Logs

Logs help you monitor your application’s build process, startup, and runtime behavior. You can use logs to debug issues, track performance, and understand what’s happening with your app’s deployments.

Types of Logs

Build Logs

• Build and installation process
• Error messages during build

When to Check: When a build fails or takes longer than expected.

Runtime Logs

Output from your running application:

• Application startup messages
• Request/response logs
• Error and exception traces
• Custom logging from your code

When to Check: To debug application errors or monitor behavior.

Viewing Logs

Through the Dashboard

You can view logs in two places:

App-Level Logs (Current Runtime Logs)

View live logs for your currently running application:

1. Navigate to your app
2. Click Logs in the navigation
3. View live runtime logs from your application

Features:

• Live runtime logs
• Search and filter
• Shows logs levels (INFO, ERROR, etc.)

Deployment-Specific Logs (Build + Runtime)

View logs for a specific deployment:

1. Navigate to your app
2. Click Deployments in the app navigation
3. Click on a specific deployment
4. View logs in the Deployment Logs section
5. Switch between Build Logs and Runtime Logs tabs

Features:

• Build Logs: Available for all deployments, shows build process output
• Runtime Logs: Available after deployment completes

Through the CLI

You can also stream logs directly from your terminal using the FastAPI Cloud CLI:

fastapi cloud logs                      # Stream logs in real-time
fastapi cloud logs --no-follow          # Fetch recent logs and exit
fastapi cloud logs --tail 50 --since 1h # Last 50 logs from the past hour

Features:

• Real-time log streaming with --follow (default)
• Fetch and exit mode with --no-follow
• Customizable number of lines with --tail
• Time range filtering with --since (e.g., 5m, 1h, 2d)
• Color-coded log levels for easy reading

See the Logs Command documentation for full details.

Log Levels

• DEBUG: Detailed diagnostic information
• INFO: General informational messages
• WARNING: Warning messages for potential issues
• ERROR: Error messages for failures
• CRITICAL: Critical errors that may cause shutdown