# Fix CDN session management and tracking issues for MediaTailor
<a name="diagnose-session-issues"></a>

AWS Elemental MediaTailor content delivery network (CDN) session management is critical for proper ad personalization and tracking. If you encounter session-related errors or inconsistent behavior across requests:

1. Check for session ID consistency:
   + Verify that your player maintains the same session ID across all requests for a single playback session
   + Check CDN logs to confirm session IDs are being forwarded correctly
   + Ensure session IDs are properly URL-encoded in query parameters
   + Use CloudWatch Logs to verify session ID consistency across requests (see validation steps below)

1. Validate session initialization:
   + Confirm that the first manifest request successfully creates a session
   + Check for proper session parameter forwarding (for example, `aws.sessionId`)
   + Verify session initialization using debug logs (see debug log setup below)

1. Enable debug logging for detailed session troubleshooting:
   + **For server-side reporting:** Add `?aws.logMode=DEBUG` to your playback request:

     ```
     GET <mediatailorURL>/v1/master/<hashed-account-id>/<origin-id>/<asset-id>?aws.logMode=DEBUG
     ```
   + **For client-side reporting:** Include `"logMode": "DEBUG"` in your session initialization request body
   + **Important:** The `DEBUG` value is case-sensitive
   + Maximum of 10 active debug sessions allowed simultaneously

1. Use CloudWatch Logs queries to validate session behavior:
   + **Verify debug session is active:**

     ```
     fields @timestamp, @message
     | filter sessionId = "your-session-id-here"
     | filter eventType = "SESSION_INITIALIZED" # client-side reporting
     or mediaTailorPath like "/v1/master" # server-side reporting HLS
     or mediaTailorPath like "/v1/dash" # server-side reporting DASH
     ```
   + **View all events for a session:**

     ```
     fields @timestamp, @message, eventType, mediaTailorPath
     | filter sessionId = "your-session-id-here"
     | sort @timestamp asc
     ```
   + **Check manifest generation for a session:**

     ```
     fields @timestamp, responseBody, @message
     | filter mediaTailorPath like "/v1/master/" and eventType = "GENERATED_MANIFEST" and sessionId = "your-session-id-here"
     ```

1. Test session parameter forwarding through CDN:
   + Test manifest requests with session parameters directly against MediaTailor (bypassing CDN)
   + Compare session behavior with and without CDN to identify forwarding issues
   + Verify CDN query parameter forwarding configuration includes session-related parameters
   + Check that CDN doesn't cache responses that should be session-specific

**Common session error messages:**
+ `ConflictException` (HTTP 409) - Multiple simultaneous playlist requests for the same session. **Solution:** Ensure your player requests playlists one at a time according to HLS specification
+ `NotFoundException` (HTTP 404) - Session is unavailable or configuration doesn't exist. **Solution:** Check your configuration validity and reinitialize the session
+ `BadRequestException` (HTTP 400) - Invalid session ID or improperly formatted request. **Solution:** Verify request formatting and session ID validity

**Additional troubleshooting resources:**
+ For complete debug logging setup and field reference, see [Generating AWS Elemental MediaTailor debug logs](debug-log-mode.md)
+ For CloudWatch Logs query examples and log analysis, see [Writing AWS Elemental MediaTailor logs directly to Amazon CloudWatch Logs](monitoring-cw-logs.md)
+ For CDN query parameter forwarding configuration, see [Set up CDN routing behaviors for MediaTailor](cdn-routing-behaviors.md)
+ For comprehensive error code reference, see [Troubleshooting playback from MediaTailor](playback-errors.md)

**Success criteria:** When resolved, sessions should initialize correctly, maintain consistent session IDs across requests, and debug logs should show proper `SESSION_INITIALIZED` events and manifest generation without errors.