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# 步驟 1：為自訂 AWS AppConfig 延伸模組建立 Lambda 函數
<a name="working-with-appconfig-extensions-creating-custom-lambda"></a>

對於大多數使用案例，若要建立自訂擴充功能，您必須建立 AWS Lambda 函數來執行擴充功能中定義的任何運算和處理。本節包含自訂 AWS AppConfig 延伸模組的 Lambda 函數範例程式碼。本節也包含承載請求和回應參考詳細資訊。如需有關建立 Lambda 函數的資訊，請參閱《 *AWS Lambda 開發人員指南*》中的 [Lambda 入門](https://docs.aws.amazon.com/lambda/latest/dg/getting-started.html)。

## 範本程式碼
<a name="working-with-appconfig-extensions-creating-custom-lambda-code-sample"></a>

叫用 Lambda 函數時，下列範例程式碼會自動將 AWS AppConfig 組態備份到 Amazon S3 儲存貯體。每當建立新組態或部署時，就會備份組態。範例使用延伸參數，因此不需要在 Lambda 函數中硬式編碼儲存貯體名稱。透過使用延伸參數，使用者可以將延伸模組連接至多個應用程式，並將組態備份至不同的儲存貯體。程式碼範例包含註解，以進一步說明函數。

** AWS AppConfig 延伸模組的範例 Lambda 函數**

```
from datetime import datetime
import base64
import json

import boto3


def lambda_handler(event, context):
    print(event)
    
    # Extensions that use the PRE_CREATE_HOSTED_CONFIGURATION_VERSION and PRE_START_DEPLOYMENT 
    # action points receive the contents of AWS AppConfig configurations in Lambda event parameters.
    # Configuration contents are received as a base64-encoded string, which the lambda needs to decode 
    # in order to get the configuration data as bytes. For other action points, the content 
    # of the configuration isn't present, so the code below will fail.
    config_data_bytes = base64.b64decode(event["Content"])
    
    # You can specify parameters for extensions. The CreateExtension API action lets you define  
    # which parameters an extension supports. You supply the values for those parameters when you 
    # create an extension association by calling the CreateExtensionAssociation API action.
    # The following code uses a parameter called S3_BUCKET to obtain the value specified in the 
    # extension association. You can specify this parameter when you create the extension 
    # later in this walkthrough.
    extension_association_params = event.get('Parameters', {})
    bucket_name = extension_association_params['S3_BUCKET']
    write_backup_to_s3(bucket_name, config_data_bytes)
    
    # The PRE_CREATE_HOSTED_CONFIGURATION_VERSION and PRE_START_DEPLOYMENT action points can 
    # modify the contents of a configuration. The following code makes a minor change 
    # for the purposes of a demonstration.
    old_config_data_string = config_data_bytes.decode('utf-8')
    new_config_data_string = old_config_data_string.replace('hello', 'hello!')
    new_config_data_bytes = new_config_data_string.encode('utf-8')
    
    # The lambda initially received the configuration data as a base64-encoded string 
    # and must return it in the same format.
    new_config_data_base64string = base64.b64encode(new_config_data_bytes).decode('ascii')
    
    return {
        'statusCode': 200,
        # If you want to modify the contents of the configuration, you must include the new contents in the 
        # Lambda response. If you don't want to modify the contents, you can omit the 'Content' field shown here.
        'Content': new_config_data_base64string
    }


def write_backup_to_s3(bucket_name, config_data_bytes):
    s3 = boto3.resource('s3')
    new_object = s3.Object(bucket_name, f"config_backup_{datetime.now().isoformat()}.txt")
    new_object.put(Body=config_data_bytes)
```

如果您想要在此演練期間使用此範例，請將其儲存為名稱，**MyS3ConfigurationBackUpExtension**並複製函數的 Amazon Resource Name (ARN)。您可以在下一節中建立 AWS Identity and Access Management (IAM) 擔任角色時指定 ARN。您可以在建立擴充功能時指定 ARN 和名稱。

