AWS Lambda for the XP Framework

Serverless infrastructure.

Example

Put this code in a file called Greet.class.php:

use com\amazon\aws\lambda\Handler;

class Greet extends Handler {

  /** @return callable|com.amazon.aws.lambda.Lambda|com.amazon.aws.lambda.Streaming */
  public function target() {
    return fn($event, $context) => sprintf(
      'Hello %s from PHP %s via %s @ %s',
      $event['name'],
      PHP_VERSION,
      $context->functionName,
      $context->region
    );
  }
}

The two parameters passed are $event (a value depending on where the lambda was invoked from) and $context (a Context instance, see below).

Initialization

If you need to run any initialization code, you can do so before returning the lambda from target(). This code is only run once during the init phase:

use com\amazon\aws\lambda\Handler;

class Greet extends Handler {

  /** @return callable|com.amazon.aws.lambda.Lambda|com.amazon.aws.lambda.Streaming */
  public function target() {
    $default= $this->environment->properties('task')->readString('greet', 'default');

    return fn($event, $context) => sprintf(
      'Hello %s from PHP %s via %s @ %s',
      $event['name'] ?? $default,
      PHP_VERSION,
      $context->functionName,
      $context->region
    );
  }
}

The lambda's environment accessible via $this->environment is an Environment instance, see below.

Logging

To write output to the lambda's log stream, use trace():

use com\amazon\aws\lambda\Handler;

class Greet extends Handler {

  /** @return callable|com.amazon.aws.lambda.Lambda|com.amazon.aws.lambda.Streaming */
  public function target() {
    return function($event, $context) {
      $this->environment->trace('Invoked with ', $event);

      return sprintf(/* Shortened for brevity */);
    };
  }
}

Any non-string arguments passed will be converted to string using util.Objects::stringOf(). To integrate with XP logging, pass the environment's writer to the console appender, e.g. by using $cat= Logging::all()->toConsole($this->environment->writer).

Response streaming

This library supports AWS Lambda response streaming as announced by AWS in April 2023. To use the stream, return a function(var, Stream, Context) from the handler's target() method instead of a function(var, Context):

use com\amazon\aws\lambda\{Context, Handler, Stream};

class Streamed extends Handler {

  public function target(): callable {
    return function($event, Stream $stream, Context $context) {
      $stream->use('text/plain');
      $stream->write("[".date('r')."] Hello world...\n");

      sleep(1);

      $stream->write("[".date('r')."] ...from Lambda\n");
      $stream->end();
    };
  }
}

Invoking this lambda will yield the following:

The Stream interface is defined as follows:

public interface com.amazon.aws.lambda.Stream extends io.streams.OutputStream, lang.Closeable {
  public function transmit(io.Channel|io.streams.InputStream $source, string $mimeType): void
  public function use(string $mimeType): void
  public function write(string $bytes): void
  public function end(): void
  public function flush(): void
  public function close(): var
}

Development

To run your lambda locally, use the following:

$ xp lambda run Greet '{"name":"Timm"}'
Hello Timm from PHP 8.2.11 via Greet @ test-local-1

This does not provide a complete lambda environment, and does not have any execution limits imposed on it! To detect this programmatically, use $this->environment->local(), which will return true.

Integration testing

To test your lambda inside a local containerized lambda environment, use the test command.

$ xp lambda test Greet '{"name":"Timm"}'
START RequestId: 9ff45cda-df9b-1b8c-c21b-5fe27c8f2d24 Version: $LATEST
END RequestId: 9ff45cda-df9b-1b8c-c21b-5fe27c8f2d24
REPORT RequestId: 9ff45cda-df9b-1b8c-c21b-5fe27c8f2d24  Init Duration: 922.19 ms...
"Hello Timm from PHP 8.2.11 via test @ us-east-1"

This functionality is provided by the AWS Lambda base images for custom runtimes. Although this also runs on your machine, $this->environment->local() will return false.

Setup

The first step is to create and publish the runtime layer:

$ xp lambda runtime
$ aws lambda publish-layer-version \
  --layer-name lambda-xp-runtime \
  --zip-file fileb://./runtime-X.X.X.zip \
  --region us-east-1

...and create a role:

$ cat > /tmp/trust-policy.json
{
  "Version": "2012-10-17",
  "Statement": [{
    "Effect": "Allow",
    "Principal": {"Service": "lambda.amazonaws.com"},
    "Action": "sts:AssumeRole"
  }]
}
$ aws iam create-role \
  --role-name InvokeLambda \
  --path "/service-role/" \
  --assume-role-policy-document file:///tmp/trust-policy.json

