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# 示例：DynamoDB CloudWatch、和 SNS
<a name="customize-environment-resources-dynamodb"></a>

此配置文件将 DynamoDB 表设置为使用适用于 PHP 的 SDK 2 的基于 PHP 的应用程序的 AWS 会话处理程序。要使用此示例，您必须拥有 IAM 实例配置文件，该文件会添加到环境中的实例，并用来访问 DynamoDB 表。

 您可以在 [DynamoDB 会话支持示例](https://elasticbeanstalk.s3.amazonaws.com/extensions/PHP-DynamoDB-Session-Support.zip)中下载该示例，我们在本步骤会用到这个示例。此示例包含以下文件：
+ 示例应用程序 `index.php`
+ 一个配置文件`dynamodb.config`，用于创建和配置 DynamoDB 表 AWS 和其他资源，并在 Elastic Beanstalk 环境中托管应用程序的 EC2 实例上安装软件
+ 配置文件 `options.config`，该文件会使用此特定安装的特定设置覆盖 `dynamodb.config` 中的默认设置

**`index.php`**

```
<?php

// Include the SDK using the Composer autoloader
require '../vendor/autoload.php';

use Aws\DynamoDb\DynamoDbClient;

// Grab the session table name and region from the configuration file
list($tableName, $region) = file(__DIR__ . '/../sessiontable');
$tableName = rtrim($tableName);
$region = rtrim($region);

// Create a DynamoDB client and register the table as the session handler
$dynamodb = DynamoDbClient::factory(array('region' => $region));
$handler = $dynamodb->registerSessionHandler(array('table_name' => $tableName, 'hash_key' => 'username'));

// Grab the instance ID so we can display the EC2 instance that services the request
$instanceId = file_get_contents("http://169.254.169.254/latest/meta-data/instance-id");
?>
<h1>Elastic Beanstalk PHP Sessions Sample</h1>
<p>This sample application shows the integration of the Elastic Beanstalk PHP
container and the session support for DynamoDB from the AWS SDK for PHP 2.
Using DynamoDB session support, the application can be scaled out across
multiple web servers. For more details, see the
<a href="https://aws.amazon.com/php/">PHP Developer Center</a>.</p>

<form id="SimpleForm" name="SimpleForm" method="post" action="index.php">
<?php
echo 'Request serviced from instance ' . $instanceId . '<br/>';
echo '<br/>';

if (isset($_POST['continue'])) {
  session_start();
  $_SESSION['visits'] = $_SESSION['visits'] + 1;
  echo 'Welcome back ' . $_SESSION['username'] . '<br/>';
  echo 'This is visit number ' . $_SESSION['visits'] . '<br/>';
  session_write_close();
  echo '<br/>';
  echo '<input type="Submit" value="Refresh" name="continue" id="continue"/>';
  echo '<input type="Submit" value="Delete Session" name="killsession" id="killsession"/>';
} elseif (isset($_POST['killsession'])) {
  session_start();
  echo 'Goodbye ' . $_SESSION['username'] . '<br/>';
  session_destroy();
  echo 'Username: <input type="text" name="username" id="username" size="30"/><br/>';
  echo '<br/>';
  echo '<input type="Submit" value="New Session" name="newsession" id="newsession"/>';
} elseif (isset($_POST['newsession'])) {
  session_start();
  $_SESSION['username'] = $_POST['username'];
  $_SESSION['visits'] = 1;
  echo 'Welcome to a new session ' . $_SESSION['username'] . '<br/>';
  session_write_close();
  echo '<br/>';
  echo '<input type="Submit" value="Refresh" name="continue" id="continue"/>';
  echo '<input type="Submit" value="Delete Session" name="killsession" id="killsession"/>';
} else {
  echo 'To get started, enter a username.<br/>';
  echo '<br/>';
  echo 'Username: <input type="text" name="username" id="username" size="30"/><br/>';
  echo '<input type="Submit" value="New Session" name="newsession" id="newsession"/>';
}
?>
</form>
```

