So let's say we have a few dozen different types of error messages in our logs, but with no error codes by which we could easily group them. Those messages have a form that could be parsed by grok like this:
Could not open %{DATA} in %{DATA}
Host %{IP} unreachable
I want to group those messages by type. I know the correct matching expressions, I just don't want what is variable about them in my field. For example, two messages Host 196.138.2.8 unreachable and Host 88.143.7.19 unreachable should both get the string Host _ unreachable in a field error_type in their events.
Could you give me a hint how to best approach this? Is there a shorter way than to use if-clauses and mutate (add_field)?