Amazon Elastic Container Service
开发人员指南 (API 版本 2014-11-13)
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处理事件

Amazon ECS 至少发送事件一次。这意味着,您可能收到给定事件的多个副本。此外,无法按事件的发生顺序将事件传送到事件侦听器。

要启用适当的事件排序,每个事件的 detail 部分均包含一个 version 属性。版本属性数值更大的事件应视为在版本号更小的事件之后发生。具有匹配版本号的事件可视为重复事件。

示例:在 AWS Lambda 函数中处理事件

以下示例显示了一个用 Python 2.7 编写的 Lambda 函数,此函数可同时捕获任务和容器实例状态更改事件,并将这些事件保存到两个 Amazon DynamoDB 表之一:

  • ECSCtrInstanceState:存储容器实例的最新状态。表 ID 是容器实例的 containerInstanceArn 值。

  • ECSTaskState:存储任务的最新状态。表 ID 是任务的 taskArn 值。

import json import boto3 def lambda_handler(event, context): id_name = "" new_record = {} # For debugging so you can see raw event format. print('Here is the event:') print(json.dumps(event)) if event["source"] != "aws.ecs": raise ValueError("Function only supports input from events with a source type of: aws.ecs") # Switch on task/container events. table_name = "" if event["detail-type"] == "ECS Task State Change": table_name = "ECSTaskState" id_name = "taskArn" event_id = event["detail"]["taskArn"] elif event["detail-type"] == "ECS Container Instance State Change": table_name = "ECSCtrInstanceState" id_name = "containerInstanceArn" event_id = event["detail"]["containerInstanceArn"] else: raise ValueError("detail-type for event is not a supported type. Exiting without saving event.") new_record["cw_version"] = event["version"] new_record.update(event["detail"]) # "status" is a reserved word in DDB, but it appears in containerPort # state change messages. if "status" in event: new_record["current_status"] = event["status"] new_record.pop("status") # Look first to see if you have received a newer version of an event ID. # If the version is OLDER than what you have on file, do not process it. # Otherwise, update the associated record with this latest information. print("Looking for recent event with same ID...") dynamodb = boto3.resource("dynamodb", region_name="us-east-1") table = dynamodb.Table(table_name) saved_event = table.get_item( Key={ id_name : event_id } ) if "Item" in saved_event: # Compare events and reconcile. print("EXISTING EVENT DETECTED: Id " + event_id + " - reconciling") if saved_event["Item"]["version"] < event["detail"]["version"]: print("Received event is a more recent version than the stored event - updating") table.put_item( Item=new_record ) else: print("Received event is an older version than the stored event - ignoring") else: print("Saving new event - ID " + event_id) table.put_item( Item=new_record )