Accessing the previous value in a field in logstash

[Tomo_M (Tomohiro Mitani)]

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Persist data between log lines with ruby filter

You should never need to use global variables. You can do this using an instance variable (@last_event). You can only use a single worker thread, so the solution does not scale, and you have to use the ruby execution engine because with java_execution enabled events get re-ordered.