aws-sdk-java-v2-lambda

What this skill does

# AWS SDK for Java 2.x - AWS Lambda

## Overview

AWS Lambda is a compute service that runs code without managing servers. Use this skill to implement AWS Lambda operations using AWS SDK for Java 2.x in applications and services.

## When to Use

- Invoking Lambda functions from Java applications
- Deploying and updating Lambda functions via SDK
- Managing function configurations and layers
- Integrating Lambda with Spring Boot applications

## Quick Reference

| Operation | SDK Method | Use Case |
|-----------|------------|----------|
| **Invoke** | `invoke()` | Synchronous/async function invocation |
| **List Functions** | `listFunctions()` | Get all Lambda functions |
| **Get Config** | `getFunction()` | Retrieve function configuration |
| **Create Function** | `createFunction()` | Create new Lambda function |
| **Update Code** | `updateFunctionCode()` | Deploy new function code |
| **Update Config** | `updateFunctionConfiguration()` | Modify settings (timeout, memory, env vars) |
| **Delete Function** | `deleteFunction()` | Remove Lambda function |

## Instructions

### 1. Add Dependencies

Include Lambda SDK dependency in `pom.xml`:

```xml
<dependency>
    <groupId>software.amazon.awssdk</groupId>
    <artifactId>lambda</artifactId>
</dependency>
```

See [client-setup.md](references/client-setup.md) for complete setup.

### 2. Create Client

Instantiate `LambdaClient` with proper configuration:

```java
LambdaClient lambdaClient = LambdaClient.builder()
    .region(Region.US_EAST_1)
    .build();
```

For async operations, use `LambdaAsyncClient`.

### 3. Invoke Lambda Function

Synchronous invocation:

```java
InvokeRequest request = InvokeRequest.builder()
    .functionName("my-function")
    .payload(SdkBytes.fromUtf8String(payload))
    .build();

InvokeResponse response = lambdaClient.invoke(request);

return response.payload().asUtf8String();
```

See [invocation-patterns.md](references/invocation-patterns.md) for patterns.

### 4. Handle Responses

Parse response payloads and check for errors:

```java
if (response.functionError() != null) {
    throw new LambdaInvocationException("Lambda error: " + response.functionError());
}

String result = response.payload().asUtf8String();
```

### 5. Manage Functions

Create, update, or delete Lambda functions:

```java
// Create
CreateFunctionRequest createRequest = CreateFunctionRequest.builder()
    .functionName("my-function")
    .runtime(Runtime.JAVA17)
    .role(roleArn)
    .code(code)
    .build();

lambdaClient.createFunction(createRequest);

// Verify function is active before proceeding
GetFunctionRequest getRequest = GetFunctionRequest.builder()
    .functionName("my-function")
    .build();
GetFunctionResponse getResponse = lambdaClient.getFunction(getRequest);
if (!"Active".equals(getResponse.configuration().state())) {
    throw new IllegalStateException("Function not active: " + getResponse.configuration().stateReason());
}

// Update code
UpdateFunctionCodeRequest updateCodeRequest = UpdateFunctionCodeRequest.builder()
    .functionName("my-function")
    .zipFile(SdkBytes.fromByteArray(zipBytes))
    .build();

lambdaClient.updateFunctionCode(updateCodeRequest);

// Wait for deployment to complete
Waiter<GetFunctionConfigurationRequest> waiter = lambdaClient.waiter();
waiter.waitUntilFunctionUpdatedActive(GetFunctionConfigurationRequest.builder()
    .functionName("my-function")
    .build());
```

See [function-management.md](references/function-management.md) for complete patterns.

