aws-lambda

# AWS Lambda AWS Lambda runs code without provisioning servers. You pay only for compute time consumed. Lambda automatically scales from a few requests per day to thousands per second. ## Table of Contents - [Core Concepts](#core-concepts) - [Common Patterns](#common-patterns) - [CLI Reference](#cli-reference) - [Best Practices](#best-practices) - [Troubleshooting](#troubleshooting) - [References](#references) ## Core Concepts ### Function Your code packaged with configuration. Includes runtime, handler, memory, timeout, and IAM role. ### Invocation Types | Type | Description | Use Case | |------|-------------|----------| | **Synchronous** | Caller waits for response | API Gateway, direct invoke | | **Asynchronous** | Fire and forget | S3, SNS, EventBridge | | **Poll-based** | Lambda polls source | SQS, Kinesis, DynamoDB Streams | ### Execution Environment Lambda creates execution environments to run your function. Components: - **Cold start**: New environment initialization - **Warm start**: Reusing existing environment - **Handler**: Entry point function - **Context**: Runtime information ### Layers Reusable packages of libraries, dependencies, or custom runtimes (up to 5 per function). ## Common Patterns ### Create a Python Function **AWS CLI:** ```bash # Create deployment package zip function.zip lambda_function.py # Create function aws lambda create-function \ --function-name MyFunction \ --runtime python3.12 \ --role arn:aws:iam::123456789012:role/lambda-role \ --handler lambda_function.handler \ --zip-file fileb://function.zip \ --timeout 30 \ --memory-size 256 # Update function code aws lambda update-function-code \ --function-name MyFunction \ --zip-file fileb://function.zip ``` **boto3:** ```python import boto3 import zipfile import io lambda_client = boto3.client('lambda') # Create zip in memory zip_buffer = io.BytesIO() with zipfile.ZipFile(zip_buffer, 'w') as zf: zf.writestr('lambda_function.py', ''' def handler(event, context): return {"statusCode": 200, "body": "Hello"} ''') zip_buffer.seek(0) # Create function lambda_client.create_function( FunctionName='MyFunction', Runtime='python3.12', Role='arn:aws:iam::123456789012:role/lambda-role', Handler='lambda_function.handler', Code={'ZipFile': zip_buffer.read()}, Timeout=30, MemorySize=256 ) ``` ### Add S3 Trigger ```bash # Add permission for S3 to invoke Lambda aws lambda add-permission \ --function-name MyFunction \ --statement-id s3-trigger \ --action lambda:InvokeFunction \ --principal s3.amazonaws.com \ --source-arn arn:aws:s3:::my-bucket \ --source-account 123456789012 # Configure S3 notification (see aws-s3 skill) ``` ### Add SQS Event Source ```bash aws lambda create-event-source-mapping \ --function-name MyFunction \ --event-source-arn arn:aws:sqs:us-east-1:123456789012:my-queue \ --batch-size 10 \ --maximum-batching-window-in-seconds 5 ``` ### Environment Variables ```bash aws lambda update-function-configuration \ --function-name MyFunction \ --environment "Variables={DB_HOST=mydb.cluster-xyz.us-east-1.rds.amazonaws.com,LOG_LEVEL=INFO}" ``` ### Create and Attach Layer ```bash # Create layer zip -r layer.zip python/ aws lambda publish-layer-version \ --layer-name my-dependencies \ --compatible-runtimes python3.12 \ --zip-file fileb://layer.zip # Attach to function aws lambda update-function-configuration \ --function-name MyFunction \ --layers arn:aws:lambda:us-east-1:123456789012:layer:my-dependencies:1 ``` ### Invoke Function ```bash # Synchronous invoke aws lambda invoke \ --function-name MyFunction \ --payload '{"key": "value"}' \ response.json # Asynchronous invoke aws lambda invoke \ --function-name MyFunction \ --invocation-type Event \ --payload '{"key": "value"}' \ response.json ``` ## CLI Reference ### Function Management | Command | Description | |---------|-------------| | `aws lambda create-function` | Create new function | | `aws lambda update-function-code` | Update function code | | `aws lambda update-function-configuration` | Update