Troubleshooting Graph Display Errors In Emoncms Dashboard After Upgrade

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Upgrading software is crucial for accessing new features, performance enhancements, and security patches. However, upgrades can sometimes lead to unexpected issues. This article addresses a specific problem encountered after upgrading Emoncms to version 11.7.4, focusing on errors related to graph displays within the dashboard. We will delve into the error details, analyze potential causes, and provide comprehensive troubleshooting steps to resolve this issue.

Understanding the Error

After upgrading to Emoncms V11.7.4 stable, users may encounter errors when displaying graphs on the dashboard. The error manifests as a PHP warning logged in the error_log file. Let's examine the error message:

[20-Jul-2025 10:23:27 Europe/London] PHP Warning: DateTime::modify(): Failed to parse time string (NaN) at position 0 (N): The timezone could not be found in the database in /home/whitbyes/public_html/emoncms/Modules/feed/feed_model.php on line 813

This error message indicates a problem with the DateTime::modify() function in PHP. Specifically, it's failing to parse a time string, which in this case is NaN (Not a Number). The error also suggests that the timezone information might be missing or improperly configured. The issue arises in the feed_model.php file within the Emoncms modules directory, specifically on line 813.

The primary symptom experienced by users is that the time window selection within the dashboard graphs does not function correctly. For example, if the default time window is set to 24 hours, selecting a different time frame, such as one week, does not update the graph display. This lack of responsiveness is accompanied by the generation of the aforementioned error in the error_log. Each graph line seems to trigger a separate error, leading to multiple log entries for a single graph.

It's crucial to note that the Graph module functions correctly when accessed directly from the feeds section (e.g., by clicking on a feed or navigating through setup -> graphs). This suggests that the core graphing functionality is intact, and the problem lies within the dashboard's implementation or integration.

Initial System Configuration

To effectively troubleshoot this issue, it's essential to understand the system's initial configuration and the changes made during the upgrade process. The user in this scenario upgraded from Emoncms version 10.2 to 11.7.4. A database update was performed as part of the upgrade procedure. The Emoncms, Graph, and Dashboard modules are all running version 11.7.4 stable. The system operates on PHP version 7.3.

Interestingly, the user attempted to resolve the issue by toggling the PHP timezonedb extension, but this did not yield any change. The system is hosted on a server, which, while not officially supported, has been running Emoncms for an extended period (10 years). This upgrade to v11 is the first instance of encountering significant problems.

Potential Causes

Based on the error message and symptoms, several potential causes can be identified:

  1. Data Type Mismatch: The DateTime::modify() function expects a valid time string. The NaN value suggests that an incorrect data type or a missing value is being passed to the function. This could stem from a problem in the data retrieved for the graph or in the way the time window is being calculated.
  2. Timezone Configuration Issues: The error message explicitly mentions that the timezone could not be found in the database. This points to potential problems with the timezone settings within Emoncms or the underlying PHP configuration. Incorrect or missing timezone data can lead to parsing errors.
  3. Dashboard-Specific Bug: Since the Graph module functions correctly outside the dashboard, the issue might be specific to the way graphs are rendered or handled within the dashboard context. This could involve how time window selections are processed or how data is passed to the graphing functions.
  4. Database Upgrade Inconsistencies: Although a database update was performed, there might be inconsistencies or missing steps in the upgrade process. This could result in incorrect data or missing fields that are required for the new version of Emoncms.
  5. Caching Issues: In some cases, caching mechanisms can interfere with the proper rendering of graphs. Old cached data or configurations might be causing conflicts with the new version.

Troubleshooting Steps

To systematically address the graph display errors, the following troubleshooting steps are recommended:

1. Review Emoncms and PHP Timezone Settings

Ensuring correct timezone settings is paramount. The error message directly implicates timezone issues, making this a crucial first step. Begin by verifying the timezone configuration within Emoncms itself. Navigate to the Emoncms settings page (usually accessible through the admin panel) and locate the timezone settings. Ensure that the correct timezone is selected for your location.

Next, examine the PHP timezone configuration. This can be done by checking the php.ini file, which is the main configuration file for PHP. Look for the date.timezone setting. If it's commented out or set to an incorrect value, uncomment it and set it to the appropriate timezone. For example, if your timezone is Europe/London, the setting should look like this:

date.timezone = Europe/London

After modifying the php.ini file, you need to restart your web server (e.g., Apache or Nginx) for the changes to take effect. This ensures that PHP picks up the new timezone configuration.

Additionally, it's worth checking the server's operating system timezone. This can be done using command-line tools specific to your operating system (e.g., timedatectl on Linux). While Emoncms and PHP timezone settings are usually the primary factors, an incorrect system timezone could potentially contribute to issues.

