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