After ensuring your dependencies are up-to-date using composer, create the function:

$ xp lambda package Greet.class.php
$ aws lambda create-function \
  --function-name greet \
  --handler Greet \
  --zip-file fileb://./function.zip \
  --runtime provided.al2 \
  --role "arn:aws:iam::XXXXXXXXXXXX:role/service-role/InvokeLambda" \
  --region us-east-1 \
  --layers "arn:aws:lambda:us-east-1:XXXXXXXXXXXX:layer:lambda-xp-runtime:1"

Invocation

To invoke the function:

$ aws lambda invoke \
  --cli-binary-format raw-in-base64-out \
  --function-name greet \
  --payload '{"name":"Timm"}'
  response.json
$ cat response.json
"Hello Timm from PHP 8.0.10 via greet @ us-east-1"

Deploying changes

After having initially created your lambda, you can update its code as follows:

$ xp lambda package Greet.class.php
$ aws lambda update-function-code \
  --function-name greet \
  --zip-file fileb://./function.zip \
  --publish

Upgrading the runtime

To upgrade an existing runtime layer, build the new runtime and publish a new version by calling the following to create a new version:

$ xp lambda runtime
$ aws lambda publish-layer-version \
  --layer-name lambda-xp-runtime \
  --zip-file fileb://./runtime-X.X.X.zip \
  --region us-east-1

Now, switch the function over to use this new layer:

$ aws lambda update-function-configuration \
  --function-name greet \
  --layers "arn:aws:lambda:us-east-1:XXXXXXXXXXXX:layer:lambda-xp-runtime:2"

Using other AWS services

In order to programmatically use other AWS services use the ServiceEndpoint class:

use com\amazon\aws\{Credentials, ServiceEndpoint};
use com\amazon\aws\lambda\Handler;

class WebSockets extends Handler {

  /** @return callable|com.amazon.aws.lambda.Lambda|com.amazon.aws.lambda.Streaming */
  public function target() {
    return function($event, $context) {

      // Send message to WebSocket connection
      $this->environment->endpoint('execute-api')
        ->in($context->region)
        ->using($event['requestContext']['apiId'])
        ->resource('/{stage}/@connections/{connectionId}', $event['requestContext'])
        ->transmit(['message' => 'Reply'])
      ;
      return ['statusCode' => 200];
    };
  }
}

To test this locally, pass the necessary environment variables via -e on the command line:

$ xp lambda test -e AWS_ACCESS_KEY_ID=... -e AWS_SECRET_ACCESS_KEY=... WebSockets '{"requestContext":...}'
# ...

Context

The context object passed to the target lambda is defined as follows:

public class com.amazon.aws.lambda.Context implements lang.Value {
  public string $awsRequestId
  public string $invokedFunctionArn
  public string $traceId
  public string $clientContext
  public string $cognitoIdentity
  public string $deadline
  public string $functionName
  public string $functionVersion
  public string $memoryLimitInMB
  public string $logGroupName
  public string $logStreamName
  public string $region
  public int $payloadLength

  public function __construct(array $headers, array $environment)

  public function remainingTime(?float $now): ?float
  public function toString(): string
  public function hashCode(): string
  public function compareTo(var $value): int
}

Environment

The runtime environment is defined as follows:

public class com.amazon.aws.lambda.Environment {
  public string $root
  public [:string] $variables
  public io.streams.StringWriter $writer
  public util.PropertySource $properties

  public function __construct(string $root, ?io.streams.StringWriter $writer)

  public function taskroot(): io.Path
  public function path(string $path): io.Path
  public function tempDir(): io.Path
  public function local(): bool
  public function variable(string $name): ?string
  public function credentials(): com.amazon.aws.Credentials
  public function trace(var... $args): void
  public function properties(string $name): util.PropertyAccess
}

Interfaces

Instead of functions, a handler's target() method may also return instances implementing the Lambda or Streaming interfaces:

public interface com.amazon.aws.lambda.Lambda {
  public function process(var $event, com.amazon.aws.lambda.Context $context): var
}

public interface com.amazon.aws.lambda.Streaming {
  public function handle(
    var $event,
    com.amazon.aws.lambda.Stream $stream,
    com.amazon.aws.lambda.Context $context
  ): void
}

See also

• What is AWS Lambda?
• AWS Lambda Webservices for the XP Framework
• AWS Core for the XP Framework
• Lambda runtimes
• AWS Lambda Custom Runtime for PHP: A Practical Example
• AWS SDK for PHP
• The Serverless LAMP stack - Community Resources
• Configuring a Lambda function to stream responses
• Implementing response streaming in a custom runtime