Parse regex to a nested field about logstash-filter-grok HOT 6 OPEN

Can't we just expand a field name that contains dots – e.g. "permission.user.read" – to a nested object or would this be breaking any conventions?

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I also have replicated this problem with Logstash 1.5.6 and Logstash 2.10. Grok Filter and Nested Objects/Fields Ambiguity, I only just found this issue and seems like it's in a more relevant location with respect to the Grok filter plugin.

What I find strange is that if you launch Logstash with --debug you can see the semantic matches like %{PATTERN:[object][field]} being expanded similar to a the custom pattern matches.

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So, turns out that the grok filter uses Oniguruma syntax. Looking into the Oniguruma syntax, you can see in L209 of the syntax guide, how the name match reflects that in the custom pattern match of the grok filter: Ruby Regex Syntax

[(?<name>subexp)]    define named group
                     (All characters of the name must be a word character.)

There you have it, it explains the invalid char in group name error in more detail by defining what characters are legal, of which the square brackets are not included. This is an upstream change and would be hard to justify to push it that far up. There may also be some regex related reasons, such as square brackets usually referencing a regex character class.

I think the only current option is to create the custom pattern file and reference it in the grok match:

Pattern File

PERMS [r-]

Grok Filter

 grok {
              patterns_dir => "/etc/logstash/conf.d/patterns"   
              match => [ "source_field", "%{PERMS:[permission][user][read]}" ]
}

Due to the requirement of no period separated fields in Elasticsearch 2.0, which is how nested fields used to be referenced, I think it might be good to disambiguate the documentation to cover this senario in detail. Additionally, the Logstsah Configuration test should probably pick this up and concisely inform you of the reason.

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Any update on this issue? I am having difficulty with the same problem (logstash 5.6.4)

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Hey, Just found this issue.. had some troubles doing a regex capture, see #66

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