LocalStack Logs Analysis

Analyze LocalStack logs to debug issues, identify errors, and understand AWS API interactions.

Capabilities

• View and filter LocalStack logs

• Identify error patterns and failures

• Analyze AWS API request/response cycles

• Track service-specific operations

• Debug Lambda function executions

Viewing Logs

Basic Log Commands

Follow logs in real-time

localstack logs -f

View last N lines

localstack logs --tail 100

Via Docker

docker logs localstack-main -f docker logs localstack-main --tail 200

Filtering Logs

Filter by service

localstack logs | grep -i s3 localstack logs | grep -i lambda localstack logs | grep -i dynamodb

Filter errors only

localstack logs | grep -i error localstack logs | grep -i exception

Filter by request ID

localstack logs | grep "request-id-here"

Debug Mode

Enable detailed logging:

Start with debug mode

DEBUG=1 localstack start -d

Enable specific debug flags

LS_LOG=trace localstack start -d

Analyzing API Requests

Request/Response Tracking

LocalStack logs include AWS API requests. Look for patterns like:

AWS <service>.<operation> => <status>

Example log entries:

AWS s3.CreateBucket => 200 AWS dynamodb.PutItem => 200 AWS lambda.Invoke => 200

Common Error Patterns

Error Possible Cause Solution

ResourceNotFoundException

Resource doesn't exist Create the resource first

AccessDeniedException

IAM policy issue Check IAM enforcement mode

ValidationException

Invalid parameters Verify request parameters

ServiceException

Internal error Check LocalStack logs for details

Lambda Debugging

View Lambda Logs

Lambda function logs appear in LocalStack logs

localstack logs | grep -A 10 "Lambda"

Or use CloudWatch Logs locally

awslocal logs describe-log-groups awslocal logs get-log-events
--log-group-name /aws/lambda/my-function
--log-stream-name <stream-name>

Enable Lambda Debug Mode

LAMBDA_DEBUG=1 localstack start -d

Health Check

Check overall health

curl http://localhost:4566/_localstack/health | jq

Check specific service

curl http://localhost:4566/_localstack/health | jq '.services.s3'

Troubleshooting Tips

• No logs appearing: Ensure LocalStack is running (localstack status )

• Missing debug info: Enable DEBUG=1 for verbose logging

• Lambda issues: Check both LocalStack logs and CloudWatch Logs

• Intermittent errors: Look for resource limits or timing issues