2. Analyze Emoncms Error Logs

Detailed error logs are invaluable for pinpointing the root cause of the problem. The initial error message provided a starting point, but a more comprehensive analysis of the Emoncms error logs can reveal further insights. Emoncms typically maintains its own error logs, separate from the PHP error log.

Locate the Emoncms error logs (the exact location may vary depending on your installation) and examine them for any additional error messages or warnings that coincide with the graph display issues. Pay close attention to any errors related to the feed_model.php file, database interactions, or date/time functions. These errors can provide crucial context and help narrow down the problem area.

Error logs often contain stack traces, which show the sequence of function calls that led to the error. Analyzing the stack trace can help identify the specific code path where the error is occurring and the variables involved. This can be particularly useful for debugging complex issues.

3. Inspect the Dashboard Configuration

The problem might stem from the specific configuration of the dashboard where the graphs are displayed. Review the dashboard settings to ensure that the graphs are configured correctly. Check the following aspects:

  • Graph Feeds: Verify that the correct feeds are selected for each graph. An incorrect feed selection can lead to data errors and unexpected behavior.
  • Time Window Settings: Examine the time window settings for the graphs. Ensure that the default time window is appropriately set and that the time window selection mechanism is functioning as expected.
  • Graph Rendering Options: Check the graph rendering options, such as the graph type (line, bar, etc.) and any specific rendering parameters. Incorrect rendering options can sometimes cause display issues.

Try creating a new, simplified dashboard with a single graph to see if the issue persists. This can help determine if the problem is specific to a particular dashboard configuration or a more general issue.

4. Database Integrity Check

As mentioned earlier, the database upgrade process could be a potential source of problems. Although a database update was performed, it's essential to verify the integrity of the database after the upgrade. This involves checking for any missing tables, incorrect data types, or inconsistencies in the database schema.

Use a database administration tool (e.g., phpMyAdmin) to inspect the Emoncms database. Verify that all the required tables are present and that their structures match the expected schema for version 11.7.4. Pay particular attention to tables related to feeds, graphs, and dashboards.

Check for any data corruption or inconsistencies in the database. Look for any unusual values or missing entries in the relevant tables. If you identify any inconsistencies, you might need to manually correct them or restore the database from a backup.

5. Code-Level Debugging

If the previous steps do not reveal the cause of the problem, code-level debugging might be necessary. This involves examining the Emoncms code, specifically the feed_model.php file mentioned in the error message, to understand how the DateTime::modify() function is being used and why it's failing.

Use a code editor or an Integrated Development Environment (IDE) to open the feed_model.php file. Locate line 813, where the error is occurring. Analyze the code around this line to understand the context and the variables involved.

Use debugging techniques, such as adding var_dump() statements or using a debugger, to inspect the values of variables at different points in the code. This can help identify where the NaN value is being introduced and why the DateTime::modify() function is failing.

6. Clear Caches

Caching mechanisms can sometimes interfere with the proper functioning of Emoncms, especially after an upgrade. Clear any caches that might be in place, including the Emoncms cache, the PHP opcode cache, and the browser cache.

Emoncms usually has a built-in cache clearing mechanism. Use this mechanism to clear the Emoncms cache. For PHP opcode caching (e.g., OPCache), you might need to restart your web server or use a specific tool to clear the cache.

Clearing the browser cache is also essential, as old cached files can sometimes cause display issues. Use your browser's settings to clear the cache and cookies.

7. Revert to Previous Version (If Possible)

If all other troubleshooting steps fail, and the issue is critical, consider reverting to the previous version of Emoncms (version 10.2 in this case). This can help restore functionality while you continue to investigate the problem.

Before reverting, make a backup of your current Emoncms installation and database. This will allow you to restore the system to its current state if needed.

Follow the instructions for downgrading Emoncms to the previous version. This might involve restoring the old code files and database, as well as performing any necessary configuration changes.

Reverting to the previous version is a temporary solution. It's crucial to continue troubleshooting the issue and identify the root cause so that you can upgrade to the latest version without encountering the same problems.

Conclusion

Troubleshooting graph display errors in Emoncms after an upgrade requires a systematic approach. By understanding the error message, analyzing potential causes, and following the troubleshooting steps outlined in this article, you can effectively diagnose and resolve the issue. Remember to carefully review timezone settings, analyze error logs, inspect dashboard configurations, check database integrity, debug code, clear caches, and, if necessary, revert to a previous version as a temporary solution. Addressing these issues ensures a smooth transition to the latest Emoncms version and maintains the integrity of your monitoring data.

By focusing on a methodical approach and leveraging the diagnostic tools available, you can restore the functionality of your Emoncms dashboard and continue to benefit from its powerful data visualization capabilities.