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