AWS Elastic Beanstalk
Developer Guide (API Version 2010-12-01)
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Example: DynamoDB, CloudWatch, and SNS

This configuration file sets up the DynamoDB table as a session handler for a PHP-based application using the AWS SDK for PHP 2. To use this example, you must have an IAM instance profile, which is added to the instances in your environment and used to access the DynamoDB table.

You can download the sample that we'll use in this step at DynamoDB Session Support Example. The sample contains the following files:

  • The sample application, index.php

  • A configuration file, dynamodb.config, to create and configure a DynamoDB table and other AWS resources as well as install software on the EC2 instances that host the application in an Elastic Beanstalk environment

  • An configuration file, options.config, that overrides the defaults in dynamodb.config with specific settings for this particular installation

index.php

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<?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="http://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

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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.*"

In the sample configuration file, we first create the DynamoDB table and configure the primary key structure for the table and the capacity units to allocate sufficient resources to provide the requested throughput. Next, we create CloudWatch alarms for WriteCapacity and ReadCapacity. We create an SNS topic that sends email to "nobody@amazon.com" if the alarm thresholds are breached.

After we create and configure our AWS resources for our environment, we need to customize the EC2 instances. We use the files key to pass the details of the DynamoDB table to the EC2 instances in our environment as well as add a "require" in the composer.json file for the AWS SDK for PHP 2. Finally, we run container commands to install composer, the required dependencies, and then remove the installer.

.ebextensions/options.config

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

Replace the SessionAlarmEmail value with the email where you want alarm notifications sent. The options.config file contains the values used for some of the variables defined in dynamodb.config. For example, dynamodb.config contains the following lines:

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

These lines that tell Elastic Beanstalk to get the value for the Endpoint property from the SessionAlarmEmail value in a config file (options.config in our sample application) that contains an option_settings section with an aws:elasticbeanstalk:customoption section that contains a name-value pair that contains the actual value to use. In the example above, this means SessionAlarmEmail would be assigned the value nobody@amazon.com.

For more information about the CloudFormation resources used in this example, see the following references: