FAQs.md

title	description
FAQs	Frequently Asked Questions

How can I use Powertools for AWS Lambda (Java) with Lombok?

Powertools uses aspectj-maven-plugin to compile-time weave (CTW) aspects into the project. In case you want to use Lombok or other compile-time preprocessor for your project, it is required to change aspectj-maven-plugin configuration to enable in-place weaving feature. Otherwise the plugin will ignore changes introduced by Lombok and will use .java files as a source.

To enable in-place weaving feature you need to use following aspectj-maven-plugin configuration:

<configuration>
    <forceAjcCompile>true</forceAjcCompile> 
    <sources/>
    <weaveDirectories>
        <weaveDirectory>${project.build.directory}/classes</weaveDirectory>
    </weaveDirectories>
    ...
    <aspectLibraries>
        <aspectLibrary>
            <groupId>software.amazon.lambda</groupId>
            <artifactId>powertools-logging</artifactId>
        </aspectLibrary>
    </aspectLibraries>
</configuration>

How can I use Powertools for AWS Lambda (Java) with Kotlin projects?

Powertools uses aspectj-maven-plugin to compile-time weave (CTW) aspects into the project. When using it with Kotlin projects, it is required to forceAjcCompile. No explicit configuration should be required for gradle projects.

To enable forceAjcCompile you need to use following aspectj-maven-plugin configuration:

<configuration>
    <forceAjcCompile>true</forceAjcCompile> 
    ...
    <aspectLibraries>
        <aspectLibrary>
            <groupId>software.amazon.lambda</groupId>
            <artifactId>powertools-logging</artifactId>
        </aspectLibrary>
    </aspectLibraries>
</configuration>

How can I use Powertools for AWS Lambda (Java) with the AWS CRT HTTP Client?

Powertools uses the url-connection-client as the default HTTP client. The url-connection-client is a lightweight HTTP client, which keeps the impact on Lambda cold starts to a minimum. With the announcement of the aws-crt-client a new HTTP client has been released, which offers faster SDK startup time and smaller memory footprint.

Unfortunately, replacing the url-connection-client dependency with the aws-crt-client will not immediately improve the lambda cold start performance and memory footprint, as the default version of the dependency contains native system libraries for all supported runtimes and architectures (Linux, MacOS, Windows, AMD64, ARM64, etc). This makes the CRT client portable, without the user having to consider where their code will run, but comes at the cost of JAR size.

Configuring dependencies

Using the aws-crt-client in your project requires the exclusion of the url-connection-client transitive dependency from the powertools dependency.

<dependency>
    <groupId>software.amazon.lambda</groupId>
    <artifactId>powertools-parameters</artifactId>
    <version>2.0.0</version>
    <exclusions>
        <exclusion>
            <groupId>software.amazon.awssdk</groupId>
            <artifactId>url-connection-client</artifactId>
        </exclusion>
    </exclusions>
</dependency>

Next, add the aws-crt-client and exclude the "generic" aws-crt dependency (contains all runtime libraries). Instead, set a specific classifier of the aws-crt to use the one for your target runtime: either linux-x86_64 for a Lambda configured for x86 or linux-aarch_64 for Lambda using arm64.

!!! note "You will need to add a separate maven profile to build and debug locally when your development environment does not share the target architecture you are using in Lambda." By specifying the specific target runtime, we prevent other target runtimes from being included in the jar file, resulting in a smaller Lambda package and improved cold start times.

<dependencies>
    <dependency>
        <groupId>software.amazon.awssdk</groupId>
        <artifactId>aws-crt-client</artifactId>
        <version>2.23.21</version>
        <exclusions>
            <exclusion>
                <groupId>software.amazon.awssdk.crt</groupId>
                <artifactId>aws-crt</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

    <dependency>
        <groupId>software.amazon.awssdk.crt</groupId>
        <artifactId>aws-crt</artifactId>
        <version>0.29.9</version>
        <classifier>linux-x86_64</classifier>
    </dependency>
</dependencies>

Explicitly set the AWS CRT HTTP Client

After configuring the dependencies, it's required to explicitly specify the AWS SDK HTTP client. Depending on the Powertools module, there is a different way to configure the SDK client.

