Advanced Debugging in VWO Feature Experimentation

Overview

Advanced debugging in VWO Feature Experimentation (FE) allows developers and product teams to monitor, identify, and resolve SDK-related issues directly within the VWO dashboard.

Traditionally, SDK errors appeared only in internal application logs, making it difficult to isolate VWO-specific issues. With advanced debugging, SDK-generated error logs are collected centrally and displayed in an intuitive console. This provides visibility into integration health, indicates the number of users affected, and enables you to quickly identify the root cause.

For example, if a feature flag fails to activate due to an incorrect key or initialization issue, the advanced debugging console displays the corresponding error, its frequency, and affected unique users. You can immediately determine whether the issue occurred in staging or production and troubleshoot without scanning large log files.

How does advanced debugging differ from SDK debug logs?

Advanced debugging exclusively captures error logs generated by the VWO SDK inside the VWO app. It does not capture internal customer application errors, logs originating from your application's code, or other external logs.

Key Benefits

With advanced debugging, you can:

• View critical SDK-generated errors such as initialization failures, retry attempts, missing feature keys, or network issues in the VWO interface without accessing internal server logs.
• Understand whether an issue is isolated or widespread by comparing total events with unique users.
• Filter logs by error category, SDK, and environment in which they occurred.
• Drill down into a specific error to view raw event data and timestamp, and identify the users who are encountering the issue.

SDK Version Compatibility

Advanced debugging in VWO FE is fully backward-compatible.

• Older SDK versions will continue sending logs in the previous format and will appear as legacy errors in the new interface.
• All VWO SDKs, including server-side SDKs and mobile SDKs (iOS & Android), are fully supported.
• For the best experience, we recommend upgrading to the latest SDK version.

Access and Use the Advanced Debugging Console

Prerequisites

Before using advanced debugging, ensure you have:

• Installed and initialized the VWO SDK in your application.
• Access to your feature experimentation project.

The advanced debugging console is located within your Feature Experimentation project in VWO. Follow the steps outlined below to access and analyze your debug logs.

1. Log in to your VWO account.
2. From the navigation menu on the left, go to Configurations > Websites and Apps.
3. Select your feature experimentation project from the list of websites and apps.
4. In the project’s top navigation bar, click Logs to open the advanced debugging console.
   

Interpret the Debug Logs

The Logs tab displays the following information:

Filter and Analyze Log Data

Once you have reviewed the log data, you can use the available filters to isolate specific issues and narrow down your investigation.

1. Use the search bar at the top to build specific queries. You can combine multiple conditions using the And / OR operators to refine your search results across different parameters.
2. Use the date picker in the top right corner to select the timeframe you want to analyze.
3. Apply quick filters directly from the table headers by clicking and selecting the available filter options:
   • Log Message: Filter by the type of log to view. You can select either Error or Info.
   • Category: Filter by Error, Retry, Network, or Legacy.
   • SDK: Filter by the specific SDK used (for example, Python, Go, Mobile).

   • Environment: Filter by environment type (for example, Production or Staging).

     Tip: Use the Unique Users column to gauge the severity of an issue. A high Total Events count with a low Unique Users count indicates that a few users are triggering the error repeatedly. In contrast, a high Unique Users count suggests a widespread issue.
4. After selecting the filters, click Apply.

The table displays data based on your applied filters.

Drill Down into Specific Errors

To investigate the root cause of an issue, you can view the detailed stack trace and affected users. In the Log Message column, click on the specific error message you want to investigate. A detailed view of the error appears.

• At the top of the page, a summary table provides a quick snapshot of the issue's impact, displaying the following metrics:
  • Total Events: The total number of times this specific error has occurred.
  • Unique Users: The number of distinct users affected by this error.
  • Last Seen: The timestamp of the most recent occurrence.
  • Platforms Impacted: The type of platform where the error occurred (for example, Server).
  • Environment: The environment where the error occurred (for example, Prod).
    
• Below the summary table, the Events View is displayed by default. This view provides granular details for every individual occurrence of the error, including:
  • Message: The full text of the error log.
  • Timestamp: The exact date and time at which the error occurred.
  • UUID: The hashed user ID associated with the error event.
  • Event ID: The unique identifier for the specific event.
  • Session ID: The identifier for the user session in which the error occurred.
  • SDK / Version: The specific SDK and version number running when the error was triggered.
    
• To analyze the impact on your user base, switch the view by selecting the dropdown menu in the top-left corner and choosing Unique Users View. This displays a consolidated list of unique users who experienced the error, the timestamp of their last occurrence, the event count per user, and the SDK associated with the error.
  

Troubleshooting

FAQs

• Are there any rate limits on the number of log messages that are displayed?
  No. There are currently no caps on displaying the logs per user, logs per minute, or logs per SDK.
   
• Are there any device or browser restrictions for using the Advanced Debugging Console?
  No. The Advanced Debugging Console is supported across all devices and browsers.
   
• Can I export debug logs?
  Exporting debug logs from the VWO dashboard is currently not supported. However, you can export logs programmatically using the SDK’s transport functionality and integrate them with your own logging systems.
   
• Does this feature offer an alerting system?
  Currently, VWO does not offer an alerting system within the Advanced Debugging Console. You must check the Logs tab manually to monitor errors.
   
• Why do I see repeated errors for the same user?
  Each time an SDK triggers the same error, it generates a new log event. As a result, if a user's device or application encounters the error repeatedly (for example, on every page load), the Total Events count will increase, while the Unique Users count remains the same.
   
• Does advanced debugging impact my application’s performance?
  No. Logging is asynchronous and non-blocking, ensuring zero-performance impact.
   
• How long are log events retained? Will older logs be purged automatically?
  Log events are retained for 30 days. Older logs are automatically purged.
   
• Does the log pipeline slow down for large-scale applications?
  No. Our systems are well-equipped to handle large-scale applications.
   
• Does offline mode in mobile apps affect how logs are captured?
  No. When a device is offline, the SDK stores events, including debug events, in an offline queue. These events are automatically batched and sent once the device comes back online.

Need more help?

For further assistance or more information, contact VWO Support.