The Ruby filter plugin for Logstash allows you to execute custom Ruby code within your Logstash pipeline. This powerful plugin enables you to implement complex data manipulation, custom logic, and advanced processing that may not be possible with other standard Logstash filters. It's particularly useful when you need to perform unique transformations or when you want to leverage Ruby's extensive libraries and capabilities.
Syntax
filter {
ruby {
code => "..."
path => "/path/to/ruby/file"
script_params => { "param1" => "value1", "param2" => "value2" }
}
}
For detailed configuration options, refer to the official Logstash Ruby filter plugin documentation.
Example Use Case and Usage
Suppose you want to calculate the time difference between two timestamp fields in your log events. Here's an example of how you might use the Ruby filter to accomplish this:
filter {
ruby {
code => '
start_time = Time.parse(event.get("start_timestamp"))
end_time = Time.parse(event.get("end_timestamp"))
duration = (end_time - start_time).to_i
event.set("duration_seconds", duration)
'
}
}
This script parses two timestamp fields, calculates the difference, and adds a new field with the duration in seconds.
Common Issues and Best Practices
Performance: Ruby code execution can be slower compared to native Logstash filters. Use it judiciously and for tasks that can't be accomplished with other filters.
Error Handling: Ensure your Ruby code includes proper error handling to prevent pipeline crashes.
Testing: Thoroughly test your Ruby scripts before deploying them in production to avoid unexpected behavior.
Versioning: Be aware that the Ruby version used by Logstash may differ from your system's Ruby version.
Security: Be cautious when executing external Ruby scripts, as they have full access to the system.
Frequently Asked Questions
Q: Can I use external Ruby gems in my Ruby filter?
A: Yes, you can use external gems, but they need to be installed in the Logstash Ruby environment. You may need to use the Logstash plugin manager to install additional gems.
Q: How can I access event fields in my Ruby code?
A: You can access and modify event fields using event.get("field_name") and event.set("field_name", value) respectively.
Q: Is it possible to load Ruby code from an external file?
A: Yes, you can use the path option instead of code to load Ruby code from an external file.
Q: Can I use Ruby's multi-threading capabilities in a Ruby filter?
A: While it's technically possible, it's generally not recommended due to potential conflicts with Logstash's own concurrency model. Stick to single-threaded operations within the Ruby filter.
Q: How can I debug my Ruby filter code?
A: You can use puts statements in your Ruby code, which will output to Logstash's logs. Additionally, you can use the Ruby logger object for more structured logging within your script.
