Stripping text from a JSON file

Elastic Stack Logstash
1

Hi all!

I have a valid JSON structure that is prepended with a fixed string and then a number. Something like:

RRR This is the leading string created at 01-01-2017 at 12:34:56:
{ 
     valid JSON 
}

So there is a fixes string "RRR This is the ...." and a variable part, the date and time. Ah, and BTW, the string is always the same length.
How do i use FileBeats or LogStash to strip off that leading string so i only get valid JSON in ES?

This is what i tried so far:

   input {
    beats {
        port => "5043"
    }
}

filter {
    mutate {
        gsub => ["message", "^(.*){", ""]
    }

    json {
        source => "data"
    }

    date {
        match => [ "receivedTime", "UNIX" ]
        target => "@timestamp"
    }
}

output {
  elasticsearch {
  hosts => [ "localhost:9200" ]
  index => filebeat
  }
}

and i keep getting the following message:

2017/03/21 18:26:01.644365 json.go:34: ERR Error decoding JSON: invalid character 'R' looking for beginning of value
2017/03/21 18:26:01.644428 json.go:34: ERR Error decoding JSON: json: cannot unmarshal number into Go value of type map[string]interface {}

Thanks,

Ton.

2

Do not configure Filebeat to treat the input as JSON, because it isn't JSON. Do make sure to configure the multiline feature so the lines are joined into a single logical message.

I don't see how the source option for your json filter could make sense. Where does the data field come from?

3

Ok, removed the JSON from FileBeat, "data" is the top field in my JSON document. If all my log entries are on the same line, do i need the multiline?

4

If all my log entries are on the same line, do i need the multiline?

No.

5

Remember i'm still a newbie. After fighting a lot with regex i just solved it like this:

filter {
    grok {
        patterns_dir => ["./patterns"]
        match => { "message" => "%{DATA:todelete}: %{GREEDYDATA:message}" }
        remove_field => "todelete"
        overwrite => ["message"]
    }
   json {
       source => "message"
   }
   date {
       match => [ "receivedTime", "UNIX_MS" ]
   }
}

This works as i want it to work. Now i face the "Objects in arrays are not well supported" issue, but i will open another topic for this.

6

Replace %{DATA:todelete} with %{DATA} and you won't need remove_field. You can also use a mutate filter's gsub option to trim the message field in-place.

7

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