## 承載參考
<a name="working-with-appconfig-extensions-creating-custom-lambda-payload"></a>

本節包含使用自訂 AWS AppConfig 擴充功能的承載請求和回應參考詳細資訊。

**請求結構**  
*AtDeploymentTick*

```
{
    'InvocationId': 'o2xbtm7',
    'Parameters': {
        'ParameterOne': 'ValueOne',
        'ParameterTwo': 'ValueTwo'
    },
    'Type': 'OnDeploymentStart',
    'Application': {
        'Id': 'abcd123'
    },
    'Environment': {
        'Id': 'efgh456'
    },
    'ConfigurationProfile': {
        'Id': 'ijkl789',
        'Name': 'ConfigurationName'
    },
    'DeploymentNumber': 2,
    'Description': 'Deployment description',
    'ConfigurationVersion': '2',
    'DeploymentState': 'DEPLOYING',
    'PercentageComplete': '0.0'
}
```

**請求結構**  
*PreCreateHostedConfigurationVersion*

```
{
    'InvocationId': 'vlns753', // id for specific invocation
    'Parameters': {
        'ParameterOne': 'ValueOne',
        'ParameterTwo': 'ValueTwo'
    },
    'ContentType': 'text/plain',
    'ContentVersion': '2',
    'Content': 'SGVsbG8gZWFydGgh', // Base64 encoded content
    'Application': {
        'Id': 'abcd123',
        'Name': 'ApplicationName'
    },
    'ConfigurationProfile': {
        'Id': 'ijkl789',
        'Name': 'ConfigurationName'
    },
    'Description': '',
    'Type': 'PreCreateHostedConfigurationVersion',
    'PreviousContent': {
        'ContentType': 'text/plain',
        'ContentVersion': '1',
        'Content': 'SGVsbG8gd29ybGQh'
    }
}
```

*PreStartDeployment*

```
{
    'InvocationId': '765ahdm',
    'Parameters': {
        'ParameterOne': 'ValueOne',
        'ParameterTwo': 'ValueTwo'
    },
    'ContentType': 'text/plain',
    'ContentVersion': '2',
    'Content': 'SGVsbG8gZWFydGgh',
    'Application': {
        'Id': 'abcd123',
        'Name': 'ApplicationName'
    },
    'Environment': {
        'Id': 'ibpnqlq',
        'Name': 'EnvironmentName'
    },
    'ConfigurationProfile': {
        'Id': 'ijkl789',
        'Name': 'ConfigurationName'
    },
    'DeploymentNumber': 2,
    'Description': 'Deployment description',
    'Type': 'PreStartDeployment'
}
```

**非同步事件**  


*OnStartDeployment、OnDeploymentStep、OnDeployment*

```
{
    'InvocationId': 'o2xbtm7',
    'Parameters': {
        'ParameterOne': 'ValueOne',
        'ParameterTwo': 'ValueTwo'
    },
    'Type': 'OnDeploymentStart',
    'Application': {
        'Id': 'abcd123'
    },
    'Environment': {
        'Id': 'efgh456'
    },
    'ConfigurationProfile': {
        'Id': 'ijkl789',
        'Name': 'ConfigurationName'
    },
    'DeploymentNumber': 2,
    'Description': 'Deployment description',
    'ConfigurationVersion': '2'
}
```

**回應結構**  
下列範例顯示 Lambda 函數傳回的內容，以回應自訂 AWS AppConfig 擴充功能的請求。

*PRE\_\* 同步事件 - 成功回應*

如果您想要轉換內容，請使用下列項目：

```
"Content": "SomeBase64EncodedByteArray"
```

*AT\_\* 同步事件 - 成功回應*

如果您想要控制部署的後續步驟 （繼續部署或復原），請在回應中設定 `Directive`和 `Description` 屬性。

```
"Directive": "ROLL_BACK"
"Description" "Deployment event log description"
```

`Directive` 支援兩個值： `CONTINUE`或 `ROLL_BACK`。在承載回應中使用這些列舉來控制部署的後續步驟。

*同步事件 - 成功回應*

如果您想要轉換內容，請使用下列項目：

```
"Content": "SomeBase64EncodedByteArray"
```

如果您不想轉換內容，則不傳回任何內容。

*非同步事件 - 成功回應*

不傳回任何內容。

*所有錯誤事件*

```
{
        "Error": "BadRequestError",
        "Message": "There was malformed stuff in here",
        "Details": [{
            "Type": "Malformed",
            "Name": "S3 pointer",
            "Reason": "S3 bucket did not exist"
        }]
    }
```