### 6. Configure Environment

Set environment variables and concurrency limits:

```java
Environment env = Environment.builder()
    .variables(Map.of(
        "DB_URL", "jdbc:postgresql://db",
        "LOG_LEVEL", "INFO"
    ))
    .build();

UpdateFunctionConfigurationRequest configRequest = UpdateFunctionConfigurationRequest.builder()
    .functionName("my-function")
    .environment(env)
    .timeout(60)
    .memorySize(512)
    .build();

lambdaClient.updateFunctionConfiguration(configRequest);
```

### 7. Integrate with Spring Boot

Configure Lambda beans and services:

```java
@Configuration
public class LambdaConfiguration {
    @Bean
    public LambdaClient lambdaClient() {
        return LambdaClient.builder()
            .region(Region.US_EAST_1)
            .build();
    }
}

@Service
public class LambdaInvokerService {
    public <T, R> R invoke(String functionName, T request, Class<R> responseType) {
        // Implementation
    }
}
```

See [spring-boot-integration.md](references/spring-boot-integration.md) for complete integration.

### 8. Test Locally

Use mocks or LocalStack for development testing.

See [testing.md](references/testing.md) for testing patterns.

## Examples

### Basic Invocation

```java
public String invokeFunction(LambdaClient client, String functionName, String payload) {
    InvokeRequest request = InvokeRequest.builder()
        .functionName(functionName)
        .payload(SdkBytes.fromUtf8String(payload))
        .build();

    InvokeResponse response = client.invoke(request);

    if (response.functionError() != null) {
        throw new RuntimeException("Lambda error: " + response.functionError());
    }

    return response.payload().asUtf8String();
}
```

### Async Invocation

```java
public void invokeAsync(LambdaClient client, String functionName, Map<String, Object> event) {
    String jsonPayload = new ObjectMapper().writeValueAsString(event);

    InvokeRequest request = InvokeRequest.builder()
        .functionName(functionName)
        .invocationType(InvocationType.EVENT)
        .payload(SdkBytes.fromUtf8String(jsonPayload))
        .build();

    client.invoke(request);
}
```

### Spring Boot Service

```java
@Service
public class LambdaService {
    private final LambdaClient lambdaClient;

    public UserResponse processUser(UserRequest request) {
        String payload = objectMapper.writeValueAsString(request);

        InvokeResponse response = lambdaClient.invoke(
            InvokeRequest.builder()
                .functionName("user-processor")
                .payload(SdkBytes.fromUtf8String(payload))
                .build()
        );

        return objectMapper.readValue(
            response.payload().asUtf8String(),
            UserResponse.class
        );
    }
}
```

See [examples.md](references/examples.md) for more examples.

## Best Practices

- **Reuse clients**: Create `LambdaClient`/`LambdaAsyncClient` once; they are thread-safe
- **Use async client**: For fire-and-forget invocations, use `LambdaAsyncClient` with `CompletableFuture`
- **Verify deployments**: Always wait for function state to be `Active` after create/update operations
- **Limit payload size**: Keep request/response payloads under 256KB for async, 6MB for sync invocations
- **Configure timeouts**: Set client read timeout slightly higher than Lambda function timeout
- **Use latest runtime**: Specify `Runtime.JAVA17` or newer for improved cold start performance

## Constraints and Warnings

- **Payload Limit**: 6MB (sync), 256KB (async invocation)
- **Timeout**: Max 900 seconds (15 minutes) per invocation
- **Cold Starts**: JVM-based functions have longer cold starts; use GraalVM Native Image for improvement
- **Deployment Size**: Function code + layers must not exceed 50MB (zipped) or 250MB (unzipped)
- **Concurrency**: Default 1000 per region; use reserved concurrency to guarantee capacity
- **Cost**: Monitor with CloudWatch metrics; set billing alerts to prevent runaway costs

## References

- **[client-setup.md](references/client-setup.md)** — Client configuration and setup
- **[invocation-patterns.md](references/invocation-patterns.md)** — Synchronous and async invocation patterns
- **[function-management.md](references/function-management.md)** — Create, update, delete functions
- **[spring-boot-integration.md](references/spring-boot-integration.md)** — Spring Boot configuration and services
- **[testing.md](references/testing.md)** — Unit and int