settings | | `aws lambda delete-function` | Delete function | | `aws lambda list-functions` | List all functions | | `aws lambda get-function` | Get function details | ### Invocation | Command | Description | |---------|-------------| | `aws lambda invoke` | Invoke function | ### Event Sources | Command | Description | |---------|-------------| | `aws lambda create-event-source-mapping` | Add event source | | `aws lambda list-event-source-mappings` | List mappings | | `aws lambda update-event-source-mapping` | Update mapping | | `aws lambda delete-event-source-mapping` | Remove mapping | ### Permissions | Command | Description | |---------|-------------| | `aws lambda add-permission` | Add resource-based policy | | `aws lambda remove-permission` | Remove permission | | `aws lambda get-policy` | View resource policy | ## Best Practices ### Performance - **Right-size memory**: More memory = more CPU = faster execution - **Minimize cold starts**: Keep functions warm, use Provisioned Concurrency - **Optimize package size**: Smaller packages deploy faster - **Use layers** for shared dependencies - **Initialize outside handler**: Reuse connections across invocations ```python # GOOD: Initialize outside handler import boto3 dynamodb = boto3.resource('dynamodb') table = dynamodb.Table('MyTable') def handler(event, context): # Reuses existing connection return table.get_item(Key={'id': event['id']}) ``` ### Security - **Least privilege IAM roles** — only grant needed permissions - **Use Secrets Manager** for sensitive data - **Enable VPC** only if needed (adds latency) - **Encrypt environment variables** with KMS ### Cost Optimization - **Set appropriate timeout** — don't use max 15 minutes unnecessarily - **Use ARM architecture** (Graviton2) for 34% better price/performance - **Batch process** where possible - **Use Reserved Concurrency** to limit costs ### Reliability - **Configure DLQ** for async invocations - **Handle retries** — async events retry twice - **Make handlers idempotent** - **Use structured logging** ## Troubleshooting ### Timeout Errors **Symptom:** `Task timed out after X seconds` **Causes:** - Function takes longer than timeout - Network call to unreachable resource - VPC configuration issues **Debug:** ```bash # Check function configuration aws lambda get-function-configuration \ --function-name MyFunction \ --query "Timeout" # Increase timeout aws lambda update-function-configuration \ --function-name MyFunction \ --timeout 60 ``` ### Out of Memory **Symptom:** Function crashes with memory error **Fix:** ```bash aws lambda update-function-configuration \ --function-name MyFunction \ --memory-size 512 ``` ### Cold Start Latency **Causes:** - Large deployment package - VPC configuration - Many dependencies to load **Solutions:** - Use Provisioned Concurrency - Reduce package size - Use layers for dependencies - Consider Graviton2 (ARM) ```bash # Enable Provisioned Concurrency aws lambda put-provisioned-concurrency-config \ --function-name MyFunction \ --qualifier LIVE \ --provisioned-concurrent-executions 5 ``` ### Permission Denied **Symptom:** `AccessDeniedException` **Debug:** ```bash # Check execution role aws lambda get-function-configuration \ --function-name MyFunction \ --query "Role" # Check role policies aws iam list-attached-role-policies \ --role-name lambda-role ``` ### VPC Connectivity Issues **Symptom:** Cannot reach internet or AWS services **Causes:** - No NAT Gateway for internet access - Missing VPC endpoint for AWS services - Security group blocking outbound **Solutions:** - Add NAT Gateway for internet - Add VPC endpoints for AWS services - Check security group rules ## References - [Lambda Developer Guide](https://docs.aws.amazon.com/lambda/latest/dg/) - [Lambda API Reference](https://docs.aws.amazon.com/lambda/latest/api/) - [Lambda CLI Reference](https://docs.aws.amazon.com/cli/latest/reference/lambda/) - [boto3 Lambda](https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/lambda.html)