-1:123456789012:event-bus/central-event-bus"
    }
  ]
}

graph LR
    subgraph 1112222333
        Lambda_function
    end

    subgraph 123456789012
        EventBridge_Bus
    end

    Lambda_function -->|PutEvents| EventBridge_Bus

Input Transformation

這邊是將原始輸出類似relabel, 輸出成其他 schema, 再利用該schema 的變數輸出成需求格式

sample event (可理解成原始的輸出範例)

{
  "version": "0",
  "id": "7bf73129-1428-4cd3-a780-95db273d1602",
  "detail-type": "EC2 Instance State-change Notification",
  "source": "aws.ec2",
  "account": "123456789012",
  "time": "2015-11-11T21:29:54Z",
  "region": "us-east-1",
  "resources": ["arn:aws:ec2:us-east-1:123456789012:instance/i-abcd1111"],
  "detail": {
    "instance-id": "i-abcd1111",
    "state": "pending"
  }
}

input transformer (可理解成relabel後的新輸出,就是重新定義key的名稱, value用原始key去代 )

{
  "timestamp" : "$.time",
  "instance" : "$.detail.instance-id",
  "state" : "$.detail.state",
  "resource" : "$.resources[0]"
}

Template (這邊就是用 transformer後的新key 根據需求輸出)

這邊template需為json格式,

{
  "timestamp": <timestamp>,
  "message": "<instance> is in state <state> at <timestamp>, with arn <resource>."
}

實際數值為

{
  "timestamp": 2015 - 11 - 11 T21: 29: 54 Z,
  "message": "i-abcd1111 is in state pending at 2015-11-11T21:29:54Z, with arn arn:aws:ec2:us-east-1:123456789012:instance/i-abcd1111."
}

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