capture-filter.rb

# Copyright 2018 Ry Biesemeyer (@yaauie)
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# USAGE:
#
# This ruby script can be used as the source of a [Ruby Filter Plugin[] for
# extracting pattern matches from a String field on an Event.
#
# For example, to extract `ORA-12345` and `ORA-67890` from an event whose
# `message` is `ORA-12345: some text ORA-67890: some other text`, and to
# put all matches into the field `ora`, you would do the following:
#
# ~~~
# filter {
#   ruby {
#     path => "capture-filter.rb"
#     script_params => {
#       "pattern"=> "ORA-[0-9]+"
#       "source" => "message"
#       "target" => "ora"
#     }
#   }
# }
# ~~~
#
def register(params)
  params = params.dup

  pattern = params.delete('pattern') || report_configuration_error('required script parameter `pattern` missing')
  @pattern = Regexp.new(pattern)

  @source = params.delete("source") || report_configuration_error('required script parameter `source` missing')
  @target = params.delete("target") || report_configuration_error('required script parameter `target` missing')

  params.empty? || report_configuration_error("unknown script parameter(s): #{params.keys}")
end

def filter(event)
  source = event.get(@source)
  return if source.nil?
  captured = source.scan(@pattern)
  return if captured.nil? || captured.empty?

  event.set(@target, captured)
rescue => e
  logger.warn("caught exception in capture script", exception: e.message, backtrace: e.backtrace)
  event.tag("_capturefailure")
ensure
  return [event]
end

def report_configuration_error(message)
  raise LogStash::ConfigurationError, message
end

test 'null value source' do
  parameters do
     {
       "source" => "message",
       "target" => "extracted",
       "pattern" => "[A-Z]{3,}-[0-9]+"
     }
  end

  in_event do
    { "not_message" => "foo" }
  end

  expect("extracted") do |events|
    event = events.first
    next false if event.include?("extracted")

    event_tags = event.get("tags") || []
    !event_tags.include?("_capturefailure")
  end
end

test 'no matches in source' do
  parameters do
     {
       "source" => "message",
       "target" => "extracted",
       "pattern" => "[A-Z]{3,}-[0-9]+"
     }
  end

  in_event do
    { "message" => "foo" }
  end

  expect("extracted") do |events|
    event = events.first
    next false if event.include?("extracted")

    event_tags = event.get("tags") || []
    !event_tags.include?("_capturefailure")
  end
end

test 'single match in source' do
  parameters do
     {
       "source" => "message",
       "target" => "extracted",
       "pattern" => "[A-Z]{3,}-[0-9]+"
     }
  end

  in_event do
    { "message" => "text ABC-123: some more text" }
  end

  expect("extracted") do |events|
    event = events.first
    event.include?("extracted") && event.get("extracted") == ["ABC-123"]
  end
end

test 'multiple matches in source' do
  parameters do
     {
       "source" => "message",
       "target" => "extracted",
       "pattern" => "[A-Z]{3,}-[0-9]+"
     }
  end

  in_event do
    { "message" => "text ABC-123: some more text and DEF-7890: even more" }
  end

  expect("extracted") do |events|
    event = events.first
    event.include?("extracted") && event.get("extracted") == ["ABC-123","DEF-7890"]
  end
end