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 application,
index.php
-
A configuration file,
dynamodb.config
, to create and configure a DynamoDB table and other AWS resources and install software on the EC2 instances that host the application in an Elastic Beanstalk environment -
A configuration file,
options.config
, that overrides the defaults indynamodb.config
with specific settings for this particular installation
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.*"
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
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:
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: