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# Menangani acara Amazon ECS
<a name="ecs_cwet_handling"></a>

Amazon ECS mengirimkan acara *setidaknya sekali*. Ini berarti Anda mungkin menerima banyak salinan dari acara tertentu. Selain itu, peristiwa mungkin tidak dikirimkan ke listener peristiwa Anda sesuai urutan peristiwa yang terjadi.

Untuk memesan acara dengan benar, `detail` bagian dari setiap acara berisi `version` properti. Setiap kali sumber daya mengubah status, `version` ini bertambah. Peristiwa duplikat memiliki `version` yang sama di objek `detail`. Jika Anda mereplikasi instans penampung Amazon ECS dan status tugas dengan EventBridge, Anda dapat membandingkan versi sumber daya yang dilaporkan oleh Amazon ECS API dengan sumber daya yang `version` dilaporkan dalam EventBridge untuk memverifikasi bahwa versi dalam aliran peristiwa Anda saat ini. Peristiwa dengan jumlah properti versi yang lebih tinggi harus diperlakukan sebagai peristiwa yang terjadi setelah peristiwa dengan jumlah versi yang lebih rendah.

## Contoh: Menangani peristiwa dalam suatu AWS Lambda fungsi
<a name="ecs_cwet_handling_example"></a>

Contoh berikut menunjukkan fungsi Lambda yang ditulis dengan Python 3.9 yang menangkap peristiwa perubahan status instance tugas dan kontainer dan menyimpannya ke salah satu dari dua tabel Amazon DynamoDB:
+ *ECSCtrInstanceState*— Menyimpan status terbaru untuk instance kontainer. ID tabel adalah nilai `containerInstanceArn` instans kontainer.
+ *ECSTaskState*— Menyimpan status terbaru untuk suatu tugas. ID tabel adalah nilai `taskArn` tugas.

```
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
        )
```

Contoh Fargate berikut menunjukkan fungsi Lambda yang ditulis dengan Python 3.9 yang menangkap peristiwa perubahan status tugas dan menyimpannya ke tabel Amazon DynamoDB berikut:

```
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"]
    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
        )
```