The following example shows how to use the Lambda Powertools Parameters module while leveraging the AWS CRT Client.

```java hl_lines="11-16 19-20 22"
import static software.amazon.lambda.powertools.parameters.transform.Transformer.base64;

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestHandler;
import software.amazon.awssdk.services.ssm.SsmClient;
import software.amazon.awssdk.http.crt.AwsCrtHttpClient;
import software.amazon.lambda.powertools.parameters.ssm.SSMProvider;

public class RequestHandlerWithParams implements RequestHandler<String, String> {

    // Get an instance of the SSMProvider with a custom HTTP client (aws crt).
    SSMProvider ssmProvider = SSMProvider
            .builder()
            .withClient(
                    SsmClient.builder()
                            .httpClient(AwsCrtHttpClient.builder().build())
                            .build()
            )
            .build();

    public String handleRequest(String input, Context context) {
        // Retrieve a single param
        String value = ssmProvider
                .get("/my/secret");
                // We might instead want to retrieve multiple parameters at once, returning a Map of key/value pairs
                // .getMultiple("/my/secret/path");

        // Return the result
        return value;
    }
}
```

The aws-crt-client was considered for adoption as the default HTTP client in Lambda Powertools for Java as mentioned in Move SDK http client to CRT, but due to the impact on the developer experience it was decided to stick with the url-connection-client.

How can I use Powertools for AWS Lambda (Java) with GraalVM?

Powertools core utilities, i.e. logging, metrics and tracing, include the GraalVM Reachability Metadata (GRM) in the META-INF directories of the respective JARs. You can find a working example of Serverless Application Model (SAM) based application in the examples directory.

These are typical steps you need to follow in a maven based Java project

Set the environment to use GraalVM

export JAVA_HOME=<path to GraalVM>

Use log4j > 2.24.0

Log4j version 2.24.0 adds support for GraalVM. Depending on your project's dependency hierarchy, older version of log4j might be included in the final dependency graph. Make sure version >2.24.0 of these dependencies are used by your maven project:

<dependencies>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <version>${log4j.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>${log4j.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-slf4j2-impl</artifactId>
        <version>${log4j.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-layout-template-json</artifactId>
        <version>${log4j.version}</version>
    </dependency>
</dependencies>

Add the AWS Lambda Java Runtime Interface Client dependency

Runtime Interface Client allow your function to receive invocation events from Lambda, send the response back to Lambda, and report errors to the Lambda service. Add the below dependency to your maven project:

<dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>aws-lambda-java-runtime-interface-client</artifactId>
    <version>2.1.1</version>
</dependency>

Also include the AWS Lambda GRM files by copying the com.amazonawsdirectory in your project's META-INF/native-image directory

Build the native image

1. Use the native-maven-plugin to build the native image. You can do this by adding the plugin to your pom.xml and creating a build profile called native-image that can build the native image of your Lambda function:

<profiles>
    <profile>
        <id>native-image</id>
        <build>
            <plugins>
                <plugin>
                    <groupId>org.graalvm.buildtools</groupId>
                    <artifactId>native-maven-plugin</artifactId>
                    <version>0.10.1</version>
                    <extensions>true</extensions>
                    <executions>
                        <execution>
                            <id>build-native</id>
                            <goals>
                                <goal>build</goal>
                            </goals>
                            <phase>package</phase>
                        </execution>
                    </executions>
                    <configuration>
                        <imageName>your-project-name</imageName>
                        <mainClass>com.amazonaws.services.lambda.runtime.api.client.AWSLambda</mainClass>
                        <buildArgs>
                            <!-- required for AWS Lambda Runtime Interface Client -->
                            <arg>--enable-url-protocols=http</arg>
                            <arg>--add-opens java.base/java.util=ALL-UNNAMED</arg>
                        </buildArgs>
                    </configuration>
                </plugin>
            </plugins>
        </build>
    </profile>
</profiles>

2. Create a docker image using a Dockerfile like this to create an x86 based build image.

docker build --platform linux/amd64 . -t your-org/your-app-graalvm-builder

3. Create the native image of you Lambda function using the docker command below.

docker run --platform linux/amd64 -it -v `pwd`:`pwd` -w `pwd` -v ~/.m2:/root/.m2 your-org/your-app-graalvm-builder mvn clean -Pnative-image package

The native image is created in the target directory.