# Reading and Analyzing Logs

> Source: https://docs.synthesized.io/tdk/latest/user_guide/080_troubleshooting/debugging/logs
> For the complete documentation index, see [llms.txt](https://docs.synthesized.io/llms.txt).

Understand TDK logs to diagnose and troubleshoot issues.

## Log Locations

### Docker Compose

```shell
# View backend logs
docker compose logs backend

# Follow logs in real-time
docker compose logs -f backend

# View last 100 lines
docker compose logs --tail=100 backend

# View worker logs
docker compose logs worker
```

### Kubernetes

```shell
# View backend logs
kubectl logs -n tdk deployment/tdk-backend

# Follow logs
kubectl logs -n tdk deployment/tdk-backend -f

# View specific pod
kubectl logs -n tdk tdk-backend-abc123-xyz

# View worker logs
kubectl logs -n tdk deployment/tdk-worker
```

### CLI Mode

Logs output to stdout/stderr:

```shell
tdk --config-file workflow.yaml 2>&1 | tee tdk.log
```

## Log Levels

TDK uses standard log levels:

- **ERROR**: Critical failures requiring attention
- **WARN**: Potential issues or deprecated features
- **INFO**: General informational messages
- **DEBUG**: Detailed diagnostic information
- **TRACE**: Very detailed execution traces

## Enabling Debug Logging

### Docker Compose

```yaml
services:
  backend:
    environment:
      LOGGING_LEVEL_IO_SYNTHESIZED: DEBUG
```

### Application Properties

```properties
logging.level.io.synthesized=DEBUG
logging.level.org.springframework=INFO
```

## Understanding Log Messages

### Successful Workflow Execution

```
INFO  Starting workflow execution: workflow_id=123
INFO  Processing table: public.customers
INFO  Rows processed: 10000/10000 (100%)
INFO  Workflow completed successfully in 45.2s
```

### Common Error Patterns

**Connection Error**:

```
ERROR Failed to connect to database: java.sql.SQLException: Connection refused
```

**Foreign Key Violation**:

```
ERROR Referential integrity error: FK constraint violated
  Table: orders, Column: customer_id
  Parent: customers, Parent Column: id
```

**Memory Error**:

```
ERROR OutOfMemoryError: Java heap space
  at io.synthesized.tdk.processor.DataProcessor.process
```

## Searching Logs

### Find Errors

```shell
docker compose logs backend | grep -i error

# With context (5 lines before/after)
docker compose logs backend | grep -i -C 5 error
```

### Find Specific Workflow

```shell
docker compose logs backend | grep "workflow_id=123"
```

### Time-Based Search

```shell
# Logs since specific time
docker compose logs backend --since 2024-01-15T10:00:00
```

## Exporting Logs

Save logs for support:

```shell
# Docker Compose
docker compose logs backend > tdk-backend.log
docker compose logs worker > tdk-worker.log

# Kubernetes
kubectl logs -n tdk deployment/tdk-backend > tdk-backend.log
kubectl logs -n tdk deployment/tdk-worker > tdk-worker.log
```

## Log Rotation

### Docker Compose

Configure in docker-compose.yml:

```yaml
services:
  backend:
    logging:
      driver: "json-file"
      options:
        max-size: "10m"
        max-file: "3"
```

## See Also

- [Diagnostic Command](https://docs.synthesized.io/tdk/latest/user_guide/080_troubleshooting/debugging/diagnostic_command)
- [Common Issues](https://docs.synthesized.io/tdk/latest/user_guide/080_troubleshooting/common_issues/)