Скачать или смотреть Fixing Logstash JRuby Filter to Avoid Bad Data in Elasticsearch

Learn how to resolve issues with Logstash JRuby filter that causes inconsistent array creation in Elasticsearch by changing class variables to local variables.
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This video is based on the question https://stackoverflow.com/q/64950249/ asked by the user 'Dean' ( https://stackoverflow.com/u/3855075/ ) and on the answer https://stackoverflow.com/a/64955111/ provided by the user 'Badger' ( https://stackoverflow.com/u/11792977/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem with Logstash Jruby Filter

When utilizing Logstash to ingest data into Elasticsearch, many users encounter frustrating issues, particularly related to data processing within the JRuby filter plugin. A common scenario involves converting two strings into integers to generate an array filled with even or odd numbers within a specified range. However, some users report that while the array is sometimes created correctly, there are instances where it returns a nonsensical array, filled with unexpected data.

The Challenge

Consider the following example:

Input Numbers: 361 and 371

Expected Output: An array of even numbers [361, 363, 365, 367, 369, 371]

Users have implemented Ruby scripts for this filtering, which seemingly work perfectly well in some cases. However, in other instances, the output can be entirely erratic. Reviewing the code can sometimes be overwhelming, but understanding the root cause is essential for effective troubleshooting.

Unpacking the Code

Here’s the relevant portion of the Logstash configuration that is causing some headaches:

[[See Video to Reveal this Text or Code Snippet]]

The structure appears to be correctly implemented for data cleaning, converting lowNumber and highNumber to integers. The issue lies deeper in the logic of the JRuby filter script itself:

[[See Video to Reveal this Text or Code Snippet]]

Issue Identification

The primary concern highlighted in this script is the use of class variables (notated with @ ). This approach ends up persisting values across multiple events, which can lead to incorrect outputs if subsequent events lack one of the required fields (lowNumber or highNumber). Here's how we can resolve this issue.

Recommended Solution

The solution involves a simple adjustment to eliminate class variables in favor of local variables. By doing so, we can ensure that every event is treated independently, thus preventing any accidental data carryover from previous events.

Implementation Steps

Remove the @ Symbol: Change the declaration of low and high to local scope variables.

Check for Inputs: Always ensure both low and high variables are defined before proceeding with validation and output generation.

Here’s the corrected version of the Ruby script:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By making these minor adjustments, you can significantly mitigate the issue of receiving bad data from your Logstash JRuby filter. It’s crucial to ensure that each event stands alone without unintended influence from preceding ones – implementing local variable scope achieves just that. As you continue working with Logstash and JRuby filters, always remember to validate your inputs and maintain isolation between events for cleaner, more accurate data processing.

Feel free to implement these changes and observe the difference in your data outputs. Happy coding!