**`.ebextensions/dynamodb.config`**

```
Resources:
  SessionTable:
    Type: AWS::DynamoDB::Table
    Properties:
      KeySchema: 
        HashKeyElement:
          AttributeName:
            Fn::GetOptionSetting:
              OptionName : SessionHashKeyName
              DefaultValue: "username"
          AttributeType:
            Fn::GetOptionSetting:
              OptionName : SessionHashKeyType
              DefaultValue: "S"
      ProvisionedThroughput:
        ReadCapacityUnits:
          Fn::GetOptionSetting:
            OptionName : SessionReadCapacityUnits
            DefaultValue: 1
        WriteCapacityUnits:
          Fn::GetOptionSetting:
            OptionName : SessionWriteCapacityUnits
            DefaultValue: 1

  SessionWriteCapacityUnitsLimit:
    Type: AWS::CloudWatch::Alarm
    Properties:
      AlarmDescription: { "Fn::Join" : ["", [{ "Ref" : "AWSEBEnvironmentName" }, " write capacity limit on the session table." ]]}
      Namespace: "AWS/DynamoDB"
      MetricName: ConsumedWriteCapacityUnits
      Dimensions:
        - Name: TableName
          Value: { "Ref" : "SessionTable" }
      Statistic: Sum
      Period: 300
      EvaluationPeriods: 12
      Threshold:
          Fn::GetOptionSetting:
            OptionName : SessionWriteCapacityUnitsAlarmThreshold
            DefaultValue: 240
      ComparisonOperator: GreaterThanThreshold
      AlarmActions:
        - Ref: SessionAlarmTopic
      InsufficientDataActions:
        - Ref: SessionAlarmTopic

  SessionReadCapacityUnitsLimit:
    Type: AWS::CloudWatch::Alarm
    Properties:
      AlarmDescription: { "Fn::Join" : ["", [{ "Ref" : "AWSEBEnvironmentName" }, " read capacity limit on the session table." ]]}
      Namespace: "AWS/DynamoDB"
      MetricName: ConsumedReadCapacityUnits
      Dimensions:
        - Name: TableName
          Value: { "Ref" : "SessionTable" }
      Statistic: Sum
      Period: 300
      EvaluationPeriods: 12
      Threshold:
          Fn::GetOptionSetting:
            OptionName : SessionReadCapacityUnitsAlarmThreshold
            DefaultValue: 240
      ComparisonOperator: GreaterThanThreshold
      AlarmActions:
        - Ref: SessionAlarmTopic
      InsufficientDataActions:
        - Ref: SessionAlarmTopic

  SessionThrottledRequestsAlarm:
    Type: AWS::CloudWatch::Alarm
    Properties:
      AlarmDescription: { "Fn::Join" : ["", [{ "Ref" : "AWSEBEnvironmentName" }, ": requests are being throttled." ]]}
      Namespace: AWS/DynamoDB
      MetricName: ThrottledRequests
      Dimensions:
        - Name: TableName
          Value: { "Ref" : "SessionTable" }
      Statistic: Sum
      Period: 300
      EvaluationPeriods: 1
      Threshold: 
        Fn::GetOptionSetting:
          OptionName: SessionThrottledRequestsThreshold
          DefaultValue: 1
      ComparisonOperator: GreaterThanThreshold
      AlarmActions:
        - Ref: SessionAlarmTopic
      InsufficientDataActions:
        - Ref: SessionAlarmTopic

  SessionAlarmTopic:
    Type: AWS::SNS::Topic
    Properties:
      Subscription:
        - Endpoint:
            Fn::GetOptionSetting:
              OptionName: SessionAlarmEmail
              DefaultValue: "nobody@amazon.com"
          Protocol: email

files:
  "/var/app/sessiontable":
    mode: "000444"
    content: |
      `{"Ref" : "SessionTable"}`
      `{"Ref" : "AWS::Region"}`

  "/var/app/composer.json":
    mode: "000744"
    content:
      {
        "require": {
           "aws/aws-sdk-php": "*"
        }
      }

container_commands:
 "1-install-composer":
   command: "cd /var/app; curl -s http://getcomposer.org/installer | php"
 "2-install-dependencies":
   command: "cd /var/app; php composer.phar install"
 "3-cleanup-composer":
   command: "rm -Rf /var/app/composer.*"
```

在示例配置文件中，我们首先创建 DynamoDB 表，并配置该表的主密钥结构和容量单位，以便分配足够的资源提供所要求的吞吐量。接下来，我们为`WriteCapacity`和创建 CloudWatch 警报`ReadCapacity`。我们会创建 SNS 主题，该主题会在警报阈值被突破时将电子邮件发送到“nobody@amazon.com”。

在我们为环境创建和配置 AWS 资源之后，我们需要自定义 EC2 实例。我们使用`files`密钥将 DynamoDB 表的详细信息传递给我们环境中的 EC2 实例，并在文件中`composer.json`为适用于 AWS PHP 的 SDK 2 添加一个 “要求”。最后，我们会运行容器命令安装编辑器和必需的依赖项，然后删除安装程序。

**`.ebextensions/options.config`**

```
option_settings:
  "aws:elasticbeanstalk:customoption":
     SessionHashKeyName                      : username
     SessionHashKeyType                      : S
     SessionReadCapacityUnits                : 1
     SessionReadCapacityUnitsAlarmThreshold  : 240
     SessionWriteCapacityUnits               : 1 
     SessionWriteCapacityUnitsAlarmThreshold : 240
     SessionThrottledRequestsThreshold       : 1
     SessionAlarmEmail                       : me@example.com
```

将该 SessionAlarmEmail 值替换为您想要发送警报通知的电子邮件。`options.config` 文件包含 `dynamodb.config` 中用于定义的部分变量的值。例如，`dynamodb.config` 包含以下行：

```
Subscription:
  - Endpoint:
      Fn::GetOptionSetting:
        OptionName: SessionAlarmEmail
        DefaultValue: "nobody@amazon.com"
```

****这些行告诉 Elastic Beanstalk **SessionAlarmEmail**从配置`options.config`文件（在我们的示例应用程序中）中的值中获取 Endpoint 属性的值，该文件包含一个 option\$1settings 部分，其中有一个 aws: elasticbeanstalk: customoption 部分，其中包含包含要使用的实际值的名称-值对。****在上面的示例中，这意味着**SessionAlarmEmail**将分配该值`nobody@amazon.com`。

有关本示例中使用的 CloudFormation 资源的更多信息，请参阅以下参考资料：
+ [AWS::DynamoDB::Table](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-dynamodb-table.html)
+ [AWS::CloudWatch::Alarm](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-cw-alarm.html)
+ [AWS::SNS::Topic](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-sns-topic.html)